@article {chu_earthquake-enhanced_2023,
	title = {Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments},
	journal = {Nature Communications},
	volume = {14},
	year = {2023},
	month = {09/2023},
	pages = {5427},
	abstract = {Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones., Earthquakes enhance dissolved carbon production and fuel the microbial activities in hadal trench subsurface sediments, and ultimately strengthen carbon accumulation and transformation in the subduction zones.},
	issn = {2041-1723},
	doi = {10.1038/s41467-023-41116-w},
	url = {https://www.nature.com/articles/s41467-023-41116-w},
	author = {Chu, Mengfan and Bao, Rui and Strasser, Michael and Ikehara, Ken and Everest, Jez and Maeda, Lena and Hochmuth, Katharina and Xu, Li and McNichol, Ann and Bellanova, Piero and Rasbury, Troy and K{\"o}lling, Martin and Riedinger, Natascha and Johnson, Joel and Luo, Min and M{\"a}rz, Christian and Straub, Susanne and Jitsuno, Kana and Brunet, Morgane and Cai, Zhirong and Cattaneo, Antonio and Hsiung, Kanhsi and Ishizawa, Takashi and Itaki, Takuya and Kanamatsu, Toshiya and Keep, Myra and Kioka, Arata and McHugh, Cecilia and Micallef, Aaron and Pandey, Dhananjai and Proust, Jean No{\"e}l and Satoguchi, Yasufumi and Sawyer, Derek and Seibert, Chlo{\'e} and Silver, Maxwell and Virtasalo, Joonas and Wang, Yonghong and Wu, Ting-Wei and Zellers, Sarah}
}
@article {2959,
	title = {The occupation history of the longest-dwelling Ad{\'e}lie penguin colony reflects Holocene climatic and environmental changes in the Ross Sea, Antarctica},
	journal = {Quaternary Science Reviews},
	volume = {284},
	year = {2022},
	month = {Jan-05-2022},
	pages = {107494},
	abstract = {As a result of climate changes, penguins are predicted to be at risk of losing their breeding habitats. Changes in penguin colony distribution suggest that some colonies have withstood environmental changes better than others, serving as initial post-glacial settlements or refuges in adverse climatic conditions. Here we have synthesized over 200 dates (including 91 new dates) of penguin remains and of guano in 107 ornithogenic profiles from abandoned nests on Inexpressible Island, one of the longest persisting Ad{\'e}lie penguin colonies in Antarctica, to investigate the dynamics of population size and the role of this island in the ecological history of this species. The results indicate that, following the retreat of Ross Ice Shelf, the Ad{\'e}lies first colonized this island at \~{}8.6 kyr BP, documenting the earliest known breeding site in the Ross Sea since deglaciation. During \~{}7-3 kyr BP the reconstructed population on Inexpressible Island was generally consistent with the change in pack ice, reaching relative peaks at 5.5{\textendash}5.0 and 4.0{\textendash}3.5 kyr BP. After brief decline at 3.5{\textendash}3.0 kyr, substantial enlargement of the penguin colony occurred between 3.0 and 1.5 kyr BP, attributed to the immigration from the abandoned colonies along the Scott Coast. During this time, the persistent efficiency of Terra Nova Bay polynya offered conditions favourable to the expansion of the penguin population on Inexpressible Island, which probably represented a refuge area under increased coastal sea-ice. This longest-dwelling penguin colony may provide a valuable refuge for the Ad{\'e}lie penguin if the recurrent Terra Nova Bay polynya persists under future climatic and environmental changes, as occurred in the past.},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2022.107494},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379122001251},
	author = {Gao, Yuesong and Salvatore, Maria Cristina and Xu, Qibin and Yang, Lianjiao and Sun, Liguang and Xie, Zhouqing and Baroni, Carlo}
}
@article {2948,
	title = {RADIOCARBON IN DISSOLVED CARBON BY UV OXIDATION: AN UPDATE OF PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMSABSTRACT},
	journal = {Radiocarbon},
	volume = {64},
	year = {2022},
	month = {Jan-02-2022},
	pages = {195 - 199},
	abstract = {This note describes improvements of UV oxidation method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). The procedural blank is reduced to 2.6 +/- 0.6 mu g C, with Fm of 0.42 +/- 0.10 and delta C-13 of -28.43 +/- 1.19 parts per thousand. The throughput is improved from one sample per day to two samples per day.},
	issn = {0033-8222},
	doi = {10.1017/RDC.2022.4},
	url = {https://www.cambridge.org/core/product/identifier/S0033822222000042/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822222000042},
	author = {Xu, Li and Roberts, Mark L and Elder, Kathryn L and Hansman, Roberta L and Gagnon, Alan R and Kurz, Mark D}
}
@article {2924,
	title = {Compound-specific radiocarbon reveals sources and land{\textendash}sea transport of polycyclic aromatic hydrocarbons in an urban estuary},
	journal = {Water Research},
	volume = {198},
	year = {2021},
	month = {Jan-06-2021},
	pages = {117134},
	abstract = {As typical chemical indicators of the Anthropocene, polycyclic aromatic hydrocarbons (PAHs) and their environmental behavior in urban estuaries can reveal the influence of anthropogenic activities on coastal zones worldwide. In contrast to conventional approaches based on concentration datasets, we provide a compound-specific radiocarbon ( 14 C) perspective to quantitatively evaluate the sources and land{\textendash}sea transport of PAHs in an estuarine{\textendash}coastal surficial sedimentary system impacted by anthropogenic activities and coastal currents. Compound-specific 14 C of PAHs and their 14 C end-member mixing models showed that 67 -73\% of fluoranthene and pyrene and 76 -80\% of five- and six-ring PAHs in the Jiulong River Estuary (JRE, China) originated from fossil fuels (e.g., coal, oil spill, and petroleum-related emissions). In the adjacent Western Taiwan Strait (WTS), the contributions of fossil fuel to these PAH groups were higher at 74 -79\% and 84 -87\%, respectively. Furthermore, as a significant biomarker for source al- location of terrigenous organic matter, perylene, a typical five-ring PAH, and its land{\textendash}sea transport from the basin through the JRE and finally to the WTS was quantitatively evaluated based on the 14 C transport models. In the JRE, fluvial erosions and anthropogenic emissions affected the 14 C signature of perylene ( 14 C perylene , -535 {\textpm}5 {\textperthousand} ) with contributions of > 38\% and < 62\%, respectively. From the JRE to the WTS, the decreased 14 C perylene (-735 {\textpm}4 {\textperthousand} ) could be attributed to the long{\textendash}range transport of {\textquotedblleft}ocean current- driven{\textquotedblright} perylene (-919 {\textpm}53 {\textperthousand} ) with a contribution of 53 {\textpm}8\%. This compound-specific 14 C approach and PAH transport model help provide a valuable reference for accurately quantifying land{\textendash}sea transport and burial of organic pollutants in estuarine{\textendash}coastal sedimentary systems.},
	issn = {00431354},
	doi = {10.1016/j.watres.2021.117134},
	url = {https://www.sciencedirect.com/science/article/pii/S0043135421003328},
	author = {Ya, Miaolei and Wu, Yuling and Xu, Li and Li, Yongyu and Chen, Hanzhe and Wang, Xinhong}
}
@article {2922,
	title = {RADIOCARBON IN DISSOLVED ORGANIC CARBON BY UV OXIDATION: PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMSABSTRACT},
	journal = {Radiocarbon},
	volume = {63},
	year = {2021},
	month = {Jan-02-2021},
	pages = {357 - 374},
	abstract = {This study describes a procedural blank assessment of the ultraviolet photochemical oxidation (UV oxidation) method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). A retrospective compilation of Fm and δ 13 C results for secondary standards (OX-II, glycine) between 2009 and 2018 indicated that a revised blank correction was required to bring results in line with accepted values. The application of a best-fit mass-balance correction yielded a procedural blank of 22.0 {\textpm} 6.0 μg C with Fm of 0.30 {\textpm} 0.20 and δ 13 C of-32.0 {\textpm} 3.0{\textperthousand} for this period, which was notably higher and more variable than previously reported. Changes to the procedure, specifically elimination of higher organic carbon reagents and improved sample and reactor handling, reduced the blank to 11.0 {\textpm} 2.75 μg C, with Fm of 0.14 {\textpm} 0.10 and δ 13 C of-31.0 {\textpm} 5.5{\textperthousand}. A thorough determination of the entire sample processing blank is required to ensure accurate isotopic compositions of seawater DOC using the UV oxidation method. Additional efforts are needed to further reduce the procedural blank so that smaller DOC samples can be analyzed, and to increase sample throughput.},
	keywords = {blank, dissolved organic carbon, radiocarbon, UV oxidation},
	issn = {0033-8222},
	doi = {10.1017/RDC.2020.102},
	url = {https://www.cambridge.org/core/journals/radiocarbon/article/abs/radiocarbon-in-dissolved-organic-carbon-by-uv-oxidation-procedures-and-blank-characterization-at-nosams/AA39A2C74772934B44D9BF81C2DF723C},
	author = {Xu, Li and Roberts, Mark L and Elder, Kathryn L and Kurz, Mark D and McNichol, Ann P and Reddy, Christopher M and Ward, Collin P and Hanke, Ulrich M}
}
@article {2914,
	title = {Carbon cycling in the deep Mariana Trench in the western north Pacific Ocean: Insights from radiocarbon proxy data},
	journal = {Deep Sea Research Part I: Oceanographic Research Papers},
	volume = {164},
	year = {2020},
	month = {Jan-10-2020},
	pages = {103370},
	abstract = {The Mariana Trench in the western North Pacific (NP) contains the deepest (11,000 m) point in the ocean and thus remains the least explored environment. Carbon cycling in the deep Mariana Trench is largely unknown and remains a curious mystery. Here, we report radiocarbon (Delta C-14) and stable carbon isotope (delta C-13) compositions of dissolved inorganic and organic carbon (DIC and DOC) and sinking particulate organic carbon (POC) for samples collected at 2000 m, 4000 m and 6000 m from the Mariana Trench in the western NP. DOC had much lower Delta C-14 values (-189 parts per thousand to -538 parts per thousand) than DIC (38 parts per thousand to -236 parts per thousand) and POC (11 parts per thousand-38 parts per thousand) at the same depths, indicating the different cycling processes and time scales of different carbon pools. The C-14 ages of DOC were approximately 1700 years and 4400 years older than those of DIC in the surface (2 m) and deep (10,000 m) waters of the Mariana Trench. Both DOC and DIC Delta C-14 values at hadal depths (>6000 m) in the trench are comparable to values at other sites in the deep NP, suggesting that water movement and mixing at hadal depths in the Mariana Trench are active and follow the deep-water circulation patterns of the NP. POC fluxes at the three deep depths showed large variations, but their modern Delta C-14 values indicate that the effective biological pump that drives fresh surface-produced particles to sink rapidly to deep depths in the trench could provide essential food sources for microbial and benthic communities living in an extremely harsh environment of the Mariana Trench.},
	keywords = {carbon cycling, Mariana trench, North pacific ocean, Particle flux, radiocarbon, stable carbon isotope},
	issn = {09670637},
	doi = {10.1016/j.dsr.2020.103370},
	url = {https://apps.webofknowledge.com/InboundService.do?product=WOS\&Func=Frame\&DestFail=http\%3A\%2F\%2Fwww.webofknowledge.com\&SrcApp=search\&SrcAuth=Alerting\&SID=5FcsGoXKXNO2xQfU7KW\&customersID=Alerting\&mode=FullRecord\&IsProductCode=Yes\&AlertId=4d48b20a-7d27-4fa2-},
	author = {Shan, Sen and Qi, Yuanzhi and Tian, Jiwei and Wang, Xuchen and Luo, Chunle and Zhou, Chun and Zhang, Xiao-Hua and Xin, Yu and Wang, Yonghong}
}
@article {2832,
	title = {Permafrost Hydrology Drives the Assimilation of Old Carbon by Stream Food Webs in the Arctic},
	journal = {Ecosystems},
	volume = {23},
	year = {2020},
	month = {Jan-03-2020},
	pages = {435 - 453},
	abstract = {Permafrost thaw in the Arctic is mobilizing old carbon (C) from soils to aquatic ecosystems and the atmosphere. Little is known, however, about the assimilation of old C by aquatic food webs in Arctic watersheds. Here, we used C isotopes (δ13C, Δ14C) to quantify C assimilation by biota across 12 streams in arctic Alaska. Streams spanned watersheds with varying permafrost hydrology, from ice-poor bedrock to ice-rich loess (that is, yedoma). We measured isotopic content of (1) C sources including dissolved organic C (DOC), dissolved inorganic C (DIC), and soil C, and (2) stream biota, including benthic biofilm and macroinvertebrates, and resident fish species (Arctic Grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma)). Findings document the assimilation of old C by stream biota, with depleted Δ14C values observed at multiple trophic levels, including benthic biofilm (14C ages = 5255 to 265 years before present (y BP)), macroinvertebrates (4490 y BP to modern), and fish (3195 y BP to modern). Mixing model results indicate that DOC and DIC contribute to benthic biofilm composition, with relative contributions differing across streams draining ice-poor and ice-rich terrain. DOC originates primarily from old terrestrial C sources, including deep peat horizons (39{\textendash}47\%; 530 y BP) and near-surface permafrost (12{\textendash}19\%; 5490 y BP). DOC also accounts for approximately half of fish isotopic composition. Analyses suggest that as the contribution of old C to fish increases, fish growth and nutritional status decline. We anticipate increases in old DOC delivery to streams under projected warming, which may further alter food web function in Arctic watersheds.},
	issn = {1432-9840},
	doi = {10.1007/s10021-019-00413-6},
	url = {https://link.springer.com/article/10.1007\%2Fs10021-019-00413-6},
	author = {O{\textquoteright}Donnell, Jonathan A. and Carey, Michael P. and Koch, Joshua C. and Xu, Xiaomei and Poulin, Brett A. and Walker, Jennifer and Zimmerman, Christian E.}
}
@article {2667,
	title = {Sources and radiocarbon ages of organic carbon in different grain size fractions of Yellow River-transported particles and coastal sediments},
	journal = {Chemical Geology},
	volume = {534},
	year = {2020},
	month = {Jan-02-2020},
	pages = {119452},
	keywords = {organic matter, RadiocarbonStable carbon isotope, Sediment grain size, Yellow River},
	issn = {00092541},
	doi = {10.1016/j.chemgeo.2019.119452},
	url = {https://www.sciencedirect.com/science/article/pii/S0009254119305819},
	author = {Ge, Tiantian and Xue, Yuejun and Jiang, Xueyan and Zou, Li and Wang, Xuchen}
}
@article {2994,
	title = {14C Blank Corrections for 25{\textendash}100 μg Samples at the National Ocean Sciences AMS Laboratory},
	journal = {Radiocarbon},
	volume = {61},
	year = {2019},
	month = {10/2019},
	pages = {1403 - 1411},
	abstract = {Replicate radiocarbon (14C) measurements of organic and inorganic control samples, with known Fraction Modern values in the range Fm = 0{\textendash}1.5 and mass range 6 μg{\textendash}2 mg carbon, are used to determine both the mass and radiocarbon content of the blank carbon introduced during sample processing and measurement in our laboratory. These data are used to model, separately for organic and inorganic samples, the blank contribution and subsequently {\textquotedblleft}blank correct{\textquotedblright} measured unknowns in the mass range 25{\textendash}100 μg. Data, formulas, and an assessment of the precision and accuracy of the blank correction are presented.},
	keywords = {AMS, AMS dating, blank corrections},
	isbn = {0033-8222, 1945-5755},
	doi = {10.1017/RDC.2019.74},
	url = {https://www.cambridge.org/core/journals/radiocarbon/article/14c-blank-corrections-for-25100-g-samples-at-the-national-ocean-sciences-ams-laboratory/494B9CF72445198570213B4A2CC303D0},
	author = {Roberts, M. L. and Elder, K. L. and Jenkins, W. J. and Gagnon, A. R. and Xu, L. and Hlavenka, J. D. and Longworth, B. E.}
}
@article {2871,
	title = {Dissolved organic carbon in basalt-hosted deep subseafloor fluids of the Juan de Fuca Ridge flank},
	journal = {Earth and Planetary Science Letters},
	volume = {513},
	year = {2019},
	month = {Jan-05-2019},
	pages = {156 - 165},
	abstract = {Marine dissolved organic carbon (DOC) is highly depleted in radiocarbon and thus inferred to be largely refractory to removal processes that operate on less than millennial timescales. However, a growing number of reports have shown that a large fraction of marine DOC can be effectively removed during circulation through submarine hydrothermal systems. What is not clear, however, is whether the DOC that remains in hydrothermal fluids is remnant non-reactive DOC from recharged seawater, or DOC that has been largely produced in the subsurface. We collected and characterized warm (\~{}65 {\textdegree}C) hydrothermal fluids from deep (18, 40, 73, 200 m) within the basalt-hosted basement of the Juan de Fuca Ridge flank in the Northeast Pacific Ocean. DOC concentrations in hydrothermal fluids were 9 to 18 μM, much lower than measured in local deep seawater (37.5 μM). DOC C values of -683{\textperthousand} to -856{\textperthousand} were much lower than the C-dissolved inorganic carbon (DIC) values of -880{\textperthousand} to -918{\textperthousand}, while DOC C values of -23.6{\textperthousand} to -27.0{\textperthousand} were much heavier than that of the particulate organic carbon (POC) pool ({\textperthousand}), suggesting that biological production in the subsurface is not a primary source of DOC. Rather, our data suggest that isotopically enriched DOC are selectively removed from recharged seawater, leaving DOC that is very isotopically depleted in the basaltic basement fluids. Despite the removal of 50{\textendash}75\% of DOC in the subsurface, nuclear magnetic resonance (NMR) functional group analyses indicate that aromatic compounds were added to basaltic basement fluids during passage through the deep subseafloor and may partly contribute to the depleted 14C DOC in the ridge-flank basement fluids.},
	keywords = {aromatic organic compound, basaltic basement fluid, carbon isotopes, dissolved organic carbon, Juan de Fuca, selective removal, subseafloor},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2019.02.008},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X19300998},
	author = {Lin, Huei-Ting and Repeta, Daniel J. and Xu, Li and Rapp{\'e}, Michael S.}
}
@article {2761,
	title = {Implications of radiocarbon ages of organic and inorganic carbon in coastal lakes in Florida for establishing a reliable chronology for sediment-based paleoclimate reconstructionAbstract},
	journal = {Quaternary Research},
	volume = {91},
	year = {2019},
	month = {Jan-03-2019},
	pages = {638 - 649},
	abstract = {Coastal lake sediments are valuable paleoclimate archives provided that they can be accurately dated. Here, we report radiocarbon ages of bulk sediment organic matter (OM), plants, shells, particulate OM, and dissolved OM from coastal lakes in Florida. Bulk sediment OM yielded ages that are consistently older than contemporaneous plants and shells, indicating significant radiocarbon deficiencies in sedimentary OM in these lakes. The data show that the OM radiocarbon deficiency varies over time and with location, making it impossible to determine a proper correction factor for radiocarbon ages of bulk sediments from these lakes. As a result, we consider ages obtained from bulk sediment OM from these lakes unreliable. The age reversals in bulk sediment OM observed in the sediment cores are likely caused by rapid increases in erosion and sedimentation resulting from large storm events. The data also show that sedimentation rate can vary considerably within a given lake, implying that an age-depth model established for one core cannot be directly applied to other cores despite their close proximity. Analyses of shells from one of the lakes suggest that fresh/brackish-water shells may serve as a good substrate for radiocarbon dating owing to a small reservoir effect on inorganic carbon.},
	issn = {0033-5894},
	doi = {10.1017/qua.2018.96},
	url = {https://www.cambridge.org/core/product/identifier/S0033589418000960/type/journal_article},
	author = {Wang, Yang and Das, Oindrila and Xu, Xiaomei and Liu, Jin and Jahan, Shakura and Means, Guy H. and Donoghue, Joseph and Jiang, Shijun}
}
@article {2728,
	title = {Sea-level, monsoonal, and anthropogenic impacts on the millennial-scale variability of siliciclastic sediment input into the western Philippine sea since 27 ka},
	journal = {Journal of Asian Earth Sciences},
	volume = {177},
	year = {2019},
	month = {Jan-06-2019},
	pages = {250 - 262},
	abstract = {Multiproxy records from Core MD06-3054 in the western Philippine Sea and published results from the nearby Core MD06-3052, which are both located at the northern margin of the Western Pacific Warm Pool (WPWP), provide precise reconstructions and evidence for the potential controls on continental erosion and weathering intensities in Luzon. These data also constrain sediment source-to-sink processes in the sea since 27 ka at the millennial scale. We demonstrate that the siliciclastic fraction is derived from Luzon volcanic rocks and eolian dust from mainland Asia. Stronger physical erosion and chemical weathering generally occurred during the last glaciation, Heinrich Event 1, the Younger Dryas, and the period from 10.3 to 11.3 ka. In contrast, the B{\o}lling-Aller{\o}d was characterized by weaker physical erosion and chemical weathering. During the last glaciation, Heinrich Event 1, and the Younger Dryas, the lower sea level led to enhanced erosion and weathering of the exposed shelf sediments. In contrast, the weaker physical erosion and chemical weathering that occurred during the B{\o}lling-Aller{\o}d and the Holocene, except after 2.1 ka, are closely correlated with the higher sea level. The stronger physical erosion and chemical weathering at 10.3{\textendash}11.3 ka may be derived from the reworking of older sediments during the time of a strengthening summer monsoon. Furthermore, enhanced human activity since 2.1 ka has become the dominant control on erosion in Luzon. Rapid weathering changes in the WPWP during the last deglaciation highlight the high variability in local controls at low latitudes during these periods and the potential influence of controls at high latitudes.},
	issn = {13679120},
	doi = {10.1016/j.jseaes.2019.04.001},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S1367912019301506},
	author = {Xu, Zhaokai and Li, Tiegang and Clift, Peter D. and Wan, Shiming and Lim, Dhongil and Chang, Fengming and Sun, Rongtao}
}
@article {2757,
	title = {Significance of Perylene for Source Allocation of Terrigenous Organic Matter in Aquatic SedimentsSignificance of Perylene for Source Allocation of Terrigenous Organic Matter in Aquatic Sediments},
	journal = {Environmental Science \& Technology},
	volume = {53},
	year = {2019},
	month = {Apr-07-2020},
	pages = {8244 - 8251},
	abstract = {Perylene is a frequently abundant, and sometimes the only polycyclic aromatic hydrocarbon (PAH) in aquatic sediments, but its origin has been subject of a longstanding debate in geochemical research and pollutant forensics because its historical record differs markedly from typical anthropogenic PAHs. Here we investigate whether perylene serves as a source-specific molecular marker of fungal activity in forest soils. We use a well-characterized sedimentary record (1735-1999) from the anoxic-bottom waters of the Pettaquamscutt River basin, RI to examine mass accumulation rates and isotope records of perylene, and compare them with total organic carbon and the anthropogenic PAH fluoranthene. We support our arguments with radiocarbon (14C) data of higher plant leaf-wax n-alkanoic acids. Isotope-mass balance-calculations of perylene and n-alkanoic acids indicate that \~{}40\% of sedimentary organic matter is of terrestrial origin. Further, both terrestrial markers are pre-aged on millennial time-scales prior to burial in sediments and are insensitive to elevated 14C concentrations following nuclear weapons testing in the mid-20th Century. Instead, changes coincide with enhanced erosional flux during urban sprawl. These findings suggest that perylene is definitely a product of soil-derived fungi, and a powerful chemical tracer to study the spatial and temporal connectivity between terrestrial and aquatic environments. },
	issn = {0013-936X},
	doi = {10.1021/acs.est.9b0234410.1021/acs.est.9b02344.s001},
	url = {https://pubs.acs.org/doi/10.1021/acs.est.9b02344},
	author = {Hanke, Ulrich M. and Lima-Braun, Ana L. and Eglinton, Timothy I. and Donnelly, Jeffrey P. and Galy, Valier and Poussart, Pascale and Hughen, Konrad and McNichol, Ann P. and Xu, Li and Reddy, Christopher M.}
}
@article {2666,
	title = {Single step Production of graphite from organic Samples for Radiocarbon Measurements},
	journal = {Radiocarbon},
	volume = {61},
	year = {2019},
	month = {Jan-12-2019},
	pages = {1843 - 1854},
	abstract = {We present a new low-cost, high-throughput method for converting many types of organic carbon samples into graphite for radiocarbon (14C) measurements by accelerator mass spectrometry (AMS). The method combines sample combustion and reduction to graphite into a single procedure. In the Single Step method, solid samples are placed directly into Pyrex containing zinc, titanium hydride and iron catalyst. The tube is evacuated, flame sealed, and placed in a muffle furnace for 7 hr. A variety of organic samples have been tested including oxalic acid, sucrose, wood, peat, collagen, humic acid, and contamination swipe samples. The method significantly reduces the time required to produce a graphite sample for 14C measurement, with analytical precision and accuracy approaching that of traditional two-step combustion and hydrogen reduction methods. The details and applicability of the method are presented.},
	keywords = {graphite, radiocarbon, sealed tube graphite, single step graphite},
	issn = {0033-8222},
	doi = {10.1017/RDC.2019.136},
	url = {https://www.cambridge.org/core/product/identifier/S003382221900136X/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S003382221900136X},
	author = {Elder, K L and Roberts, M L and Walther, T and Xu, L}
}
@article {2730,
	title = {Bathyal records of enhanced silicate erosion and weathering on the exposed Luzon shelf during glacial lowstands and their significance for atmospheric CO2 sink},
	journal = {Chemical Geology},
	volume = {476},
	year = {2018},
	month = {Jan-01-2018},
	pages = {302 - 315},
	abstract = {We present a new high-resolution multiproxy data set of mass accumulation rates, Sr-Nd isotopes, as well as major and trace elements for the siliciclastic sediment fraction from International Marine Global Change Study Core MD06-3052, located on the continental slope of the western Philippine Sea. We integrate our new data with published grain sizes and sea surface temperatures from the same core, as well as with Equatorial Pacific sea level, and East Asian summer monsoon precipitation, in order to constrain at high-resolution changes in physical erosion and chemical weathering intensities on Luzon, and sediment source-to-sink processes. We assess the potential significance of chemical weathering of arc silicates in regulating global atmospheric CO2 since 156 kyr BP. Sr-Nd isotopes show that the siliciclastic sediments were dominantly sourced from volcanic rocks exposed on Luzon (~ 68{\textendash}100\%), with a lesser contribution from Asian dust (~ 0{\textendash}32\%). Different indices indicate that stronger physical erosion and chemical weathering occurred during Marine Isotope Stage (MIS) 6 (130{\textendash}156 kyr BP), as well as in the latter stage of MIS 3 and MIS 2 (14{\textendash}40 kyr BP). The large sea-level lowstands and associated significant exposure of continental shelf in the western Philippine Sea during these two cold periods should favor physical erosion and chemical weathering of unconsolidated sediments on the exposed shelf. Furthermore, we notice the relatively good coherence between chemical weathering intensities on Luzon and global atmospheric CO2 concentrations over these cold intervals. We suggest that strengthening of chemical weathering of silicates on Luzon and other tropical arcs (within 20{\textdegree} of the Equator) during the Quaternary glacial sea-level lowstands may significantly contribute to the lowering of atmospheric CO2 concentrations during ice ages. We estimate that a significant fraction, up to ~ 16\% (i.e., ~ 8 ppmv), of all atmospheric CO2 ultimately sequestered by silicate weathering may be processed through an area corresponding to only ~ 1\% of the exorheic drainage area worldwide.},
	keywords = {Atmospheric CO2 concentration, Chemical weathering, East Asian summer monsoon, sea level, Western Philippine Sea},
	issn = {00092541},
	doi = {10.1016/j.chemgeo.2017.11.027},
	url = {https://www.sciencedirect.com/science/article/pii/S0009254117306587},
	author = {Xu, Zhaokai and Li, Tiegang and Clift, Peter D. and Wan, Shiming and Qiu, Xiaohua and Lim, Dhongil}
}
@article {2881,
	title = {The collapse of the North Song dynasty and the AD 1048{\textendash}1128 Yellow River floods: Geoarchaeological evidence from northern Henan Province, China},
	journal = {The Holocene},
	volume = {28},
	year = {2018},
	month = {Jun-11-2018},
	pages = {1759 - 1770},
	abstract = {From AD 1048 to 1128, Yellow River flooding killed over a million people, left many more homeless and destitute, and turned parts of the once fertile North China Plain into a silted-up agricultural wasteland. Brought on in part by climate change and the Northern Song dynasty{\textquoteright}s (AD 960{\textendash}1127) mismanagement of the environment, the Yellow River floods likely hastened the collapse of the Northern Song dynasty. Despite the magnitude of this flood event, no sedimentary deposits have yet been linked to these historically recorded floods. In this research paper, we provide archaeological, sedimentary, and radiocarbon evidence of the AD 1048{\textendash}1128 Yellow River floods at the Dazhanglongcun, Xidacheng, and Daguxiancun sites in Neihuang County, Henan Province. Based on our data, we argue that the AD 1048{\textendash}1128 Yellow River floods deposited over 5 m of alluvium on villages in the North China Plain, radically changing both the physical and political landscape of Northern Song dynasty China.},
	keywords = {floods, Geoarchaeology, land use, North China Plain, Song dynasty, Yellow River},
	issn = {0959-6836},
	doi = {10.1177/0959683618788682},
	url = {http://journals.sagepub.com/doi/10.1177/0959683618788682},
	author = {Storozum, Michael J and Zhen, Qin and Xiaolin, Ren and Haiming, Li and Yifu, Cui and Kui, Fu and Haiwang, Liu}
}
@article {2888,
	title = {Decreased sedimentation efficiency of petro- and non-petro-carbon caused by a dispersant for Macondo surrogate oil in a mesocosm simulating a coastal microbial community},
	journal = {Marine Chemistry},
	volume = {206},
	year = {2018},
	month = {Jan-10-2018},
	pages = {34 - 43},
	abstract = {Large amounts of mucous-rich oil-containing marine snow formed in surface waters adjacent to the Deepwater Horizon spill. This marine oil snow (MOS) was implicated in oil delivery to the seafloor. Whether the use of chemical dispersants increased or decreased MOS sedimentation remains controversial. We conducted mesocosm experiments testing the effects of oil and oil plus a dispersant on MOS formation and sedimentation, in coastal seawater. The four treatments used were a surrogate Macondo oil water accommodated fraction ({\textquotedblleft}WAF{\textquotedblright}), two concentrations of chemically-enhanced WAF ({\textquotedblleft}CEWAF{\textquotedblright} and diluted CEWAF, {\textquotedblleft}DCEWAF{\textquotedblright}) containing a dispersant and oil, and Controls (no additions). Based on radiocarbon and 13C NMR results, the presence of dispersants enhanced the amounts of petro-carbon being incorporated into the sinking oil-carrying aggregates (aka MOS). However, most of the chemically-dispersed oil preferentially partitioned into the colloidal and suspended particulate fractions rather than into the rapidly forming MOS. Thus the oil and non-petro-carbon sedimentation efficiency in treatments with a dispersant was much lower, compared to those in the Control and WAF treatments, during the four-day mesocosm experiment. Formation of MOS and its subsequent sinking sequestered the oil in two stages: first via terrestrial-derived detritus containing humic compounds, and subsequently via freshly produced material, such as exopolymeric substances produced by phytoplankton and bacteria.},
	issn = {03044203},
	doi = {10.1016/j.marchem.2018.09.002},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0304420318301415},
	author = {Xu, Chen and Zhang, Saijin and Beaver, Morgan and Wozniak, Andrew and Obeid, Wassim and Lin, Youmin and Wade, Terry L. and Schwehr, Kathleen A. and Lin, Peng and Sun, Luni and Hatcher, Patrick G. and Chin, Wei-Chun and Chiu, Meng-Hsuen and Knap, Anthony H. and Dean, Kendra and Quigg, Antonietta and Santschi, Peter H.}
}
@article {2613,
	title = {Dimensions of Radiocarbon Variability within Sedimentary Organic MatterABSTRACT},
	journal = {Radiocarbon},
	volume = {60},
	year = {2018},
	month = {Jan-06-2018},
	pages = {775 - 790},
	abstract = {Organic carbon (OC) radiocarbon (14C) signatures in marine surface sediments are highly variable and the
causes of this heterogeneity remain ambiguous. Here, we present results from a detailed 14C-based investigation of an Arabian Sea sediment, including measurements on organic matter (OM) in bulk sediment, specific grain size fractions, and OC decomposition products from ramped-pyrolysis-oxidation (RPO). Our results show that 14C ages of OM increase with increasing grain size, suggesting that grain size is an important factor controlling the 14C heterogeneity in marine sediments. Analysis of RPO decomposition products from different grain size fractions reveals an overall increase in age of corresponding thermal fractions from finer to coarser fractions. We suggest that hydrodynamic properties of sediment grains exert the important control on the 14C age distribution of OM among grain size fractions. We propose a conceptual model to account for this dimensionality in 14C variability that invokes two predominant modes of OM preservation within different grain size fractions of Arabian Sea sediment: finer (<63 μm) fractions are influenced by OM-mineral grain aggregation processes, giving rise to relatively uniform 14C ages, whereas OM preserved in coarser (>63 μm) fractions includes materials encapsulated within microfossils and/or entrained fossil (14C-depleted) OC hosted in detrital mineral grains. Our findings highlight the value of RPO for assessment of 14C age variability in sedimentary OC, and for assessing mechanisms of OM preservation in aquatic sediments.},
	keywords = {arabian sea, grain size, hydrodynamic processes, organicmatter, radiocarbon, ramped pyrolysis-oxidation},
	issn = {0033-8222},
	doi = {10.1017/RDC.2018.22},
	url = {https://www.cambridge.org/core/journals/radiocarbon/article/dimensions-of-radiocarbon-variability-within-sedimentary-organic-matter/A81022494F34D8C3B88D39A43112BB08},
	author = {Bao, Rui and McNichol, Ann P and McIntyre, Cameron P and Xu, Li and Eglinton, Timothy I}
}
@article {2777,
	title = {Dual-Isotope Constraints on Seasonally Resolved Source Fingerprinting of Black Carbon Aerosols in Sites of the Four Emission Hot Spot Regions of China},
	journal = {Journal of Geophysical Research: Atmospheres},
	volume = {123},
	year = {2018},
	month = {Mar-10-2020},
	pages = {11,735 - 11,747},
	abstract = {Despite much recent efforts, the emission sources of black carbon (BC) aerosols--central input to understanding and predicting environmental and climate impact--remain highly uncertain. Here we present observational δ13C/Δ14C-based constraints on the sources of BC aerosols over the four seasons in each of the four key hot spot emission regions of China: Beijing-Tianjin-Hebei (BTH-Wuqing; where Wuqing is the sampling location), Yangtze River Delta (YRD-Haining), Pearl River Delta (PRD-Zhongshan), and Sichuan Basin (SC-Deyang). Overall, BC loadings were highest in winter, yet elevated loadings were also observed in other seasons, for example, spring at SC-Deyang and fall at PRD-Zhongshan. Annually, the dominant BC sources were coal (50 {\textpm} 20\%) for BTH-Wuqing, liquid fossil for YRD-Haining (46 {\textpm} 8\%) and PRD-Zhongshan (48 {\textpm} 18\%), whereas liquid fossil (42 {\textpm} 17\%) and biomass burning (41 {\textpm} 14\%) equally affected SC-Deyang. There is also different but distinct seasonalities in BC sources for the different sites. As an example, for BTH-Wuqing coal burning increased from summer to winter, while summer and spring BTH-Wuqing were more influenced by liquid fossil. In contrast, for YRD-Haining, the relative importance of emission sources was more constant over the year. These quantitative observational constraints on source-seasonality of BC aerosols in receptor sites located in China{\textquoteright}s four key economic zones highlight that regulatory control on BC aerosol emissions from different fuels should consider both seasonal and regional variations. Our results also suggest that models on estimates of BC-induced climate and air quality should consider variations over both regional and seasonal scales.},
	keywords = {aerosol, BLACK CARBON, carbon isotope, china, emission sources, seasonality},
	doi = {10.1029/2018JD028607},
	url = {http://doi.wiley.com/10.1029/2018JD028607},
	author = {Fang, Wenzheng and Du, Ke and Andersson, August and Xing, Zhenyu and Cho, Chaeyoon and Kim, Sang-Woo and Deng, Junjun and Gustafsson, {\"O}rjan}
}
@article {2891,
	title = {Fossil Fuel-Derived Polycyclic Aromatic Hydrocarbons in the Taiwan Strait, China, and Fluxes across the Air{\textendash}Water InterfaceFossil Fuel-Derived Polycyclic Aromatic Hydrocarbons in the Taiwan Strait, China, and Fluxes across the AirWater Interface},
	journal = {Environmental Science \& Technology},
	volume = {52},
	year = {2018},
	month = {Mar-07-2018},
	pages = {7307 - 7316},
	abstract = {On the basis of the application of compound-specific radiocarbon analysis (CSRA) and air{\textendash}water exchange models, the contributions of fossil fuel and biomass burning derived polycyclic aromatic hydrocarbons (PAHs) as well as their air{\textendash}water transport were elucidated. The results showed that fossil fuel-derived PAHs (an average contribution of 89\%) presented the net volatilization process at the air{\textendash}water interface of the Taiwan Strait in summer. Net volatile fluxes of the dominant fluorene and phenanthrene (>58\% of the total PAHs) were 27 {\textpm} 2.8 μg m{\textendash}2 day{\textendash}1, significantly higher than the dry deposition fluxes (average 0.43 μg m{\textendash}2 day{\textendash}1). The Δ14C contents of selected PAHs (fluorene, phenanthrene plus anthracene, fluoranthene, and pyrene) determined by CSRA in the dissolved seawater ranged from -997 {\textpm} 4{\textperthousand} to -873 {\textpm} 6{\textperthousand}, indicating that 89{\textendash}100\% (95 {\textpm} 4\%) of PAHs were supplied by fossil fuels. The South China Sea warm current originating from the southwest China in summer (98\%) and the Min-Zhe coastal current originating from the north China in winter (97\%) input more fossil fuel PAHs than the Jiulong River estuary (90\%) and Xiamen harbor water (93\%). The more radioactive decayed 14C of fluoranthene (a 4-ring PAH) than that of phenanthrene and anthracene (3-ring PAHs) represented a greater fossil fuel contribution to the former in dissolved seawater.},
	issn = {0013-936X},
	doi = {10.1021/acs.est.8b01331},
	url = {https://pubs.acs.org/doi/10.1021/acs.est.8b01331},
	author = {Ya, Miaolei and Xu, Li and Wu, Yuling and Li, Yongyu and Zhao, Songhe and Wang, Xinhong}
}
@article {2616,
	title = {Large Variability of Dissolved Inorganic Radiocarbon in the Kuroshio Extension of the Northwest North PacificABSTRACT},
	journal = {Radiocarbon},
	volume = {60264317255},
	year = {2018},
	month = {Jan-04-2018},
	pages = {691 - 704},
	abstract = {Radiocarbon (C-14) in dissolved inorganic carbon (DIC) was measured for water samples collected from six deep stations in the Kuroshio Extension (KE) region in the northwestern North Pacific in April-May 2015. Vertical profiles of Delta C-14-DIC indicate that bomb-produced Delta
C-14 was present from the surface to similar to 1500 m water depth. Large variations in Delta C-14-DIC values (300 parts per thousand) were
observed at 500 m water depth among the stations and the differences were likely controlled by transport and mixing dynamics of different
water masses in the region. The major Pacific western boundary currents, such as Kuroshio and Oyashio and regional mesoscale eddies, could play important roles affecting the observed Delta C-14-DIC variability. The depth profiles of both Delta C-14-DIC and DIC concentrations can be predicted by the solution mixing model and can be used as conservative tracers of water mass movement and water parcel homogenization in the
ocean.},
	keywords = {bomb radiocarbon, carbon, intermediate water, MIXED WATER REGION, ocean, WESTERN BOUNDARY CURRENTS},
	issn = {0033-8222},
	doi = {10.1017/RDC.2017.143},
	url = {https://www.cambridge.org/core/product/identifier/S0033822217001436/type/journal_articlehttps://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822217001436},
	author = {Ding, Ling and Ge, Tiantian and Gao, Huiwang and Luo, Chunle and Xue, Yuejun and Druffel, Ellen R M and Wang, Xuchen}
}
@article {2605,
	title = {Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean},
	journal = {Geophysical Research Letters},
	volume = {45},
	year = {2018},
	month = {01/2018},
	pages = {872 - 879},
	abstract = {We report four profiles of the radiocarbon content of dissolved organic carbon (DOC) spanning the South Indian Ocean (SIO), ranging from the Polar Front (56{\textdegree}S) to the subtropics (29{\textdegree}S). Surface waters held mean DOC Δ14C values of -426 {\textpm} 6{\textperthousand} (~4,400 14C years) at the Polar Front and DOC Δ14C values of -252 {\textpm} 22{\textperthousand} (~2,000 14C years) in the subtropics. At depth, Circumpolar Deep Waters held DOC Δ14C values of -491 {\textpm} 13{\textperthousand} (~5,400 years), while values in Indian Deep Water were more depleted, holding DOC Δ14C values of -503 {\textpm} 8{\textperthousand} (~5,600 14C years). High-salinity North Atlantic Deep Water intruding into the deep SIO had a distinctly less depleted DOC Δ14C value of -481 {\textpm} 8{\textperthousand} (~5,100 14C years). We use multiple linear regression to assess the dynamics of DOC Δ14C values in the deep Indian Ocean, finding that their distribution is characteristic of water masses in that region. },
	keywords = {dissolved organic carbon, indian ocean, radiocarbon},
	doi = {10.1002/grl.v45.210.1002/2017GL076295},
	url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL076295},
	author = {Bercovici, S. K. and McNichol, A. P. and Xu, L. and Hansell, D. A.}
}
@article {2731,
	title = {Rapid precipitation changes in the tropical West Pacific linked to North Atlantic climate forcing during the last deglaciation},
	journal = {Quaternary Science Reviews},
	volume = {197},
	year = {2018},
	month = {Jan-10-2018},
	pages = {288 - 306},
	abstract = {The cause of rapid hydrological changes in the tropical West Pacific during the last deglaciation remains controversial. In order to test whether these changes were triggered by abrupt climate change events in the North Atlantic Ocean, variations in precipitation during the last deglaciation (18-10 ka) were extracted from proxy records of chemical weathering and terrigenous input in the western Philippine Sea (WPS). The evolution of chemical weathering and terrigenous input since 27 ka was reconstructed using the chemical index of alteration (CIA), elemental ratios (K/Al, TOC/TN and Ti/Ca), δ13Corg, terrigenous fraction abundance and flux data from International Marine Global Change Study Program (IMAGES) core MD06-3054 collected on the upper continental slope of eastern Luzon (northern Philippines). Sediment deposited during the Last Glacial Maximum (LGM) shows weathering equal to or slightly greater than Holocene sediment in the WPS. This unusual state of chemical weathering, which is inconsistent with lower air temperatures and decreased precipitation in Luzon during the LGM, may be due to reworking of poorly consolidated sediments on the eastern Luzon continental shelf during the LGM sea-level lowstand. Rapid changes in chemical weathering, characterized by higher intensity during the Heinrich event 1 (H1) and Younger Dryas (YD) and lower intensity during the B{\o}lling-Aller{\o}d (B/A), were linked to rapid variations in precipitation in the WPS during the last deglaciation. The higher terrigenous inputs during the LGM relative to those of the Holocene were controlled by sea-level changes rather than precipitation. The terrigenous inputs show a long-term decline during the last deglaciation, punctuated by brief spikes during the H1 and YD related to sea-level rises and rapid precipitation changes in the WPS, respectively. The proxy records of chemical weathering and terrigenous input from eastern Luzon suggest high rainfall during the H1 and YD events, consistent with inferred rainfall patterns based on Fe/Ca records from offshore Mindanao. Rapid precipitation changes in the WPS did not coincide with migrations of the Intertropical Convergence Zone (ITCZ) but, rather, were related to state shifts of the El Ni{\~n}o-Southern Oscillation (ENSO) during the last deglaciation. Based on proxy records and modeling results, we argue that the Atlantic meridional overturning circulation (AMOC) controlled rapid precipitation changes in the tropical West Pacific through zonal shifts of ENSO or meridional migration of the ITCZ during the last deglaciation. Our findings highlight the dominant role of the North Atlantic Ocean in the tropical hydrologic cycle during the last deglaciation. },
	keywords = {AMOC, Chemical weathering, enso, ITCZ, Terrigenous input, Western Philippine Sea},
	issn = {02773791},
	doi = {10.1016/j.quascirev.2018.07.040},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0277379117309484https://api.elsevier.com/content/article/PII:S0277379117309484?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0277379117309484?httpAccept=text/plain},
	author = {Xiong, Zhifang and Li, Tiegang and Chang, Fengming and Algeo, Thomas J. and Clift, Peter D. and Bretschneider, Lisa and Lu, Zhengyao and Zhu, Xiao and Frank, Martin and Sauer, Peter E. and Jiang, FuQing and Wan, Shiming and Zhang, Xu and Chen, Shuangxi and Huang, Jie}
}
@article {2766,
	title = {Sources and radiocarbon ages of aerosol organic carbon along the east coast of China and implications for atmospheric fossil carbon contributions to China marginal seas},
	journal = {Science of The Total Environment},
	volume = {619-620},
	year = {2018},
	month = {Jan-04-2018},
	pages = {957 - 965},
	abstract = {Aerosol deposition is an important mechanism for the delivery of terrestrial organic carbon (OC) to marginal seas, but OC age characteristics of aerosols are not well constrained and their contributions to sediment OC burial have not been quantified. Total suspended particle samples were collected along the east coast of China at Changdao (CD), Qingdao (QD) and Huaniao Island (HNI), and were analyzed for total organic carbon (TOC) isotopes (13C and 14C) in order to bridge this information gap. TOC δ13C and Δ14C values ranged from - 23.6 to - 30.5{\textperthousand}, and - 153 to - 687{\textperthousand}, respectively, with the latter corresponding to 14C ages ranging from 1280 to 9260 yr. Estimated contributions of fossil carbon to TOC based on 14C mass balance approach ranged from 26 to 73\%, with strong seasonal variations in fossil carbon observed at CD. Fossil carbon at CD showed the highest proportion (73\%) in winter, reflecting anthropogenic emissions and the lowest proportion (26\%) in summer, caused by biomass contribution (annual ave., 52\% {\textpm} 17\%). In contrast, the fossil carbon at both QD (57{\textendash}64\%) and HNI (57{\textendash}67\%) dominated throughout the year, reflecting local anthropogenic influences and long-range transport. Mass balance estimates indicate that atmospheric deposition and riverine export accounted for 31\% and 69\% of fossil carbon inputs to the China marginal seas (CMS) respectively, with fossil carbon burial efficiencies approaching 100\% in the CMS. On a global scale, an atmospheric fossil carbon deposition flux of 17.2 Tg C yr- 1 was estimated, equivalent to 40\% of the estimated fluvial flux to the ocean, and potentially accounting for 24{\textendash}41\% of fossil OC burial in marine sediments. Therefore, the atmospheric deposition constitutes an important source of fossil carbon to marine sediments, and could play a key role in regional and global scale OC budgets and biogeochemical cycles.},
	keywords = {AEROSOLS, China marginal seas, Fossil carbon, Radiocarbon (14C) tracer, Total organic carbon},
	issn = {00489697},
	doi = {10.1016/j.scitotenv.2017.11.201},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S004896971733259X},
	author = {Yu, Meng and Guo, Zhigang and Wang, Xuchen and Eglinton, Timothy Ian and Yuan, Zineng and Xing, Lei and Zhang, Hailong and Zhao, Meixun}
}
@article {1284,
	title = { Allochthonous sources and dynamic cycling of ocean dissolved organic carbon revealed by carbon isotopes},
	journal = {GEOPHYSICAL RESEARCH LETTERS},
	volume = {44},
	year = {2017},
	month = {03/2017},
	pages = {2407-2415},
	abstract = {We present concentration and isotopic profiles of total, size, and polarity fractionated dissolved organic carbon (DOC) from Station ALOHA (A Long-term Oligotrophic Habitat Assessment), an oligotrophic site in the North Pacific Ocean. The data show that, between the surface and 3500 m, low molecular weight (LMW) hydrophilic DOC, LMW hydrophobic DOC, and high molecular weight (HMW) DOC constitute 22-33\%, 45-52\%, and 23-35\% of DOC, respectively. LMW hydrophilic DOC is more isotopically depleted (delta C-13 of -23.9 parts per thousand to -31.5 parts per thousand and Delta C-14 of -304 parts per thousand to -795 parts per thousand; mean age of 2850 to 15000 years) than the LMW hydrophobic DOC (delta C-13 of -22 parts per thousand to -23 parts per thousand and Delta C-14 of -270 parts per thousand to -568 parts per thousand; 2470 to 6680 years) and HMW DOC (delta C-13 of similar to-21 parts per thousand and Delta C-14 of -24 parts per thousand to -294 parts per thousand; 135-2700 years). Our analyses suggest that a large fraction of DOC may be derived from allochthonous sources such as terrestrial and hydrothermal DOC and cycle on much longer time scales of > 10000 years or enter the ocean as preaged carbon.},
	keywords = {ATLANTIC BIGHT, BLACK CARBON, C-14, HUMIC SUBSTANCES, MATTER, NORTH PACIFIC-OCEAN, RADIOCARBON ANALYSIS, SARGASSO SEA, SEAWATER, SPECTROMETRY},
	doi = {10.1002/2016GL071348},
	author = {Zigah, Prosper K. and McNichol, Ann P. and Xu, Li and Johnson, Carl and Santinelli, Chiara and Karl, David M. and Repeta, Daniel J.}
}
@article {Zigah2017,
	title = {Constraining the sources and cycling of dissolved organic carbon in a large oligotrophic lake using radiocarbon analyses},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {208},
	year = {2017},
	pages = {102-118},
	abstract = {Abstract We measured the concentrations and isotopic compositions of solid phase extracted (SPE) dissolved organic carbon (DOC) and high molecular weight (HMW) \{DOC\} and their constituent organic components in order to better constrain the sources and cycling of \{DOC\} in a large oligotrophic lacustrine system (Lake Superior, North America). \{SPE\} \{DOC\} constituted a significant proportion (41-71\%) of the lake \{DOC\} relative to \{HMW\} \{DOC\} (10-13\%). Substantial contribution of 14C-depleted components to both \{SPE\} \{DOC\} (Δ14C = 25 to 43{\textperthousand}) and \{HMW\} \{DOC\} (Δ14C = 22 to 32{\textperthousand}) was evident during spring mixing, and depressed their radiocarbon values relative to the lake dissolved inorganic carbon (DIC; Δ14C \~{} 59{\textperthousand}). There was preferential removal of 14C-depleted (older) and thermally recalcitrant components from \{HMW\} \{DOC\} and \{SPE\} \{DOC\} in the summer. Contemporary photoautotrophic addition to \{HMW\} \{DOC\} was observed during summer stratification in contrast to \{SPE\} DOC, which decreased in concentration during stratification. Serial thermal oxidation radiocarbon analysis revealed a diversity of sources (both contemporary and older) within the \{SPE\} DOC, and also showed distinct components within the \{HMW\} DOC. The thermally labile components of \{HMW\} \{DOC\} were 14C-enriched and are attributed to heteropolysaccharides (HPS), peptides/amide and amino sugars (AMS) relative to the thermally recalcitrant components reflecting the presence of older material, perhaps carboxylic-rich alicyclic molecules (CRAM). The solvent extractable lipid-like fraction of \{HMW\} \{DOC\} was very 14C-depleted (as old as 1270-2320 14C years) relative to the substances isolated by acid hydrolysis of \{HMW\} DOC. Our data constrain relative influences of contemporary \{DOC\} and old DOC, and \{DOC\} cycling in a modern freshwater ecosystem.},
	keywords = {atmospheric co2, Carbohydrate-like substance, Carboxylic-rich alicyclic molecules (CRAM), Contemporary DOC, dissolved inorganic carbon, dissolved organic carbon, Freshwater carbon cycling, Heteropolysaccharides (HPS), High molecular weight DOC, Lake Superior, Lipid-like fraction, Old DOC, Oligotrophic lake, Protein-like substance, radiocarbon, Serial thermal oxidation, Solid phase extracted DOC, Stable isotope, Unhydrolysable material},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2017.03.021},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703717301722},
	author = {Prosper K. Zigah and Elizabeth C. Minor and Ann P. McNichol and Li Xu and Josef P. Werne}
}
@article {2527,
	title = {Mobilization and export of millennial-aged organic carbon by the Yellow River},
	journal = {Limnology and Oceanography},
	year = {2017},
	month = {Jan-04-2017},
	abstract = {A combined carbon isotope (13C and 14C) study was carried out to investigate the sources and fate of organic carbon (OC) transported by the Yellow River and preserved in the sediments of the Bohai and Yellow Seas. In 2015, the Yellow River delivered 3.14 {\texttimes} 1010 g C and 4.12 {\texttimes} 1010 g C of dissolved organic carbon (DOC) and particulate organic carbon (POC) to the Bohai Sea. Carbon isotope signatures revealed that the Yellow River transports millennial-aged DOC and POC during all seasons. The values of δ13C-DOC ranged from -24.7{\textperthousand} to -28.8{\textperthousand} in the river basin, and -21.0{\textperthousand} to -27.0{\textperthousand} in the lower reach. The 14C ages of DOC were 415{\textendash}1690 yr before present (BP) in the river basin, and they were relatively constant seasonally (1320{\textendash}1690 yr BP) in the lower reach of the river. In comparison, POC δ13C values in the river were less variable (-22.8{\textperthousand} to -25.0{\textperthousand}), but much older in both the river basin (4960 {\textpm} 1690 yr BP) and in the lower reach (4040 {\textpm} 1050 yr BP). Calculations using a dual-isotopic three-end member model revealed that biomass OC derived from C3 plants was the major source of riverine DOC, contributing 65\% {\textpm} 8\% and 52\% {\textpm} 2\% in the river basin and lower reach seasonally. Pre-aged soil OC and fossil OC from weathering contributed 21{\textendash}42\% and 6{\textendash}14\% of the DOC, respectively. In contrast, pre-aged soil OC and fossil OC contributed 60{\textendash}70\% and 17{\textendash}27\% of POC, and biomass OC contributed a minor fraction (13\% {\textpm} 7\%) of riverine POC. Our results further revealed that aged riverine POC had a major influence on OC preservation in the delta and coastal sediments of the Bohai and Yellow Seas. The age of OC in surface sediments varied widely (1610{\textendash}8275 yr) due to the influence of Yellow River input. Pre-aged soil OC and fossil OC each contributed 32\% {\textpm} 8\% and 22\% {\textpm} 14\% of OC preserved in the sediments. We estimate that about 0.27 Mt yr-1 and 0.07 Mt yr-1 of pre-aged soil OC and fossil OC accumulate in the surface sediments from POC delivered by the modern Yellow River, and 0.013 Mt yr-1 and 0.002 Mt yr-1 of pre-aged soil OC and fossil OC enters the coastal DOC cycle from riverine DOC. The millennial-aged OC delivered to coastal seas by the Yellow River therefore has profound impacts not only on carbon cycling and the carbon budget in the marginal sea, but also on coastal ecosystems and biogeochemical processes.},
	doi = {10.1002/lno.10579},
	url = {http://doi.wiley.com/10.1002/lno.10579http://onlinelibrary.wiley.com/wol1/doi/10.1002/lno.10579/fullpdfhttps://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002\%2Flno.10579},
	author = {Xue, Yuejun and Zou, Li and Ge, Tiantian and Wang, Xuchen}
}
@article {2805,
	title = {What on Earth Have We Been Burning? Deciphering Sedimentary Records of Pyrogenic CarbonWhat on Earth Have We Been Burning? Deciphering Sedimentary Records of Pyrogenic Carbon},
	journal = {Environmental Science \& Technology},
	volume = {51},
	year = {2017},
	month = {Jul-11-2017},
	pages = {12972 - 12980},
	abstract = {Humans have interacted with fire for thousands of years, yet the utilization of fossil fuels marked the beginning of a new era. Ubiquitous in the environment, pyrogenic carbon (PyC) arises from incomplete combustion of biomass and fossil fuels, forming a continuum of condensed aromatic structures. Here, we develop and evaluate 14C records for two complementary PyC molecular markers, benzene polycarboxylic acids (BPCAs) and polycyclic aromatic hydrocarbons (PAHs), preserved in aquatic sediments from a suburban and a remote catchment in the United States (U.S.) from the mid-1700s to 1998. Results show that the majority of PyC stems from local sources and is transferred to aquatic sedimentary archives on subdecadal to millennial time scales. Whereas a small portion stems from near-contemporaneous production and sedimentation, the majority of PyC (\~{}90\%) experiences delayed transmission due to {\textquotedblleft}preaging{\textquotedblright} on millennial time scales in catchment soils prior to its ultimate deposition. BPCAs (soot) and PAHs (precursors of soot) trace fossil fuel-derived PyC. Both markers parallel historical records of the consumption of fossil fuels in the U.S., yet never account for more than 19\% total PyC. This study demonstrates that isotopic characterization of multiple tracers is necessary to constrain histories and inventories of PyC and that sequestration of PyC can markedly lag its production.},
	issn = {0013-936X},
	doi = {10.1021/acs.est.7b03243},
	url = {https://pubs.acs.org/doi/10.1021/acs.est.7b03243},
	author = {Hanke, Ulrich M. and Reddy, Christopher M. and Braun, Ana L. L. and Coppola, Alysha I. and Haghipour, Negar and McIntyre, Cameron P. and Wacker, Lukas and Xu, Li and McNichol, Ann P. and Abiven, Samuel and Schmidt, Michael W. I. and Eglinton, Timothy I.}
}
@article { ISI:000375679100005,
	title = {Carbon isotopic (C-14 and C-13) characterization of fossil-fuel derived dissolved organic carbon in wet precipitation in Shandong Province, China},
	journal = {JOURNAL OF ATMOSPHERIC CHEMISTRY},
	volume = {73},
	number = {{2}},
	year = {2016},
	month = {JUN},
	pages = {207-221},
	type = {Article},
	abstract = {We present results from a 1-year study of radiocarbon and stable carbon isotope measurement of dissolved organic carbon (DOC) of wet precipitation samples collected in the Shandong province of China. A total of 32 rainfall and 4 snow samples were collected from two coastal cities (Qingdao and Yantai) and one inland site (Taian) during 2014. Concentrations of DOC in the rainwater and snow samples varied widely from 28 to 616 mu M. In general, rainwater originating from marine sources had relatively low DOC concentrations compared with continentally generated precipitation. Values of delta C-13-DOC and Delta C-14-DOC in the snow and rainwater ranged from -19.0 to -29.4 \% and -23 to -494 \%, with corresponding radiocarbon ages of 125 to 5410 years before present. The dominant DOC in the wet precipitation had a relatively old C-14 age (average 2841 years) and a depleted C-13 value (average -24.4 Years), indicating the mixing of contemporary organic carbon with C-14-depleted fossil fuel-derived soluble organic carbon in the atmosphere. Using a dual isotopic two-endmember model, we calculate that 7 \% to 52 \% of DOC in the snow and rainfall originated from fossil fuels. It is estimated that the flux of DOC in continental rainfall of China is 23 x 10(12) g C yr(-1) and of this, 7.1 x 10(12) g C yr(-1) could be fossil-fuel OC. On a global scale, the DOC flux in rainfall is estimated to be 357 Tg C yr(-1), and 110 Tg C yr(-1) could be fossil fuel-derived. Our study demonstrates that wet precipitation is an important removal process for old fossil fuel carbon from the atmosphere. This removal mechanism could play an important role in the carbon cycle, especially for the anthropogenically derived fraction, and it should be taken into consideration in global carbon cycle models.},
	keywords = {Atmospheric pollution, Fossil fuelemission, organic carbon, radiocarbon, Wet precipitation},
	issn = {0167-7764},
	doi = {10.1007/s10874-015-9323-3},
	author = {Wang, Xuchen and Ge, Tiantian and Xu, Caili and Xue, Yuejun and Luo, Chunle}
}
@article { ISI:000383622900016,
	title = {Controls on the sources and cycling of dissolved inorganic carbon in the Changjiang and Huanghe River estuaries, China: C-14 and C-13 studies},
	journal = {LIMNOLOGY AND OCEANOGRAPHY},
	volume = {61},
	number = {{4}},
	year = {2016},
	month = {JUL},
	pages = {1358-1374},
	type = {Article},
	abstract = {The Changjiang (Yangtze River) and Huanghe (Yellow River) are the two largest rivers in China, and they transport large amounts of terrestrial carbon to the coastal waters of the East China Sea and the Bohai Sea. The sources and cycling of riverine carbon in these two large river estuaries, however, have not been well studied. In this article, we present the results of dual isotope (Delta C-14 and delta C-13) measurements of dissolved inorganic carbon (DIC) collected in the low reaches of the Changjiang and Huanghe and their estuaries during two cruises in 2014. Our results indicate that both the Changjiang and Huanghe carry very high concentrations of DIC ranging from 1384 mu mol kg(-1) to 1732 mu mol kg(-1) and 2711 mu mol kg(-1) to 4120 mu mol kg(-1), respectively, and DIC levels varied with flow rates during high and low discharge periods. The cycling of DIC exhibited conservative behavior in both the Changjiang and Huanghe estuaries, suggesting DIC levels were controlled mainly by physical mixing processes. Delta C-14-DIC values indicate that the Changjiang and Huanghe transport aged DIC (1060-1380 yr old). Both Delta C-14-DIC and delta C-13-DIC values also showed conservative mixing in the two estuaries. Using a dual carbon isotopic model, we calculated that atmospheric CO2 consumed mainly by silicate weathering was a major source, contributing 65.2 +/- 9.0\% and 73.4 +/- 3.0\% of DIC in the Changjiang and Huanghe, and 96.9-97.7\% (by air-sea exchange) of DIC in the coastal waters of the East China Sea (ECS) and Bohai Sea, respectively. Our results indicate that carbonate dissolution was an important (12.3-17.4\%) but not major process controlling the high DIC levels in both rivers, as suggested previously. Compared with the large Amazon River, respiration of riverine organic matter (OM) played a less important role, contributing only 15.4-17.2\% of DIC in the two Asian rivers. Flux calculations indicate that the Changjiang and Huanghe discharged 1.46 x 10(13) g and 6.28 x 10(11) g DIC into the ECS and Bohai Sea in 2014, which were 9 and 17 times higher than the DOC fluxes in the two rivers. These large fluxes of riverine DIC, especially of aged DIC, could have significant impacts on primary production and carbon cycling in the ECS and Bohai Sea.},
	issn = {0024-3590},
	doi = {10.1002/lno.10301},
	author = {Wang, Xuchen and Luo, Chunle and Ge, Tiantian and Xu, Caili and Xue, Yuejun}
}
@article { ISI:000389875700006,
	title = {DISSOLVED INORGANIC RADIOCARBON IN THE NORTHWEST PACIFIC CONTINENTAL MARGIN},
	journal = {RADIOCARBON},
	volume = {58},
	number = {{3}},
	year = {2016},
	month = {SEP},
	pages = {517-529},
	type = {Article},
	abstract = {This article presents a modified method for extraction of dissolved inorganic carbon (DIC) from seawater for radiocarbon measurement by accelerator mass spectrometry (AMS). Standard tests indicate that the extraction efficiencies of DIC are >96\%, and the respective precisions of. Delta C-14-DIC and delta C-13-DIC analyses are 6\% and 0.1\% or better. Using the method, we report. Delta C-14-DIC profiles collected from the shelf and slope in the East China Sea (ECS) of the northwest Pacific Ocean. Both the DIC concentration and. Delta C-14-DIC in the shelf and slope regions seem primarily affected by the Kuroshio Current. It is estimated that 54-65\% of the bottom water in the shelf region could be from the intrusion of Kuroshio intermediate water, which carries a high concentration and low. Delta C-14 values of DIC, and which influenced the DIC and its Delta C-14 signature on the shelf. Compared with the. Delta C-14-DIC profiles at other sites in the northwest Pacific reported previously, it appears that the. Delta C-14-DIC distributions are mainly controlled by the major oceanic currents in the region, and large variations in. Delta C-14-DIC occurred mostly in the upper 800m of the water column. The similarity of. Delta C-14-DIC at depth suggests that the deep-water circulation patterns have been relatively stable in the northwest Pacific Ocean in the last 20 yr.},
	keywords = {continental margin, dissolved inorganic carbon, East China Sea, radiocarbon, stable carbon isotope},
	issn = {0033-8222},
	doi = {10.1017/RDC.2016.23},
	author = {Ge, Tiantian and Wang, Xuchen and Zhang, Jing and Luo, Chunle and Xue, Yuejun}
}
@article {Li2016282,
	title = {Late Quaternary fingerprints of precession and sea level variation over the past 35~kyr as revealed by sea surface temperature and upwelling records from the Indian Ocean near southernmost Sumatra},
	journal = {Quaternary International},
	volume = {425},
	year = {2016},
	pages = {282 - 291},
	abstract = {Abstract We report high-resolution paleoclimatic reconstructions using isotope, alkenone sea surface temperature (SST), productivity, and terrigenous proxy variations over the past 35~kyr from core SO184-10043 (07{\textdegree}18.57'S, 105{\textdegree}03.53'E) in the eastern tropical Indian Ocean offshore of southernmost (S) Sumatra. The core was retrieved at 2171~m water depth, from the monsoon driven seasonal upwelling area off southernmost Sumatra. Our paleoclimatic reconstructions show that an enhanced marine productivity was closely linked to strengthening of coastal upwelling during the increases of boreal summer insolation and associated southeastern (SE) monsoon strength, with pronounced semi-precession cycles (\~{}11~kyr). In contrast, our record of alkenone \{SSTs\} shows glacial to interglacial, a sea-level variation, but this fluctuates at dominant precession cycles (\~{}21~kyr). We also observed four \{SST\} {\textquotedblleft}plateaus{\textquotedblright} with relatively warmer hydrographic stability in our records over the past 35~kyr: 32-27~ka, 24-20~ka, 17-12~ka, and 9-4~ka. The time scale of each plateau is \~{}4-6~kyr. Our study indicates that since the last glacial maximum (LGM), the sea level rise has been responsible for the Sunda shelf flooding and the Indonesian Throughflow (ITF) from the South China Sea (SCS) to the eastern Indian Ocean, leaving a dominant fingerprint of a glacial to interglacial increase in \{SSTs\} since \~{}9.5~ka We further argue that the a most recent centennial to millennial scale cooling at \~{}3.5~ka observed in our \{SST\} record is a widespread event in the tropical Pacific, which has implications for advancing our understanding of the climate dynamics of the tropical oceans at these time scales.},
	keywords = {Quaternary},
	issn = {1040-6182},
	doi = {http://doi.org/10.1016/j.quaint.2016.07.013},
	url = {http://www.sciencedirect.com/science/article/pii/S1040618216308722},
	author = {Ziye Li and Xuefa Shi and Min-Te Chen and Houjie Wang and Shengfa Liu and Jian Xu and Haiyan Long and Rainer Arief Troa and Rina Zuraida and Eko Triarso}
}
@article { ISI:000392927300002,
	title = {Two black carbon pools transported by the Changjiang and Huanghe Rivers in China},
	journal = {GLOBAL BIOGEOCHEMICAL CYCLES},
	volume = {30},
	number = {{12}},
	year = {2016},
	month = {DEC},
	pages = {1778-1790},
	type = {Article},
	abstract = {Major rivers play important roles in transporting large amounts of terrestrial organic matter from land to the ocean each year, and the organic matter carried by rivers contains a significant fraction of black carbon (BC). A recent study estimated that 0.027 Gt of BC is transported in the dissolved phase by rivers each year, which accounts for similar to 10\% of the global flux of dissolved organic carbon. The relative sources of this large amount of riverine dissolved black carbon (DBC) from biomass burning (young, modern C-14) and fossil fuel (old, C-14 free) combustion are not known. We present radiocarbon measurements of BC in both dissolved and particulate phases transported by the Changjiang and Huanghe Rivers, the two largest rivers in China, during 2015. We show that two, distinct BC pools (young and old) were carried by the rivers. The DBC pool was much younger than the particulate BC (PBC) pool. Mass balance calculations indicate that most (78-85\%) of the DBC in the Changjiang and Huanghe Rivers was derived from biomass burning, and only 15-22\% was from fossil fuel combustion. In contrast, PBC from biomass burning and fossil fuel combustion were approximately equal in these two rivers. Export of PBC and DBC by the rivers are decoupled, and fluxes of PBC were 4.1 and 6.7 times higher than DBC in the Changjiang and Huanghe Rivers, respectively. The C-14 age differences of the two BC pools suggest that BC derived from biomass burning and fossil fuel combustion are mobilized in different phases and on different time scales in these rivers.},
	issn = {0886-6236},
	doi = {10.1002/2016GB005509},
	author = {Wang, Xuchen and Xu, Caili and Druffel, Ellen M. and Xue, Yuejun and Qi, Yuanzhi}
}
@article { ISI:000364572000008,
	title = {An effective method of UV-oxidation of dissolved organic carbon in natural waters for radiocarbon analysis by accelerator mass spectrometry},
	journal = {JOURNAL OF OCEAN UNIVERSITY OF CHINA},
	volume = {14},
	number = {{6}},
	year = {2015},
	month = {DEC},
	pages = {989-993},
	type = {Article},
	abstract = {Radiocarbon (C-14) measurement of dissolved organic carbon (DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry (AMS). The UV-oxidation system and method show 95\%+/- 4\% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low (about 3 A mu g C) that is critical for C-14 analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for C-14 studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.},
	keywords = {AMS, dissolved organic carbon, natural waters, radiocarbon, UV-oxidation},
	issn = {1672-5182},
	doi = {10.1007/s11802-015-2935-z},
	author = {Xue Yuejun and Ge Tiantian and Wang Xuchen}
}
@article {2569,
	title = {Glacial-interglacial changes in central tropical Pacific surface seawater property gradients},
	journal = {Paleoceanography},
	volume = {30},
	year = {2015},
	month = {Jan-05-2015},
	pages = {423 - 438},
	abstract = {Much uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical Pacific over the last glacial cycle. Studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical Pacific, with little information from the central tropical Pacific. Here we present information from a suite of sediment cores collected from the Line Islands Ridge in the central tropical Pacific, which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations. Based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera Globigerinoides ruber, we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of G. ruber between the equator and 8{\textdegree}N is enhanced during glacial stages relative to interglacial stages. This stronger gradient could reflect enhanced equatorial cooling (perhaps reflecting a stronger Walker circulation) or an enhanced salinity gradient (perhaps reflecting increased rainfall in the central tropical Pacific).},
	doi = {10.1002/2014PA002746},
	url = {http://doi.wiley.com/10.1002/2014PA002746},
	author = {Lynch-Stieglitz, Jean and Polissar, Pratigya J. and Jacobel, Allison W. and Hovan, Steven A. and Pockalny, Robert A. and Lyle, Mitchell and Murray, Richard W. and Ravelo, A. Christina and Bova, Samantha C. and Dunlea, Ann G. and Ford, Heather L. and Hertzberg, Jennifer E. and Wertman, Christina A. and Maloney, Ashley E. and Shackford, Julia K. and Wejnert, Katherine and Xie, Ruifang C.}
}
@article {14,
	title = {Quantification of refractory organic material in Amazon mudbanks of the French Guiana Coast},
	journal = {Marine Geology},
	volume = {363},
	year = {2015},
	pages = {93-101},
	abstract = {Sub-oxic overturning mudbanks originating in the Amazon outlet and traveling northwestward along the coast of South America store 3.5 Tg organic carbon on the Amazon shelf, annually. The predominance of old soil carbon burial associated with the sediment has been supported by relatively old bulk radiocarbon ages (~ 2200{\textendash}3200 14C y) reported, but this amount has yet to be quantified for this dynamic setting. Here, we employ ramped pyrolysis radiocarbon dating to mudbank sediments from three cores to further constrain the amount of refractory sedimentary organic carbon present. Using radiocarbon age as a proxy for reactivity, we find that at least 36\% of this organic carbon is pre-aged refractory terrestrial organic carbon, likely sourced from terrestrial soils and averaging ages of 16,100 {\textpm} 300 14C y. This implies significant preservation of pre-aged terrestrial soil material in this marine environment despite the mobility and oxygen availability in the muds. Concurrently, an average of 77\% of this organic material is aged over 1000 14C y, consistent with previous estimates that the majority of organic carbon buried along the shelf is refractory. Analyses of extracted lignin phenols and terrestrial humic acids also support this preservation of refractory terrestrial material. These data indicate that sediment discharged from the Amazon River may preserve refractory terrestrial carbon in marine sediments at a minimum of 3.1 Tg C/y, which is more efficient than originally thought.},
	issn = {0025-3227},
	doi = {10.1016/j.margeo.2015.02.009},
	url = {http://www.sciencedirect.com/science/article/pii/S0025322715000456},
	author = {Williams, Elizabeth K. and Rosenheim, Brad E. and Allison, Mead and McNichol, Ann P. and Xu, Li}
}
@article {22,
	title = {Source-age dynamics of estuarine particulate organic matter using fatty acid delta C-13 and Delta C-14 composition},
	journal = {Limnology and Oceanography},
	volume = {60},
	year = {2015},
	note = {PT: J; TC: 0; UT: WOS:000351126500020},
	pages = {611-628},
	abstract = {This study used a multiproxy approach to elucidate the source and age composition of estuarine particulate organic matter (POM) using bulk stable isotopes (C-13(POC)), fatty acid (FA) biomarkers, and compound specific isotopic analyses in surface waters along the Delaware River and Bay (Delaware Estuary, hereafter). C-13 values of FA (C-13(FA)) ranged more widely (-30.9 parts per thousand to -21.8 parts per thousand) than C-13(POC) (-27.5 parts per thousand to -23.5 parts per thousand), providing greater insight about POM sources along the estuary. C-13 values of C-16:0 phospholipid FA (primarily, aquatic sources) increased along the salinity gradient (-29.8 parts per thousand to -23.4 parts per thousand), while C-13(FA) values of long-chain neutral fatty acid (terrestrial sources) decreased (-28.6 parts per thousand to -30.9 parts per thousand). C-13(FA) values for C-18{\textquoteright}s FA indicated the importance of marsh-derived organic matter within Delaware Estuary. Compound specific radiocarbon analysis showed the heterogeneous age structure of FA associated with POM (FA(POM)). C-14 ages of FA ranged from modern (postbomb) to 1790BP; aged FA (120BP to 1700BP) derived primarily from the watershed, whereas modern FA were produced within Delaware Estuary. C-14 ages of short-chain FA (aquatic sources) reflected differences in the age of dissolved inorganic carbon along the estuary and had older C-14 ages at the river end-member. C-14 ages of FA from terrigenous sources were older than water and sediment residence times indicating this source derived from the watershed. This study is the first to document the complex age distribution of FA(POM) along the estuarine salinity gradient and shows that inorganic carbon sources, watershed inputs and autochthonous production contribute to variation in the ages of POM.},
	issn = {0024-3590},
	doi = {10.1002/lno.10053},
	author = {McIntosh, Hadley A. and McNichol, Ann P. and Xu, Li and Canuel, Elizabeth A.}
}
@article {2638,
	title = {Hidden cycle of dissolved organic carbon in the deep ocean},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {111},
	year = {2014},
	month = {Jan-11-2016},
	pages = {16706 - 16711},
	abstract = {Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via [Formula: see text]C and age via [Formula: see text]C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30\% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.},
	keywords = {Carbon cycle, carbon isotopes, dissolved organic carbon, Oceanography, radiocarbon},
	issn = {0027-8424},
	doi = {10.1073/pnas.1407445111},
	url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1407445111https://syndication.highwire.org/content/doi/10.1073/pnas.1407445111},
	author = {Follett, Christopher L. and Repeta, Daniel J. and Rothman, Daniel H. and Xu, Li and Santinelli, Chiara}
}
@article {73,
	title = {Isotopic evidence for anthropogenic impacts on aquatic food web dynamics and mercury cycling in a subtropical wetland ecosystem in the US},
	journal = {Science of The Total Environment},
	volume = {487},
	year = {2014},
	pages = {557-564},
	abstract = {Quantifying and predicting the food web consequences of anthropogenic changes is difficult using traditional methods (based on gut content analysis) because natural food webs are variable and complex. Here, stable and radioactive carbon isotopes are used, in conjunction with nitrogen isotopes and mercury (Hg) concentration data, to document the effects of land-use change on food webs and Hg bioaccumulation in the Everglades {\textendash} a subtropical wetland ecosystem in the US. Isotopic signatures of largemouth bass and sunfish in reference (relatively pristine) wetlands indicate reliance on the food supply of modern primary production within the wetland. In contrast, both fish in areas impacted by agricultural runoff had radiocarbon ages as old as 540 years B.P., and larger isotopic variability than counterparts in reference wetlands, reflecting differences in the food web between impacted and reference wetlands. Consistent with this difference, particulate and dissolved organic matter in impacted areas had old radiocarbon ages (> 600 years B.P.), indicating that old carbon derived from historic peat deposits in the Everglades Agricultural Area was passed along the food chain to consumers. Significant radiocarbon deficiencies in largemouth bass and sunfish, relative to mosquitofish, in impacted areas most likely indicate a reduced dependence on small fish. Furthermore, largemouth bass and sunfish from impacted areas had much lower Hg contents than those from reference wetlands. Taken together, these data suggest a shift toward lower trophic levels and a possible reduction in mercury methylation in impacted wetlands. Our study provides clear evidence that hydrological modification and land-use change in the Everglades have changed the system from one driven primarily by in-situ productivity to one that is partially dependent on allochthonous carbon input from peat soils in the agricultural area and altered the Hg biogeochemical cycle in the wetlands. The results have implications for the restoration and management of wetland ecosystems.},
	issn = {0048-9697},
	doi = {10.1016/j.scitotenv.2014.04.060},
	url = {http://www.sciencedirect.com/science/article/pii/S0048969714005701},
	author = {Wang, Yang and Gu, Binhe and Lee, Ming-Kuo and Jiang, Shijun and Xu, Yingfeng}
}
@article {108,
	title = {14C and 13C characteristics of higher plant biomarkers in Washington margin surface sediments},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {105},
	year = {2013},
	note = {id: 2267},
	pages = {14-30},
	abstract = {Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their 13C and 14C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for 14C analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the 13C and 14C compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both δ13C (-28.3{\textperthousand} to -37.5{\textperthousand}) and Δ14C values (-204{\textperthousand} to +2{\textperthousand}), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar δ13C values (between -30{\textperthousand} and -34{\textperthousand}) and a relatively narrow range of Δ14C values (-45{\textperthousand} to -150{\textperthousand}; HPLC-based measurement) that were similar to, or younger than, bulk OM (-195{\textperthousand} to -137{\textperthousand}). Moreover, lignin phenol 14C age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average \~{}500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol 14C measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2012.11.034},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703712006874},
	author = {Feng, Xiaojuan and Benitez-Nelson, Bryan C. and Montlu{\c c}on, Daniel B. and Prahl, Fredrick G. and McNichol, Ann P. and Xu, Li and Repeta, Daniel J. and Eglinton, Timothy I.}
}
@article { ISI:000315194800002,
	title = {C-14 and C-13 characteristics of higher plant biomarkers in Washington margin surface sediments},
	journal = {GEOCHIMICA ET COSMOCHIMICA ACTA},
	volume = {105},
	year = {2013},
	month = {MAR 15},
	pages = {14-30},
	type = {Article},
	abstract = {Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their C-13 and C-14 compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for C-14 analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the C-13 and C-14 compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both delta C-13 (-28.3 parts per thousand to -37.5 parts per thousand) and Delta C-14 values (-204 parts per thousand to +2 parts per thousand), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar delta C-13 values (between -30 parts per thousand and -34 parts per thousand) and a relatively narrow range of Delta C-14 values (-45 parts per thousand to -150 parts per thousand; HPLC-based measurement) that were similar to, or younger than, bulk OM (-195 parts per thousand to -137 parts per thousand). Moreover, lignin phenol C-14 age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average similar to 500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol C-14 measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics. (C) 2012 Elsevier Ltd. All rights reserved.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2012.11.034},
	author = {Feng, Xiaojuan and Benitez-Nelson, Bryan C. and Montlu{\c c}on, Daniel B. and Prahl, Fredrick G. and McNichol, Ann P. and Xu, Li and Repeta, Daniel J. and Eglinton, Timothy I.}
}
@article {114,
	title = {Organic carbon export from the Greenland ice sheet},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {109},
	year = {2013},
	note = {id: 2276},
	pages = {329-344},
	abstract = {Glacial meltwater exports a unique type of organic carbon to marine systems, distinct from non-glacially derived riverine export, potentially capable of stimulating downstream marine primary productivity. Here, we describe for the first time the bulk-level dissolved organic carbon (DOC) and particulate organic carbon (POC) isotopic composition of glacial meltwater draining the Greenland ice sheet (GrIS). These data, in conjunction with an earlier study that investigated the molecular-level composition of GrIS dissolved organic matter, collectively describe the concentration, radiocarbon content, and lability of organic carbon in subglacial discharge from a land-terminating outlet glacier during a melt season. By scaling up our measurements across the ice sheet, we estimate that the annual DOC flux from the GrIS (0.08 Tg/y) is equivalent to that from a small Arctic river (discharge (Q) 200 km3/y). The DOC flux is derived primarily from beneath the glacier (subglacial) (>75\%) in the early season, and from surface ice-melt (up to 100\%) transmitting through the subglacial environment at the peak of the meltseason. The POC flux is primarily derived from the subglacial environment throughout the meltseason. The early season (low flow) glacier discharge contains higher DOC concentrations (0.5{\textendash}4.1 mg L-1), and exports more enriched carbon (Δ14CDOC \~{} -250{\textperthousand}) compared to the peak season (high flow) discharge, when the concentrations are lower (0.1{\textendash}0.6 mg L-1) and the Δ14C is more depleted (Δ14CDOC \~{} -400{\textperthousand}). Conversely, the POC export (1.4{\textendash}13.2 mg L-1, Δ14CPOC \~{} -250{\textperthousand}) shows no temporal variation in either concentration or radiocarbon content throughout the meltseason. Dissolved ion loads in concomitant samples reflected the seasonal evolution of the subglacial drainage system, confirming the influence of subglacial hydrology on the composition of the bulk carbon pools. Based on this work, we conclude that (1) different mechanisms control the DOC and POC flux from glacial systems; (2) chemically-distinct DOC pools are accessed by seasonally-evolving hydrological flow-paths; and (3) the GrIS can deliver labile carbon, which may also be 14C-depleted, to downstream proglacial and marine environments.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2013.02.006},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703713000835},
	author = {Bhatia, Maya P. and Das, Sarah B. and Xu, Li and Charette, Matthew A. and Wadham, Jemma L. and Kujawinski, Elizabeth B.}
}
@article {153,
	title = {Carbon dynamics in the western Arctic Ocean: insights from full-depth carbon isotope profiles of DIC, DOC, and POC},
	journal = {Biogeosciences},
	volume = {9},
	year = {2012},
	note = {id: 2254; PT: J; TC: 4; UT: WOS:000302179500026},
	pages = {1217-1224},
	abstract = {Arctic warming is projected to continue throughout the coming century. Yet, our currently limited understanding of the Arctic Ocean carbon cycle hinders our ability to predict how changing conditions will affect local Arctic ecosystems, regional carbon budgets, and global climate. We present here the first set of concurrent, full-depth, dual-isotope profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and suspended particulate organic carbon (POCsusp) at two sites in the Canada Basin of the Arctic Ocean. The carbon isotope composition of sinking and suspended POC in the Arctic contrasts strongly with open ocean Atlantic and Pacific sites, pointing to a combination of inputs to Arctic POCsusp at depth, including surface-derived organic carbon (OC), sorbed/advected OC, and OC derived from in situ DIC fixation. The latter process appears to be particularly important at intermediate depths, where mass balance calculations suggest that OC derived from in situ DIC fixation contributes up to 22\% of POCsusp. As in other oceans, surface-derived OC is still a dominant source to Arctic POCsusp. Yet, we suggest that significantly smaller vertical POC fluxes in the Canada Basin make it possible to see evidence of DIC fixation in the POCsusp pool even at the bulk isotope level.},
	issn = {1726-4170},
	doi = {10.5194/bg-9-1217-2012},
	author = {Griffith, D. R. and McNichol, A. P. and Xu, L. and McLaughlin, F. A. and Macdonald, R. W. and Brown, K. A. and Eglinton, T. I.}
}
@article {121,
	title = {Correction to" Isotopic characterization of aerosol organic carbon components over the eastern United States" (vol 117, D13303, 2012)},
	journal = {Journal of Geophysical Research-Atmospheres},
	volume = {117},
	year = {2012},
	note = {id: 2251; PT: J; TC: 0; UT: WOS:000307471700004},
	pages = {D15399-D15399},
	issn = {0148-0227},
	doi = {10.1029/2012JD018478},
	author = {Wozniak, Andrew S. and Bauer, James E. and Dickhut, Rebecca M. and Xu, Li and McNichol, Ann P.}
}
@article {122,
	title = {Isotopic characterization of aerosol organic carbon components over the eastern United States},
	journal = {Journal of Geophysical Research-Atmospheres},
	volume = {117},
	year = {2012},
	note = {id: 2252; PT: J; TC: 1; UT: WOS:000306237000001},
	pages = {D13303-D13303},
	abstract = {Carbon isotopic signatures (delta C-13, Delta C-14) of aerosol particulate matter total organic carbon (TOC) and operationally defined organic carbon (OC) components were measured in samples from two background sites in the eastern U. S. TOC and water-soluble OC (WSOC) delta C-13 values (-27 to -24 parts per thousand) indicated predominantly terrestrial C-3 plant and fossil derived sources. Total solvent extracts (TSE) and their aliphatic, aromatic, and polar OC components were depleted in delta C-13 (-30 to -26 parts per thousand) relative to TOC and WSOC. Delta C-14 signatures of aerosol TOC and TSE (-476 to +25 parts per thousand) suggest variable fossil contributions (similar to 5-50\%) to these components. Aliphatic OC while comprising a small portion of the TOC (},
	issn = {0148-0227},
	doi = {10.1029/2011JD017153},
	author = {Wozniak, Andrew S. and Bauer, James E. and Dickhut, Rebecca M. and Xu, Li and McNichol, Ann P.}
}
@article { ISI:000299864400020,
	title = {Modern and Fossil Contributions to Polycyclic Aromatic Hydrocarbons in PM2.5 from North Birmingham, Alabama in the Southeastern U.S.},
	journal = {ENVIRONMENTAL SCIENCE \& TECHNOLOGY},
	volume = {46},
	number = {{3}},
	year = {2012},
	month = {FEB 7},
	pages = {1422-1429},
	type = {Article},
	abstract = {Analyzing the radiocarbon (C-14) content of polycyclic aromatic hydrocarbons (PAHs) in atmospheric particulate matter can provide estimates on the source contributions from biomass burning versus fossil fuel. The relative importance of these two sources to ambient PAHs varies considerably across regions and even countries, and hence there is a pressing need to apportion these sources. In this study, we advanced the radiocarbon analysis from bulk carbon to compound class specific radiocarbon analysis (CCSRA) to determine Delta C-14 and delta C-13 values of PAHs in PM2.5 samples for investigating biomass burning and fossil fuel source contributions to PAHs from one of the Southeastern Aerosol Research and Characterization (SEARCH) sites in North Birmingham (BHM), Alabama during winter (December 2004-February 2005) and summer (June-August 2005) by accelerator mass spectrometry. To compare our ambient samples to known sources, we collected and analyzed fenceline samples from the vicinity of a coke plant in BHM. As expected, PAHs from the coke plant fenceline samples had very low radiocarbon levels. Its Delta C-14 varied from -990 to -970 parts per thousand, indicating that 97 to 99\% were of fossil source. PAHs in the ambient PM2.5 had Delta C-14 from -968 to -911 parts per thousand, indicating that 92-97\% of PAHs were from fossil fuel combustion. These levels indicated the dominance of fossil sources of ambient PAHs. The radiocarbon level of ambient PAHs was higher in winter than in summer. Winter samples exhibited depleted delta C-13 value and enriched Delta C-14 value because of the increased contribution of PAHs from biomass burning source. However, biomass burning contributed more to heavier PAHs (modern source accounting for 6-8\%) than fighter ones with a modern contribution of 3\%.},
	issn = {0013-936X},
	doi = {10.1021/es2043189},
	author = {Xu, Li and Zheng, Mei and Ding, Xiang and Edgerton, Eric S. and Reddy, Christopher M.}
}
@article {119,
	title = {A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis},
	journal = {Sedimentary Geology},
	volume = {281},
	year = {2012},
	note = {id: 2312},
	pages = {88-100},
	abstract = {Future anthropogenic sea-level rise and its impact on coastal regions is an important issue facing human civilizations. Due to the short nature of the instrumental record of sea-level change, development of proxies for sea-level change prior to the advent of instrumental records is essential to reconstruct long-term background sea-level changes on local, regional and global scales. Here, we employ numerical methods to partition sediment grain size using a combined database of marine surface and core samples, and to quantitatively reconstruct sea-level variation since the late Pleistocene in the south Bohai Sea, China. Our sea-level reconstruction indicates that relative sea-level changes in the southern Bohai Sea track global sea-level variation for the duration of the record. The results also indicate substantial regression from 70 to 30 cal kyr BP, and potentially subarial exposure from 38 to 20 cal kyr BP. Our results document the feasibility of reconstructing relative sea-level change by numerical partitioning of sediment grain size data, demonstrating the potential for future applications.},
	issn = {0037-0738},
	doi = {10.1016/j.sedgeo.2012.08.007},
	url = {http://www.sciencedirect.com/science/article/pii/S0037073812002333},
	author = {Yi, Liang and Yu, Hongjun and Ortiz, Joseph D. and Xu, Xingyong and Qiang, Xiaoke and Huang, Haijun and Shi, Xuefa and Deng, Chenglong}
}
@article {164,
	title = {A two-dimensional, heart-cutting preparative gas chromatograph facilitates highly resolved single-compound isolations with utility towards compound-specific natural abundance radiocarbon (14C) analyses},
	journal = {Journal of Chromatography A},
	volume = {1220},
	year = {2012},
	note = {id: 2152},
	pages = {122-131},
	abstract = {Motivated by the need to develop clean, high purity preparative enrichments of individual compounds for micro-scale compound-specific natural abundance isotope and radiocarbon (14C) analyses, we describe a new, two-dimensional, heart-cutting, low-bleed, three-oven, single GC preparative system, demonstrate its resolving capabilities as applied to a typically complex environmental sample matrix, and investigate the robustness with which it preserves the authigenic 13C/12C and 14C/12C ratios of individual compounds it targets for preparative enrichment. The system is comprised of a programmable temperature vaporizing (PTV) inlet, a single GC oven, two modular, door-mounted, resistively heated low thermal mass (LTM) columns, a preparative fraction collector (PFC), and a Deans pneumatic switching device which facilitates heart-cutting between the system{\textquoteright}s 1{\textdegree} and 2{\textdegree} chromatographic dimensions. Further, the system{\textquoteright}s inlet and trapping parameters are optimized for the efficient preparative enrichment of the methyl ether and ester derivatives of the lignin phenol compound class. The lignin phenols include such compounds as the vanillyl and syringyl aldehydes, ethanones, and acids and are unrivaled biomarkers of terrestrial organic matter, some of which are also important components of fragrances and flavors. Using this suite of compounds, the suitability of this augmented preparative capillary GC (PCGC) system was investigated for micro-scale compound-specific (CS) stable isotope and natural abundance radiocarbon analyses (RA). Analysis of a >300 injection enrichment scheme reveals the instrument to fractionate 13C in predictable ways and to preserve the authigenic Δ14C of compounds it targets for preparative enrichment to within 6.7 {\textpm} 5.0{\textperthousand}, demonstrating the promising new utility of such systems towards micro-scale CSRA investigations for which clean and high resolution separation techniques are prerequisite.},
	issn = {0021-9673},
	doi = {10.1016/j.chroma.2011.11.021},
	url = {http://www.sciencedirect.com/science/article/pii/S0021967311017031},
	author = {Ball, Gregory Ian and Xu, Li and McNichol, Ann P. and Aluwihare, Lihini I.}
}
@article {168,
	title = {Rare earth element geochemistry in the inner shelf of the East China Sea and its implication to sediment provenances},
	journal = {Journal of Rare Earths},
	volume = {29},
	year = {2011},
	note = {id: 2177},
	pages = {702-709},
	abstract = {Gravity core EC2005, located in the mud wedge off the Zhejiang-Fujian coast in the inner shelf of the East China Sea (ECS), was analyzed for its lithology, grain size, rare earth elements (REE) and AMS14C dating. Results revealed high-resolution paleoenvironmental evolution and multiple switches of sediment provenances in the inner shelf of ECS. The lithology, grain size and REE concentrations of sediments varied significantly down the core. Mean grain size ranged from 8 to 121 μm, and the values of ΣREE were 152.8{\textendash}227.9 μg/g. The chondrite- and shale-normalized REE patterns indicated their similarity to the terrigenous sediments in the study area. Between 17.3{\textendash}12.3 ka BP the sediments in the inner shelf of ECS were mainly originated from local drainage basins. The source then gradually switched to the Yangtze River between 12.3 and 9.8 ka BP. Since about 10{\textendash}9.8 ka BP, the sediments in the study area were dominantly derived from the Yangtze River. The continuous rising of sea level and formation of coastal current along the inner shelf played a key role in the switches of sediment provenances.},
	issn = {1002-0721},
	doi = {10.1016/S1002-0721(10)60526-1},
	url = {http://www.sciencedirect.com/science/article/pii/S1002072110605261},
	author = {Xu, Fangjian and Li, Anchun and Li, Tiegang and Xu, Kehui and Chen, Shiyue and Qiu, Longwei and Cao, Yingchang}
}
@article { ISI:000277965100004,
	title = {Coastal New England pilot study to determine fossil and biogenic formaldehyde source contributions using radiocarbon},
	journal = {JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES},
	volume = {115},
	year = {2010},
	month = {MAY 18},
	type = {Article},
	abstract = {Compound specific radiocarbon analyses of atmospheric formaldehyde are reported as fraction modern (Fm) for a limited number of winter and summer air samples collected in coastal southern New England in 2007. The 11 of 13 samples with Fm < 0.2 were collected under the influence of the semipermanent Bermuda high-pressure system with transport from the Washington, D. C., to New York City urban corridor. The two samples with Fm > 0.2 (max similar to 0.35) were collected on days with strong northwesterly flow and the least urban impact. The Fm data were combined with VOC observations from the Rhode Island Department of Environmental Management, estimates of oxygenated VOC (OVOC), and back trajectories to interpret the relative contributions of biogenic and fossil carbon sources. It is argued that CH2O sources were dominated by pollutant VOCs and OVOCs from upwind coastal cities as opposed to more local biogenic VOCs at the times of sample collection.},
	issn = {2169-897X},
	doi = {10.1029/2009JD012810},
	author = {Shen, Haiwei and Heikes, Brian G. and Merrill, John T. and McNichol, Ann P. and Xu, Li}
}
@article {231,
	title = {Late Holocene Evolution of the Mekong Subaqueous Delta, Southern Vietnam},
	journal = {Marine Geology},
	volume = {269},
	year = {2010},
	note = {id: 848; 560AN Times Cited:0 Cited References Count:53Y},
	pages = {46-60},
	abstract = {As Asia{\textquoteright}s third largest river. with regard to sediment load, the Mekong River delivers approximately 160 million tons of sediment per year to the South China Sea. High-resolution seismic profiling and coring during 2006 and 2007 cruises revealed a low gradient, subaqueous delta system, up to 20 m thick, surrounding the modern Mekong River Delta (MRD) in the west of the South China Sea. Based on clinoform structure, grain size Pb-210, AMS C-14, and delta C-13 results, the subaqueous delta is divided into four zones defined by different sedimentary processes and depositional features. Over the past 3000 yr, the evolution of the MRD has shown a morphological asymmetry indicated by a large down-drift area and a rapid progradation around Cape Camau, similar to 200 km downstream from the river mouth. This asymmetric feature is consistent with increased wave influence. The strong southwestward coastal current, strengthened by the Strong NE monsoon, plays an important role locally in longshore transport of resuspended sediments into the Gulf of Thailand. A late Holocene sediment budget for the MRD has been determined, based on the area and thickness of deltaic sediment. Approximately 80\% of Mekong delivered sediment has been trapped within the delta area, which, together with a falling sea-level, resulted in a rapidly prograding MRD over the past 3000 yr. (C) 2009 Elsevier B.V. All rights reserved.},
	issn = {0025-3227},
	doi = {10.1016/J.Margeo.2009.12.005},
	author = {Xue, Z. and Liu, J. P. and DeMaster, D. and Van Nguyen, L. and Ta, T. K. O.}
}
@conference {1277,
	title = {Radiocarbon in the Canada Basin: Carbon Transfer Processes in the Changing Arctic},
	booktitle = {Proceedings from the 2010 AGU Ocean Sciences Meeting},
	year = {2010},
	note = {Date revised - 2010-09-01SuppNotes - Abstracts AvailableLast updated - 2016-12-22},
	month = {February 2010},
	publisher = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [URL:http://www.agu.org]},
	organization = {American Geophysical Union, 2000 Florida Ave., N.W. Washington DC 20009 USA, [URL:http://www.agu.org]},
	abstract = {We are developing full water column depth [delta]14C profiles for dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and suspended particulate organic carbon (POC) collected in 2008 from the Canada Basin in the Arctic Ocean. These samples provide an opportunity to study the current distribution of radiocarbon in different carbon pools and set a baseline for future investigations of the carbon cycle in this key oceanic region where climate change is anticipated to have a major and imminent impact on carbon storage and cycling. Our first DI14C depth profile from 75, 150 is similar to one taken in 1992 (Jones et al. 1994) in demonstrating a well-ventilated surface layer overlying an older but recently ventilated deeper basin. Significant increases in DI14C, up to 30 ppt, are observed in the mid-depth region between 500 to 1500 m, roughly coincident with a warm layer underlying cold surface waters. The differences that have occurred over 16 years may lend insight to the observed warming of Atlantic water in the Canada Basin over the past decades. We will present the first DO14C profile from the central Canada Basin. Measurements are being made using a UV oxidation system established at NOSAMS. Most of the samples collected for DO14C measurement were acidified to preserve them. Results from frozen duplicates for a few of the samples will be compared to validate the preservation technique. In most regions of the ocean, the shape of DO14C depth profiles parallel those of DI14C profiles but are shifted to significantly older values. This reflects the fact that general oceanographic circulation and remineralization processes dominate the overall profile, but that the sources of carbon to the DOC pool are more complex than those of DIC. It is unknown whether this will be the case in the Arctic Ocean which, while representing only ~1\% of the worlds ocean volume, receives approximately 13\% of the global flux of terrigeneous DOC. Jones, G. A. et al. (1994). NIMS B, 92, 426-430.},
	keywords = {and modeling, Biogeochemical cycles, carbon cycling, processes, Radioactivity and radioisotopes},
	url = {https://search.proquest.com/docview/754883766?accountid=29119},
	author = {McNichol, A P and Xu, L and Griffith, D R and Eglinton, T I and Macdonald, R and McLaughlin, F A}
}
@mastersthesis {1342,
	title = {A Source-to-Sink Study of the Mekong River Delta: Hydrology, Delta Evolution, and Sediment Transport Modeling},
	volume = {Ph.D.},
	year = {2010},
	month = {2010},
	school = {North Carolina State University},
	author = {Xue, Z.}
}
@article {272,
	title = {Chemical and isotopic characterization of size-fractionated organic matter from cryoturbated tundra soils, northern Alaska},
	journal = {Journal of Geophysical Research-Biogeosciences},
	volume = {114},
	year = {2009},
	note = {id: 1828; 475IS Times Cited:0 Cited References Count:61Y},
	abstract = {Recent studies indicate a second layer of organic matter often accumulates in the lower active layer and upper permafrost in arctic tundra soils as a result of cryoturbation. In this study, cryoturbated organic matter was characterized using a combination of physical size fractionation and modern analytical techniques for elemental composition (C and N), stable isotopes (delta(13) C and delta N-15), radiocarbon content (Delta C-14), and molecular fingerprinting (pyrolysis-gas chromatography/mass spectrometry, Py-GC/MS). The results indicated that cryoturbated organic matter could be highly bioavailable. Soil organic matter (SOM) associated with fine sand particles was considered to be the organic carbon pool most sensitive to the changing climate. More organic matter is stabilized on clay minerals in arctic tundra soils compared to those in temperate and tropical soils. The bioavailable soluble organic matter extracted from cryoturbated soil was found to have significant long-term effects on carbon cycling. The similar molecular composition between cryoturbated and surface soil organic matter suggests that the vegetation cover has not significantly changed since the early Holocene. Furthermore, the SOM quality in moist acidic tundra was found to be higher than that of wet nonacidic tundra. With thawing permafrost and a deepening of the active layer, cryotrubated organic matter could reenter the biogeochemical cycles in the Arctic, resulting in a positive feedback to climate change.},
	issn = {0148-0227},
	doi = {10.1029/2008jg000846},
	author = {Xu, C. H. and Guo, L. D. and Ping, C. L. and White, D. M.}
}
@article {479,
	title = {Chemical and isotopic composition of high-molecular-weight dissolved organic matter from the Mississippi River plume},
	journal = {Marine Chemistry},
	volume = {114},
	year = {2009},
	note = {id: 1827; 465CM Times Cited:1 Cited References Count:51Y},
	pages = {63-71},
	abstract = {In order to examine the source and transformation of high-molecular-weight dissolved organic matter (HMW-DOM) in the mixing zone of the Mississippi River plume, HMW-DOM with sizes between 1 kDa and 0.2 mu m was collected along a salinity gradient using cross-flow ultrafiltration. Isolated OM samples were desalted, freeze-dried and characterized for elemental (C and N) and biochemical composition (proteins, carbohydrates and uronic acids), stable isotopic (delta C-13 and delta N-15) and radiocarbon (Delta C-14) signatures, and relative molecular composition using pyrolysis-gas chromatography/mass spectrometry. The organic carbon content of HMW-DOM samples ranged from 31 to 36 wt.\%, indicating that isolated colloids are mostly organic in nature. Contents of N ranged from 1.9\% to 3.3\%, resulting in a C/N ratio of 19-20 at lower salinity stations with a strong influence by terrestrial DOM and 12-15 at higher salinity stations with more freshly photosynthesized marine DOM. While OC-normalized protein contents decreased with increasing salinity, both carbohydrate and uronic acid contents increased with increasing salinity. Variations of pyrograms demonstrated that the proportion of furfural (an indicator of polysaccharides) in HMW-DOM also increased with increasing salinity, while the proportion of phenols decreased with increasing salinity. Changes in carbohydrate, (acid) polysaccharide and phenol contents of HMW-DOM samples reflect the variation in DOM sources along the salinity gradient, with higher phenol and low polysaccharide contents in lower salinity areas but higher polysaccharide and low phenol contents in coastal waters. Values of delta C-13 increased from -25.24 parts per thousand at the Mississippi River fresh water end-member station to -21.86 parts per thousand at an offshore station in the Gulf of Mexico. Changes in stable isotope composition resemble the changes in molecular composition from freshwater to coastal waters. Values of delta N-15, on the other hand, varied little, from 3.5 parts per thousand to 4.9 parts per thousand without a consistent trend, indicating that delta N-15 is a less sensitive source tracer. Measured radiocarbon signatures (Delta C-14) expressed as apparent C-14 ages ranged from > modern at lower salinity stations to 400-800 y BP at coastal stations. Results of isotopic mass balance revealed that, in addition to end-member organic matter from river and marine sources, at least 10-25\% of the HMW-DOM could derive from reworked or regenerated DOM in the Mississippi River plume, most likely through sediment-water interactions and lateral transport. Thus, reworking processes are important in governing the chemical and isotopic composition of DOM in the estuarine mixing zone. (C) 2009 Elsevier B.V. All rights reserved.},
	issn = {0304-4203},
	doi = {10.1016/j.marchem.2009.04.002},
	author = {Guo, L. D. and White, D. M. and Xu, C. and Santschi, P. H.}
}
@article {519,
	title = {Palaeoenvironmental changes from pollen record in deep sea core PC-1 from northern Okinawa Trough, East China Sea during the past 24 ka},
	journal = {Chinese Science Bulletin},
	volume = {54},
	year = {2009},
	note = {id: 1931; PT: J; UT: WOS:000271175500023},
	pages = {3739-3748},
	abstract = {A pollen record of core PC-1 from the northern Okinawa Trough, East China Sea (ECS), provides information on vegetation and climate changes since 24 cal. kaBP. A total of 103 samples were palynologically analyzed at 8 cm intervals with a time resolution of 230 a. Four pollen zones are recognized: zone I (812-715 cm, 24.2-21.1 cal. kaBP), zone II (715-451 cm, 21.1-15.2 cal. kaBP), zone III (451-251 cm, 15.2-10.8 cal. kaBP), zone IV (251-0 cm, 10.8-0.3 cal. kaBP), corresponding to Late MIS 3, Last Glacial Maximum (LGM), deglaciation and Holocene, respectively. The LGM is characterized by the dominance of herbs, mainly Artemisia, and high pollen influx, implying an open vegetation on the exposed continental shelf and a cool and dry climate. The deglaciation is a climate warming stage with Pinus percentage increased and Artemisia percentage decreased and a rapid sea-level rise. The Holocene is characterized by predominance of tree pollen with rapid increase in Castanea-Castanopsis indicating the development of mixed evergreen and deciduous broad-leaved forest and a warm, humid climate. Low pollen influx during the Holocene probably implies submergence of the continental shelf and retreat of the pollen source area. The vegetation indicated by pollen assemblage found in this upper zone is consistent with the present vegetation found in Kyushu, Japan. Originating from the humid mountain area of North Luzon of the Philippines, Tasmania and New Zealand, Phyllocladus with sporadic occurrence throughout PC-1 core probably suggests the influence of Palaeo-Kuroshio Current or intense summer monsoon. The observed changes in Pinus and Herbs percentage indicate fluctuations of the sea level, and high Pinus percentage corresponds to high sea level. Spectrum analysis of the pollen percentage record reveals many millennial-scale periodicities, such as periodicities of 6.8, 3.85 2.2, 1.6 ka.},
	issn = {1001-6538},
	doi = {10.1007/s11434-009-0227-y},
	author = {Xu, HongYan and Chang, Fengming and Luo, YunLi and Sun, XiangJun}
}
@article { ISI:000268455600046,
	title = {Radiocarbon Analysis of Atmospheric Formaldehyde Using Cystamine Derivatization},
	journal = {ANALYTICAL CHEMISTRY},
	volume = {81},
	number = {{15}},
	year = {2009},
	month = {AUG 1},
	pages = {6310-6316},
	type = {Article},
	abstract = {A compound specific radiocarbon analysis method was developed to evaluate the C-14 composition of atmospheric formaldehyde. In this method, gaseous formaldehyde was collected with a high-volume air sampler using glass-fiber filters pretreated with sodium bisulfite. Collected formaldehyde was then released into water and derivatized with cysteamine to thiazolidine. The thiazolidine was extracted into dichloromethane and concentrated by evaporation. Concentrated thiazolidine was separated from other compounds using preparative capillary gas chromatography and uniquely collected as a phosphate salt with a fraction collector. The C-14 composition of the salt was analyzed by accelerator mass spectrometry after combustion to CO2 and subsequent reduction to graphite. In a pilot study, ambient formaldehyde samples collected on the roof of the CACS building at Narragansett Bay Campus, Narragansett, RI, showed a significantly larger fraction of fossil carbon than modern carbon.},
	issn = {0003-2700},
	doi = {10.1021/ac9004666},
	author = {Shen, Haiwei and McNichol, Ann P. and Xu, Li and Gagnon, Alan and Heikes, Brian G.}
}
@article {400,
	title = {Determination of biodiesel blending percentages using natural abundance radiocarbon analysis: Testing the accuracy of retail biodiesel blends},
	journal = {Environmental Science \& Technology},
	volume = {42},
	year = {2008},
	note = {id: 1864; 281JN Times Cited:3 Cited References Count:39; YY},
	pages = {2476-2482},
	abstract = {Blends of biodiesel and petrodiesel are being used increasingly worldwide. Due to several factors, inaccurate blending of these two mixtures can occur. To test the accuracy of biodiesel blending, we developed and validated a radiocarbon-based method and then analyzed a variety of retail biodiesel blends. Error propagation analysis demonstrated that this method calculates absolute blend content with +/- 1\% accuracy, even when real-world variability in the component biodiesel and petrodiesel sources is taken into account. We independently confirmed this accuracy using known endmembers and prepared mixtures. This is the only published method that directly quantifies the carbon of recent biological origin in biodiesel blends. Consequently, it robustly handles realistic chemical variability in biological source materials and provides unequivocal apportionment of renewable versus nonrenewable carbon in a sample fuel blend. Analysis of retail biodiesel blends acquired in 2006 in the United States revealed that inaccurate blending happens frequently. Only one out of ten retail samples passed the specifications that the United States Department of Defense requires for blends that are 20\% biodiesel (v/v; referred to as B20).},
	issn = {0013-936X},
	doi = {10.1021/Es071814j},
	author = {Reddy, C. M. and DeMello, J. A. and Carmichael, C. A. and Peacock, E. E. and Xu, L. and Arey, J. S.}
}
@article {403,
	title = {Evaluation of gas chromatographic isotope fractionation and process contamination by carbon in compound-specific radiocarbon analysis},
	journal = {Analytical Chemistry},
	volume = {79},
	year = {2007},
	note = {id: 615; 140ID Times Cited:11 Cited References Count:32},
	pages = {2042-2049},
	abstract = {The relevance of both modern and fossil carbon contamination as well as isotope fractionation during preparative gas chromatography for compound-specific radiocarbon analysis (CSRA) was evaluated. Two independent laboratories investigated the influence of modern carbon contamination in the sample cleanup procedure and preparative capillary gas chromatography (pcGC) of a radiocarbon-dead 3,3{\textquoteright},4,4{\textquoteright},5,5{\textquoteright}-hexachlorobiphenyl (PCB 169) reference. The isolated samples were analyzed for their C-14/C-12 ratio by accelerator mass spectrometry. Sample Delta C-14 values of -996 +/- 20 and -985 +/- 20\% agreed with a Delta C-14 of -995 +/- 20\% for the unprocessed PCB 169, suggesting that no significant contamination by nonfossil carbon was introduced during the sample preparation process at either laboratory. A reference compound containing a modern C-14/C-12 ratio (vanillin) was employed to evaluate process contamination from fossil C. No negative bias due to fossil C was observed (sample Delta C-14 value of 165 +/- 20\% agreed with Delta C-14 of 155 +/- 12\% for the unprocessed vanillin). The extent of isotopic fractionation that can be induced during pcGC was evaluated by partially collecting the vanillin model compound of modern C-14/C-12 abundance. A significant change in the delta C-13 and delta C-14 values was observed when only parts of the eluting peak were collected (delta C-13 values ranged from -15.75 to -49.91\% and delta C-14 values from -82.4 to +4.71\%). Delta C-14 values, which are normalized to a delta C-13 of -25\%, did not deviate significantly (-58.9 to -5.8\%, considering the uncertainty of similar to +/- 20\%). This means that normalization of radiocarbon results to a delta C-13 of -25\%, normally performed to remove effects of environmental isotope fractionation on C-14-based age determinations, also cor-rects sufficiently for putative isotopic fractionation that may occur during pcGC isolation of individual compounds for CSRA.},
	issn = {0003-2700},
	doi = {10.1021/Ac061821a},
	author = {Zencak, Z. and Reddy, C. M. and Teuten, E. L. and Xu, L. and McNichol, A. P. and Gustafsson, O.}
}
@article {584,
	title = {Flux and fate of Yangtze river sediment delivered to the East China Sea},
	journal = {Geomorphology},
	volume = {85},
	year = {2007},
	note = {244vyTimes Cited:286Cited References Count:84},
	month = {Mar 30},
	pages = {208-224},
	abstract = {Numerous cores and dating show the Yangtze River has accumulated about 1.16 x 10(12) t sediment in its delta plain and proximal subaqueous delta during Holocene. High-resolution seismic profiling and coring in the southern East China Sea during 2003 and 2004 cruises has revealed an elongated (similar to 800 km) distal subaqueous mud wedge extending from the Yangtze River mouth southward off the Zhejiang and Fujian coasts into the Taiwan Strait. Overlying what appears to be a transgressive sand layer, this distal clinoform thins offshore, from similar to 40 in thickness between the 20 and 30 m water depth to < 1-2 in between 60 and 90 m water depth, corresponding to an across shelf distance of less than 100 km. Total volume of this distal mud wedge is about 4.5 x 10(11) m(3), equivalent to similar to 5.4 x 10(11) t of sediment. Most of the sediment in this mud wedge comes from the Yangtze River, with some input presumably coming from local smaller rivers. Thus, the total Yangtze-derived sediments accumulated in its deltaic system and East China Sea inner shelf have amounted to about 1.7 x 10(12) t. Preliminary analyses suggest this longshore and across-shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid-Holocene highstand, and after re-intensification of the Chinese longshore current system. Sedimentation accumulation apparently increased around 2000 yrs BP, reflecting the evolution of the Yangtze estuary and increased land erosion due to human activities, such as fanning and deforestation. The southward-flowing China Coastal Current, the northward-flowing Taiwan Warm Current, and the Kuroshio Current appear to have played critical roles in transporting and trapping most of Yangtze-derived materials in the inner shelf, and hence preventing the sediment escape into the deep ocean. (c) 2006 Elsevier B.V. All rights reserved.},
	issn = {0169-555x},
	doi = {10.1016/j.geomorph.2006.03.023},
	author = {Liu, J. P. and Xu, K. H. and Li, A. C. and Milliman, J. D. and Velozzi, D. M. and Xiao, S. B. and Yang, Z. S.}
}
@article {663,
	title = {Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record},
	journal = {Palaeogeography Palaeoclimatology Palaeoecology},
	volume = {243},
	year = {2007},
	note = {134kzTimes Cited:48Cited References Count:62},
	month = {Jan 22},
	pages = {378-393},
	abstract = {Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since similar to 18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at similar to 11.2 cal. kyr B.P. due to a rapid rise of sea level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bolling-Allerod (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5-9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3-4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough. (c) 2006 Elsevier B.V. All rights reserved.},
	issn = {0031-0182},
	doi = {10.1016/j.palaeo.2006.08.016},
	author = {Xiang, R. and Sun, Y. B. and Li, T. G. and Oppo, D. W. and Chen, M. H. and Zheng, F.}
}
@article {1896,
	title = {Radiocarbon dating of a very large African baobab},
	journal = {Tree Physiology},
	volume = {27},
	year = {2007},
	note = {230afTimes Cited:35
Cited References Count:43
},
	month = {Nov},
	pages = {1569-1574},
	abstract = {In late 2004, Grootboom, probably the largest known African baobab (Adansonia digitata L.), collapsed unexpectedly in northeastern Namibia. Ten wood samples collected from different areas of the trunk were processed and investigated by accelerator mass spectrometry radiocarbon dating. The radiocarbon dates of three samples were greater than 1000 years BP (radiocarbon years before present, i.e., before AD 1950). The corresponding calibrated calendar age of the oldest sample was 1275 +/- 50 years, making Grootboom the oldest known angiosperm tree with reliable dating results. Variations in radiocarbon dates among the wood samples indicated that, morphologically, Grootboom was a quintuple tree, whereas genetically, it was a single individual. Ages of extreme lateral samples revealed that, over the past 500-600 years, Grootbooom had almost ceased growing, providing information about climate changes in central southern Africa. The sudden demise of Grootboom coincided with the spread of the poorly studied baobab disease, which has become epidemic in Namibia.},
	keywords = {Adansonia digitata, Age, Age determination, amazonia, c-14 content, cal kyr bp, Calibration, dendrochronology, dendroclimatology, holocene logs, location-dependent differences, southern-hemisphere, tasmanian conifers, Trees, tropical trees},
	isbn = {0829-318x},
	author = {Patrut, A. and von Reden, K. F. and Pohlman, J. W. and Wittmann, R. and Mitchell, C. S. and Lowy, D. A. and Alberts, A. H. and Gerlach, D. and Xu, L.}
}
@article {613,
	title = {Tropical Pacific - mid-latitude teleconnections in medieval times},
	journal = {Climatic Change},
	volume = {83},
	year = {2007},
	note = {160ufTimes Cited:125Cited References Count:151},
	month = {Jul},
	pages = {241-285},
	abstract = {Terrestrial and marine late Holocene proxy records from the western and central US suggest that climate between approximately 500 and 1350 A.D. was marked by generally arid conditions with episodes of severe centennial-scale drought, elevated incidence of wild fire, cool sea surface temperatures (SSTs) along the California coast, and dune mobilization in the western plains. This Medieval Climate Anomaly (MCA) was followed by wetter conditions and warming coastal SSTs during the transition into the "Little Ice Age" (LIA). Proxy records from the tropical Pacific Ocean show contemporaneous changes indicating cool central and eastern tropical Pacific SSTs during the MCA, with warmer than modern temperatures in the western equatorial Pacific. This pattern of mid-latitude and tropical climate conditions is consistent with the hypothesis that the dry MCA in the western US resulted (at least in part) from tropically forced changes in winter NH circulation patterns like those associated with modern La Nina episodes. We examine this hypothesis, and present other analyses showing that the imprint of MCA climate change appears in proxy records from widely distributed regions around the planet, and in many cases is consistent with a cool medieval tropical Pacific. One example, explored with numerical model results, is the suggestion of increased westerlies and warmer winter temperatures over northern Europe during medieval times. An analog technique for the combined use of proxy records and model results, Proxy Surrogate Reconstruction (PSR), is introduced.},
	issn = {0165-0009},
	doi = {10.1007/s10584-007-9239-2},
	author = {Graham, N. E. and Hughes, M. K. and Ammann, C. M. and Cobb, K. M. and Hoerling, M. P. and Kennett, D. J. and Kennett, J. P. and Rein, B. and Stott, L. and Wigand, P. E. and Xu, T. Y.}
}
@article {665,
	title = {Coherence between solar activity and the East Asian winter monsoon variability in the past 8000 years from Yangtze River-derived mud in the East China Sea},
	journal = {Palaeogeography Palaeoclimatology Palaeoecology},
	volume = {237},
	year = {2006},
	note = {072kpTimes Cited:52Cited References Count:61},
	month = {Aug 4},
	pages = {293-304},
	abstract = {AMS(14)C dating and grain-size analysis for Core PC-6, located in the middle of a mud area on the inner shelf of the East China Sea (ECS), were used to rebuild the Holocene history of the East Asian winter monsoon (EAWM). The 7.5-m core recorded the history of environmental changes during the postglacial transgression. The core{\textquoteright}s mud section (the upper 450 cm) has been formed mainly by suspended sediment delivered from the Yangtze River mouth by the ECS Winter Coastal Current (ECSWCC) since 7.6 kyr BP. Using a mathematical method called "grain size vs. standard deviatioW{\textquoteright}, we can divide the Core PC-6{\textquoteright}s grain-size distribution into two populations at about 28 mu m. The fine population (< 28 mu m) is considered to be transported by the ECSWCC as suspended loads. Content of the fine population changes little and represents a stable sedimentary environment in accord with the present situation. Thus, variation of mean grain-size from the fine population would reflect the strength of ECSWCC, which is mainly controlled by the East Asian winter monsoon.Abrupt increasing mean grain size in the mud section is inferred to be transported by sudden strengthened ECSWCC, which was caused by the strengthened EAWM. Thus, the high resolution mean grain-size variation might serve as a proxy for reconstruction of the EAWM. A good correlation between sunspot change and the mean grain-size of suspended fine population suggests that one of the primary controls on centennial- to decadal-scale changes of the EAWM in the past 8 ka is the variations of sun irradiance, i.e., the EAWM will increase in intensity when the number of sunspots decreases. Spectral analyses of the mean grain-size time series of Core PC-6 show statistically significant periodicities centering on 2463, 1368, 128, 106, 100, 88-91, 7678, and 70-72 years. The EAWM and the East Asian summer monsoon (EASM) agree with each other well on these cycles, and the East Asian Monsoon (EAM) and the Indian Monsoon also share in concurrent cycles in Holocene, which are in accord with the changes of the sun irradiance. (c) 2005 Elsevier B.V. All rights reserved.},
	issn = {0031-0182},
	doi = {10.1016/j.palaeo.2005.12.003},
	author = {Xiao, S. B. and Li, A. C. and Liu, J. P. and Chen, M. H. and Xie, Q. and Jiang, F. Q. and Li, T. G. and Xiang, R. and Chen, Z.}
}
@article {915,
	title = {New evidence for remnant deposits recorded by columnar sediments in the shelf of the northern South China Sea},
	journal = {Marine Geology \& Quaternary Geology},
	volume = {26},
	year = {2006},
	note = {id: 568},
	pages = {1-5},
	isbn = {0256-1492},
	author = {Xiao, S. B. and Chen, M. H. and Lu, J.}
}
@article {602,
	title = {Sedimentary features of the Yangtze River-derived along-shelf clinoform deposit in the East China Sea},
	journal = {Continental Shelf Research},
	volume = {26},
	year = {2006},
	note = {109ueTimes Cited:158Cited References Count:62},
	month = {Nov},
	pages = {2141-2156},
	abstract = {A predominant sigmoidal clinoform deposit extends from the Yangtze River mouth southwards 800 kin along the Chinese coast. This clinoform is thickest (similar to 40m) between the 20 and 30 m isobaths and progressively thins offshore, reaching water depths of 60 and 90 m and distances up to 100 km offshore. Clay mineral, heavy metal, geochemical and grain-size analyses indicate that the Yangtze River is the primary source for this longshore-transported clinoform deposit. (210)Pb chronologies show the highest accumulation rates (> 3 cm/yr) occur immediately adjacent to the Yangtze subaqueous delta (north of 30 degrees N), decreasing southward alongshore and eastward offshore. The interaction of strong tides, waves, the China Coastal Current, winter storms, and offshore upwelling appear to have played important roles in trapping most Yangtze-derived sediment on the inner shelf and transporting it to the south. (c) 2006 Elsevier Ltd. All rights reserved.},
	issn = {0278-4343},
	doi = {10.1016/j.csr.2006.07.013},
	author = {Liu, J. P. and Li, A. C. and Xu, K. H. and Veiozzi, D. M. and Yang, Z. S. and Milliman, J. D. and DeMaster, D.}
}
@article {707,
	title = {Tracking the weathering of an oil spill with comprehensive two-dimensional gas chromatography},
	journal = {Environmental Forensics},
	volume = {7},
	year = {2006},
	note = {032ldTimes Cited:62Cited References Count:21},
	month = {Mar},
	pages = {33-44},
	abstract = {Comprehensive two-dimensional gas chromatography (GC x GC) was used to investigate the Bouchard 120 oil spill. The latter occurred on April 25, 2003, when the barge Bouchard 120 spilled similar to 375,000 liters of No. 6 fuel oil into Buzzards Bay, Massachusetts. In order to gain a better understanding of the natural processes affecting the fate of the spilled product, we collected and analyzed oil-covered rocks from Nyes Neck beach in North Falmouth, Massachusetts. Here we discuss the data from samples collected on May 9, 2003, and six months later, on November 23, 2003. Along with standard two-dimensional gas chromatographic analysis, we employed unique data-visualization techniques such as difference, ratio, and addition chromatograms to highlight how evaporation, water washing, and biodegradation weathered the spilled oil. These approaches provide a new perspective to studying oil spills and aid attempts to remediate them.},
	issn = {1527-5922},
	doi = {10.1080/15275920500506758},
	author = {Nelson, R. K. and Kile, B. M. and Plata, D. L. and Sylva, S. P. and Xu, L. and Reddy, C. M. and Gaines, R. B. and Frysinger, G. S. and Reichenbach, S. E.}
}
@article {922,
	title = {Abundance, composition, and vertical transport of PAHs in marsh sediments},
	journal = {Environ Sci Technol},
	volume = {39},
	year = {2005},
	note = {White, Helen KXu, LiLima, Ana Lucia CEglinton, Timothy IReddy, Christopher MengResearch Support, Non-U.S. Gov{\textquoteright}tResearch Support, U.S. Gov{\textquoteright}t, Non-P.H.S.2005/11/22 09:00Environ Sci Technol. 2005 Nov 1;39(21):8273-80.},
	month = {Nov 01},
	pages = {8273-80},
	abstract = {Petroleum-derived hydrocarbons continue to persist in Wild Harbor, West Falmouth, MA, following a spill of No. 2 fuel oil in 1969 from the barge Florida. Recent analysis of marsh sediments revealed that residues of degraded oil are present with concentrations of total petroleum hydrocarbons as high as approximately 9 mg g(-1). Polycyclic aromatic hydrocarbons (PAHs) constitute only a minor fraction of these residues with maximum concentrations of 134 mirog g(-1), but their fate is of interest because of their potential toxicity to organisms. As compared to typical unweathered No. 2 fuel oil, the current distribution of PAHs in the sediments reflects substantial weathering by abiotic and biotic processes, specifically a preferential loss of naphthalenes relative to phenanthrenes, as well as isomer-specific biodegradation of alkylated PAHs. Based on comparison to results from an earlier study, it appears that little or no change has occurred to the distribution of PAHs since 1989, indicating that weathering at this site has stalled or is now proceeding at a significantly slower rate. To assess whether sediment-water partitioning and molecular diffusion in the interstitial medium are now the dominant processes controlling the vertical distribution of PAHs, downcore profiles were compared to a numerical model. While in some cases the model accurately reproduced the measured data, there were instances where the distribution of PAHs was slightly under or overestimated. Reasons for these discrepancies are discussed and are likely due to bioturbation, colloid-facilitated transport, or both. Assessment of the influence of these processes on the spilled oil expands our understanding of the overall fate of these compounds and their potential long-term effects on the environment.},
	issn = {0013-936X},
	doi = {10.1021/es050475w},
	author = {White, H. K. and Xu, L. and Lima, A. L. and Eglinton, T. I. and Reddy, C. M.}
}
@article {1984,
	title = {Contribution of biomass burning to polycyclic aromatic hydrocarbons in European background aerosols},
	journal = {Environmental Science and Technology},
	volume = {39},
	year = {2005},
	note = {id: 510},
	month = {2005},
	pages = {2976-2982},
	author = {Mandalakis, M. and Gustafsson, O. and Alsberg, T. and Reddy, C. and Xu, L. and Klanova, J. and Holoubek, I. and Stephanou, E.}
}
@article {914,
	title = {Geochemical characteristics of recent 2 ka mud on the inner shelf of the East China Sea},
	journal = {GEOCHIMICA},
	volume = {34},
	year = {2005},
	note = {id: 570},
	month = {11/2005},
	pages = {595-604},
	abstract = {The particle size of DD2 in the northern part of the muddy area along the continental margin of the East China Sea was analyzed. AMS 14 C age test and the main elements, trace elements
The relationship between the content of each element and the particle size was discussed and analyzed. The relationship between them was discussed by R factor analysis. Studies have shown that nearly 2 ka to DD2
The majority of the main elements and trace elements in the pores are stable; the content of most of the elements with the grain size becomes increasing, while the content of Sr and SiO 2
The decreasing tendency of CaO, Na 2 O, Hf, Zr and Ti is poor in particle size. The results of factor analysis show that the chemical composition of DD2 pore can be
It is divided into four kinds of combination types: the main characteristics of the distribution of elements in sediments are reflected, and the samples are not treated by salt beforehand to cause the combination of main elements and trace elements
The Zr, Hf and Nb elements are enriched in the specific particle size components (silt), and the addition of calcareous biological components and the redistribution of elements during early diagenesis
Wait. The results show that Rb, Cu, Ni, V, P, Sc, Fe 2 O 3 , Cr, K 2 O, Nb, Co, Th, Ti and Al 2 O 3 are relatively inactive elements in DD 2 pores,
They can be compared with the modern Yangtze River, the Yellow River sediments, for genetic analysis. The Ti J Zr and Cr J Th ratios indicate that the pore deposits are mainly derived from the granitic
Source area. },
	keywords = {East China Sea continental shelf, factor analysis, geochemical characteristics, particle size},
	author = {Xiao, S. B. and Li, A. C. and Jiang, F. and Xu, F. J. and Zheng, F. and Chen, Z.}
}
@article {1964,
	title = {Last deglaciation in the Okinawa Trough: Subtropical northwest Pacific link to Northern Hemisphere and tropical climate},
	journal = {Paleoceanography},
	volume = {20},
	year = {2005},
	note = {975ipTimes Cited:53
Cited References Count:55
},
	month = {Oct 7},
	abstract = {[1] Detailed deglacial and Holocene records of planktonic delta O-18 and Mg/Ca - based sea surface temperature (SST) from the Okinawa Trough suggest that at similar to 18 to 17 thousand years before present (kyr B. P.), late spring/ early summer SSTs were approximately 3 degrees C cooler than today, while surface waters were up to 1 practical salinity unit saltier. These conditions are consistent with a weaker influence of the summer East Asian Monsoon (EAM) than today. The timing of suborbital SST oscillations suggests a close link with abrupt changes in the EAM and North Atlantic climate. A tropical influence, however, may have resulted in subtle decoupling between the North Atlantic and the Okinawa Trough/EAM during the deglaciation. Okinawa Trough surface water trends in the Holocene are consistent with model simulations of an inland shift of intense EAM precipitation during the middle Holocene. Millennial-scale alternations between relatively warm, salty conditions and relatively cold, fresh conditions suggest varying influence of the Kuroshio during the Holocene.},
	keywords = {cal kyr bp, deep-ocean circulation, equatorial current, kuroshio current, late pleistocene, oxygen-isotope, planktonic-foraminifera, radiocarbon age calibration, south china sea, surface-water},
	isbn = {0883-8305},
	doi = {10.1029/2004PA001061},
	url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2\&amp;SrcAuth=Alerting\&amp;SrcApp=Alerting\&amp;DestApp=WOS\&amp;DestLinkType=FullRecord;UT=WOS:000232654500001},
	author = {Sun, Y. B. and Oppo, D. W. and Xiang, R. and Liu, W. G. and Gao, S.}
}
@article {912,
	title = {Provenance analysis of mud along the Min-zhe coast since 2 ka BP},
	journal = {Acta Sedimentologica Sinica},
	volume = {23},
	year = {2005},
	note = {id: 567},
	pages = {268-274},
	author = {Xiao, S. B. and Li, A. C. and Jiang, F.}
}
@article {1977,
	title = {Radiocarbon dating of alkenones from marine sediments: I. Isolation protocol},
	journal = {Radiocarbon},
	volume = {47},
	year = {2005},
	note = {993nkTimes Cited:13
Cited References Count:22
},
	month = {2005},
	pages = {401-412},
	abstract = {The chemical and isotopic compositions of long-chain (C-36-C-39) unsaturated ketones (alkenones), a unique class of algal lipids, encode surface ocean properties useful for paleoceanographic reconstruction. Recently, we have sought to extend the utility of alkenones as oceanic tracers through measurement of their radiocarbon contents. Here. we describe a method for isolation of alkenones from sediments as a compound class based on a sequence of wet chemical techniques. The steps involved, which include silica gel column chromatography, urea adduction, and silver nitrate-silica gel column chromatography, exploit various structural attributes of the alkenones. Amounts of purified alkenones estimated by GC/FID measurements were highly correlated with CO2 yields after sample combustion, indicating purities of greater than 90\% for samples containing >= 100 mu g C. The degree of alkenone unsaturation (U-37(K{\textquoteright})) also varied minimally through the procedure. We also describe a high-performance liquid chromatography (HPLC) method to isolate individual alkenones for molecular-level structural and isotopic determination.},
	keywords = {AMS, carbon, indicators, proxy, records, tool},
	isbn = {0033-8222},
	author = {Ohkouchi, N. and Xu, L. and Reddy, C. M. and Montlucon, D. and Eglinton, T. I.}
}
@article {670,
	title = {Recent 2000-year geological records of mud in the inner shelf of the East China Sea and their climatic implications},
	journal = {Chinese Science Bulletin},
	volume = {50},
	year = {2005},
	note = {923yeTimes Cited:20Cited References Count:58},
	month = {Mar},
	pages = {466-471},
	abstract = {AXIS(14)C dating and grain-size analysis for Core DD2, located at the north of the Yangtze River-derived mud off the Zhejiang-Fujian coasts in the inner shelf of the East China Sea, provide us a high-resolution grain-size distribution curve varying with depth and time. Data in the upper mud layer of Core DD2 indicate that there are at least 9 abrupt grain-size increasing in recent 2000 years, with each corresponding very well with the low-temperature events in Chinese history, which might result from the periodical strengthening of the East Asian Winter Monsoon (EAWM), including the first-revealed maximum temperature lowering event at around 990 a BP. At the same time, the finer grain size section in Core DD2 agrees well with the Sui-Tang Warming Period (600-1000 a AD) defined previously by Zhu Kezhen, during which the climate had a warm, cold and warm fluctuation, with a dominated cooling period of 750-850 a AD. The Little Ice Age (LIA) can also be identified in the core. It starts around 1450 a AD and was followed by a subsequent cooling events at 1510, 1670 and 1840 a AD. Timing of these cold events revealed here still needs to be further verified owing to some current uncertainty of dating we used in this study.},
	issn = {1001-6538},
	doi = {10.1360/03wd0571},
	author = {Xiao, S. B. and Li, A. C. and Jiang, F. Q. and Li, T. G. and Huang, P. and Xu, Z. K.}
}
@article {913,
	title = {Recent 8 ka mud records of the East Asian Winter Monsoon from the inner shelf of the East China Sea},
	journal = {Earth Science - Journal of China University of Geosciences},
	volume = {30},
	year = {2005},
	note = {id: 569},
	pages = {573-581},
	issn = {1000-2383},
	author = {Xiao, S. B. and Li, A. C. and Chen, M. H. and Liu, J. P. and Jiang, F. G. and Li, T. G. and Xie, Q. and Xiang, R. and Chen, Z.}
}
@article {696,
	title = {Two abundant bioaccumulated halogenated compounds are natural products},
	journal = {Science},
	volume = {307},
	year = {2005},
	note = {Teuten, Emma LXu, LiReddy, Christopher MengResearch Support, Non-U.S. Gov{\textquoteright}tResearch Support, U.S. Gov{\textquoteright}t, Non-P.H.S.2005/02/12 09:00Science. 2005 Feb 11;307(5711):917-20.},
	month = {Feb 11},
	pages = {917-20},
	abstract = {Methoxylated polybrominated diphenyl ethers (MeO-PBDEs) have been found bioaccumulated in the tissues of a variety of aquatic animals and at concentrations comparable to those of anthropogenic halogenated organic compounds, including polychlorinated biphenyls (PCBs). The origin of the MeO-PBDEs has been uncertain; circumstantial evidence supports a natural and/or an industrial source. By analyzing the natural abundance radiocarbon content of two MeO-PBDEs isolated from a True{\textquoteright}s beaked whale (Mesoplodon mirus), we show that these compounds were naturally produced.},
	issn = {0036-8075 (Linking)},
	doi = {10.1126/science.1106882},
	author = {Teuten, E. L. and Xu, L. and Reddy, C. M.}
}
@article {404,
	title = {Using comprehensive two-dimensional gas chromatography retention indices to estimate environmental partitioning properties for a complete set of diesel fuel hydrocarbons},
	journal = {Analytical Chemistry},
	volume = {77},
	year = {2005},
	note = {id: 1700; 985UM Times Cited:30 Cited References Count:56},
	pages = {7172-7182},
	abstract = {Comprehensive two-dimensional gas chromatography (GC x GC) provides nearly complete composition data for some complex mixtures such as petroleum hydrocarbons. However, the potential wealth of physical property information contained in the corresponding two-dimensional chromatograms is largely untapped. We developed a simple but robust method to estimate GC x GC retention indices for diesel-range hydrocarbons. By exploiting n-alkanes as reference solutes in both dimensions, calculated retention indices were insensitive to uncertainty in the enthalpy of gas-stationary-phase transfer for a suite of representative diesel components. We used the resulting two-dimensional retention indices to estimate the liquid vapor pressures, aqueous solubilities, air-water partition coefficients, octanol-water partition coefficients, and vaporization enthalpies of a nearly complete set of diesel fuel hydrocarbons. Partitioning properties were typically estimated within a factor of 2; this is not as accurate as some previous estimation or measurement methods. However, these relationships may allow powerful and incisive analysis of phase-transfer processes affecting petroleum hydrocarbon mixtures in the environment. For example, GC x GC retention data might be used to quantitatively deconvolve the effects of water washing and evaporation on environmentally released diesel fuels.},
	issn = {0003-2700},
	doi = {10.1021/Ac051051n},
	author = {Arey, J. S. and Nelson, R. K. and Xu, L. and Reddy, C. M.}
}
@article {698,
	title = {Abrupt tropical vegetation response to rapid climate changes},
	journal = {Science},
	volume = {304},
	year = {2004},
	note = {Hughen, Konrad AEglinton, Timothy IXu, LiMakou, MatthewengResearch Support, Non-U.S. Gov{\textquoteright}t2004/05/25 05:00Science. 2004 Jun 25;304(5679):1955-9. Epub 2004 May 20.},
	month = {Jun 25},
	pages = {1955-9},
	abstract = {Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered. Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago. Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades.},
	issn = {0036-8075 (Linking)},
	doi = {10.1126/science.1092995},
	author = {Hughen, K. A. and Eglinton, T. I. and Xu, L. and Makou, M.}
}
@article {2010,
	title = {Plans for Expanded 14C Analyses at the NOSAMS Facility--a status and progress report. 9th International Conference on Accelerator Mass Spectrometry, Nagoya, Japan, 9/2002},
	journal = {Nuclear Instruments and Methods in Physics Research},
	volume = {B 223-224},
	year = {2004},
	note = {id: 1810},
	month = {2004},
	pages = {50-54},
	author = {von Reden, K. and Donoghue, J. and Elder, K. and Gagnon, A. and Gerlach, D. and Griffin, V. S. and Healy, R. and Long, P. and McNichol, A. P. and Percy, D. and Roberts, M. L. and Schneider, R. J. and Xu, L. and Hayes, J.}
}
@article {2040,
	title = {Radiocarbon apportionment of fossil versus biofuel combustion sources of polycyclic aromatic hydrocarbons in the Stockholm metropolitan area},
	journal = {Environ Sci Technol},
	volume = {38},
	year = {2004},
	note = {Mandalakis, ManolisGustafsson, Orjan
Reddy, Christopher M
Xu, Li
eng
Comparative Study
Research Support, Non-U.S. Gov{\textquoteright}t
Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S.
2004/11/17 09:00
Environ Sci Technol. 2004 Oct 15;38(20):5344-9.
},
	month = {Oct 15},
	pages = {5344-9},
	abstract = {Source-diagnostic markers and the isotopic composition of polycyclic aromatic hydrocarbons (PAHs) were examined in surface sediments from the greater Stockholm waterways to deduce the contribution from biomass sources to the environmental PAH load. The summed concentration of 20 PAHs ranged from 0.8 to 45.1 microg/g (dry weight) and exhibited a steep decline with increasing distance from the city center evidencing that sources within the metropolitan area of Stockholm dominate its PAH burden. Several diagnostic PAH ratios indicated an overwhelming predominance of pyrogenic sources over the petrogenic ones, while retene and 1,7-dimethylphenanthrene were unable to correctly evaluate the contribution from biomass combustion. The stable carbon isotope composition (delta13C) of individual PAHs ranged from -24.8 to -27.0\% but also was proved inefficient to discriminate between different types of fuels due to the overlapping signals in various sources. The delta14C values of PAHs ranged between -550.4 and -934.1\%, indicating a clear predominance of fossil fuel sources. By using an isotopic mass balance approach, we estimated that on average 17+/-9\% of PAHs derived from biomass combustion. This radiocarbon apportionment, in conjunction with detailed energy statistics for the Stockholm region, revealed that the ambient PAH burden is roughly similar, per unit energy produced, from fossil fuels and biofuels. Societies{\textquoteright} shifting energy policies toward a larger reliance on biofuels may thus not lead to further deterioration of air quality and respiratory ailments for the urban population.},
	keywords = {*Bioelectric Energy Sources, *Fossil Fuels, Biomass, Carbon Radioisotopes, Cities, Environmental Monitoring, Fresh Water, Geologic Sediments/*analysis, Polycyclic Aromatic Hydrocarbons/*analysis/isolation \& purification, Sweden, Water Pollutants, Chemical/*analysis/isolation \& purification},
	isbn = {0013-936X (Print)0013-936X (Linking)},
	doi = {10.1021/es049088x},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/15543735},
	author = {Mandalakis, M. and Gustafsson, O. and Reddy, C. M. and Xu, L.}
}
@article {2027,
	title = {Radiocarbon evidence for a naturally-produced, bioaccumulation halogenated organic compound},
	journal = {Environmental Science and Technology},
	volume = {38},
	year = {2004},
	note = {id: 1806},
	month = {2004},
	pages = {1992-1997},
	author = {Reddy, C. M. and Xu, L. and O{\textquoteright}Neil, G. W. and Nelson, R. K. and Eglinton, T. I. and Faulkner, D. J. and Norstrom, R. and Ross, P. S. and Tittlemier, S. A.}
}
@article {2068,
	title = {Heterogeneity in the radiocarbon content of Polycyclic aromatic hydrocarbons in household soot},
	journal = {Environmental Forensics},
	volume = {4},
	year = {2003},
	note = {id: 507},
	month = {2003},
	pages = {191-197},
	author = {Reddy, C. M. and Xu, L. and O{\textquoteright}Connor, R.}
}
@article {708,
	title = {Using radiocarbon to apportion sources of polycyclic aromatic hydrocarbons in household soot},
	journal = {Environmental Forensics},
	volume = {4},
	year = {2003},
	note = {731ytTimes Cited:16Cited References Count:42},
	month = {Sep},
	pages = {191-197},
	abstract = {To determine whether polycyclic aromatic hydrocarbons (FAHs) in household soot were derived from the combustion of scrap wood or creosote that was impregnated in the wood (or some combination of both), the molecular composition and radiocarbon (C-14) content of the total carbon and several PAHs in the soot was investigated. The 5730-year half-life of C-14 makes it an ideal marker for identifying creosote-derived PAHs (C-14-free) versus those derived from the combustion of wood (contemporary C-14). The C-14 abundance of phenanthrene, fluoranthene, pyrene, and retene was determined by accelerator mass spectrometry after solvent extraction and purification by preparative capillary gas chromatography. The molecular analysis (presence of retene and 1,7-dimethylphenanthrene) and bulk C-14 content (contemporary) of the soot indicated that wood combustion was a strong source of carbon to the soot. The C-14 of retene in two soot samples was also contemporary, indicating that it was derived from the combustion of the scrap wood. These results are consistent with previous work that has suggested that retene is an excellent marker of wood combustion. However, the C-14 content of phenanthrene, fluoranthene, and pyrene in one soot sample was much lower and revealed that these compounds had a mixed creosote and wood source. Using an isotopic mass balance approach, we estimate that 40 to 70\% of phenanthrene, fluoranthene, and pyrene were derived from the combustion of the scrap wood. The results of this study show that molecular marker and bulk C-14 analysis can be potentially misleading in apportioning sources of every PAH, and that molecular-level C-14 analysis of PAHs can be a powerful tool for environmental forensics.},
	issn = {1527-5922},
	doi = {10.1080/15275920390230778},
	author = {Reddy, C. M. and Xu, L. and O{\textquoteright}Connor, R.}
}
@conference {1744,
	title = {Plans for expanded 14C analyses at the NOSAMS facility - a status and progress report},
	booktitle = {International Conference on Accelerator Mass Spectrometry},
	year = {2002},
	note = {id: 1685},
	month = {2002},
	address = {Nagoya, Japan},
	author = {von Reden, K. F. and Donoghue, J. and Elder, K. and Gagnon, A. and Gerlach, D. and Griffin, V. and Healy, R. and Long, P. and McNichol, A. and Percy, D. and Roberts, M. L. and Schneider, R. J. and Xu, L. and Hayes, J. M.}
}
@article {637,
	title = {Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples},
	journal = {Environmental Science \& Technology},
	volume = {36},
	year = {2002},
	note = {541gfTimes Cited:133Cited References Count:59},
	month = {Apr 15},
	pages = {1774-1782},
	abstract = {To determine the relative inputs of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) in environmental samples from the combustion of fossil fuels and biomass we have developed two independent analytical methods for determining the C-14 abundance of PAHs and BC. The 5730 yr half-life of C-14 makes it an ideal tracer for identifying combustion products derived from fossil fuels (C-14-free) versus those stemming from modern biomass (contemporary C-14). The C-14 abundance of PAHs in several environmental Standard Reference Materials was measured by accelerator mass spectrometry after extraction and then purification by high-performance liquid chromatography and preparative capillary gas chromatography. This method yields pure compounds that allow for a high degree of confidence in the C-14 results. The PAHs data were then used to compare and evaluate results from an operationally defined thermal oxidation method used to isolate a BC fraction. The C-14 compositions of PAHs and BC were very similar and suggest that the thermal oxidation method employed for isolating BC is robust and free from interferences by non-BC components. In addition, these data indicate that both the PAHs and the BC species derive mostly from fossil fuels and/or their combustion products.},
	issn = {0013-936x},
	doi = {10.1021/es011343f},
	author = {Reddy, C. M. and Pearson, A. and Xu, L. and McNichol, A. P. and Benner, B. A. and Wise, S. A. and Klouda, G. A. and Currie, L. A. and Eglinton, T. I.}
}
@article {2103,
	title = {Radiocarbon content of synthetic and natural semi-volatile halogenated organic compounds},
	journal = {Environ Pollut},
	volume = {120},
	year = {2002},
	note = {Reddy, Christopher MXu, Li
Eglinton, Timothy I
Boon, Jan P
Faulkner, D John
eng
Research Support, Non-U.S. Gov{\textquoteright}t
Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S.
England
2002/10/25 04:00
Environ Pollut. 2002;120(2):163-8.
},
	month = {2002},
	pages = {163-8},
	abstract = {Some halogenated organic compounds, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polybrominated diphenyl ethers (PBDEs), have been suggested to have natural sources but separating these compounds from their commercially synthesized counterparts is difficult. Molecular-level 14C analysis may be beneficial since most synthetic compounds are manufactured from petrochemicals (14C-free) and natural compounds should have "modern" or "contemporary" 14C levels. As a baseline study, we measured, for the first time, the 14C abundance in commercial PCB and PBDE mixtures, a number of organochlorine pesticides, as well as one natural product 2-(3{\textquoteright},5{\textquoteright}-dibromo-2{\textquoteright}-methoxyphenoxy)-3,5-dibromoanisole. The latter compound was isolated from a marine sponge and is similar in structure to a PBDE. All of the synthetic compounds were 14C-free except for the pesticide toxaphene. which had a modern 14C abundance, as did the brominated natural compound. The result for toxaphene was not surprising since it was commercially synthesized by the chlorination of camphene derived from pine trees. These results suggest that measuring the 14C content of halogenated organic compounds may be quite useful in establishing whether organic compounds encountered in the environment have natural or synthetic origins (or both) provided that any synthetic counterparts derive from petrochemical feedstock.},
	keywords = {Animals, Carbon Radioisotopes/*analysis, Environmental Pollutants/*analysis, Hydrocarbons, Halogenated/chemical synthesis/*chemistry, Insecticides/chemistry, Polychlorinated Biphenyls/chemistry, Porifera/*chemistry, Toxaphene/chemistry},
	isbn = {0269-7491 (Print)0269-7491 (Linking)
},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/12395826},
	author = {Reddy, C. M. and Xu, L. and Eglinton, T. I. and Boon, J. P. and Faulkner, D. J.}
}
@article {2104,
	title = {The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments},
	journal = {Environ Sci Technol},
	volume = {36},
	year = {2002},
	note = {Reddy, Christopher MEglinton, Timothy I
Hounshell, Aubrey
White, Helen K
Xu, Li
Gaines, Richard B
Frysinger, Glenn S
eng
Research Support, Non-U.S. Gov{\textquoteright}t
Research Support, U.S. Gov{\textquoteright}t, Non-P.H.S.
2002/12/19 04:00
Environ Sci Technol. 2002 Nov 15;36(22):4754-60.
},
	month = {Nov 15},
	pages = {4754-60},
	abstract = {The long-term fate of petroleum hydrocarbons in marsh sediments (West Falmouth, MA) contaminated in 1969 by the spill of the barge Florida was investigated. A 36-cm-long sediment core was collected in August 2000, and sediment extracts were analyzed by gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GC x GC). The latter technique is capable of separating 1 order of magnitude more compounds than the former and was used to observe whether any compositional changes in the unresolved complex mixture (UCM) occurred. No evidence of petroleum residues was detected in the top 6 cm (0-6 cm) and the lower 8 cm (28-36 cm) of the core. However, the central sections 16-28 cm) were dominated by a UCM in the boiling range of n-C13-n-C25 alkanes, consistent with a No. 2 fuel oil source. The 12-14- and 14-16-cm sections had the highest concentrations of UCM approximately 8 mg g(-1)). These values are similar to concentrations observed shortly after the spill. Initial GC x GC analysis revealed that only the n-alkanes were completely degraded, and contrary to previous studies, pristane and phytane as well as numerous other branched alkanes are still present in the sediments. These results suggestthatatthis site hydrocarbon contamination will persist indefinitely in the sedimentary record.},
	keywords = {*Accidents, Chromatography, Gas, Environmental Monitoring, Geologic Sediments/*chemistry, Hydrocarbons/*analysis, Massachusetts, Petroleum/*analysis, Ships, Time Factors, Water Pollutants, Chemical/*analysis},
	isbn = {0013-936X (Print)0013-936X (Linking)},
	doi = {10.1021/es020656n},
	url = {https://www.ncbi.nlm.nih.gov/pubmed/12487296},
	author = {Reddy, C. M. and Eglinton, T. I. and Hounshell, A. and White, H. K. and Xu, L. and Gaines, R. B. and Frysinger, G. S.}
}
@article {1003,
	title = {Algal and archaeal polyisoprenoids in a recent marine sediment: Molecular isotopic evidence for anaerobic oxidation of methane},
	journal = {Geochemistry Geophysics Geosystems},
	volume = {2},
	year = {2001},
	note = {458jvTimes Cited:51Cited References Count:79},
	month = {Jan 17},
	abstract = {Analyses of C-13 contents of individual organic molecules in a marine sediment show that crocetane, 2,6,11,15-tetramethylhexadecane, an isomer of phytane, is produced by microorganisms that use methane as their main source of carbon. The sediments lie at a water depth of 68 m in the Kattegat, the strait between Denmark and Sweden. Crocetane appears first 185 cm below the sediment-water interface, in the zone marking the transition from sulfate reduction to methanogenesis. Its delta C-13 value is -90 +/- 10 parts per thousand versus Vienna Pee Dee Belemnite (VPDB). Its structure, which includes four isoprene units arranged symmetrically around a tail-to-tail linkage, suggests that it is produced by a member of the archaea. Growing at the intersection of the diffusion gradients for sulfate and methane in sedimentary pore waters, the source organism apparently function as a methane-consuming member of the microbial consortium responsible for the anaerobic oxidation of methane [Hoehler et al., 1994], in which, as first demonstrated quantitatively in these sediments [Iversen and Jorgensen, 1985], electrons are transferred from methane to sulfate. The presence of archaeal biomass throughout the sediment section is indicated by significant concentrations of 2,6,10,15,19-pentamethylicosane (PMI) and of ether-bound phytane and biphytane. The PMI reaches a minimum delta value of -47 parts per thousand well below the transition zone. Its isotopic depletion could reflect either methanogenic or methanotrophic sources. The ether-bound lipids are isotopically uniform throughout the section and are presumed to derive from archaea that utilize a carbon source unaffected by the oxidation of methane.},
	issn = {1525-2027},
	doi = {10.1029/2000GC000112},
	author = {Bian, L. Q. and Hinrichs, K. U. and Xie, T. M. and Brassell, S. C. and Iversen, H. and Fossing, H. and Jorgensen, B. B. and Hayes, J. M.}
}
@article {409,
	title = {Identification of a novel alkenone in Black Sea sediments},
	journal = {Organic Geochemistry},
	volume = {32},
	year = {2001},
	note = {id: 1946; PT: J; UT: WOS:000168692100002},
	pages = {633-645},
	abstract = {We report the identification of a novel long-chain ketone in Holocene Black Sea sediments. Based on chemical properties, and chromatographic and mass spectrometric characteristics, this compound has been identified as a diunsaturated C-36 ethyl ketone. Further analyses indicated the position and configuration of the double bonds, and the novel alkenone was determined to be hexatriaconta-(16E,21E)-dien-3-one. While this compound is present in only trace quantities in Unit I sediments, it is the most abundant alkenone in portions of Unit II. Its presence thus apparently pre-dates the invasion of Emiliania huxleyi in the Black Sea. The down-core profiles and isotopic compositions suggest that the precursor for the C-36:2 alkenone may be distinct from that of the C37-39 alkenones, however the biological origin of this novel compound is presently unknown. (C) 2001 Elsevier Science Ltd. All rights reserved.},
	issn = {0146-6380},
	doi = {10.1016/S0146-6380(01)00019-5},
	author = {Xu, L. and Reddy, C. M. and Farrington, J. W. and Frysinger, G. S. and Gaines, R. B. and Johnson, C. G. and Nelson, R. K. and Eglinton, T. I.}
}
@article {911,
	title = {Identification of a novel alkenone in Black Sea sediments},
	journal = {Organic Geochemistry},
	volume = {32},
	year = {2000},
	note = {id: 1719},
	pages = {633-645},
	abstract = {We report the identification of a novel long-chain ketone in Holocene Black Sea sediments. Based on chemical properties, and chromatographic and mass spectrometric characteristics, this compound has been identified as a di-unsaturated C36 ethyl ketone. Further analyses indicated the position and configuration of the double bonds, and the novel alkenone was determined to be hexatriaconta-(16E,21E)-dien-3-one. While this compound is present in only trace quantities in Unit I sediments, it is the most abundant alkenone in portions of Unit II. Its presence thus apparently pre-dates the invasion of Emiliania huxleyi in the Black Sea. The down-core profiles and isotopic compositions suggest that the precursor for the C36:2 alkenone may be distinct from that of the C37-39 alkenones, however the biological origin of this novel compound is presently unknown.},
	keywords = {Alkenone, Black Sea, Haptophytes, Holocene, Sediment, Structure characterization},
	doi = {10.1016/S0146-6380(01)00019-5},
	author = {Xu, L. and Reddy, C. M. and Farrington, J. W. and Frysinger, G. S. and Gaines, R. B. and Johnson, C. G. and Nelson, R. K. and Eglinton, T. I.}
}
@article {636,
	title = {Stable chlorine isotopic compositions of aroclors and aroclor-contaminated sediments},
	journal = {Environmental Science \& Technology},
	volume = {34},
	year = {2000},
	note = {330rcTimes Cited:39Cited References Count:16},
	month = {Jul 1},
	pages = {2866-2870},
	abstract = {An exploratory investigation was conducted to evaluate if stable chlorine isotopic ratios of polychlorinated biphenyls (PCBs) could be useful in studying the processes that determine their transport and fate in the environment First, we determined the variability of delta(37)Cl in the source materials for PCBs. Second, we determined if the delta(37)Cl values of contaminated environmental samples fell outside the range in source variability. The isotopic variability among the source materials (Aroclors) was rather small; delta(37)- Cl values ranged from -3.37 to -2.11\% (mean and standard deviation, -2.78 +/- 0.39\%, n = 12). There was no correlation between the delta(37)Cl values and percentages of chlorine in the mixtures. We also found very similar values in several Clophen mixtures and one Phenoclor. The delta(37)Cl values in the total PCBs isolated from Aroclor-contaminated sediments from the Hudson River, New Bedford Harbor, and Turtle River Estuary ranged from -4.54 to -2.25\% (n = 19). While most of the delta(37)Cl values were within 2 standard deviations of the mean Aroclor value (our assumed estimate for overall source variability), two of the PCB contaminated sediment samples from New Bedford Harbor did appear to be isotopically distinct. The PCBs in these sediments had lower amounts of less chlorinated congeners (when compared to the source material) and were likely isotopically affected by alteration processes that preferentially removed these congeners. Compound specific measurements of two congeners in Aroclor 1268 suggest that there are no large congener-specific differences in the stable chlorine isotope ratios in Aroclors. This study shows that the delta(37)Cl Values of PCBs may be a potentially useful diagnostic tool in studying the transport and fate of PCBs and indicates that additional research is warranted.},
	issn = {0013-936x},
	doi = {10.1021/es9908220},
	author = {Reddy, C. M. and Heraty, L. J. and Holt, B. D. and Sturchio, N. C. and Eglinton, T. I. and Drenzek, N. J. and Xu, L. and Lake, J. L. and Maruya, K. A.}
}
