TY - JOUR T1 - Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments JF - Nature Communications Y1 - 2023 A1 - Chu, Mengfan A1 - Bao, Rui A1 - Strasser, Michael A1 - Ikehara, Ken A1 - Everest, Jez A1 - Maeda, Lena A1 - Hochmuth, Katharina A1 - Xu, Li A1 - McNichol, Ann A1 - Bellanova, Piero A1 - Rasbury, Troy A1 - Kölling, Martin A1 - Riedinger, Natascha A1 - Johnson, Joel A1 - Luo, Min A1 - März, Christian A1 - Straub, Susanne A1 - Jitsuno, Kana A1 - Brunet, Morgane A1 - Cai, Zhirong A1 - Cattaneo, Antonio A1 - Hsiung, Kanhsi A1 - Ishizawa, Takashi A1 - Itaki, Takuya A1 - Kanamatsu, Toshiya A1 - Keep, Myra A1 - Kioka, Arata A1 - McHugh, Cecilia A1 - Micallef, Aaron A1 - Pandey, Dhananjai A1 - Proust, Jean Noël A1 - Satoguchi, Yasufumi A1 - Sawyer, Derek A1 - Seibert, Chloé A1 - Silver, Maxwell A1 - Virtasalo, Joonas A1 - Wang, Yonghong A1 - Wu, Ting-Wei A1 - Zellers, Sarah AB - 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. VL - 14 UR - https://www.nature.com/articles/s41467-023-41116-w ER - TY - JOUR T1 - Pre-aged terrigenous organic carbon biases ocean ventilation-age reconstructions in the North Atlantic JF - Nature Communications Y1 - 2023 A1 - Liu, Jingyu A1 - Wang, Yipeng A1 - Jaccard, Samuel L. A1 - Wang, Nan A1 - Gong, Xun A1 - Fang, Nianqiao A1 - Bao, Rui KW - Carbon cycle KW - Marine chemistry KW - Palaeoceanography AB - Changes in ocean ventilation have been pivotal in regulating carbon sequestration and release on centennial to millennial timescales. However, paleoceanographic reconstructions documenting changes in deep-ocean ventilation using 14C dating, may bear multidimensional explanations, obfuscating the roles of ocean ventilation played on climate evolution. Here, we show that previously inferred poorly ventilated conditions in the North Atlantic were linked to enhanced pre-aged organic carbon (OC) input during Heinrich Stadial 1 (HS1). The 14C age of sedimentary OC was approximately 13,345 ± 692 years older than the coeval foraminifera in the central North Atlantic during HS1, which is coupled to a ventilation age of 5,169 ± 660 years. Old OC was mainly of terrigenous origin and exported to the North Atlantic by ice-rafting. Remineralization of old terrigenous OC in the ocean may have contributed to, at least in part, the anomalously old ventilation ages reported for the high-latitude North Atlantic during HS1. VL - 14 UR - https://www.nature.com/articles/s41467-023-39490-6 N1 - Number: 1 Publisher: Nature Publishing Group ER - TY - JOUR T1 - Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass SpectrometryABSTRACT JF - Radiocarbon Y1 - 2019 A1 - Bao, Rui A1 - McNichol, Ann P A1 - Hemingway, Jordon D A1 - Lardie Gaylord, Mary C A1 - Eglinton, Timothy I AB - In practice, obtaining radiocarbon (C-14) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting C-14 content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on C-14 content of sedimentary OM, we examine the variability in C-14 content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (Rinse(HCl)) and HCl fumigation (Fume(HCl))], we demonstrate that the two acid-treatments can affect C-14 content differentially. Our findings suggest that, for low-carbonate samples, Rinse(HCl) affects the Fm values due to loss of young labile organic carbon (OC). Fume(HCl) makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during Rinse(HCl), causing the Fm values of remaining OC to increase. Fume(HCl) can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix. VL - 61 UR - https://www.researchgate.net/publication/328913959_Influence_of_different_acid_treatments_on_the_radiocarbon_content_spectrum_of_sedimentary_organic_matter_determined_by_RPOAccelerator_Mass_Spectrometry IS - 2 ER - TY - JOUR T1 - INFLUENCE OF DIFFERENT ACID TREATMENTS ON THE RADIOCARBON CONTENT SPECTRUM OF SEDIMENTARY ORGANIC MATTER DETERMINED BY RPO/ACCELERATOR MASS SPECTROMETRY JF - RADIOCARBON Y1 - 2019 A1 - Bao, Rui A1 - McNichol, Ann P. A1 - Hemingway, Jordon D. A1 - Gaylord, Mary C. Lardie A1 - Eglinton, I, Timothy AB - In practice, obtaining radiocarbon (C-14) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting C-14 content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on C-14 content of sedimentary OM, we examine the variability in C-14 content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (Rinse(HCl)) and HCl fumigation (Fume(HCl))], we demonstrate that the two acid-treatments can affect C-14 content differentially. Our findings suggest that, for low-carbonate samples, Rinse(HCl) affects the Fm values due to loss of young labile organic carbon (OC). Fume(HCl) makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during Rinse(HCl), causing the Fm values of remaining OC to increase. Fume(HCl) can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix. VL - 61 ER - TY - JOUR T1 - On the Origin of Aged Sedimentary Organic Matter Along a River‐Shelf‐Deep Ocean Transect JF - Journal of Geophysical Research: Biogeosciences Y1 - 2019 A1 - Bao, Rui A1 - Zhao, Meixun A1 - McNichol, Ann A1 - Wu, Ying A1 - Guo, Xinyu A1 - Haghipour, Negar A1 - Eglinton, Timothy I. KW - Carbon cycle KW - hydrodynamic processes KW - organic carbon KW - radiocarbon KW - sediments AB - To assess the influences of carbon sources and transport processes on the C-14 age of organic matter (OM) in continental margin sediments, we examined a suite of samples collected along a river-shelf-deep ocean transect in the East China Sea (ECS). Ramped pyrolysis-oxidiation was conducted on suspended particulate matter in the Yangtze River and on surface sediments from the ECS shelf and northern Okinawa Trough. C-14 ages were determined on OM decomposition products within different temperature windows. These measurements suggest that extensive amounts of pre-old (i.e., millennial age) organic carbon (OC) are subject to degradation within and beyond the Yangtze River Delta, and this process is accompanied by an exchange of terrestrial and marine OM. These results, combined with fatty acid concentration data, suggest that both the nature and extent of OM preservation/degradation as well as the modes of transport influence the C-14 ages of sedimentary OM. Additionally, we find that the age of (thermally) refractory OC increases during across-shelf transport and that the age offset between the lowest and highest temperature OC decomposition fractions also increases along the shelf-to-trough transect. Amplified interfraction spread or C-14 heterogeneity is the greatest in the Okinawa Trough. Aged sedimentary OM across the transect may be a consequence of several reasons including fossil OC input, selective degradation of younger OC, hydrodynamic sorting processes, and aging during lateral transport. Consequently, each of them should be considered in assessing the C-14 results of sedimentary OM and its implications for the carbon cycle and interpretation of sedimentary records. VL - 124 UR - https://doi.org/10.1029/2019JG005107 IS - 8 ER - TY - JOUR T1 - Temporal constraints on lateral organic matter transport along a coastal mud belt JF - Organic Geochemistry Y1 - 2019 A1 - Bao, Rui A1 - Zhao, Meixun A1 - McNichol, Ann A1 - Galy, Valier A1 - McIntyre, Cameron A1 - Haghipour, Negar A1 - Eglinton, Timothy I. KW - 14C aging KW - Continental shelf seas KW - East China Sea KW - Mud belt KW - organic matter KW - Sediment resuspension AB - Constraints on timescales of lateral transport of sedimentary organic carbon (OC) over continental shelves and associated influences on the distribution and abundance of OC remain sparse. Preferential degradation of labile, young OC during lateral transport results in apparent “diagenetic aging” of OC. Additionally, sediment translocation can also result in “transport time-associated aging” of associated organic matter (OM) as a function of the lateral transport time (LTT). Here, we use a coupled thermal decomposition and radiocarbon (14C) approach to constrain timescales of lateral transport and concomitant loss of OC associated with different grain size fractions of sediments collected from two locations ∼275 km apart along a dispersal pathway on the inner shelf of the East China Sea. The 14C age contrasts between corresponding thermal fractions are used to distinguish these two components of sedimentary OM “aging”. To minimize interferences from hydrodynamic sorting and diagenetic aging of OC accompanying lateral transport, we assess 14C age differences of decomposition products from the most thermally-refractory OC components associated with specific grain size fractions between locations. We show that LTTs vary among different grain size fractions, and examine relationships between LTTs and sedimentary OC loss in order to assess the decomposition of OC as a consequence of lateral transport. We suggest that the decomposition of OC associated with protracted lateral transport exerts a strong influence on OC burial efficiency, with broad implications for carbon cycling over continental shelves. VL - 128 UR - https://www.sciencedirect.com/science/article/pii/S0146638019300075 ER - TY - JOUR T1 - Dimensions of Radiocarbon Variability within Sedimentary Organic MatterABSTRACT JF - Radiocarbon Y1 - 2018 A1 - Bao, Rui A1 - McNichol, Ann P A1 - McIntyre, Cameron P A1 - Xu, Li A1 - Eglinton, Timothy I KW - arabian sea KW - grain size KW - hydrodynamic processes KW - organicmatter KW - radiocarbon KW - ramped pyrolysis-oxidation AB - 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. VL - 60 UR - https://www.cambridge.org/core/journals/radiocarbon/article/dimensions-of-radiocarbon-variability-within-sedimentary-organic-matter/A81022494F34D8C3B88D39A43112BB08 IS - 03 ER - TY - JOUR T1 - Organic Carbon Aging During Across‐Shelf Transport JF - Geophysical Research Letters Y1 - 2018 A1 - Bao, Rui A1 - Uchida, Masao A1 - Zhao, Meixun A1 - Haghipour, Negar A1 - Montlucon, Daniel A1 - McNichol, Ann A1 - Wacker, Lukas A1 - Hayes, John M. A1 - Eglinton, Timothy I. AB - Compound-specific radiocarbon analysis (CSRA) was performed on different grain-size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long-chain leaf wax fatty acids along two dispersal pathways of fluvially-derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins. VL - 45 UR - https://core.ac.uk/download/pdf/222887698.pdf IS - 16 ER - TY - JOUR T1 - Tectonically-triggered sediment and carbon export to the Hadal zone JF - Nature Communications Y1 - 2018 A1 - Bao, Rui A1 - Strasser, Michael A1 - McNichol, Ann P. A1 - Haghipour, Negar A1 - McIntyre, Cameron A1 - Wefer, Gerold A1 - Eglinton, Timothy I. AB - Sediments in deep ocean trenches may contain crucial information on past earthquake history and constitute important sites of carbon burial. Here we present 14C data on bulk organic carbon (OC) and its thermal decomposition fractions produced by ramped pyrolysis/oxidation for a core retrieved from the >7.5 km-deep Japan Trench. High-resolution 14C measurements, coupled with distinctive thermogram characteristics of OC, reveal hemipelagic sedimentation interrupted by episodic deposition of pre-aged OC in the trench. Low δ13C values and diverse 14C ages of thermal fractions imply that the latter material originates from the adjacent margin, and the co-occurrence of pre-aged OC with intervals corresponding to known earthquake events implies tectonically triggered, gravity-flow-driven supply. We show that 14C ages of thermal fractions can yield valuable chronological constraints on sedimentary sequences. Our findings shed new light on links between tectonically driven sedimentological processes and marine carbon cycling, with implications for carbon dynamics in hadal environments. VL - 9 UR - http://www.nature.com/articles/s41467-017-02504-1http://www.nature.com/articles/s41467-017-02504-1.pdfhttp://www.nature.com/articles/s41467-017-02504-1.pdfhttp://www.nature.com/articles/s41467-017-02504-1 IS - 1 ER -