@article {399,
	title = {Radiocarbon-based assessment of fossil fuel-derived contaminant associations in sediments},
	journal = {Environmental Science \& Technology},
	volume = {42},
	year = {2008},
	note = {id: 881; 332HW Times Cited:1 Cited References Count:43Y},
	pages = {5428-5434},
	abstract = {Hydrophobic organic contaminants (HOCs) are associated with natural organic matter (OM) in the environment via mechanisms such as sorption or chemical binding. The latter interactions are difficult to quantitatively constrain, as HOCs can reside in different OM pools outside of conventional analytical windows. Here, we exploited natural abundance variations in radiocarbon (C-14) to trace various fossil fuel-derived HOCs (C-14- free) within chemically defined fractions of contemporary OM (modern C-14 content) in 13 samples including marine and freshwater sediments and one dust and one soil sample. Samples were sequentially treated by solvent extraction followed by saponification. Radiocarbon analysis of the bulk sample and resulting residues was then performed. Fossil fuel-derived HOCs released by these treatments were quantified from an isotope mass balance approach as well as by gas chromatography-mass spectrometry. For the majority of samples (n = 13), 98-100\% of the total HOC pool was solvent extractable. Nonextracted HOCs are only significant (29\% of total HOC pool) in one sample containing pp-2,2-bis(chlorophenyl)1,1,1-trichloroethane and its metabolites. The infrequency of significant incorporation of HOCs into nonextracted OM residues suggests that most HOCs are mobile and bioavailable in the environment and, as such, have a greater potential to exert adverse effects.},
	issn = {0013-936X},
	doi = {10.1021/Es800478x},
	author = {White, H. K. and Reddy, C. M. and Eclinton, T. I.}
}
@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 {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 {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.}
}
