@article { ISI:000309889600007,
	title = {Carbon isotopic (C-13 and C-14) composition of synthetic estrogens and progestogens},
	journal = {RAPID COMMUNICATIONS IN MASS SPECTROMETRY},
	volume = {26},
	number = {{22}},
	year = {2012},
	month = {NOV 30},
	pages = {2619-2626},
	type = {Article},
	abstract = {RATIONALE Steroids are potent hormones that are found in many environments. Yet, contributions from synthetic and endogenous sources are largely uncharacterized. The goal of this study was to evaluate whether carbon isotopes could be used to distinguish between synthetic and endogenous steroids in wastewater and other environmental matrices. METHODS Estrogens and progestogens were isolated from oral contraceptive pills using semi-preparative liquid chromatography/diode array detection (LC/DAD). Compound purity was confirmed by gas chromatography/flame ionization detection (GC/FID), gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) and liquid chromatography/mass spectrometry using negative electrospray ionization (LC/ESI-MS). The C-13 content was determined by gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and C-14 was measured by accelerator mass spectrometry (AMS). RESULTS Synthetic estrogens and progestogens are C-13-depleted (delta C-13(estrogen) = 30.0 +/- 0.9 parts per thousand; delta C-13(progestogen) = 30.3 +/- 2.6 parts per thousand) compared with endogenous hormones (delta C-13 similar to -16 to 26 parts per thousand). The C-14 content of the majority of synthetic hormones is consistent with synthesis from C-3 plant-based precursors, amended with {\textquoteleft}fossil{\textquoteright} carbon in the case of EE2 and norethindrone acetate. Exceptions are progestogens that contain an ethyl group at carbon position 13 and have entirely {\textquoteleft}fossil{\textquoteright} C-14 signatures. CONCLUSIONS Carbon isotope measurements have the potential to distinguish between synthetic and endogenous hormones in the environment. Our results suggest that C-13 could be used to discriminate endogenous from synthetic estrogens in animal waste, wastewater effluent, and natural waters. In contrast, C-13 and C-14 together may prove useful for tracking synthetic progestogens. Copyright (c) 2012 John Wiley \& Sons, Ltd.},
	issn = {0951-4198},
	doi = {10.1002/rcm.6385},
	author = {Griffith, David R. and Wacker, Lukas and Gschwend, Philip M. and Eglinton, Timothy I.}
}
@article { ISI:000290199000003,
	title = {Multiple-source heterotrophy fueled by aged organic carbon in an urbanized estuary},
	journal = {MARINE CHEMISTRY},
	volume = {124},
	number = {{1-4}},
	year = {2011},
	month = {MAR 20},
	pages = {14-22},
	type = {Article},
	abstract = {The lower Hudson River is a highly urbanized estuary that receives large inputs of treated wastewater. To determine how organic matter from wastewater influences carbon cycling in this type of system, we measured chlorophyll a, pCO(2). dissolved organic carbon (DOC), delta(13)C-DOC, and Delta(14)C-DOC along the salinity gradient and at wastewater treatment plants. Isotopic mixing curves indicate a net removal of DOC that is (13)C enriched and (14)C depleted. The amount of DOC removed was consistent with CO(2) evasion from the estuary. During two transects at average to low flow, the lower Hudson River Estuary was a heterotrophic system with CO(2) evasion balanced by the utilization of aged DOC derived from wastewater and marine phytoplankton that enter the estuary at the seaward end-member. DOC removals were largest during a period of high river flow, when isotopic mixing curves also suggest large contributions from labile terrestrial OC sources. Overall, our results suggest that net heterotrophy in the lower Hudson River Estuary is fueled by aged labile DOC derived from a combination of sources, which are influenced by seasonal phytoplankton blooms, hydrological conditions, and the nature of wastewater inputs. (C) 2010 Elsevier B.V. All rights reserved.},
	keywords = {(13)C, (14)C, Carbon cycle, Carbon dioxide, Chlorophyll, dissolved organic carbon, Heterotrophy, Hudson River Estuary, Isotope mixing curves, Sewage, USA, Wastewater},
	issn = {0304-4203},
	doi = {10.1016/j.marchem.2010.11.003},
	author = {Griffith, David R. and Raymond, Peter A.}
}
@article { ISI:000284192000011,
	title = {The radiocarbon age of organic carbon in marine surface sediments},
	journal = {GEOCHIMICA ET COSMOCHIMICA ACTA},
	volume = {74},
	number = {{23}},
	year = {2010},
	month = {DEC 1},
	pages = {6788-6800},
	type = {Article},
	abstract = {Long-term carbon cycling and climate change are strongly dependent on organic carbon (OC) burial in marine sediments. Radiocarbon ((14)C) has been widely used to constrain the sources, sinks, and processing of sedimentary OC. To elucidate the dominant controls on the radiocarbon content of total organic carbon ((14)C(TOC)) accumulating in surface sediments we construct a box model that predicts (14)C(TOC) in the sediment mixed layer (measured as fraction modern, Fm). Our model defines three distinct OC pools ({{\textquoteright}{\textquoteright}}degradable,{{\textquoteright}{\textquoteright}} {\textquoteleft}{\textquoteleft}semi-labile,{{\textquoteright}{\textquoteright}} and {\textquoteleft}{\textquoteleft}refractory{{\textquoteright}{\textquoteright}}) and assumes that (14)C(TOC) flux to sediments is exclusively derived from surface ocean primary productivity, and hence follows a {\textquoteleft}{\textquoteleft}generic{{\textquoteright}{\textquoteright}} surface ocean dissolved inorganic carbon (DIC) bomb curve. Model predictions are compared to a set of 75 surface sediment samples, which span a wide geographic range and reflect diverse water column and depositional conditions, and for which sedimentation rate and mixed-layer depth are well characterized. Our model overestimates the Fm value for a majority (65\%) of these sites, especially at shallow water depths and for sites characterized by depleted delta(13)C(TOC) values. The model is most sensitive to sedimentation rate and mixed-layer depth. Therefore, slight changes to these parameters can lead to a match between modeled and measured Fm values at many sites. Yet, in some cases, we find that measured Fm values cannot be simulated without large and unrealistic changes to sedimentation rate and mixed-layer depth. These results point to sources of pre-aged OC to surface sediments and implicate soil-derived terrestrial OC, reworked marine OC, and/or anthropogenic carbon as important components of the organic matter present in surface sediments. This approach provides a valuable framework within which to explore controls on sedimentary organic matter composition and carbon burial over a range of spatial and temporal scales. (C) 2010 Elsevier Ltd. All rights reserved.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2010.09.001},
	author = {Griffith, David R. and Martin, William R. and Eglinton, Timothy I.}
}
