@article {599,
	title = {Variability in radiocarbon ages of biochemical compound classes of high molecular weight dissolved organic matter in estuaries},
	journal = {Estuarine Coastal and Shelf Science},
	volume = {68},
	year = {2006},
	note = {057ogTimes Cited:6Cited References Count:41},
	month = {Jun},
	pages = {188-194},
	abstract = {High molecular weight dissolved organic matter (HMW-DOM, > 1000 Da) represents a major fraction (> 30\%) of dissolved organic carbon (DOC) in the ocean and thus plays an important role in the global biogeochemical cycling of carbon and many other elements. Its organic sources and formation mechanisms, however, are still not well understood especially in estuarine and coastal regions where multiple natural and anthropogenic sources contribute to total HMW-DOM. In this paper we report our measurements of natural radiocarbon (C-14) abundances and stable carbon isotope (C-13) compositions of the major biochemical compound classes: amino acids, carbohydrates and lipids separated from eight HMW-DOM samples collected from five US estuaries as part of our on-going study of sources, distribution and transport of chromophoric dissolved organic matter (CDOM) in estuarine and coastal waters. Distinct differences in both C-14 and C-13 values were found among the bulk HMW-DOM samples as well as the individual compound classes. Radiocarbon ages of the major compound classes varied by as much as 27,000 years in a single sample. The calculated average radiocarbon ages of the compound fractions of HMW-DOM indicate that the total lipid fraction is very "old", while the acid-insoluble fraction is slightly younger. Total amino acid and carbohydrate fractions, however, have relatively modern apparent C-14 ages. The significant variability in C-14 ages among the compound classes indicates not only multiple organic carbon sources but also different formation and turnover pathways controlling the cycling of different biochemical components of HMW-DOM in estuarine and coastal waters. (c) 2006 Elsevier Ltd. All rights reserved.},
	issn = {0272-7714},
	doi = {10.1016/j.eccs.2006.01.018},
	author = {Wang, X. C. and Callahan, J. and Chen, R. F.}
}
@article {2009,
	title = {Stable carbon and nitrogen isotopic compositions of organic compound classes in high molecular weight dissolved organic matter from four U. S. estuaries},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {68},
	year = {2004},
	note = {id: 515},
	month = {2004},
	pages = {2681-2691},
	author = {Wang, X. C. and Altabet, A. M. and Callahan, J. and Chen, R. F.}
}
@article {891,
	title = {Chemical composition and cycling of dissolved organic matter in the Mid-Atlantic Bight},
	journal = {Deep-Sea Research Part Ii-Topical Studies in Oceanography},
	volume = {49},
	year = {2002},
	note = {607kxTimes Cited:74Cited References Count:44},
	pages = {4421-4437},
	abstract = {This study focuses on the chemical characterization of high molecular-weight dissolved organic matter (HMW DOM) isolated from the Middle Atlantic Bight in April 1994 and March 1996. Using proton nuclear magnetic resonance spectroscopy ((HNMR)-H-1) and monosaccharide analysis we compared both spatial and temporal variations in the chemical structure of HMW DOM across this region. Our analyses support the presence of at least two compositionally distinct components to HMW DOM. The major component is acyl polysaccharide (APS), a biopolymer rich in carbohydrates, acetate and lipid, accounting for between 50\% and 80\% of the total high molecular-weight dissolved organic carbon (HMW DOC) in surface samples. APS is most abundant in fully marine, surface-water samples, and is a product of autochthonous production. Organic matter with spectral properties characteristic of humic substances is the second major component of HMW DOM. Humic substances are most abundant (up to 49\% of the total carbon) in samples collected from estuaries, near the coast, and in deep water, suggesting both marine and perhaps terrestrial sources. Radiocarbon analyses of neutral monosaccharides released by the hydrolysis of APS have similar and modern (average 71parts per thousand) Delta(14)C values. Radiocarbon data support our suggestion that these sugars occur as part of a common macromolecule, with an origin via recent biosynthesis. Preliminary radiocarbon data for total neutral monosaccharides isolated from APS at 300 and 750m show this fraction to be substantially enriched relative to total HMW DOC and DOC. The relatively enriched radiocarbon values of APS at depth suggest APS is rapidly transported into the deep ocean. (C) 2002 Elsevier Science Ltd. All rights reserved.},
	issn = {0967-0645},
	doi = {10.1016/S0967-0645(02)00124-8},
	author = {Aluwihare, L. I. and Repeta, D. J. and Chen, R. F.}
}
@article {767,
	title = {Contribution of "old" carbon from natural marine hydrocarbon seeps to sedimentary and dissolved organic carbon pools in the Gulf of Mexico},
	journal = {Geophysical Research Letters},
	volume = {28},
	year = {2001},
	note = {467jmTimes Cited:20Cited References Count:25},
	month = {Sep 1},
	pages = {3313-3316},
	abstract = {Natural radiocarbon (C-14) abundances and stable carbon isotope (delta C-13) compositions were measured for sediment total organic carbon (TOC), and total lipid fractions of sediments, bottom water, and hydrate-water collected from two hydrocarbon seepage sites in Green Canyon, Northern Gulf of Mexico to determine the contribution of "old" carbon from seeps to sediment TOC and dissolved organic carbon (DOC) pools. Our results indicate that 40-60\% of the organic carbon preserved in the sediments and 30\% of the DOC in the deep water above the seeps were seep-derived C-14-depleted organic carbon. This new evidence along with our previous studies suggest that natural marine hydrocarbon seepage could be a significant source contributing "old" carbon to the marine environment. Our findings suggest that the global importance and the long-term impact of this contribution to biogeochemical carbon cycling in the ocean need to be more thoroughly investigated.},
	issn = {0094-8276},
	doi = {10.1029/2001gl013430},
	author = {Wang, X. C. and Chen, R. F. and Whelan, J. and Eglinton, L.}
}
