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Powers, L.C.* ; Lapham, L.L.* ; Malkin, S.Y.* ; Heyes, A.* ; Schmitt-Kopplin, P. ; Gonsior, M.*

Molecular and optical characterization reveals the preservation and sulfurization of chemically diverse porewater dissolved organic matter in oligohaline and brackish Chesapeake Bay sediments.

Org. Geochem. 161:104324 (2021)

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	Open Access Green

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In this study, we conducted a detailed analysis of porewater downcore chemical properties and porewater dissolved organic matter (PDOM) composition using elemental C, N and S analysis, fluorescence spectroscopy, and ultrahigh resolution mass spectrometry (FT-ICR MS) at two contrasting sites in Chesapeake Bay. The sites, situated in the oligohaline upper bay and in the seasonally hypoxic mesohaline mid bay, receive fundamentally different detrital inputs predominantly from allochthonous and autochthonous sources, respectively. Unsurprisingly, we observed greater molecular oxygenation and degree of aromaticity in downcore PDOM profiles from the upper bay. At the mid bay station, PDOM composition was more indicative of non-aromatic algal-derived material. Unexpectedly, this autochthonous PDOM had lower C:S ratios. Hence, algal-derived organic matter appeared to be readily sulfurized, which was confirmed by quantification of dissolved organic sulfur as well as by qualitative interpretation of FT-ICR MS data. This finding suggests addition reactions of hydrogen sulfide to double bonds in unsaturated, but non-aromatic, organic molecules in autochthonous PDOM. Intriguingly, we also observed increases in humic-like fluorescence and dissolved organic carbon (DOC) concentrations in downcore PDOM profiles from both sites. Given the differences in molecular composition between sites, these results show that humic-like fluorescence can arise from different sources and biogeochemical processes. In the upper bay, we infer that these fluorescence signals reflect solubilization of terrestrially derived organic matter with a high aromatic and polyphenolic composition. By contrast, in the mid bay, these fluorescence peaks correlated negatively with hydrogen sulfide and are more likely linked to bacterial sulfate reduction.

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Publication type Article: Journal article

Document type Scientific Article

Corresponding Author

Keywords Algal Dom ; Brackish ; Chesapeake Bay ; Eem ; Ft-icr Ms ; Oligohaline ; Porewater Dom ; Sulfurization; Resolution Mass-spectrometry; Pore-water; Natural Sulfurization; Inorganic Polysulfides; Laboratory Simulation; Formula Assignment; Sulfur Enrichment; Hydrogen-sulfide; Humic Substances; Low-temperature

ISSN (print) / ISBN 0146-6380

e-ISSN 1873-5290

Journal Organic Geochemistry

Quellenangaben Volume: 161, Article Number: 104324

Publisher Elsevier

Publishing Place The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England

Non-patent literature Publications

Reviewing status Peer reviewed

Institute(s) Research Unit Analytical BioGeoChemistry (BGC)

Grants University of Maryland Center for Environmental Science
American Chemical Society Petroleum Research Fund
National Science Foundation