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Harir, M. ; Cawley, K.M.* ; Hertkorn, N. ; Schmitt-Kopplin, P. ; Jaffe, R.*

Molecular and spectroscopic changes of peat-derived organic matter following photo-exposure: Effects on heteroatom composition of DOM.

Sci. Total Environ. 838:155790 (2022)
Postprint DOI PMC
The temporal evolution of molecular compositions and changes in structural features of Hillsboro Canal (Florida, USA) dissolved organic matter (DOM) was studied with an emphasis on nitrogen and sulfur containing molecules, after a 13 day time-series exposure to simulated sunlight. The Hillsboro Canal drains from the ridge and slough wetland environment underlain by peat soils from the northern extent of the Greater Everglades Ecosystem. The Hillsboro Canal-DOM was characterized by combining ultrahigh-resolution mass spectrometry (FT-ICR-MS), high-field nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC) with UV detection, and ultraviolet/visible (UV/vis) absorbance and excitation emission matrix (EEM) fluorescence spectroscopy. Size exclusion chromatography (SEC) demonstrated progressive depletion of higher mass molecules and a concomitant decrease of absorbance during photo-irradiation. NMR and FT-ICR-MS revealed nonlinear temporal evolution of DOM. In fact, FT-ICR-MS showed an initial depletion of supposedly chromophoric molecules often carrying major unsaturation accompanied by an uneven evolution of numbers of CHO, CHOS and CHNO compounds. While CHNO compounds continually increased throughout the entire photo-exposure time, CHO and CHOS compounds temporarily increased but declined after further light exposure. Progressive loss of highly unsaturated compounds was accompanied by production of low mass CHO and CHNO compounds with high O/C ratios. Area-normalized 1H NMR spectra of DOM in water and of the water insoluble fraction (~5%) in methanol revealed clear distinctions between irradiated and non-irradiated samples and congruent evolution of DOM structural features during irradiation, with more uniform trends in methanolic-DOM. Photoirradiation caused initial photoproduction of oxygenated aliphatic compounds, continued depletion of phenols and oxygenated aromatics, substantial change from initial natural product derived olefins to photoproduced olefins, and uneven evolution of carboxylated and alkylated benzene derivatives. This study demonstrates longer-term heteroatom-dependent photochemistry of DOM, which will affect the speciation of N and S heteroatoms, their connections to inorganic nutrients, and potentially their bioavailability.
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Publikationstyp Artikel: Journalartikel
Dokumenttyp Wissenschaftlicher Artikel
Korrespondenzautor
Schlagwörter Dom Photo-evolution ; Eem-parafac ; Ft-icr-ms ; Heteroatom Dom ; Nmr
ISSN (print) / ISBN 0048-9697
e-ISSN 1879-1026
Zeitschrift Science of the Total Environment, The
Quellenangaben Band: 838, Heft: , Seiten: , Artikelnummer: 155790 Supplement: ,
Verlag Elsevier
Nichtpatentliteratur Publikationen
Begutachtungsstatus Peer reviewed
Institut(e) Research Unit BioGeoChemistry and Analytics (BGC)
Förderungen Science and Engineering Research Council
Bard Graduate Center, Bard College
Helmholtz Munich
National Science Foundation