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Relating carbon monoxide photoproduction to dissolved organic matter functionality

Lookup NU author(s): Dr Aron Stubbins, Dr Guenther Uher, Professor Robert Upstill-Goddard

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Abstract

Aqueous solutions of humic substances (HSs) and pure monomeric aromatics were irradiated to investigate the chemical controls upon carbon monoxide (CO) photoproduction from dissolved organic matter (DOM). HSs were isolated from lakes, rivers, marsh, and ocean. Inclusion of humic, fulvic, hydrophobic organic, and hydrophilic organic acid fractions from these environments provided samples diverse in source and isolation protocol. In spite of these major differences, HS absorption coefficients (a) and photoreactivities (a bleaching and CO production) were strongly dependent upon HS aromaticity (r2 >0.90; n = 11), implying aromatic moieties are the principal chromophores and photoreactants within HSs, and by extension, DOM. Carbonyl carbon and CO photoproduction were not correlated, implying that carbonyl moieties are not quantitatively important in CO photoproduction. CO photoproduction efficiency of aqueous solutions of monomeric aromatic compounds that are common constituents of organic matter varied with the nature of ring substituents. Specifically, electron donating groups increased, while electron withdrawing groups decreased CO photoproductivity, supporting our conclusion that carbonyl substituents are not quantitatively important in CO photoproduction. Significantly, aromatic CO photoproduction efficiency spanned 3 orders of magnitude, indicating that variations in the CO apparent quantum yields of natural DOM may be related to variations in aromatic DOM substituent group chemistry.


Publication metadata

Author(s): Stubbins A, Hubbard V, Uher G, Law CS, Upstill-Goddard RC, Aiken GR, Mopper K

Publication type: Article

Journal: Environmental Science and Technology

Year: 2008

Volume: 42

Issue: 9

Pages: 3271-3276

ISSN (print): 1086-931X

ISSN (electronic): 1520-6912

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/es703014q

DOI: 10.1021/es703014q


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