Chemistry of Superoxide Radical in Seawater: CDOM Associated Sink of Superoxide in Coastal Waters
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- 作者：Jared V. Goldstone and Bettina M. Voelker
- 刊名：Environmental Science & Technology
- 出版年：2000
- 出版时间：March 15, 2000
- 年：2000
- 卷：34
- 期：6
- 页码：1043 - 1048
- 全文大小：134K
- 年卷期：v.34,no.6(March 15, 2000)
- ISSN：1520-5851
文摘
Colored dissolved organic matter (CDOM) and humicsubstances contain a nonmetallic redox-cycling componentcapable of catalyzing superoxide (O2-) dismutation. First-order rate coefficients (kpseudo) measured for this O2- sink ina number of coastal and Chesapeake Bay water samplesrange up to 1.4 s-1, comparable in magnitude to catalyzeddismutation by Cu species. A significant (r 2 = 0.73) correlationis observed between kpseudo and the optical absorptionand salinity of individual coastal water samples, suggestingan association with non-marine-derived CDOM. Theactivity of this sink is not changed by acidification orboiling of samples but is removed by photooxidation, indicatingthat it is an organic compound, but that it is neitherenzymatic nor likely to consist of tightly bound metals.The stoichiometry of hydrogen peroxide formation from O2-decay indicates that this sink is capable of a redoxcycle catalyzing the dismutation of O2-. This CDOM sinkcombined with the organic copper sink previously describedwill produce a steady-state superoxide concentration incoastal waters that is 100-1000-fold lower than that predictedfrom bimolecular dismutation alone. Catalyzed O2- decaywas also observed in a variety of humic and fulvic acidsamples, possibly occurring through quinone functionalities.Although the presence of quinone moieties in humic andfulvic acids has been demonstrated, there do not appear tobe good correlations between several measures ofquinone content and the O2- dismutation rates of thesesamples.