Direct Evidence of a Light-Dependent Sink of Superoxide within Chromophoric Dissolved Organic Matter.
Environ Sci Technol
; 57(49): 20627-20635, 2023 Dec 12.
Article
em En
| MEDLINE
| ID: mdl-38044674
ABSTRACT
Superoxide (O2â¢â¯-) is produced photochemically in natural waters by chromophoric dissolved organic matter (CDOM) via the reaction of molecular oxygen with photoproduced one-electron reductants (OERs) within CDOM. In the absence of other sinks (metals or organic radicals), O2â¢â¯- is believed to undergo primarily dismutation to produce hydrogen peroxide (H2O2). However, past studies have implicated the presence of an additional light-dependent sink of O2â¢â¯- that does not lead to H2O2 production. Here, we provide direct evidence of this sink through O2â¢â¯- injection experiments. During irradiations, spikes of O2â¢â¯- are consumed to a greater extent (â¼85-30% loss) and are lost much faster (up to â¼0.09 s-1) than spikes introduced post-irradiation (â¼50-0% loss and â¼0.03 s-1 rate constant). The magnitude of the loss during irradiation and the rate constant are wavelength-dependent. Analysis of the H2O2 concentration post-spike indicates that this light-dependent sink does not produce H2O2 at low spike concentrations. This work further demonstrates that simply assuming that the O2â¢â¯- production is twice the H2O2 production is not accurate, as previously believed.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Superóxidos
/
Peróxido de Hidrogênio
Idioma:
En
Revista:
Environ Sci Technol
Ano de publicação:
2023
Tipo de documento:
Article
País de afiliação:
Estados Unidos