Understanding the Photoreactivity of Dissolved Organic Carbon in Natural Waters: The Role of the Triplet Excited-State of Allochthonous and Autochthonous DOC
Abstract
The photochemical reactivity of DOC in sunlit waters is a major factor for the in situ processing of DOC itself and trace contaminants in streams, lakes and the ocean. There is an increasing interest in the use of wetlands to mitigate contaminant removal. Laser flash photolysis is used to determine the reaction rate constants of dissolved organic carbon (DOC) with emerging contaminants in natural waters. DOC, produced by the decomposition of plant and microbial material, is one of the most complex naturally occurring mixtures. DOC plays a major role in the global carbon cycle, the sequestration and transport of trace chemicals and contaminants, and the biogeochemistry of natural waters. Hydrolysis, direct photolysis and reactions with singlet oxygen and the hydroxyl radical account for up to 25% of the photo reactivity of natural organic matter. The remaining 75% is attributed to reactions with the triplet-excited state of DOC (3DOC*). In this study, 1H NMR is used to characterize DOC from the Black River (NC), the San Joaquin Wetlands (Irvine, CA), and coastal seawater (Crystal Cove, CA). These sites encompass both allochthonous and autochthonous organic matter from catchment, wetlands, and marine waters. We then determine the reaction rate constants of known triplet state reactants and pharmaceuticals with the 3DOC* in the natural waters and with the DOC isolated by solid phase extraction. Studies of 3DOC* could provide a measure of DOC reactivity, essential in the design of constructed wetlands for contaminant removal.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B21E0423C
- Keywords:
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- 0432 BIOGEOSCIENCES / Contaminant and organic biogeochemistry;
- 0432 BIOGEOSCIENCES / Contaminant and organic biogeochemistry;
- 0442 BIOGEOSCIENCES / Estuarine and nearshore processes;
- 0497 BIOGEOSCIENCES / Wetlands