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Issue 4, 2014
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Photo-reactivity of natural dissolved organic matter from fresh to marine waters in the Florida Everglades, USA

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Abstract

Natural dissolved organic matter (DOM) is the major absorber of sunlight in most natural waters and a critical component of carbon cycling in aquatic systems. The combined effect of light absorbance properties and related photo-production of reactive species are essential in determining the reactivity of DOM. Optical properties and in particular excitation–emission matrix fluorescence spectroscopy combined with parallel factor analysis (EEM-PARAFAC) have been used increasingly to track sources and fate of DOM. Here we describe studies conducted in water from two estuarine systems in the Florida Everglades, with a salinity gradient of 2 to 37 and dissolved organic carbon concentrations from 19.3 to 5.74 mg C L−1, aimed at assessing how the quantity and quality of DOM is coupled to the formation rates and steady-state concentrations of reactive species including singlet oxygen, hydroxyl radical, and the triplet excited state of DOM. These species were related to optical properties and PARAFAC components of the DOM. The formation rate and steady-state concentration of the carbonate radical was calculated in all samples. The data suggests that formation rates, particularly for singlet oxygen and hydroxyl radicals, are strongly coupled to the abundance of terrestrial humic-like substances. A decrease in singlet oxygen, hydroxyl radical, and carbonate radical formation rates and steady-state concentration along the estuarine salinity gradient was observed as the relative concentration of terrestrial humic-like DOM decreased due to mixing with microbial humic-like and protein-like DOM components, while the formation rate of triplet excited-state DOM did not change. Fluorescent DOM was also found to be more tightly coupled to reactive species generation than chromophoric DOM.

Graphical abstract: Photo-reactivity of natural dissolved organic matter from fresh to marine waters in the Florida Everglades, USA

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Supplementary files

Article information


Submitted
06 Nov 2013
Accepted
07 Feb 2014
First published
10 Feb 2014

Environ. Sci.: Processes Impacts, 2014,16, 866-878
Article type
Paper
Author version available

Photo-reactivity of natural dissolved organic matter from fresh to marine waters in the Florida Everglades, USA

S. A. Timko, C. Romera-Castillo, R. Jaffé and W. J. Cooper, Environ. Sci.: Processes Impacts, 2014, 16, 866
DOI: 10.1039/C3EM00591G

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