Zepp, R. G. U. S. EPA/NERL-Ecosystems Assessment Branch, firstname.lastname@example.org
Moran, M. University of Georgia,
Gao, H. Oak Ridge Institute for Science and Education,
DYNAMICS OF COLORED ORGANIC MATTER IN A COASTAL ESTUARY: CHANGES IN SPECTRAL AND PHOTOCHEMICAL PROPERTIES
Dissolved organic matter can affect the color, oxidizing capacity, nutrient dynamics, and trace gas exchange of surface waters. Here we report observations of the changes in photochemical properties, UV-visible spectra and relevant ancillary data along a transect of increasing salinity in the well-mixed estuary of the Satilla River, a high-DOC river located of the Georgia coast. Filtered water samples (0.2 um) and DOM samples that were obtained by ultrafiltration were used in these studies. Results indicated that the absorption spectra of the colored dissolved organic matter (CDOM) undergo pronounced changes in the estuary. The exponential decrease in absorption coefficients with increasing wavelength becomes progressively more pronounced as salinity increases. Action spectra for CDOM photoreactions (e.g. carbon monoxide production) exhibited an approximately exponential decrease with increasing wavelength. The photoreactions are accompanied by a bleaching of the CDOM color, UV absorbance and fluorescence and by formation of particles. Iron-DOM complexes play an important role in the photoreactions of the CDOM in the low salinity part of the estuary.
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