Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Thursday, February 15, 2001, Time: 11:15:00 AM

Location: San Miguel

Opsahl, S, P, J. W. Jones Ecological Research Center, Newton, GA, USA, stephen.opsahl@jonesctr.org

Zepp, R, G, U.S. EPA, Athens, GA, USA, zepp.richard@epa.gov

Photochemically-Induced Transformations of Dissolved Organic Matter in Riverine Waters

We demonstrated that exposure of riverine water to natural sunlight initiated degradation and corresponding alteration to the stable carbon isotope ratio and biochemical composition of the associated dissolved organic carbon (DOC). Water samples were collected from two distinct river systems-the Satilla River which has high DOC concentrations, and the Altamaha River which has relatively low DOC concentrations. Approximately 21-29% of the DOC was remineralized to DIC during the incubations. The stable carbon isotope ratio of DIC that was produced was isotopically "light" relative to the initial DOC, leaving a residual fraction of DOC that was isotopically "heavy". Fractionation of carbon during photochemically-induced degradation of terrigenous DOC was selective for certain biochemical constituents. These results are consistent with shifts in the isotopic signature of DOC that are observed during the mixing of fresh-and marine waters, and we propose that photochemically-induced alterations are a significant factor in determining these changes.

This Session Listing

Aquatic Sciences Meeting, Albuquerque 2001

Quicklinks