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NITROUS OXIDE CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT
Burke Jr., R A. AND J. Molinero. NITROUS OXIDE CONCENTRATIONS IN SMALL STREAMS OF THE GEORGIA PIEDMONT. Presented at American Society of Agronomy-Crop Science Society of America-Soil Science Society of America Annual Meeting, Indianapolis, IN, November 10-14, 2002.
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
We are measuring the dissolved nitrous oxide concentration in 17 headwater streams in the South Fork Broad River, Georgia watershed on a monthly basis. The selected small streams drain watersheds dominated by forest, pasture, developed, or mixed land uses. Nitrous oxide concentrations vary widely from 10 nM (atmospheric equilibrium concentration) to nearly 80 nM among the streams. Our measurements to date imply that many of the streams have nearly constant dissolved nitrous oxide concentrations regardless of season. Some of the streams have fluctuating nitrous oxide concentrations but the variations are not obviously related to temperature. Overall, the streams draining watersheds dominated by developed land use have the highest dissolved nitrous oxide concentrations although the difference is statistically significant only for comparisons with the forest and mixed land use watersheds. Also, the streams draining watershed dominated by pasture have significantly greater nitrous oxide concentrations overall than streams draining forested watersheds. These results suggest that small streams could be a significant source of nitrous oxide to the atmosphere in some watersheds.