Citation:

Burke Jr., R A. AND J. Molinero. BIOGEOCHEMICAL INDICATORS OF ORGANIC WASTE CONTAMINATION IN GEORGIA PIEDMONT STREAMS. Presented at Soil Science Society of America Annual Meeting, Seattle, WA, October 31-November 4, 2004.

Impact/Purpose:

The overall objective of this task is to identify or develop useful indicators of organic waste enrichment in aquatic systems that are easily measured and based on basic underlying ecosystem processes so that they will be widely applicable. These activities will primarily contribute to an APG within Long Term Goal 2 of the Water Quality Research Program Multiyear Plan: the 2008 APG on equipping EPA Regions, States, and Tribes with knowledge, skills and tools to determine the causes of impairments for freshwater and coastal systems required in various regulations and will also contribute to EPA Strategic Plan 2003-2008 Sub-objective 2.2.2: Improve Coastal and Ocean Waters. Activities that address the 2008 Water Quality APG will focus primarily on small streams of the Georgia Piedmont, which receive human and agricultural waste inputs. The activities related to EPA Sub-objective 2.2.2 will focus on the nearshore marine ecosystem of the Pacific Ocean, which receives treated wastes from the approximately 15 million people who live in the coastal zone of southern California and northern Baja California, Mexico, and on the nearshore marine ecosystem of the Gulf of California, which receives little anthropogenic pollution. The indicators that will be evaluated or developed will include concentrations of trace gases (N2O, CH4, and CO2), dissolved oxygen (DO), nutrients, and dissolved organic matter (DOM), other key parameters such as temperature, conductivity or salinity, flow rate, alkalinity, and pH, rates of key processes such as denitrification and DO consumption, and stable isotope ratios of various pools and substrates such as plants, animals, sediments, and DO.

Description:

We monitored concentrations of nitrous oxide, methane, carbon dioxide, nutrients and other parameters (T, conductivity, dissolved oxygen, alkalinity, pH, DOC, DON, flow rate) in 17 headwater streams (watershed sizes from 0.5 to 3.4 km2) of the South Fork Broad River, Georgia watershed on a monthly basis for a year. We also measured the stable nitrogen isotope ratio of plants growing in the channel and potential denitrification rate in the sediments at selected sites on a few dates. Watershed land use was derived from the National Land Cover Data (NLCD) database. Our monthly monitoring results suggest that : (1) TDN, DOC, and dissolved concentrations of nitrous oxide and methane in streams are all effective indicators of stream impairment by nutrients and organic wastes from septic tanks and/or animal manure; and (2) trace gas concentrations are more sensitive indicators that respond to lower levels of nutrient and organic waste contamination than do TDN and DOC. The stable nitrogen isotope and denitrification measurements generally support the trace gas, TDN, and DOC measurements and appear to reflect waste contamination levels in these watersheds. Elevated levels of nitrous oxide and methane appear to be viable early warning indicators of incipient stream impairment and these indicators, largely being developed through this research, may have great value to water quality managers and regulators.

Record Details: