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Biogeochemical indicators of Organic Waste Contamination in Small Streams of the Georgia Piedmont

Roger A. Burke 1 and Jon Molinero 2

1 U.S. Environmental Protection Agency (USEPA), ORD,NERL,ERD, Athens, GA
2 National Research Council, c/o USEPA, Athens, GA

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 in EPA Program Offices and Regions and in state and local governments. Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Keywords: surface water, monitoring, indicators, watershed, land use, organic waste, stream impairment

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