In-situ Measurement of Denitrification in Agricultural Streams
Principal Investigators: Patrick Brezonik, Professor, Department of Civil Engineering, University of Minnesota; and L. K. Hatch, Assistant Professor, Department of Biology, Macalester College
Additional Staff: B. O’Connor, Research Assistant, Department of Civil Engineering, University of Minnesota
USGS-WRRI 104G National Competitive Grants Program
September 2000 - August 2002
Nitrate contamination of ground water and streams is common in landscapes dominated by agricultural activities. Associated impacts of this pollution range from local violations of drinking water standards designed to prevent methemoglobinemia to national concerns (e.g., Gulf of Mexico hypoxia). Significant quantities of nitrate are exported from agricultural lands through drainage ditches and low-order natural streams, but our understanding of nitrogen transport and transformation in these agricultural streams is far from complete. Denitrification may be an important mechanism for nitrate removal in these streams, and this would mitigate water quality and health hazards downstream. Several methods can be used to measure denitrification, but the most common ones involve laboratory experiments with sediment cores, where conditions are not conducive to obtaining in situ rates. Our research is comparing several methods used to assess in situ denitrification rates in agricultural streams and evaluating their accuracy. We also are evaluating how variations in key environmental factors may affect the importance of this process as a nitrogen sink.