SS2.02 Biogeochemical Process at the Sediment-Water Interfaces
Date: Tuesday, June 11, 2002
Time: 3:00:00 PM
Location: Carson B
 
WarrenE, U.S. Geological Survey, Menlo Park, USA, ewarren@usgs.gov
Duff, J, H, U.S.Geological Survey, Menlo Park, USA, jhduff@usgs.gov
Godsy, E, M, U.S. Geological Survey, Menlo Park, USA, emgodsy@usgs.gov
Triska, F, J, U.S. Geological Survey, Menlo Park, USA, fjtriska@usgs.gov
Jackman, A, P, University of California, Davis, USA, apjackman@ucdavis.edu
Sheibley, R, W, University of California, Davis, USA, rwsheibley@ucdavis.edu
 
THE INFLUENCE OF DISSOLVED ORGANIC CARBON ON NITRATE REMOVAL IN UPPER MISSISSIPPI RIVER SEDIMENTS, POOL 8, LA CROSSE, WI
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We report here the results of preliminary in situ and laboratory microcosm studies of microbial nitrate metabolism in Mississippi River sediments containing low, medium, and high porewater DOC levels (2-12 mg C/L). Nitrate reduction was observed within in situ microcosms at background nitrate and DOC concentrations; however nitrate reduction was higher when background DOC was 6 mg C/L or more. Adding low levels of acetate (7 mg C/L) to sediments had little effect on nitrate reduction rates. Adding high levels of acetate (75-150 mg C/L) doubled the nitrate reduction rates. Including only background DOC assays, zero-order nitrate disappearance rates were 0.15 mg N/L-hr. With high levels of acetate, the rates increased to 0.3 mg N/L-hr. Nitrate reduction kinetics in laboratory microcosms were compared to the in situ rates. These results, while preliminary, suggest that nitrate reduction at in situ nitrate levels (5-10 mg N/L) may be enhanced by adding a labile carbon source (electron donor) to the sediments.