HR: 17:45h
AN: H54D-08    [Abstracts]
TI: Aquifer Denitrification: Is it a Zero-Order or First-Order Reaction?
AU: * Korom, S F
EM: scott.korom@mail.und.nodak.edu
AF: University of North Dakota, Department of Geology and Geological Engineering, Grand Forks, ND 58202-8358, United States
AB: Results from a network of 16 in situ mesocosms (ISMs) used to study aquifer denitrification at 5 sites in North Dakota and 4 sites in Minnesota (with 2 more installations planned for Iowa) are considered. At the Elk Valley aquifer (EVA) site in northeastern North Dakota, denitrification rates from six denitrification experiments were all better modeled as zero-order (0.16 +/- 0.05 mg nitrate-N/L/day), as determined by squared values of the linear correlation coefficient. Denitrification experiments at the other sites showed that denitrification was either below detection (< 0.01 mg nitrate-N/L/day) or was better modeled as a first-order reaction (0.00021/day to 0.0020/day), although squared values of the linear correlation coefficients for both rate models were nearly equal for some of the experiments. Not only were denitrification rates at the EVA site highest compared to the other sites in the ISM network, but sediment concentrations of electron donors at the EVA site were also greatest [ferrous iron about 0.3%, inorganic S (as pyrite) about 0.4%, organic C about 0.4%, weight basis]. These observations support the Michaelis- Menten model for reaction rates, which indicates that reaction rates will be zero-order when the substrate (electron donor) is abundant and first-order when the substrate availability is limited.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0469 Nitrogen cycling
DE: 0471 Oxidation/reduction reactions (4851)
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting