MODELING GROUNDWATER DENTRIFICATION BY FERROUS IRON USING

Nitrate is one of the most common groundwater contaminants (Freeze and Cherry, 1979). Nitrate concentrations may be reduced by denitrification, which is a natural process that converts nitrate irreversibly into harmless nitrogen gas (Korom, 1992). Denitrification requires an anaerobic environment, denitrifying bacteria, and sufficient and reactive electron donating species (Firestone, 1982). Korom (1992) indicated that the three common electron donors for denitrification in aquifers are organic carbon, sulfide (usually as pyrite), and ferrous iron. Numerous researchers show that the availability of electron donors within aquifer sediments limits the denitrification potential of aquifers (e.g., Trudell et al., 1986; Robertson et al., 1996). Efforts by members of the UND denitrification research team show organic carbon and sulfide are active electron donors for denitrification in aquifers in North Dakota and Minnesota. We also believe ferrous iron is an active electron donor; however, the geochemical evidence for ferrous iron is more difficult to interpret. To do so require