Technical Report No: 13-04 COMPARISON OF DENITRIFICATION POTENTIAL AROUND A TILE DRAIN AND IN AQUIFER SEDIMENTS: OAKES, ND by

Denitrification, the microbial reduction of nitrate (NO3) in groundwater, has three requirements: limited oxygen, bacteria capable of mediating the reaction, and electron donors for the bacteria to use in the redox reactions. The critical factor for aquifer denitrification is the concentrations of electron donors. Without an adequate supply of electron donors, bacteria cannot reduce concentrations of either oxygen or NO3. Artificial drainage within agricultural areas may allow contaminants to bypass, or increase conveyance through, reduced areas in which denitrification is likely to occur. This contributes to elevated NO3 yields as it is discharged directly into surface water. Depending on site geology, however, bacterial biofilms capable of NO3 reduction may cultivate within the tile drainage. This study aims to quantify and compare the potential for denitrification, as well as denitrification rates, within tile drainage and aquifer sediments at the Best Management Practices (BMP) site, within the Oakes Irrigation Test Area (OITA) near Oakes, North Dakota. For the aquifer sediment study, sediment samples (n=43) were collected from 10 locations at the BMP site. All samples were analyzed for the following potential electron