Nitrate in Ohio's Ground Water

Geologically sensitive aquifers were identified by analyzing nitrate concentrations from Public Water System water quality compliance data, using average nitrate concentrations of greater than 2.0 mg/L as the criteria. Nitrate is a useful indicator of sensitive hydrogeologic settings because of its association with human activities. The surface areas above sensitive aquifers exhibit high recharge rates, resulting in rapid transport of surface water to the ground water resource. This recharge can transport surface contaminants along with oxygenated surface water to the subsurface and significantly affect ground water chemistry. Generally, sand and gravel aquifers and bedrock aquifers overlain by thin glacial tills are considered to be the most sensitive aquifers in Ohio.

The data reflected in the nitrate-nitrite concentration map are from primarily treated water, but it is generally accepted that the standard treatments do not significantly alter nitrate-nitrite concentrations.