LONG-TERM GROUNDWATER QUALITY CHANGES FROM A ONE-TIME SURFACE BROMIDE APPLICATION

The purpose of this experiment was to use a conservative tracer to study the impacts on groundwater quality of a one-time application of a water soluble chemical. Potassium bromide was applied at a rate of 168 kg Br-/ha to two 1.1-ha pasture watersheds in east-central Ohio. The watersheds had well-drained residual silt loam soils and with slopes of 12 to 25%. A nearly impermeable clay layer under the watersheds created a perched aquifer from which groundwater samples could be taken at developed springs. There were seasonal variations in Br- concentrations in the groundwater and the highest concentrations (9.2 mg/L maximum peak) occurred within 3 yr following the Br- application. Ten years following the Br- application, Br- concentration in the groundwater was still slightly above initial baseline levels. Even with a one-time application of a soluble chemical constituent on the surface of a small aquifer system, a multiyear impact was produced on the quality of groundwater.