Mitigation of metolachlor-associated agricultural runoff using constructedwetlands in Mississippi, USA

A loss of marginal wetland acreage adjoining agricultural fields has create d a potential problem with water quality enhancement of agricultural runoff via wetlands. Current research is investigating the utility of constructed wetlands for pesticide mitigation purposes, thereby restoring water qualit y enhancement capability to the area. Constructed wetland mesocosms (59-73 mx 14 m), located at the University of Mississippi Field Station (Lafayette County, MS), were amended with metolachlor to simulate a cropland runoff e vent. Target concentrations for wetlands were 73 and 147 mug/l metolachlor in addition to an unamended control (0 mug/l). Water, sediment, and plant s amples were collected weekly for 35 days following metolachlor amendment. S amples were collected from sites, longitudinally distributed within each we tland, and analyzed for metolachlor using gas chromatography. Between 7 and 25% of measured metolachlor mass was in the first 30-36 m (from inflow) of wetlands immediately following application and simulated rainfall. Approxi mately 10% of measured metolachlor mass was in plant samples. Suggested wet land travel distances for effective mitigation of metolachlor runoff ranged from 100 to 400 m. According to the results from this research, aquatic re ceiving system impacts due to metolachlor runoff could be mitigated by usin g constructed wetlands as buffers. Landowners and, government agencies can integrate this information into a water management plan, allowing fur bette r control of both quantity and quality of runoff water from individual agri cultural fields. Published by Elsevier Science B.V.