National Water Quality Assessment Program: Eastern Iowa Basins

Occurrence Of Acetochlor And Acetochlor Metabolites In Alluvial Aquifers In Iowa

S.J. , M.E. Savoca, E.M. Sadorf, D.W. Kolpin, and E.M.Thurman

Abstracts of Papers, Part 1, 218th American Chemical Society Meeting, New Orleans, LA, August 22-26, 1999

Acetochlor was detected in 5 of 197 wells completed in alluvial aquifers in Iowa during 1995-98. Detected concentrations range from 0.003 to 0.77 micrograms per liter. The sulfonic and oxanilic acid metabolites of acetochlor were detected in 26 and 12 wells, respectively. Samples from monitoring wells in agricultural areas had the greatest number of detections and concentrations of acetochlor compounds followed by municipal supply, rural domestic, and urban monitoring wells. The number of detections and concentrations are increasing with time for the metabolites but not for the parent compound. Although not frequently detected in wells, ground water from alluvial aquifers can be a source of acetochlor compounds in Iowa streams. During baseflow when streamflow originates primarily from groundwater inflow, acetochlor was detected in 4 percent, the sulfonic acid metabolite in 66 percent and the oxanilic acid metabolite in 25 percent of 185 samples from 12 streams.

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