Analysis and Detection of the New Corn Herbicide Acetochlor in River Water and Rain

摘要

The use of herbicides on corn has become common and important. In the United States, the herbicides used most often on corn in 1989 were alachlor, atrazine, butylate, cyanazine, dicamba, EPTC, metolachlor, and 2,4-D. The 1989 estimated use in the United States of these eight herbicides on corn was 89 x 10~6 kg. In March 1994, the U.S. EPA conditionally registered the herbicide acetochlor (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl)-acetamide) as a partial replacement for many of these other corn herbicides. As part of the registration criteria, the use of acetochlor must result in a reduction in use of the most common corn herbicides (alachlor, atrazine, butylate, EPTC, metolachlor, and 2,4-D). Total use of these six herbicides on corn must decline by 1.8 x 10~6 kg by the end of 18 months (November 1995) and by 3.0 x 10~6 kg by the end of 5 years (March 1999) based on 1992 use, adjusting for differences in planted acreage. Thus, acetochlor is destined to be a high-use herbicide. Other criteria in its conditional registration are based on concerns of surface water and ground water contamination and include a mandate for industry, state, and Federal participation in surface water and ground water monitoring programs. As an example of these criteria with regard to surface water, the registration will be cancelled if the annual acetochlor concentration is ≥ 2 μg/L in two large community water supply systems (systems serving over 100000 people) or in 10 community water supply systems of any size that derive their water primarily from surface water. As an example with regard to groundwater, the registration will be cancelled if the acetochlor concentration is ≥ 0.1 μg/L in ≥ 20 wells in a state monitoring program followed by two subsequent detections of ≥ 0.1 μg/L in monthly sampling of each of these wells conducted over the following 6 months.