Pesticides and Metabolites
Pesticide samples were analyzed for 117 wells. Thirty domestic wells were sampled in the deep glacial-drift buried bedrock valley, 30 wells in the shallow Illinoian glacial drift not overlying a buried bedrock valley, and 57 wells in the shallow Wisconsinan. Twenty-nine in the shallow Wisconsinan glacial drift do not overlie buried bedrock valleys. Those that do not overly buried bedrock valleys are most often located on glacial moraines.

All Glacial Drift Detections

• No pesticides were detected above drinking water standards.
• Atrazine, deethyl atrazine, and metolachlor were the most frequently detected pesticides.
• At least one pesticide was detected in 40 to 60 percent of all shallow wells.
• Atrazine is the most frequently detected in the older Illinoian deposits.

Deep Glacial Detections

• Pesticides were detected in low concentrations in the deep aquifer in the initial sampling in 1996 in 10 of 30 wells. Concentrations ranged from non-detect to 0.019 micrograms per liter.
• Atrazine was the most frequently detected pesticide.
• Deep aquifer wells with detections were resampled in 1998 with pestcides detected in 4 out of the 10 wells.
• No tritium detected in wells.

Ground-water samples from 28 shallow wells in the Wisconsinan deposits overlying the buried bedrock valley were analyzed for pesticide degradates.

List of Pesticide Degradates

• Deethylatrazine
• Deisoproplatrazine
• Hydroxy-atrazine
• Metolachlor ethane sulfonic acid (ESA)
• Metolachlor oxanilic acid
• Acetochlor ESA
• Acetochlor oxanilic acid
• Cyanazine-amide

Results

• Pesticide degradates were detected more frequently than parent compounds.
• Atrazine and metolachlor degradates were most commonly detected.
• Metolachlor ESA concentrations were much higher than metolachlor concentrations.
• Pesticide concentrations appear lower on moraines than off moraines.