In the spring of 2009, the Minnesota Depa rtment of Agriculture (MDA) conducted triazine immunoassay analyses for water sa mples collected from a pre-existing network of volunteered, private drinking water wells in Minnesota's s outheastern karst region to screen for atrazine. Previous work indicat ed that wells with high nitrate-nitrogen concentrations had a higher likelihood of pesticide contaminati on. Therefore available wells in the network with high nitrate levels were selected for sampling and the results should be viewed as representative of vulnerabl e wells rather than al l wells in southeast Minnesota. All samples were collected by the well owner and MDA provided the immunoassay analysis at no charge to the well owner. Ninety-two of the 100 sample kits mailed out were returned for analysis. Of the 92 samples, 44 had detectable levels of triazine compounds that were assumed to be atrazine compounds. The median triazine concentration across the re gion was <0.05 ug/L, the 90 th percentile was 0.22 ug/L, and the maximum was 1.26 ug/L. All 92 samples re sults were below the currently applicable Minnesota Department of Health (MDH) drin king water standard of 3 ug/L for atrazine. The results were analyzed in conjunction with additional information on nitrate-nitrogen concentration in the well, well installation date, and the presence, or lack, of an overlaying confining layer.
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Minnesota Water Research Digital Library