From USGS via Journal of Environmental Quality:
…Atrazine is one of the most extensively used agricultural herbicides in the United States, with an average annual use (1992–1995) of 29 million kg active ingredient applied to about 231,000 km2 of cropland (primarily corn and sorghum) (Thelin and Gianessi, 2000). National models of atrazine occurrence in shallow groundwater were previously developed by Kolpin et al. (2002) and Stackelberg et al. (2006a) to evaluate atrazine detection frequencies in well networks (typically 20–30 wells each) associated with NAWQA land-use studies (Gilliom et al., 2006).
…Results show that only about 5% of agricultural areas have greater than a 10% probability of exceeding the USEPA maximum contaminant level of 3.0 mg L−1.
…the Tobit models described here represent an approach that provides the most reliable predictions of atrazine residue concentrations in shallow agricultural groundwater across the United States.
Please click here to read the original PDF version of this technical report at crops.org.
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