Screening method for assessing pesticide leaching potential.

Screening methods are required in order to determine which pesticides should receive greatest attention with respect to environmental problems. Several authors have proposed screening methods for determining whether a pesticide is likely to leach to groundwater. The Groundwater Ubiquity Score (GUS) developed by GUSTAFSON (5) has been used, as the first step of a tiered approach for specifying which chemicals should deserve longer attention and expensive studies of leachability. However, GUS is empirically based and has a deficiency due to the prediction of anomalous negative values for pesticides with short half-life and/or large sorption coefficient