Abstract |
A method is presented for estimating the number of samples needed to evaluate pesticide leaching threats to ground water at a desired level of precision. Sample size projections are based on desired precision (exhibited as relative tolerable error), level of confidence (90 or 95%) and estimates of variability (expressed as the coefficient of variation) for selected pesticide and soil characteristics. Summary tables of descriptive statistics are provided as guides for projecting variability of various soil characteristics, pesticide properties (sorption, degradation), pesticide concentration profiles and inorganic solutes. These data were compiled through a comprehensive search of review articles and of reports of laboratory and field studies. The parameters selected are measurements generally required for conducting field pesticide leaching studies. They are also useful for evaluating ground water contamination by calibrating and conducting sensitivity testing with solute transport models. (Copyright (c) Environmental Toxicology and Chemistry, Vol. 6, pp. 343-357, 1987.) |