Agrichemicals in ground water of the midwestern USA: Relations to soil characteristics

A comprehensive set of soil characteristics were examined to determine the effect of soil on the transport of agrichemicals to ground water. This pape r examines the relation of local soil characteristics to concentrations and occurrence of nitrate, atrazine (2-chloro-4 ethylamino-6-isopropylamino-s- trazine), and atrazine residue [atrazine + deethylatrazine (2-amino-4-chlor o-6-isopropylamino-s-triazine) + de-isopropylatrazine (2-amino-4-chloro-6-e thylamino-s-triazine)] from 99 wells completed in unconsolidated aquifers a cross the midwestern USA. The occurrence and concentrations of nitrate and atrazine in ground water were directly related to soil characteristics that determine the rate of water movement. The substantial differences in the r elations found among soil characteristics and nitrate and atrazine in groun d water suggest that different processes affect the transformation, adsorpt ion, nod transport of these contaminants, A multivariate analysis determine d that the soil characteristics examined explained the amount of variabilit y in concentrations for nitrate (19.0%), atrazine (33.4%), and atrazine res idue (28.6%). These results document that, although soils do affect the tra nsport of agrichemicals to ground water, other factors such as hydrology, l and use, and climate must also be considered to understand the occurrence o f agrichemicals in ground water.