PESTICIDE DISTRIBUTIONS IN SURFACE-WATER

Distributions of concentrations of 46 pesticides were documented from May 1992 through March 1994 for Maple Creek near Nickerson, Neb, and P latte River at Louisville, Neb. As their source of public water suppli es, Lincoln and the western part of groundwater from the adjacent allu vium near the Platte River site, which is hydraulically connected to t he Platte River. Organonitrogen herbicides dominated the pesticide dis tributions at each site. Variations in the distributions of pesticides at the two sites partly reflect differences in land use and land mana gement practices. Diazinon, an insecticide used in areas, was commonly detected at the Platte River site but not at the Maple Creek site. Of the 46 pesticides analyzed at the Platte River site, the herbicides a trazine and alachlor were more likely to exceed their respective maxim um contaminant levels of 3.0 and 2.0 mu g/L; cyanazine was more likely to exceed the health level of 1.0 mu g/L.