Association Between Local Land Use and Herbicide Concentrations in Wetlands of the Platte River Basin, Nebraska

Association between local land use and concentrations of selected herbicides in wetlands was examined at 31 sites in Nebraska. Sites were selected based on water depth, surface area, and the management of sites as wildlife habitat. In May and August 1994, water-column samples were collected at each of the sites and were analyzed for selected herbicides. The wetlands were categorized into three groups consisting of 8 to 13 sites, each based on a cluster analysis of land use within a 1-kilometer radius. Sites in group 1 contained about 74 percent rangeland; group-2 sites contained about 14 to 30 percent each of rangeland, cropland, and wetland; and group-3 sites contained about 78 percent cropland. Significant differences in herbicide concentrations in the water column between groups were identified using Wilcoxon-Mann-Whitney tests. Atrazine and total herbicide concentrations in the water column were found to be significantly different between groups 1 and 3 and groups 2 and 3 in both May and August. Atrazine and total herbicide concentrations between groups 1 and 2 were not significantly different in May or August samples. These results indicate that herbicide concentrations in the water column in wetlands within the Platte River Basin may be directly related to local land use.