Time of Travel and Dispersion in a selected Reach of Roberts Creek, Clayton County, Iowa by D.W. Kolpin and S.J. Kalkhoff; Prepared in cooperation with the Iowa Department of Natural Resources, 1992

(1992) Time of Travel and Dispersion in a selected Reach of Roberts Creek, Clayton County, Iowa by D.W. Kolpin and S.J. Kalkhoff; Prepared in cooperation with the Iowa Department of Natural Resources, 1992. Natural Resources, Department of

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Abstract

The eventual fate of the agricultural use of nitrogen fertilizers and pesticides in the environment is unknown. Numerous studies have indicated that runoff from precipitation transports these chemicals into nearby streams and lakes (Schuman and others, 1973; University Hygienic Laboratory, 1977, 1979, 1983; Hallberg and others, 1983; Goolsby and others, 1989). Once in the stream, the nitrate and ammonia from fertilizers are readily available for biological processes. Less is known of the fate of the pesticides in streams. Previous investigations (Kalkhoff, 1989; Kalkhoff and Kuzniar, 1990) have indicated a decrease in both the concentration and load of nitrate and atrazine (a tnazme herbicide) downstream in Roberts Creek during low-flow conditions. Loss of flow from seepage can account, at least partially, for decreases in the chemical load, but has no effect on chemical concentration. Consequently, the change in concentration might be due to physical processes, chemical processes, or the sampling procedure. Because chemical inputs into surface water might vary with time, changes in concentrations measured downstream might be because the same discrete parcel of water was not sampled at each sampling site.