Modeling of Overland Flow Contamination Due to Heavy Metals in Shallow Soil Horizons

Heavy metals in southeast Kansas are frequently found in the shallow soil layers. Rainfall events in this region often generate overland flows which cause the release and migration of these chemicals into surface waters. The chemicals are then transported in surface waters to downstream locations and, as such, pose a threat to the quality of both fields along streams and surface and ground waters. In many instances, overland flow does not develop immediately as a sheet over the land surface, but gradually increases in extent in accordance with the variable source area (VSA) concept. The overland flow regions diminish once the surface water application rate ceases. This paper deals with the modeling of surface contamination under such circumstances. Results were obtained for a single hypothetical plot. These simulation results indicate that source area for heavy metal removal varies in a similar manner to source area of water. Some comparisons were made regarding the relative amounts of solute lost to overland flow and to those leached into the soil as a function of time. The subsurface response was found to be slower than surface response to the rainfall event.