Retention of Pesticides by Alluvial Soils in Western Washington: Experimental Variables, Relation to Soil Properties, and Spatial Variability.

摘要

Interactions of carbofuran, simazine, and metalaxyl with western Washington soils were examined. The project also investigated measurement, interpretation and use of adsorption parameters and the application of geostatistics to pesticide transport problems. Batch equilibration adsorptions were performed, using C-14 labelled pesticides and a range of soil samples reflecting varying properties. Selected experimental conditions were varied to determine their effect on the adsorption parameters. Soil analyses were performed by standard procedures, and results were correlated with pesticide adsorption data. Spatial varability of transport parameters was examined using a sampling scheme designed to optimize the ability to detect spatial dependence. Associated properties were determined by standard methods, and spatial variability was determined using variograms. Information obtained from the batch and spatial studies were used to evaluate conceptual models for describing pesticide transport. Soil/solution ratio and electrolyte concentration both affected batch adsorption parameter determination, although effects were relatively small. Carbofuran adsorption was strongly correlated to organic carbon content, but metalaxyl adsorption was not. Simazine adsorption appeared to be related to organic carbon, but regression analyses failed to show organic carbon as a significant predictor of simazine behavior. For all three pesticides, adsorption to fine-textured subsurface horizons was as strong or stronger than adsorption to surface soils. Transport parameter values were statistically related in space. Under the conditions of the experiments, the movement of water was adequately described by equilibrium transport concepts, while kinetic factors influenced matalxyl transport.