Interaction of synthetic organic contaminants with natural colloidal materials. Research technical completion report, 14-08-0001-G1559-02

Approximately 90 percent of the public water supply in Idaho originates from groundwater, thus making potential pesticide contamination a key issue. A small, but significant portion of the applied pesticide is transported through the soil column more quickly than predicted by currently available models. It has been proposed that increased pesticide mobility occurs as a result of pesticide complexation with a water soluble soil organic fraction, in which the pesticide-organic complex moves faster than the pesticide alone. The present research project is being conducted to (1) develop the methodologies for qualitatively and quantitatively studying pesticide complexation with water soluble soil materials, (2) define the key variables controlling complexation, (3) compare predicted complexation and pesticide mobility alteration with actual results obtained in simulated field situations, and (4) propose a model input variable to produce more accurate estimates of pesticide transport in soil. This report presents the second year results of the three-year study, focusing on objectives 1 and 2. It is organized in chapters, each of which is intended as a separate peer review publication. We have: obtained the spectra of humic materials in aqueous solution; developed methods to obtain unaltered organo-mineral colloids from soils and non-destructively measured the C and N content of these colloids; extensively studied the fluorescence characteristics of a cationic herbicide (difenzoquat); and confirmed that humic acid interacts with nonionic synthetic organic compounds in a partitioning manner and therefore is a potential carrier for nonionic contaminants in the soil