CHARACTERIZATION OF MECHANISMS OF PESTICIDE RETENTION IN SOILS USING THE SUPERCRITICAL-FLUID EXTRACTION TECHNIQUE

This research determined the relative effectiveness of supercritical f luid extraction (SFE) in extracting atrazine and its metabolites from soils which had been treated with atrazine for varying periods of time in order to characterize binding mechanisms. Aqueous methanol extract ion was more effective than SFE in removing C-14-atrazine residues fro m ''aged'' soils. The more polar the solvent system, the more C-14-atr azine residues were extracted. The order of polarity and extractabilit y was aqueous methanol > SF-CO2/5% methanol > SF-CO2. Atrazine extract ion efficiency using SF-CO2 and SF-CO2/5% methanol decreased as sample s ''aged'' in the field. The less than complete recovery of atrazine r esidues using the SFE technique could be seen as an indication that di fferent binding mechanisms were involved in the retention of atrazine as well as its metabolites and that the binding mechanisms changed wit h time.