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

This research determined the relative effectiveness of supercritical fluid 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 extraction was more effective than SFE in removing C-14-atrazine residues from ''aged'' soils. The more polar the solvent system, the more C-14-atrazine residues were extracted. The order of polarity and extractability was aqueous methanol > SF-CO2/5% methanol > SF-CO2. Atrazine extraction efficiency using SF-CO2 and SF-CO2/5% methanol decreased as samples ''aged'' in the field. The less than complete recovery of atrazine residues using the SFE technique could be seen as an indication that different binding mechanisms were involved in the retention of atrazine as well as its metabolites and that the binding mechanisms changed with time.