| PUBLICATION NUMBER | | AAT 9718795 |  | | TITLE | | Extraction of pesticide residues in soils using multivariate optimization and supercritical fluid extraction | | | AUTHOR | | Zhou, Min Michael | | | DEGREE | | PhD | | | SCHOOL | | UNIVERSITY OF DELAWARE | | | DATE | | 1996 | | | PAGES | | 259 | | | ADVISER | | Sparks, Donald L. | | | ISBN | | 0-591-27127-3 | | | SOURCE | | DAI-B 58/01, p. 171, Jul 1997 | | | SUBJECT | | CHEMISTRY, AGRICULTURAL (0749); ENVIRONMENTAL SCIENCES (0768); CHEMISTRY, ANALYTICAL (0486) | | | DIGITAL FORMATS | |  8.14Mb image-only PDF | | | | Sorption/desorption equilibria and kinetics of atrazine, diuron, and bensulfuron methyl were conducted on several selected soils. The low 1/n$/rm/sb[d]$ (isotherm slope for desorption) values showed that these pesticides were not readily desorbed from the soils tested. The slow rates of desorption were presumably associated with the heterogeneous nature of the soil, and potential hysteresis phenomena. The energy of activation values for both sorption (E$/rm/sb[a]$ = 11-25 kJ/mol) and desorption (E$/rm/sb[d]$ = 18-38 kJ/mol) suggested that transport or diffusion control is rate-limiting for both processes. Pesticide residence time had a major influence on binding extents for all tested pesticides. Extractability as a function of soil composition was greatly dependent on the particular pesticide examined. Effects of supercritical fluid extraction (SFE) parameters on extractability were apparently related to the nature of residues (e.g., freshly fortified versus aged residues), suggesting different desorption mechanisms. Several aged soil samples were extracted by Soxhlet, sonication, surfactant extraction, accelerated solvent extraction (ASE), and SFE for comparison. SFE was the best method to recover aged residues from the soils. Elevated temperature appeared to be a significant factor in effectively recovering aged residues from soils. Prewetting of aged samples was found to be effective in accelerating the extraction rate. Pesticide degradation occurred mostly in soils, but in some cases, it was also observed under laboratory conditions. Degradation basically depended on the characteristics of the pesticide and the nature of the environment.
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