Extraction and photolysis of pesticides on soil

Fitzpatrick, Lisa (2000) Extraction and photolysis of pesticides on soil. Doctoral thesis, University of Northumbria at Newcastle.

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Abstract

Pressurised fluid extraction (PFE), or under the Dionex tradename, Accelerated solvent extraction (ASE TM) is a solvent extraction technique based on high pressure and temperature. PFE has been used to extract a wide range of analytes from both spiked and unspiked soils. The PFE extraction parameters of temperature, pressure, static extraction time, and number of static flush cycles were optimised for each of the chosen analytes, pentachlorophenol (PCP), bupirimate (5-butyl-2-ethylamino-6-niethylpyrimidin-4-yldimethylsulphamate), ethirimol (5-butyl-2-ethylamoino-6-methylpyrimidin-4-ol), DDT (1, 1, 1-trichloro-2,2-bis(p-chlorophenyl) ethane), DDD (1, 1-dichloro-2,2-bis(p-chlorophenyl) ethane) and DDE (1, 1-dichloro-2,2-bis(p-chlorophenyl) ethylene). The PFE methodology was validated by extracting natively contaminated soil, aged spiked matrices and a certified reference material. Further investigation into the extraction procedure prompted a more detailed investigation into the selection of the extraction solvent, culminating in a model to predict the optimum solvent for extraction. The model is based on the Hildebrand solubility parameter, and has been applied to spiked and aged matrices, a certified reference material, and examples from the literature. The model was determined to be robust for contaminated soil and sediment.
An investigation into the photolysis of selected pesticides, PCP and bupirimate on soil was performed. The soil matrix was deemed to have a significant effect on the rate of degradation. PCP degradation followed first order kinetics, with a soil dependent rate constant between - 8.69 x 10-6 s-1 for compost and - 2.00 x 10-6 s-1 for mix 2. PLS determined that the sand and organic matter content of the soil was important in the degradation of PCP. Application of PLS to the results of bupirimate photolysis
determined that percentage sand and organic matter content significantly effected the rate of photolysis, and that percentage silt and percentage clay influenced the rate to a lesser extent.

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