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GLOBAL EFFECTS OF VARIOUS SOIL TREATMENTS ON TRANSFORMATIONS OF CHIRAL PESTICIDES
Citation:
Lewis, D L. AND A W. Garrison. GLOBAL EFFECTS OF VARIOUS SOIL TREATMENTS ON TRANSFORMATIONS OF CHIRAL PESTICIDES. Presented at 20th Annual Society of Environmental Toxicology and Chemistry Meeting, Philadelphia, PA, November 14-18, 1999.
Description:
Many pesticides and other organic pollutants are chiral, and their enantiomers exhibit differences in biological properties, including rates of microbial degradation. We have measured by chiral GC and capillary electrophoresis the enantioselectivity of biodegradation of three pesticides --ruelene (an organophosphorus insecticide) and dichlorprop and methyl dichlorprop (phenoxyacid herbicides) -- as probes of the microbial population character of disturbed/treated and control soil samples from field plots located in Brazil, North America and Norway. We found that each type of disturbance (deforestation) and treatment (nutrient amendments and warming at 5oC above ambient temperature to simulate global warming) shifted enantiomer specificity of the soil microbial populations for biodegradaion of the pesticides. For example, soil microorganisms in most forest samples from Brazil removed the (+) enantiomer of dichlorprop, the active form of the herbicide. By comparison, those in pasture samples almost exclusively preferred the (-) enantiomer. Consequently, in the tropical forests herbicide concentrations determined by conventional achiral methods largely represented the presence of the inactive form. Nutrient enrichments shifted enantioselectivity for the herbicide ester strongly toward preferentially removing the (-) enantiomer, thus potentially increasing the phytotoxicity of herbicide residues. These results show that historical correlations between pollutant exposure and health effects or environmental damage may be unreliable in many cases where chirality has been neglected. Any valid adverse effects of these pollutants could either be abated or exacerbated by future environmental change affecting enantioselectivity of biodegradation processes.