Isoproturon, tebuconazole, and chlorpyrifos are commonly used in Europe for the control of weeds, pathogens and pests in cereals. Within the framework of the IAPP Marie Curie project 'LOVE-TO-HATE', the dissipation/metabolism and soil microbial toxicity of these pesticides were investigated following a lab-to-field experimental approach. Thus, a microcosm laboratory experiment was initially set up where three pesticides were applied at four dose levels, x0, x1, x2, and x10 the recommended dose, establishing a worst-case exposure scenario. Subsequently, a field experiment on a site in Piacenza, Italy cultivated with winter wheat was employed to assess pesticide dissipation and soil microbial toxicity under a more realistic exposure scheme (x0, x1, x2 and x5 the recommended dose). In both studies, subsamples were collected at regular intervals and used for the determination of pesticide dissipation/metabolism and for the detection of possible effects on soil microbial activity. In the laboratory study, tebuconazole and isoproturon showed a dose-dependent increase in their persistence with DT50s ranging from 63 to 99 days for the former and from 16.5 to 25.7 for the latter in the x1 and x10 dose rates, respectively. The dissipation of isoproturon proceeded via sequential demethylation to monodesmethyl-isoproturon (main metabolite), while low concentrations of didesmethylisoproturon were also detected. Chlorpyrifos was metabolized in soil via hydrolysis to trichloropyridinol with its persistence reducing at increasing dose rates (DT50s 28.4 to 77 days in the x10 and x1 dose rate, respectively). Analysis of pesticides dissipation in the field study is on the way. In parallel, the impact of pesticides on nine key soil enzymatic activities was determined at both laboratory and field level. Esterase and leucine aminopeptidase were the most sensitive enzymes which were significantly affected by the pesticides mostly in the laboratory experiment.

Lab-to-field experimental approach to study the dissipation, metabolism, and soil microbial ecotoxicity of isoproturon, tebuconazole, and chlorpyrifos

248th National Meeting (2014)

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