Environmental Fate of Two Organophosphorus Insecticides in Soil Microcosms under Mediterranean Conditions and Their Effect on Soil Microbial Communities

ABSTRACTAssessing dissipationis an integral part of determining pesticide risk. The adsorption and dissipationcharacteristics of two model insecticides, chlorpyrifos(CHP) and dimethoate(DMT), in a Mediterranean soil were investigated in order to evaluate soil microbial toxicity and to study their soil bioavailability for the purpose of managing pesticide residuewith potential bioremediationof contaminated soil. The aim of this study was also to define novel methods for assessing the ecotoxicityof CHP and DMT on microorganisms in the soil. Koc values ranged between 33420–91601 cm3/g and 129–184 cm3/g for CHP and DMT, respectively, indicating that the former is characterized by a strong adsorption affinity, whereas, the latter has a weaker one. In the dissipationstudy, the half-life(T1/2) of CHP in top soil was 11.55days; whereas, when dissipationwas studied in the same soil sterilized, the half-lifewas 13.86 days, showing a relatively important abiotic degradation effect. For DMT, however, T1/2 ...