Dissipation processes of 14 C-carbofuran in soil from Northwest Morocco as influenced by soil water content, temperature and microbial activity

Abstract

In order to predict the fate of carbofuran in soil, this study was undertaken to evaluate the influence of soil temperature, soil moisture and soil microbial activity on mineralisation and dissipation rate of carbofuran on a typical sugar beet clayey soil of Loukkos area (Northwest Morocco). Results of incubation studies showed that soil temperature and soil water contents have great influence on mineralization and dissipation rates of carbofuran, and soil autoclaving process significantly increased the half-life of the insecticide. The degradation and mineralization rates in non-autoclaved soil increased with increasing soil temperature and soil moisture content. Carbofuran dissipation rates followed first-order kinetics with half-lives ranged from 26 to >90 days in natural soil. In the autoclaved soil however, the half-life increased 3.2-folds from 39 to 142 days. Mineralization was inhibited by autoclaving, indicating the importance of microorganisms in the breakdown process of the insecticide, and in mean time, the insecticide seems to have been degraded by non-biological process since bound residues were formed with high amount (19%) in the autoclaved soil. These data could be helpful for risk assessment studies of the insecticide and for validating pesticide dissipation models for clayey soils in Moroccan sugar beet-growing areas. Key words: Carbofuran, 14C radiotracer, dissipation, soil.