Heterogeneous photo-oxidation of pesticides and its implication to their environmental fate

Yael Dubowski, Civil and Environmental Engineering, Technion, Haifa, Israel

The environmental fate and impact of pesticides strongly depend on their post application degradation processes. While most existing knowledge on pesticides degradation refers to processes within bulk soil and water, applied pesticides may remain on treated surfaces for long duration, exposed to atmospheric oxidants and solar radiation. The resulting photo-oxidation processes may have significant effect on the pesticides` fate, especially in semiarid regions where pesticide application take place during the dry season and targeted irrigation is common.

Here we present our studies on heterogeneous photo-oxidation of few commonly used pesticides, including: kinetics, quantum yields, and identification of gaseous and condensed products. In addition, the reactivity of the selected pesticides was investigated as a function of their matrix (analytical vs. commercial formula),  phase (thin film vs. airborne aerosols), and the substrate they are sorbed on (leaf, soil, and glass). Different techniques and novel laboratory setups have been used, which combines FTIR spectroscopy and chromatography for simultaneous analysis of both phases.

Complimentarily to these laboratory studies, field measurements of pesticides concentrations in few streams in northern Israel during the first rain events have also shown the important role of surface processing on pesticides fate and transport in semi-arid climate.