Current-use pesticides in ambient air - evaluation of deposition sampling and soil fugacity techniques

The atmospheric fate of current-use pesticides (CUPs) is incompletely understood, and CUPs' air-surface mass exchange has hardly been investigated. In this study, we evaluated techniques to improve our understanding of CUPs’ depositions and volatilisation from soil. Simultaneous sampling of gas-phase air, particulate phase air, wet and dry depositions, soil, and air equilibrated with soil was conducted during the pesticide application season, followed by analysis of 46 CUPs (22 herbicides, 16 insecticides and 12 fungicides) common in European agriculture. CUP deposition fluxes observed suggest that dry deposition of most CUPs is more effective than wet deposition in central Europe. Potential soil fugacity derived from CUP concentration in soil indicated the significance of soil organic matter on the absorption and retention of CUPs in soil. Using a fugacity meter, empirical evidence for net volatilisation of CUPs including the high-risk pesticides chlorpyrifos and pendimethalin from a non-agricultural soil is found for the first time. This suggests that CUPs can be subject to multiple emission-deposition cycles, which enhances their long-range transport potential. More method refinements and field measurements are needed for a mechanistic understanding of diffusive soil-air exchange processes.