Legacy and current-use pesticides in Western Canadian mountain air: Influence of pesticide sales, source proximity, and altitude

Abstract

Large amounts of pesticides are applied in agriculture in Canada and around the world. A considerable fraction can be dispersed in the atmosphere and deposited in non-target ecosystems. Our knowledge of the factors controlling the movement of pesticides in the atmosphere is still limited. In order to investigate the atmospheric distribution of pesticides under the influence of diverse environmental variables, we deployed XAD-2 resin-based passive air samplers (PAS) at multiple elevations of four mountains across Southern British Columbia and derived annually averaged concentrations of twelve current-use pesticides (CUPs) and five legacy organochlorine pesticides (OCPs) in air. The four mountains have similar altitude and latitude but vary in their proximity to source regions. Hexachlorobenzene, endosulfan I, and simazine were most abundant with median concentrations exceeding 50 pg/m3. While concentrations were generally lower than elsewhere in Canada, especially in agricultural regions, they varied greatly across the four mountains. Remote Mount Anderson had lower CUP levels than the other three mountains. CUP concentrations correlated well with regional pesticide sales, with two distinct spatial patterns becoming apparent. The OCP concentrations in the air of the four mountains were relatively uniform. CUP concentrations in air usually decreased with increasing altitude, when under the strong influence of ground-level sources. Source proximity and altitude appear to play a much more important role than precipitation and vegetation cover in the distribution of pesticides in the atmosphere. This study also highlights the value of a good registration system for pesticide sales for explaining environmental concentration variability.