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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. [Display omitted] • Twelve CUPs and five legacy OCPs were measured in air at four mountains across Southern British Columbia. • Air concentrations for CUPs varied greatly from mountain-to-mountain and site-to-site. • CUP concentrations correlated well with regional pesticide sales. • Declining source proximity and cold-trapping together contribute to lower concentrations of CUPs in higher-altitude air. • OCP concentrations in the air of all mountains were relatively uniform. [ABSTRACT FROM AUTHOR]

Abstract: Gas-phase and particle-phase atmospheric samples collected in a sparsely populated sub-Arctic environment in the Yukon Territory, Canada were analyzed for a wide range of organic pollutants including polycyclic aromatic hydrocarbons (PAH). Receptor modeling using positive matrix factorization (PMF) was applied to a PAH data set from samples collected between August 2007 and December 2008 to afford four factors. These factors were designated as fossil fuel combustion emissions, particle-phase wood combustion emissions, gas-phase wood combustion emissions, and unburned petroleum/petrogenic emissions. The multiple linear regression-derived average contributions of these factors to the total PAH concentrations were 14% for fossil fuel combustion, 6% for particle-phase wood combustion emissions, 46% for gas-phase wood combustion emissions and 34% for petrogenic emissions. When the total PAH concentrations (defined as the sum of twenty-two PAH) and the PMF-modeled PAH concentrations set were compared, the correlation was excellent (R 2 = 0.97). Ten-day back trajectories starting at four different heights were used in a potential source contribution function analysis (PSCF) to assess the potential source regions of these PAH factors. Mapping the computed PSCF values for the four PMF factors revealed different source regions in the northern hemisphere for each PMF factor. Atmospheric transport of PAH occurred from both relatively short and long distances with both continental (North American) and trans-oceanic (Asian) sources contributing significantly to the total PAH. This study provides evidence of the transport of fossil fuel and wood combustion emissions from Asia, continental North America and northern Europe to sub-Arctic Canada (and by extension to the Canadian Arctic) primarily during cooler (fall-winter) months. This study demonstrates for the first time that the combined PMF-PSCF methodology can be used to identify geographically-disperse PAH source contributors on a hemispherical scale. [Copyright &y& Elsevier]