Atmospheric concentrations of current-use pesticides across south-central Ontario using monthly-resolved passive air samplers

In this study passive air samplers (PAS) were deployed on a monthly basis at a number of sites along a south-north transect, extending 700 km north from Toronto, Ontario, characterizing an urban-agricultural-forested gradient, to investigate the spatial and temporal trends of current-use pesticides (CUPs), between spring 2003 and spring 2004. The most frequently detected CUPs were chlorpyrifos, dacthal, trifluralin, and alpha-endosulfan. Highest air concentrations of chlorpyrifos were observed in May, whereas a-endosulfan and dacthal peaked in July and August. reflecting differences in usage patterns. At the agricultural site, representing the source region of CUPs, chlorpyrifos air concentrations (pg m(-3)) varied from 2700 to 3.2 and alpha-endulsulfan from 1600 to 19. The most frequently detected legacy pesticides were the hexachlorocylcohexanes (alpha-HCH and gamma-HCH). For the forested sites, located on the Precambrian Shield, a region with limited agricultural activity, seasonal differences were less pronounced and air concentrations were observed to be much lower. For instance, air concentrations (pg m(-3)) of chlorpyrifos and a-endosulfan ranged from 7.6 to 0.3 and 50 to 2.0, respectively. By combining PAS data with trajectory air shed maps it is demonstrated that potential source-receptor relationships can be assessed. Air shed maps produced in this study indicate a potential of increased deposition of CUPs to Lake Erie and Lake Ontario. (C) 2008 Elsevier Ltd. All rights reserved.