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The Canadian Atmospheric Network for Currently Used Pesticides (CANCUP) was the first comprehensive, nationwide air surveillance study of pesticides in Canada. This paper presentsthe atmospheric occurrence and distribution of pesticides including organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), acid herbicides (AHs), and neutral herbicides (NHs) during the spring to summer of 2004 and 2005 across agricultural regions in Canada. Atmospheric concentrations of pesticides varied within years and time periods, and regional characteristics were observed including the following: (i) highest air concentrations of several herbicides (e.g., mecoprop, triallate, and ethalfluralin) were found at Bratt's Lake, SK, a site in the Canadian Prairies; (ii) the west-coast site at Abbotsford, BC, had the maximum concentrations of diazinon; (iii) the fruit and vegetable growing region in Vineland, ON, showed highest levels for several insecticides including chlorpyrifos, endosulfan, and azinphos-methyl; (iv) high concentrations of atrazine and metolachlor were measured at St. Anicet, QC, a corn-growing region; (v) the Kensington site in PEI, Canada's largest potato-producing province, exhibited highest level of dimethoate. Analysis of particle- and gas-phase fractions of air samples revealed that most pesticides including OCPs, OPPs, and NHs exist mainly in the gas phase, while AHs exhibit more diversity in particle-gas partitioning behavior. This study also demonstrated that stirred up soil dust does not account for pesticides that are detected in the particle phase. The estimated dry and wet deposition fluxes indicate considerable atmospheric inputs for some current-use pesticides (CUPs). This data set represents the first measurements for many pesticides in the atmosphere, precipitation, and soil for given agricultural regions across Canada.

[1] Contributions to atmospheric sulphate aerosol and precipitation in the Fraser Valley and at Saturna Island, Canada, from oxidation of biogenic dimethyl sulphide were determined using an isotopic mass balance approach. The S-isotope composition of aerosol sulphate, and sulphur dioxide from a variety of industrial sources in the region were investigated and were found to have d 34 S values ranging between À1.6 and +9%. Isotopic analysis suggests a U.S. oil refinery and/or H 2 S from tidal flats on the coast contributes to the aerosol sulphate load in both summer and winter. On average, wellmixed air in the region had d34 S values for SO 2 near +1%. Assuming this represents the average isotope composition of multiple sulphate sources from urban pollution, refinery emissions, and H 2 S, the DMS contributions to sulphate aerosol were calculated. On average, biogenic DMS-sulphate made up 30% of the non-sea salt sulphate in precipitation at Saturna Island in the Strait of Georgia. In contrast, it comprised only 13% of the aerosol sulphate load in the Fraser Valley. Proportionately more DMS aerosol sulphate is observed at Powell River and on Vancouver Island than in the vicinity of the city of Vancouver. Estimated concentrations are highest in the north, reaching 1.4 mgS/m 3 . These results are consistent with the isotope composition of oxygen in sulphate which show that at least half the aerosol sulphate in the Fraser Valley is formed from oxidation of SO 2 at ambient temperatures.

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