Arctic lower tropospheric aerosol trends and composition at Alert, Canada - 1980-1995

Fifteen years (1980 to 1995) of observations of weekly mean concentrations of 18 constituents in the aerosol of the lower Arctic troposphere at Alert, Canada, are analyzed by time series analysis for seasonal and long-term trends and by positive matrix factorization for aerosol components. The dominant anthropogenic constituent measured is SO4(2-), which is composed of two major components: a neutralized ammonium sulphate salt and a highly acidic sulphate salt. The latter component becomes increasingly prominent as the Arctic atmosphere goes from complete darkness in January to complete sunlight in April, and SO2 is oxidized to sulphuric acid in the northern troposphere. In winter/spring the 18 observed constituents are associated with 10 distinct aerosol factors (components). Most winter/spring pollution comes to Alert from Eurasia. In the 1980s, trends in the winter/spring levels of anthropogenic constituents are evident for some (Pb, Zn, Cu, xV, and xMn) but not for SO4(2-). The lack of trend in SO4(2-) is consistent with no change in emissions in the former Soviet Union between 1985 and 1990. However, since 1991, all of these constituents show a marked decrease, suggesting that the collapse of industry in the early years of the new Eurasian republics has left its mark in the Arctic. (Author)