Elemental and base anions deposition in the snow cover of north-eastern Estonia - The impact of industrial emissions

Snow samples from 18 sites in Estonia were collected in February and March 1996 after 72-110 days of permanent snow cover. Three snow layers correspon ding to different snow accumulation periods were separated in each sampling site. Snow water samples were analysed for sulphate (SO42-), nitrate (NO3- ), and chloride (Cl-) ions and elemental composition. Deposition fluxes of 27 chemical species were used for factor, cluster and correlation analysis. The effects of cement dust, oil shale fly ash, sulphur dioxide and chlorin e from emissions of thermal power plants were distinguished. A large number of trace metals are strongly correlated with each other (R > 0.8) and with macro-components (except NO3-), which refers to a common origin, identifie d as the mineral part of oil shale. Deposition fluxes of Ca, Mg, SO42- and a number of mineral components exceed near the power plants 1-2 decimal ord ers the background value. The deposition fluxes in forested sites are up to 2 times higher than in open land sites. This difference may be caused by m ore efficient turbulent transfer over rougher surface. It is suggested, tha t NO3- and Zn originate mainly and Pb, Cd and Cu partially from non-local o r diffuse sources (traffic, domestic heating, far transport). The results o f this research could be used to evaluate the air pollution deposition mode ls and for ecological impact estimations.