Perturbation of background aerosol at rural sites in the nordic countries

Concentrations of several trace elements have been measured in air samples collected simultaneously at four remote stations from SW Sweden, along the Norwegian coast to north Finland. The samples showed that the background aerosol had a large spatial variation in elemental composition. During cases of long-range transported air pollution (episodes), concentrations of pollutants were several times higher than the background concentrations. Generally, the background concentration profile varied, showing a decrease in concentrations towards northwest. The levels of some elements were elevated at the northernmost station as a result of influence from the industrialised areas at the Kola Peninsula. Trends of concentrations from 1985 and onwards were followed at one of the sites. The highest concentration of trace elements in the fine fraction of particles was observed in the mid-1980s, and a considerable decrease is observed during later years. Elemental signatures were calculated and compared with the same ratios from large source areas.