Atmospheric deposition in Fenno-Scandia: Characteristics and trends

An overview is presented of the current long-range transport and deposition of sulphur and nitrogen compounds in northern Europe. The discussion is based on known emission trends and changes in fossil fuel consumption patterns, and records of precipitation chemistry and air quality data for background sampling stations since the 1970's. Emission sources contributing to the major part of the sulphate and nitrate concentrations in precipitation are mostly 500 to 100 km from the receptor area. Trend evaluations based on such relatively short data series are uncertain unless meteorological data are available, but measurements do indicate decreasing concentrations of sulphur in air and precipitation at some stations. Less data are available on nitrogen compounds, and no conclusion can be drawn. Photochemical oxidants played an increasing role in relation to large-scale environmental effects, and they had to be considered alongside acidic deposition in future studies.