Nitrate and Sulphate Wet Deposition in Europe

Abstract

The chemical composition of precipitation and its temporal and spatial pattern were evaluated for Europe. The results base upon data collected under the ECE’s EMEP programme covering the period 1980 to 1984. The average annual nitrate and sulphate concentration in precipitation varies within Europe from 0.1 to 1.0 mgN/1 and 0.2 to 2 mgS/1, respectively. The spatial pattern for both pollutants is very much the same. The main feature is the increase of the values towards central Europe. The annual cycle of nitrate and sulphate in precipitation is less pronounced than the annual cycle of their precursers nitrogen dioxide and sulphur dioxide in ambient air, and the highest concentrations occur later in the year. The nitrate to sulphate equivalent ratio demonstrates the relative contribution of nitrates and sulphates to acid deposition. On yearly average nitrate contributes up to 40% to the acidity in wet deposition. Generally the nitrate to non-marine sulphate ratio is higher in wintertime than in summertime, except at some stations in central Europe. The spatial pattern show higher values at stations in central and northern Europe and lower values in eastern Europe. The wet deposition of nitrate in Europe is governed by the precipitation pattern. Long-range transport of nitrate in precipitation is shown by sector analysed data at several sites. Generally, transport directions associated with high concentrations are directed towards major emission areas.