ACID DEPOSITION TO NATURE AREAS IN THE NETHERLANDS .1. METHODS AND RESULTS

In this paper estimates of dry and wet deposition of acidifying substa nces in the Netherlands are presented. The deposition was estimated fr om measured concentrations in the atmosphere and in precipitation or i f these were not available, from modelled concentrations. The method w as applied for the Netherlands on a 5 x 5 km scale. The most important components are sulphur oxides and ammonia and their reaction products . It was estimated that the annual average deposition of SO(x), in the Netherlands decreased from 1570 to 670 mol ha-1 a-1 between 1980 and 1989. In 1989, the annual average NO, deposition was estimated to be 1 220 mol ha-1 a-1 in 1980 and 1160 mol ha-1 a-1 in 1989. The annual ave rage NH(x) deposition in the Netherlands was estimated to be 2330 and 2190 mol ha-1 a-1 in 1980 and 1989 respectively. HCl deposition was ab out 100 mol ha-1 a-1 in all years. Dry deposition contributes most to the total deposition for each component. The spatial distribution of t he total deposition shows a gradient over the Netherlands with highest values in the South and lowest in the North of the country. Meteorolo gical conditions are also of influence on the deposition fluxes for al l components. During 1988 and 1989 meteorological conditions favoured low deposition. The estimated uncertainty in the average fluxes of SO( x), NO(y) and NH(x) for the Netherlands is 15, 25, and 30% respectivel y. The wet deposition fluxes can be estimated more accurately than the dry deposition.