Trends in soil water composition at a heavily polluted site - Effects of decreased S-deposition and variations in precipitation

Precipitation, soils and soil water in a forested catchment in western Pola nd have been studied during the period 1992 - 96 (see also Vogt et al., thi s conf.). The S-deposition in the area during the study period was 2 - 3g S m(-2) yr(-1). In spite of decreasing anthropogenic emissions the S-deposit ion in the area did not change much during the study period mainly because the first years were exceptionally dry. However, the S-deposition was consi derably higher during the previous decade. Based on soil water sulphate con centration, pH, acid neutralising capacity and the ratio of Al3+/(Ca2+ + Mg 2+), there is apparently an amelioration in the conditions. A study using i nter alia principal component analysis, indicates that this improvement is mainly due to more precipitation in the later part of the study period. Var iations in precipitation amount have a pronounced effect on the soil-water chemistry, which makes it difficult to establish trends caused by changes i n anthropogenic deposition. Long time series are therefore necessary to est ablish recovery due to reduced S-emissions.