Water chemistry of Swedish forest lakes - influence of lime treatment and acidification

摘要

The deposition of long-range airborne sulphur and nitrogen compounds during the last century has caused an extensive acidification of water systems in large parts of Scandinavia dominated by poorly weathered volcanic bedrock. About 15000 lakes in Sweden were affected by anthropogenic acidification in 1990 (Swedish EPA 1991). As a remedial measure, a large-scale lime treatment programme was implemented in the 1970s, and to date about 7500 lakes have been treated at least once (Swedish EPA 2002). In order to study the long-term consequences of the treatment, a national monitoring programme was started in 1989, with simultaneous measurements in national reference lakes (ISELAW programme; Ap-pelberg et al. 1995). Today, the two groups of lakes include 17 and 15 lakes respectively. The water chemistry of the two groups of lakes and possible signs of recovery are discussed here, with a focus on trace metals.