The 12-year report: Acidification of Surface Water in Europe and North America Trends, biological recovery and heavy metals (ICP Waters report 52/2000)

Abstract

The International Cooperative Programme on Assessment and Monitoring of Acidification of Rivers and Lakes (ICP Waters) is designed to assess the degree and geographical extent of acidification of surface waters, evaluate dose/response relationships and long-term trends in aquatic chemistry and biota. The aim of the 12-year report is to provide an overall synthesis and assessment of information on water chemistry and biology accumulated in the ICP Waters Programme within the last 3 years (1996-98) related to previous findings. The report includes an evaluation of the ICP Waters database and the representativeness of ICP Waters sites, long-term trends in water chemistry at the single ICP sites and on regional scales, characterisation of invertebrates on a regional scale and an assessment of heavy metals. The current ICP Waters database includes only active sites well suited to monitor changes in acidification in response to changes in acid deposition. In the 10-year periode 1989-1998, sulphate concentrations showed significant downward trends while nitrate concentrations showed no regional patterns of change. pH and ANC and also DOC have increased in most regions during the past 10 years. Biological response, reflecting improved water quality, is positive for sites in Scandinavia. In the most acidified sites in Central Europe improvements in water quality have not reached the level at which effects on biology can be detected. Concentrations of heavy metals are generally low in ICP Waters sites not influenced by local pollution sources.