Articles | Volume 5, issue 3
Hydrol. Earth Syst. Sci., 5, 283–298, 2001

Special issue: Assessment of recovery of European surface waters from...

Hydrol. Earth Syst. Sci., 5, 283–298, 2001

  30 Sep 2001

30 Sep 2001

Recovery from acidification in European surface waters

C. D. Evans1, J. M. Cullen1, C. Alewell2, J. Kopácek3, A. Marchetto4, F. Moldan5, A. Prechtel2, M. Rogora3, J. Veselý6, and R. Wright7 C. D. Evans et al.
  • 1Centre for Ecology and Hydrology, Wallingford, Oxon OX10 8BB, UK
  • 2Institute for Terrestrial Ecosystem Research (BITÖK), University of Bayreuth, D-95440 Bayreuth,Germany
  • 3Hydrobiological Institute AS CR, Na sádkách 7, 370 05 Èeské Budejovice, Czech Republic
  • 4Consiglio Nazionale delle Richerche – Istituto Italiano di Idrobiologia, 28922 Verbania Pallanza, Italy
  • 5Swedish Environmental Research Institute (IVL), Dagjämningsgatan 1, Box 47086, S-402 58 Göteborg, Sweden
  • 6Czech Geological Survey, Geologická 6, 152 00 Praha 5, Czech Republic
  • 7Norwegian Institute for Water Research (NIVA), Box 173, Kjelsas, N-0411 Oslo, Norway
  • Email for corresponding author:

Abstract. Water quality data for 56 long-term monitoring sites in eight European countries are used to assess freshwater responses to reductions in acid deposition at a large spatial scale. In a consistent analysis of trends from 1980 onwards, the majority of surface waters (38 of 56) showed significant (p ≤0.05) decreasing trends in pollution-derived sulphate. Only two sites showed a significant increase. Nitrate, on the other hand, had a much weaker and more varied pattern, with no significant trend at 35 of 56 sites, decreases at some sites in Scandinavia and Central Europe, and increases at some sites in Italy and the UK. The general reduction in surface water acid anion concentrations has led to increases in acid neutralising capacity (significant at 27 of 56 sites) but has also been offset in part by decreases in base cations, particularly calcium (significant at 26 of 56 sites), indicating that much of the improvement in runoff quality to date has been the result of decreasing ionic strength. Increases in acid neutralising capacity have been accompanied by increases in pH and decreases in aluminium, although fewer trends were significant (pH 19 of 56, aluminium 13 of 53). Increases in pH appear to have been limited in some areas by rising concentrations of organic acids. Within a general trend towards recovery, some inter-regional variation is evident, with recovery strongest in the Czech Republic and Slovakia, moderate in Scandinavia and the United Kingdom, and apparently weakest in Germany.

Keywords: acidification, recovery, European trends, sulphate, nitrate, acid neutralising capacity