Are there signs of acidification reversal in freshwaters of the low mountain ranges in Germany?

Abstract

The reversal of freshwater acidification in the low mountain ranges of Germany is of public, political and scientific concern, because these regions are near natural ecosystems and function as an important drinking water supply. The aim of this study was to evaluate the status and trends of acidification reversal after two decades of reduced anthropogenic deposition in selected freshwaters of the low mountain ranges in the Harz, the Fichtelgebirge, the Bavarian Forest, the Spessart and the Black Forest. In response to decreased sulphate deposition, seven out of nine streams investigated had significantly decreasing sulphate concentrations (all trends were calculated with the Seasonal Kendall Test). The decrease in sulphate concentration was only minor, however, due to the release of previously stored soil sulphur. No increase was found in pH and acid neutralising capacity (defined by Reuss and Johnson, 1986). Aluminum concentrations in the streams did not decrease. Thus, no major acidification reversal can currently be noted in spite of two decades of decreased acid deposition. Nevertheless, the first signs of improvement in water quality were detected as there was a decrease in the level and frequency of extreme values of pH, acid neutralising capacity and aluminium concentrations in streams. With respect to nitrogen, no change was determined for either nitrate or ammonium concentrations in precipitation or stream water. Base cation fluxes indicate increasing net loss of base cations from all ecosystems investigated, which could be interpreted as an increase in soil acidification. The latter was due to a combination of continued high anion leaching and significant reduction of base cation deposition. No major improvement was noted in biological recovery, however, initial signs of recovery were detectable as there was re-occurrence of some single macroinvertebrate species which were formerly extinct. The results of this study have important implications for water authorities, forest managers and policy makers: the delay in acidification reversal suggests a need for ongoing intensive amelioration of waters, a careful selection of management tools to guarantee sustainable management of forests and the reduction of nitrogen deposition to prevent further acidification of soils and waters.

Modelling long-term changes in stream water and soil chemistry in catchments with contrasting vulnerability to acidification (Lysina and Pluhuv Bor, Czech Republic)

“…Thus, the total deposition of S declined by approximately 75%. Evans et al, 2001;Alewell et al, 2001;Fölster and Wilander, 2002). It appears that sulphur stores in the upper soil horizons at Pluhuv Bor declined markedly in the last decade (Shanley et al, 2004).…”

Land use influences on acidification and recovery of freshwaters in Galloway, south-west Scotland

“…Monitoring the response of surface water chemistry to costly emission reduction programmes is important, as such strategies are partly based on the assumption that improvements in water quality will result (Soulsby et al, 1995). Recent evidence on the reversibility of surface water acidification in acid sensitive areas in Europe is ambiguous: some areas have shown improvement in water quality (Evans and Jenkins, 2000;Tipping et al, 1998;Harriman et al, 1995) whilst other areas show little or no change (Alewell et al, 2001). The degree of reversibility is related to regional differences in deposition inputs, catchment physicochemical characteristics and land use change.…”

Constraints on the biological recovery of the Bohemian Forest lakes from acid stress

“…In contrast, early data on macroinvertebrates gathered during the first decades of chemical recovery and encompassing mostly species with generally longer generation times and limited dispersal, mainly documented the reappearance of acid‐sensitive species and/or increase in their abundance, yet only minor effects on the assemblage composition (e.g. Alewell et al ., ; Tipping et al ., ; Monteith et al ., ; Stendera & Johnson, ). The trends towards more acid‐sensitive assemblages explained by chemical measures of acidity were confirmed for macroinvertebrates in more recent studies (Murphy et al ., ; Stockdale et al ., ).…”