Long-term changes in acidification and recovery at nine calibrated catchments in Norway, Sweden and Finland

International audienceInternational agreements to reduce the emissions of acidifying pollutants have resulted in major changes in deposition of sulphur and nitrogen in southern Scandinavia over the past 25 years. Long-term monitoring of deposition and run-off chemistry over the past 12-25 years at nine small calibrated catchments in Finland, Norway and Sweden provide the basis for analysis of trends with special attention to recovery in response to decreased sulphur and nitrogen deposition in the 1980s and 1990s. During the 1980s and 1990s sulphate deposition in the region decreased by 30 to 60%, whereas inorganic nitrogen deposition showed very little change until the mid-1990s. Deposition of non-marine base cations (especially calcium) declined in the 1990s most markedly in southern Finland. Run-off response to these changes in deposition has been rapid and clear at the nine catchments. Sulphate and base cations (mostly calcium) concentrations declined and acid neutralising capacity increased. Occasional years with unusually high inputs of sea-salt confound the general trends. Trends at all the catchments show the same general picture as that from small lakes in Scandinavia and in acid-sensitive waters elsewhere in Europe. Keywords: acidification, recovery, Scandinavia, catchment, trend analysi

A modelling assessment of acidification and recovery of European surface waters

The increase in emission of sulphur oxides and nitrogen (both oxidised and reduced forms) since the mid-1800s caused a severe decline in pH and ANC in acid-sensitive surface waters across Europe. Since c.1980, these emissions have declined and trends towards recovery from acidification have been widely observed in time-series of water chemistry data. In this paper, the MAGIC model was applied to 10 regions (the SMART model to one) in Europe to address the question of future recovery under the most recently agreed emission protocols (the 1999 Gothenburg Protocol). The models were calibrated using best available data and driven using S and N deposition sequences for Europe derived from EMEP data. The wide extent and the severity of water acidification in 1980 in many regions were illustrated by model simulations which showed significant deterioration in ANC away from the pre-acidification conditions. The simulations also captured the recovery to 2000 in response to the existing emission reductions. Predictions to 2016 indicated further significant recovery towards pre-acidification chemistry in all regions except Central England (S Pennines), S Alps, S Norway and S Sweden. In these areas it is clear that further emission reductions will be required and that the recovery of surface waters will take several decades as soils slowly replenish their depleted base cation pools. Chemical recovery may not, however, ensure biological recovery and further reductions may also be required to enable these waters to achieve the "good ecological status" as required by the EU Water Framework Directive

Review of the Gothenburg Protocol: Chemical and biological responses in surface waters and soils (ICP Waters report 89/2007)

Monitoring data from ICP Waters and ICP Integrated Monitoring as well as other sources show clear and large regional recovery in surface water chemistry in response to the large decreases in deposition of sulphur and to a lesser extent nitrogen since the mid-1980s. Waters have become less acidic and less toxic to biota. At many sites sulphate concentrations now approach the low levels expected following full implementation of the Gothenburg protocol. Nitrate, on the other hand, does not show consistent trends, and most sites are far from steady-state conditions. Results of multivariate statistical gradient analysis suggest that coniferous defoliation, discolouration and lifespan of needles in the diverse phenomena of forest damage are explained by the combined action of ozone and acidifying sulphur and nitrogen compounds in air. Dynamic models and critical load mapping indicate that a significant number of sites in several regions of Europe will continue to be acidified after 2010. Biological recovery has begun in many regions, but lags behind chemical recovery. Future climate change will affect acidification and recovery

Joint Workshop on Confounding Factors in Recovery from Acid Depositon in Surface Waters, 9-10 October 2006, Bergen, Norway; Summary and Abstracts (ICP Waters report 88/2006)

Statens ForurensningstilsynUnited Nations Economic Commission for Europe (UNECE)Swedish Environmental Protection AgencyMinistry of the Environment, FinlandCommission of European Communities, Directorate General for Researc