Target loads for acidification of Norwegian surface waters

Abstract

Target load is a logical extension of the critical load concept and incorporates the time delays in the chemical recovery from acidification. Calculations based on data from the Norwegian monitoring lakes and the dynamic acidification model MAGIC show that the increased ANC in Norwegian surface waters observed since 1990 can be expected to continue to increase to 2010 if the planned emission reductions of the Gothenburg protocol and other legislation are implemented. With no further reductions after 2010 the ANC will still increase slightly, but very slowly due to slow build up of base cations in the soils. A scenario assuming deposition reduction to background levels of sulphur and nitrogen show that there remains potential for additional increases in ANC if deposition is reduced beyond the Gothenburg protocol. Target loads are considerably lower than critical loads for southern Norway, showing that deposition reductions below the critical load are needed if the goal is to restore conditions suitable for sustainable fish populations within a few decades.