Modelling the impacts of European emission and climate change scenarios on acid-sensitive catchments in Finland

摘要

The dynamic hydro-chemical Model of Acidification of Groundwater inCatchments (MAGIC) was used to predict the response of 163 Finnish lakecatchments to future acidic deposition and climatic change scenarios. Futuredeposition was assumed to follow current European emission reductionpolicies and a scenario based on maximum (technologically) feasiblereductions (MFR). Future climate (temperature and precipitation) was derivedfrom the HadAM3 and ECHAM4/OPYC3 general circulation models under two globalscenarios of the Intergovernmental Panel on Climate Change (IPCC: A2 andB2). The combinations resulting in the widest range of future changes wereused for simulations, i.e., the A2 scenario results from ECHAM4/OPYC3(highest predicted change) and B2 results from HadAM3 (lowest predictedchange). Future scenarios for catchment runoff were obtained from theFinnish watershed simulation and forecasting system. The potential influenceof future changes in surface water organic carbon concentrations was alsoexplored using simple empirical relationships based on temperature andsulphate deposition. Surprisingly, current emission reduction policieshardly show any future recovery; however, significant chemical recovery ofsoil and surface water from acidification was predicted under the MFRemission scenario. The direct influence of climate change (temperate andprecipitation) on recovery was negligible, as runoff hardly changed; greaterprecipitation is offset by increased evapotranspiration due to highertemperatures. However, two exploratory empirical DOC models indicatedthat changes in sulphur deposition or temperature could have a confoundinginfluence on the recovery of surface waters from acidification, and that thecorresponding increases in DOC concentrations may offset the recovery in pHdue to reductions in acidifying depositions.