Episodic acidification in northern Sweden: a regional assessment of the anthropogenic component

Spring flood is the period in boreal ecosystems that is most sensitive to acid deposition since as much as half of the yearʹs precipitation melts and enters streams or the soil in the space of a few weeks. The ‘Episode Project‘ in northern Sweden found a consistent relationship between the SO42− concentration of snow and the anthropogenic component of acid neutralization capacity (ANC) decline during spring flood. This correlation creates the possibility for a regional prediction of the severity of anthropogenic episodic acidification during spring flood episodes using SO42− deposition data together with chemical data from 1240 lakes selected to be representative of northern Sweden. The regional assessment found that in 1998, ca 6% of the region was seriously affected by anthropogenic acidification during spring flood. The results from this study have important implications for both the national liming strategy and international negotiations to further reduce emissions of air pollutants in Europe.