Acid rain

At the UN conference on the ‘Human Environment’ in 1972, in Stockholm, a Swedish case study on transport of air pollutants over national boundaries was presented. Its political and scientific message led to immediate consequences for legislation and research (Anonymous 1972, 1982). The large-scale effects of combustion of fossil fuels containing sulfur and nitrogen, as well as roasting of sulfide ore containing copper and other metals, were now acknowledged as harmful to organisms and ecosystems. The small-scale effects of mining operations have, on the other hand, been well known for hundreds of years. Linnaeus' (1734) experience from the copper mine in Falun, in the province of Dalecarlia, central Sweden (Box Pro.1), is one example. Here the production of copper from ore with high levels of sulfur led to emissions of sulfur dioxide that had direct toxic effects on trees and other vegetation. The soils in the surroundings were acidified and heavy metals accumulated, with consequences for soil biological processes. Nearby lakes were also acidified (Ek et al. 2001).