Beginning of Essay
Lake Barkevatn in Aust-Agder county used to have healthy stocks of trout and perch. As a result of acid rain, the trout stock died out in the mid-1970s and the perch stock at the beginning of the 1980s. · Precipitation that is polluted by sulphur dioxide (SO2) ....

Middle of Essay
.... were reduced by more than 70 per cent. · As a result of higher precipitation in recent years, sulphur deposition has not dropped as much as might be expected from the reductions in emissions. · Estimates of how much pollution the environment can absorb without damage are called critical loads. · Sulphur, like nitrogen, is essential to all animals and plants. The natural sulphur cycle includes volcanic emissions, sulphate in sea salts, and sulphur compounds produced by marine organisms. On a global basis, emissions from such sources are of about the same order of magnitude as those from the combustion of fossil fuels (coal and oil), ....