Sulphur pollution – past trends, current levels

Sulphur (S) is an essential element for the growth and activity of organisms, occuring free in abundant quantities. It is found in valence states ranging from +6 in sulphates to -2 in sulphides, the most stable state being S6+. Globally, natural emissions of S into the atmosphere from biogenic sources have been estimated to range between 78.9 and 142.6 Tg yr-1, of which 5.0 to 63.9 Tg yr-1 arises from land (Schlesinger, 1991; Andreae & Jaeschke, 1992; Germida, Wainwright & Gupta, 1992). Estimates of the relative significance of anthropogenic to natural sulphur emissions are variable, but globally the ratio is probably about 4: 1 (Möller, 1984), atmospheric S emissions from land being in the order: anthropogenic 93 Tg yr-1 > biogenic gases 22 > dust 20 > volcanoes 10 (Brimblecombe et al., 1989). Sulphur emissions to the atmosphere are not constant with time, having increased dramatically since the industrial revolution as a result of combustion of fossil fuels. Global anthropogenic emissions have increased from an estimated 5 Tg in 1860 to 180 Tg in 1985, with considerable increases predicted up to 2000 (Fig. 6.1; Möller, 1984; Schlesinger, 1991), despite electives by European countries to have reduced emissions by 1993 to 30% of 1980 emissions.