Seasonal changes in the sulphate content of deciduous woodland soils exposed to atmospheric pollution

Seasonal changes in soil pH, sulphate concentration and total-S were measured in two brown earth soils, sampled from deciduous woodlands. One site studied was exposed to severe atmospheric pollution from a coking works while the other site was relatively unpolluted but located in an area receiving wet and dry deposited acidity of greater than 1.0 and 2.4 kg H(+) ha(-1) year(-1), respectively The pH of soil at the heavily polluted site was lower than the relatively unpolluted soil at each monthly sample point, except during November. Annual average sulphate concentrations (LiCl-extractable) were highest in the soil exposed to coking pollution, where they peaked during summer and autumn. A marked difference in total-S was found in soils from the two sites, the heavily polluted soil showing the highest concentration with peaks again occurring during late summer and autumn. Only 4.0% (w/w) of the total-S of the heavily polluted soil occurred as LiCl-extractable sulphate, compared to 21.4% (w/w) for the relatively unpolluted soil, showing that organic sulphur is increased in brown earths following exposure to severe atmospheric pollution from the coking works.