Influence of soil moisture on sulphur oxidation in brown earth soils exposed to atmospheric pollution.

Laboratory studies were conducted to determine the influence of soil moisture on S oxidation in atmospheric-polluted brown earth soils. Elemental S was oxidized to sulphate over a wide range of soil moisture treatments (10%-60% w/w), but occurred optimally at around 40%-50% soil moisture content (0.08 MPa). Thiosulphate and tetrathionate were found only in soils incubated at low moisture contents. S-oxidation generally acidified the soils, but an increase in soil pH occurred at high moisture levels, where soils were waterlogged. The S oxidative ability of soil samples collected at monthly intervals and incubated with elemental S in the field-moist state was also strongly influenced by soil moisture content. The rate of sulphate production was greatest in the brown earth soil exposed to heavy atmospheric pollution from a coking works. [ABSTRACT FROM AUTHOR]