Abstract:

Sulphite (SO32-), the major solution product of SO2, has been shown to inhibit leaf litter decomposition at concentrations occurring in urban rainfall. The rate of oxidation of SO2-3 on leaf litter is a major factor in determining the effect of this inhibition and this study investigated the oxidation rate of SO2-3 to sulphate (SO2-4) when applied to decomposing Scots pine ( Pinus sylvestris L.) needle litter under laboratory conditions. Measurements showed that SO2 has a short life under atmospheric conditions and oxidises very quickly in the presence of metal ions and in alkaline conditions. After addition of sulphite (0.1 mM SO2-3) to Scots pine litter, about 80% of the SO2-3 oxidised in 5 h, and SO2-3 was not detected after 24 h. The time period over which SO2-3 underwent oxidation at environmentally-realistic concentrations was sufficient to affect microbial decomposition processes in soil and leaf litter.

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