Oxidation Rate of Sulphite on Decomposing Leaf Litter

Authors: Şükrü DURSUN, Lynne BODDY, Juliet C. FRANKLAND, Phil INESON

Abstract: Sulphite (SO_3^{2-}), the major solution product of SO_2, has been shown to inhibit leaf litter decomposition at concentrations occurring in urban rainfall. The rate of oxidation of SO^{2-}_3 on leaf litter is a major factor in determining the effect of this inhibition and this study investigated the oxidation rate of SO^{2-}_3 to sulphate (SO^{2-}_4) when applied to decomposing Scots pine ( Pinus sylvestris L.) needle litter under laboratory conditions. Measurements showed that SO_2 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 SO^{2-}_3) to Scots pine litter, about 80% of the SO^{2-}_3 oxidised in 5 h, and SO^{2-}_3 was not detected after 24 h. The time period over which SO^{2-}_3 underwent oxidation at environmentally-realistic concentrations was sufficient to affect microbial decomposition processes in soil and leaf litter.

Keywords: Leaf Litter, Scots Pine, Sulphite Measurement, Sulphite Oxidation

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