MEASUREMENT OF SULFUR OXIDATION IN SOILS

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Abstract
We developed a new method of measuring sulfur oxidation in soils that would permit a quantitative evaluation of the factors governing oxidation. This method, which is applicable to a wide range of field and laboratory conditions, assumes that oxidation of elemental sulfur proceeds as a function of its total surface area. The oxidation rate was expressed in terms of sulfur oxidized per unit instantaneous surface area per unit time, thereby making it theoretically independent of sulfur particle size and duration of incubation. The method was used to assay the oxidative capacity (rate of oxidation under favorable conditions) of 40 diverse Saskatchewan [Canada] soils. All soils demonstrated a significant capacity to oxidize sulfur (mean rate = 4.8 .mu.g S cm-2 d-1; standard deviation = 1.4 .mu.g S cm-2 d-1). The oxidative capacity of the soils was negatively correlated with soil clay content and positively correlated with soil pH, air-filled porosity, organic carbon content, and sand content. Theoretical analyses, based on the experimentally determined rates of oxidation, were used to illustrate the relative effects of sulfur particle size and soil oxidative capacity on the production of sulfate from elemental sulfur.