SULFUR ISOTOPE FRACTIONATION DURING THE OXIDATION OF ELEMENTAL SULFUR BY THIOBACILLI IN A SOLONETZIC SOIL

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Abstract
The oxidation rate of elemental S added to a Solonetzic soil was compared between an uninoculated soil and soils inoculated with two species of thiobacilli. Twelve weeks after S was added, 24% was oxidized to soluble S anions in the uninoculated soil, 34% in soil inoculated with Thiobacillus thiooxidans, and 84% in soil inoculated with Thiobacillus thioparus. The SO42− produced during S oxidation by thiobacilli was enriched in the lighter isotope by an average of 1‰ in comparison with the substrate S. Therefore, 34S-enriched S could be applied to Solonetzic soils and the migration of biologically produced H2SO4 into the soil profile may be followed by isotopic analysis of the soil sulfate.