CHARACTERIZATION OF THE SULFUR RETAINED BY SOILS EXPOSED TO HYDROGEN-SULFIDE

We recently reported studies showing that air-dry and moist soils have substantial capacities for sorption of hydrogen sulfide (H2S) from air. Studies to characterize the S retained when air-dry and moist soils were exposed to air containing 2% H2S showed that a large fraction (average 79%) of this S was in the form of elemental S (S(o)) and that very little (0.1% or less) was in the form of sulfide. The recovery of sorbed S as sulfate averaged 5.9% with the air-dry soils and 3.0% with the moist soils. The 42 soils used in this work were selected so that they differed markedly in physical and chemical properties. Statistical analyses of the relationships between these properties and the recovery of sorbed S as elemental S showed that this recovery was significantly correlated with the amount of soil Mn that was extractable by dithionite-citrate buffer. This suggests that Mn compounds in soils catalyze oxidation of sulfide-S to elemental-S when soils are exposed to air containing H2S.