Oxidation of sulphite originating from flue gas desulphurization waste in soil.

The rate of catalyzed oxidation of sulphite originating from flue gas desulphurization (FGD) waste was studied under varying conditions. The pH dependence was examined in aqueous solution at the pH range of 5 to 8, the effect of soil moisture was studied in sieved soil of different moisture contents, and the oxidation of sulphite to a soil as FGD waste, was measured at different depths in a field experiment. The experiments that the half-lives of sulphite in aqueous solution were between 0.5 and 2 hours and that the oxidation rate was highest at the lowest pH. In sieved soil the half-lives of sulphite were in the range of 3 to 20 days with the oxidation rate at the highest moisture content, indication that oxygen availability was the limiting factor. The slowest decrease of the sulphite concentration was found at a soil depth of 8-10 cm which was the where the highest background concentration of sulphite was found in control plots, too.