The initial sulfate concentration quantified using the procedure described below for the soils used was: (i) 16 μmol g−1 dry soil for the sulfidic soil in the Finniss River, (ii) 32 μmol g−1 dry soil for the manufactured “sulfuric soil” from the sulfidic soil in the Finniss River and (iii) 23 μmol g−1 dry soil for the Gillman neutralized sulfuric soil.