This study covered soils containing sulphides (Potential Acid Sulphate Soils - PASS), located on Karsiborska Kępa Island (NW Poland). The aim was to analyse changes in some soil properties caused by the oxidation of sulphides to sulphates for developing a new methodology. Soil samples taken from one representative pedon were oxidized under laboratory conditions for 8 weeks (incubation method). During this period the concentration of sulphates and pH in the soil extract was measured at multi-day intervals. Soil organic horizons characterized by a relatively high content of total sulphur (> 0.75%) showed no decrease in pH below 4 due to the oxidation. The opposite was observed in the case of sandy horizons, poor in sulphur. The rate of pH decline during incubation was the highest in the initial period of oxidation, which justifies the need to perform some soil analyses in samples of fresh /wet soil within 48 hours of sampling. The results enabled us to propose a procedure for soils containing sulphides, which included both field and laboratory tests, with special care taken to preserve as much as possible the natural reducing environment.

17.3.2012