SULPHATE RELATIONSHIPS IN SOME CENTRAL ONTARIO FOREST SOILS

Abstract

The [Formula: see text] status of sandy, podzolic soils from central Ontario was examined. Water-soluble [Formula: see text] was positively correlated with soil organic C concentrations but not with Fe and Al oxides (citrate-dithionite-bicarbonate minus pyrophosphate extractable Fe and Al). For adsorbed [Formula: see text] the reverse was true. Surface horizons were high in soluble [Formula: see text] and low in adsorbed [Formula: see text] whereas B horizons containing high levels of Fe and Al oxides contained large amounts of adsorbed [Formula: see text] and little soluble [Formula: see text]. Successive distilled water extractions of some samples indicated the removal of almost all soluble [Formula: see text] from surface horizons in one or two extractions. Sulphate, however, remained present in the B horizons after five extractions. The amount of soluble [Formula: see text] extracted was dependent on horizon type and amount of water used for extraction. This makes evident the importance of moisture status, residence time and hydrologic pathways in determining [Formula: see text] release from the soil, and demonstrates the need for in situ studies. Plastic Lake B horizons adsorbed added [Formula: see text] in the laboratory but it was not determined whether this is occurring in the field. Key words: Soluble [Formula: see text], adsorbed [Formula: see text], sulphate, iron oxide, aluminum oxide, podzol