Chemical composition of soil solutions from forest lands under anthropogenic pressure: comparing two extract recovery methods

Investigations were carried out on sandy forest soils from Wielkopolski National Park (west-central Poland), which have been exposed for a long time to anthropogenic pressure. Two comparative extract recovery methods were performed for aqueous soil extracts (ME) at ratios 1:1, and those obtained from so-called saturated paste (MP). Recovered extracts were analyzed for sodium, potassium, magnesium, calcium, aluminium, chloride, fluoride, nitrate and sulphate concentrations, at various depths of two slightly different soil profiles. Higher levels of alkaline cations were obtained in extracts recovered at ratios 1:1, in the case of sandy soils along the entire profile, whereas in profiles with variable lithology, the granulometric composition clearly affected the mechanism of ion release. The patterns of changes in the contents of chlorides and sulphates were similar to those of calcium and magnesium, while fluoride levels in the topsoil differed significantly, depending on the method applied. Differences between the two methods were also significant in the case of aluminium content. The elaboration of aluminium toxicity indices should consider such approaches.