Techniques for preserving and determining aluminium fractions in soil solution from podzolic forest soils

The purpose of the study was 1) to determine techniques for minimising the effects of transportation and storage on the concentrations of different A1 fractions in soil solution samples, and 2) to determine a suitable method for analysing monomeric A1 concentrations in water samples from humus-rich podzolic soils. Aluminium fractionation was performed on a cation exchange column and the fractions were analysed by ICP/AES and FIA. A time lag of a few hours to two days between sampling and pretreatment appeared to have no effect on total A1 concentrations, even though the samples were not preserved with acid. Freezing the samples was not an appropriate storage technique because it resulted in a strong decrease in total A1 concentrations. Storage (+4°C) had a detrimental effect on the proportion of exchangeable monomeric A1, but this problem was overcome by fractionating the samples immediately on arrival at the laboratory. Adjustment of sample pH to <3.7 permitted storage of the fraction for at least 2 weeks before analysis by ICP/AES or FIA. Either of these two techniques can be used for determining exchangeable monomeric A1, but if the non-exchangeable reactive A1 fraction (i.e. organically complexed A1) is required then analysis by FIA is necessary.