TECHNIQUES FOR PRESERVING AND DETERMINING ALUMINUM 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 di fferent Al fractions in soil solution samples, and 2) to determine a s uitable method for analysing monomeric Al concentrations in water samp les from humus-rich podzolic soils. Aluminium fractionation was perfor med on a cation exchange column and the fractions were analysed by ICP /AES and FIA. A lime lag of a few hours to two days between sampling a nd pretreatment appeared to have no effect on total Al concentrations, even though the samples were not preserved with acid. Freezing the sa mples was not an appropriate storage technique because it resulted in a strong decrease in total Al concentrations. Storage (+4 degrees C) h ad a detrimental effect on the proportion of exchangeable monomeric Al , but this problem was overcome by fractionating the samples immediate ly on arrival at the laboratory. Adjustment of sample pH to <3.7 permi tted storage of the fraction for at least 2 weeks before analysis by I CP/AES or FIA. Either of these two techniques can be used for determin ing exchangeable monomeric Al, but if the non-exchangeable reactive Al fraction (i.e. organically complexed Al) is required then analysis by FIA is necessary. (C) 1998 Elsevier Science Ltd.