Problems of selenium fractionation in soils rich in organic matter

Hydride generation atomic absorption spectrometry (HGAAS) was used for the determination of Se in soils. Potential interferences from metal ions and s pectral interference in the heated quartz tube were documented and eliminat ed. The efficiency of four acid-based closed vessel decomposition procedure s was checked with certified reference soils and a pressured microwave samp le preparation using (1 + 1) HNO3 : H2SO4 was recommended for the determina tion of total Se components in soils. The effect of a high content of organ ic matter on the reliable determination of Se was examined and eliminated. A sequential extraction procedure was developed for the determination of th e speciation of Se in a forest soil profile. The detection Limit for the to tal Se determination was 6 ng Se/g soil, and the relative standard deviatio ns were <5% after application of the sequential extraction procedure. The p roposed method was applied to a red forest soil sample and the vertical dis tribution of Se species in the soil profile was investigated and evaluated. (C) 2000 Elsevier Science B.V. All rights reserved.