APPLICABILITY OF HNO3-H2O2 DIGESTION FOR ELEMENTAL ANALYSIS OF ORGANIC-MATTER IN MOR HUMUS FORMS

Wet acid digestion is commonly used for the elemental analysis of the labile (i.e. organic, exchangeable plus soluble) pool in organic soil horizons. However, this method is not entirely specific for this pool in samples containing mineral admixtures. In this study, these admixtu res are found to release significant amounts of elements. although the se admixtures are highly quartzitic. A statistical evaluation of ash a nd element concentrations shows that, for a wide range of ash concentr ations, only for phosphorus and calcium reliable concentrations of the ir labile pool were obtained. Acid extraction after dry ashing showed to produce somewhat better results at low ash concentrations, but suff ered from large overestimations at high ash contents as well. Therefor e, elemental analyses in element dynamics studies merit a critical con sideration of the digestion technique used. Implications of overestima tions for such studies are discussed.