Element-pool balances in soils containing rock fragments

The quantification of element pools and their changes in time is an importa nt part of the analysis of ecosystems. This quantification is more difficul t in soils with rock fragments because of their heterogeneity and because o f the difficult analysis of the rock fraction for the pool substance. Repea ted sampling and geostatistical analysis were used to quantify spatial hete rogeneity in rock fragment content. Cs-137 measurements were used to quanti fy fine-earth contamination of dry-sieved and washed rock fragments because they are nondestructive and allowed for Pu239 + 240, C and N were repeated analysis of the same sample after different treatments. determined fur com parison. They are typical for substances that are difficult to be determine d directly in lock fragments and they also occur mainly in topsoils. Small distance heterogeneity may cause an error in rock fragment content of 10% with similar errors biasing the determination of other pools. After dr y-sieving, up to 10% of the Cs-137 pool may still adhere to the rock fragme nts. Washing could remove a further 9% but 1% still remained on the rock fr agments. These fractions will normally be ignored in analyses, which cannot be applied to the rock fragment fraction. Pu, C and N were distributed sim ilarly to Cs-137 between the fine Cs-137 technique therefore allows an easy and less earth from dry-sieving and the wash-off. The laborious estimation of the part of other element pools associated with rock fragments than dir ect measurement, which in many cases is difficult. Where the Cs-137 techniq ue is used to estimate past erosion, since the: beginning of nuclear bomb t esting, errors of several 100 t ha(-1) soil loss may result if heterogeneit y and Cs contamination of rock fragments are ignored. (C) 2000 Elsevier Sci ence B.V. All rights reserved.