Spatial Variability and Topographic Factors of 137Cs Soil Contamination at a Field Scale

Abstract

The spatial variability of 137Cs contamination was evaluated at a field scale, at three study sites marked by different landscape positions. Two of them are situated in a forest, and one – in a meadow. The sites are located 170 km away from the Chernobyl Nuclear Power Plant. The objectives of the research were (a) to characterise variability of 137Cs contamination across the sites, and (b) to determine and describe any relation of 137Cs contamination with topography. Soil radioactive contamination was measured using in situ radiometric technique. Field radiometry data were analysed using classical statistics and geostatistics. To describe local geometry of the sites, Laplacian models were derived from digital elevation models. A generalised additive model was used to model the dependence of 137Cs spatial distribution on the relief features. For hydromorphic areas of the sites, the variogram analysis showed that the 137Cs spatial distribution consists in patchy patterns with the typical size from meters to tens of meters. For watershed areas, the 137Cs spatial distribution was random and did not form any patterns. The 137Cs distribution is depend crucially on the local topography in hydromorphic conditions. Laplacian is the most informative index for the process of the 137Cs lateral migration while elevation is of subsidiary importance.