Comparison of spatial patterns of 137 Cs and 40 K in natural grassland soil and soil-to-plant relationship

Abstract

l37 Cs and 40 K activity in natural grassland was studied at two sampling locations in the North-East of Italy, during 1997 and 1999. The present spatial patterns of 137 Cs and 40 K, their mobility and availability for uptake and transfer to grass. To know the spatial and temporal variation of these factors is essential for prediction the radioelement transfer; GIS tools (ILWIS) were applied. The spatial pattern of distribution evidence element redistribution in soil as consequence of the following parts : 1.- 40 K migration allows 137 Cs adsorption by clay soil components, although clays have low retention capacity. 2.- Lateral migration is predominant over vertical migration for both radioelements as consequence of: clay content of low retention capacity, higher porosity and strong acidic pH in site 1 ; low O.M. content, clay content of low retention capacity and moderate acidic pH in site 2. Multitemporal analysis evidences high increment of 137 Cs soil inventory which varies between one and six times. The spatial and temporal variation in 137 Cs soil inventory might be attributed to radioelement redistribution in soil, as shown by the spatial and temporal pattern. Radiocaesium redistribution determines changes in spatial patterns of soil contamination in time. Multitemporal analysis evidences loss of 40 K soil inventory.