TRANSECT SURVEY OF RADIOCESIUM IN SOILS AND PLANTS OF 2 ALPINE PASTURES

The spatial distribution of fallout Cs-137 and natural K-40 in soils a nd vegetation of alpine pastures growing on dystric cambisols was stud ied along two transects of approximately 100 m in length following the slopes from top to bottom. Ten years after the Chernobyl accident, th e Cs-137-activity is still concentrated in the upper 5 cm of these soi ls - in most cases in the uppermost two centimeters. The variability o f the radiocesium concentration in the soil along the transects is hig h (coefficient of variance CV = 92%), whereas K-40 is more homogenousl y distributed (CV = 18%). The Cs-137 concentration in the soil is not significantly related to the distance downslope indicating the absence of long-range erosion processes. The variability of the distribution of Cs-137 in plants is also large (CV = 91%). No significant correlati on between Cs-137 and K-40 in vegetation was found. The resulting aggr egated transfer-factors (T-ag) are approximately one order of magnitud e lower than reported for semi-natural environments in other upland ar eas in Europe. A significant relationship of the altitude with the rad iocesium concentration in plants or the resulting T-ag can be explaine d by the occurence of different plant communities along the transect. The significant positive correlation of the radiocesium content in pla nts with the organic matter content in soils, or with the potential ac tivity of microorganisms indicate the importance of biological paramet ers for the in situ availability of radionuclides. (C) 1998 Elsevier S cience B.V.