Transfer characteristics of radiocaesium from soils to permanent pasture

Abstract

Depth profile measurements of ¹³⁷Cs and ¹³⁴Cs were carried out in 11 permanent pastures that had been exposed to fallout from the Chernobyl accident. In addition to gamma-ray spectrometric analysis, the selected pastures were characterized by several soil parameters, the influence of which on transfer was investigated. Sampling of soil and pasture grass was undertaken during a period extending from the Spring of 1987 to the Autumn of 1988. The results show that there has been limited downward migration of Chernobyl-derived caesium. In October 1988 more than 88% of the ¹³⁷Cs attributable to Chernobyl was mainly confined to the top 10 cm of undisturbed soil, with 79% on average in the top 5 cm. The distribution of pre-Chernobyl caesium at the 11 sites was also evaluated. In an investigation of the influence of soil parameters on transfer to grass, a negative correlation with pH was observed in 1987. In April 1987 concentration ratios for ¹³⁷Cs in grass ranged from 0.03 to 0.49. In general, comparison of the concentration ratio values showed a decreasing trend over the 18 months.