EFFECT OF SOIL-BASED COUNTERMEASURES ON SOLID-LIQUID EQUILIBRIA IN AGRICULTURAL SOILS CONTAMINATED WITH RADIOCESIUM AND RADIOSTRONTIUM

The effect of applying soil-based countermeasures to agricultural soils contaminated with radiocaesium and radiostrontium is discussed in terms of their effects on solid-liquid equilibria in soils. This information is then used as a basis for producing preliminary guidelines for determining the applicability of potential soil treatments under a range of soil conditions. Potassium is the most effective soil-based countermeasure for radiocaesium contaminated soils, whilst calcium and to a lesser extent organic matter are good ameliorants for radiostrontium. Soils contaminated with radiocaesium should be tested for their potassium supply characteristics, organic matter status, clay mineralogy and lime requirements so that optimum levels of potassium fertilisation can be set. In a similar way, determining the calcium status and Ca:Sr selectivity of radiostrontium-contaminated soils enables optimum rates of liming to be set for different soil types. Complementary batch equilibrium studies may then be conducted on contaminated soils in order to check the effects of these different treatments and treatment rates on radionuclide desorption and Sr-90:Ca and Cs-137:K ratios in soil solution. Special attention must be given to soils contaminated with mixed deposits of radiocaesium and radiostrontium as the beneficial effects of a countermeasure for reducing soil-to-plant transfer of one radionuclide might be offset by detrimental effects on the uptake of the other radionuclides present.