LABORATORY INVESTIGATION INTO THE POTENTIAL EFFECTIVENESS OF SOIL-BASED COUNTERMEASURES FOR SOILS CONTAMINATED WITH RADIOCESIUM AND RADIOSTRONTIUM

Accidental releases of radioactive material into the environment have prompted the search for effective soil-based chemical treatments to re duce the transfer of radiocaesium and radiostrontium along foodchains. As field studies can be impractical and protracted, a simple laborato ry method has been evaluated for use after an accident to predict the effect that different soil treatments may have on radionuclide availab ility to plants. The study involved a batch equilibrium approach in wh ich in situ conditions were replicated by the use of field moist soils and their associated soil solutions. The technique was used to invest igate the effects of common agricultural treatments (potassium as sulp hate of potash, calcium as garden lime and ammonium as ammonium sulpha te) on the distribution of Cs-137, Sr-90, K and Ca between solid and l iquid phases of loam, sand and peat soils. A treatment that decreased the Cs-137+:K+ or Sr-90(2+):Ca2+ quotient in the liquid phase compared with controls could be considered a potentially effective countermeas ure for reducing uptake of the appropriate radionuclide by plants. Pot assium decreased Cs-137+:K+ quotients in the liquid phase of all soil types, and in peat in particular. The potential effectiveness of potas sium as a soil based countermeasure for reducing radiocaesium uptake t o plants in peat soils was supported by field evidence from highly org anic soils in Cumbria. Application of the ammonium treatment increased Cs-137+:K+ quotients in the liquid phase of all soil types and in the sand in particular. As an increase in this ratio is associated with a n enhanced uptake of radiocaesium by plants, the application of ammoni um based fertilisers to soils contaminated with radiocaesium should th erefore be considered very carefully. No firm conclusions could be rea ched regarding the effectiveness of garden lime as a countermeasure be cause of its low solubility and the very high calcium status of the ex perimental soils at the start of the experiment.