Accidental releases of radioactive material into the environment have prompted the search for effective soil-based chemical treatments to reduce the transfer of radiocaesium and radiostrontium along foodchains. As field studies can be impractical and protracted, a simple laboratory method has been evaluated for use after an accident to predict the effect that different soil treatments may have on radionuclide availability to plants. The study involved a batch equilibrium approach in which in situ conditions were replicated by the use of field moist soils and their associated soil solutions. The technique was used to investigate the effects of common agricultural treatments (potassium as sulphate of potash, calcium as garden lime and ammonium as ammonium sulphate) on the distribution of 137Cs, 90Sr, K and Ca between solid and liquid phases of loam, sand and peat soils. A treatment that decreased the 137Cs+:K+ or 90Sr2+:Ca2+ quotient in the liquid phase compared with controls could be considered a potentially effective countermeasure for reducing uptake of the appropriate radionuclide by plants. Potassium decreased 137Cs+:K+ quotients in the liquid phase of all soil types, and in peat in particular. The potential effectiveness of potassium as a soil based countermeasure for reducing radiocaesium uptake to plants in peat soils was supported by field evidence from highly organic soils in Cumbria. Application of the ammonium treatment increased 137Cs+: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 an enhanced uptake of radiocaesium by plants, the application of ammonium based fertilisers to soils contaminated with radiocaesium should therefore be considered very carefully. No firm conclusions could be reached regarding the effectiveness of garden lime as a countermeasure because of its low solubility and the very high calcium status of the experimental soils at the start of the experiment.
Bibliographical noteFunding Information:
This study received partial financial support from the Commission of European Communities (CEC Contract B17-0011-C). N. Mocanu would like to thank the IAEA for a 6-month attachment to NRPB to conduct this work. The authors would also like to thank Dr B.T. Wilkins for his constructive criticism of this manuscript.
- Batch equilibrium
- Solid-liquid equilibria