High plant uptake of radiocesium from organic soils due to Cs mobility andlow soil K content

Post-Chernobyl experience has demonstrated that persistently high plant tra nsfer of Cs-137 occurs from organic soils in upland and seminatural ecosyst ems. The soil properties influencing this transfer have been known for some time but have not: been quantified. A pot experiment was conducted using 2 3 sails collected from selected areas of Great Britain, which were spiked w ith Cs-134, and Agrostis capillaris grown for 19-45 days. The plant-to-soil Cs-134 concentration ratio (CR) varied from 0.06 to 44; log CR positively correlated to soil organic matter content (R-2 = 0.84), and CR values were highest for soils with low distribution coefficients (K-d) Of Cs-134. Soils With high organic matter contents and high concentrations of NH4+ in solut ion showed high Cs-134 mobility (low K-d). The plant; to-soil solution Cs-1 34 ratio decreased sharply with increasing soil solution K+. A two paramete r linear model, used to predict log CR from soil solution K+ and K-d, expla ined 94% of the variability in CR values. In conclusion, the high transfer of Cs-134 in soils is related to both the high Cs-134 mobility (low clay co ntent and high NH4+ concentrations) and low K availability.