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

Post-Chernobyl experience has demonstrated that persistently high plant transfer of Cs-137 occurs from organic soils in upland and seminatural ecosystems. The soil properties influencing this transfer have been known for some time but have not: been quantified. A pot experiment was conducted using 23 sails collected from selected areas of Great Britain, which were spiked with 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 solution showed high Cs-134 mobility (low K-d). The plant; to-soil solution Cs-134 ratio decreased sharply with increasing soil solution K+. A two parameter linear model, used to predict log CR from soil solution K+ and K-d, explained 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 content and high NH4+ concentrations) and low K availability.