The concentration ratios plant to soil for the stable elements Cs, Rb and K

Cs, Rb and K have been determined in needles of Norway spruce (Picea abies) growing on nine different sites and in the respective soils. These values were used to calculate the concentration ratio (CR) plant/soil. CR(K) was found to be almost constant at the various sites, but CR(Rb) and especially CR(Cs) show large variations. Most sites show the order CR(Cs) < CR(Rb) < CR(K). These results make it highly probable that the adsorption property of the soil is responsible for the differences in the uptake between elements and between sites. The same soil property must also be the main reason for the different Rb and Cs concentrations observed in various other conifers.