Plant uptake of radiocaesium from artificially contaminated soil monoliths covering major European soil types.

Uptake of 137Cs was measured in different agricultural plant species (beans, lettuce, barley and ryegrass) grown in 5 undisturbed soil monoliths covering major European soil types. The first cultivationwas made three years after soil conta-mination and plants were grown during 3 successive years. The plant–soil 137Cs transfer factors varied maximally 12-fold among soils and 35-fold among species when grown on the same soil. Single correlations between transfer factors and soil properties were found, but they varied widely with plant type and can hardly be used as a predictive tool because of the few soils used. The variation of 137Cs concentrations in plants among soils was related to differences in soil solution 137Cs and K concentrations, consistent with previous observations in hydroponics and pot trials. Absolute values of transfer factors could not be predicted based on a model validated for pot trials. The 137Cs activity concen-tration in soil solution decreased significantly (11- to 250-fold) for most soils in the 1997–1999 period and is partly explained by decreasing K in soil solution. Trans-fer factors of lettuce showed both increasing and decreasing trends between 2 consecutive years depending on soil type.