Measurement of stable and radioactive cesium in natural waters by the diffusive gradients in thin films technique with new selective binding phases.

A cesium-specific diffusive gradients in thin films (DGT) technique was developed using copper ferrocyanide (CFCN) as the binding agent. Two types of DGT binding phases were evaluated, one by immobilizing CFCN on Chelex 100 resin gels (Chelex-CFCN) and the other on poly(acrylic acid) gels (PAA-CFCN). Both DGT devices were successfully applied to the measurement of low levels of stable 133Cs and radioactive 137Cs in synthetic solutions and in natural river waters. In all cases, the DGT labile concentrations measured with the PAA-CFCN DGT agreed very well with total dissolved Cs concentrations, whereas those measured by the Chelex-CFCN DGT were much lower than total Cs concentrations. The difference was attributed to the different binding kinetics of Cs+ on the two gels suggesting that this might be a promising means of measuring biologically relevant Cs concentrations in natural waters.