Development and performance of the diffusive gradients in thin-films technique for the measurement of Technetium-99 in seawater

A novel technique for obtaining time-integrated Tc-99 concentrations in seawater has been developed, using diffusive gradients in thin films (DGT). The performance of TEVA resin as a binding agent for Tc-99 was investigated via laboratory experiments. The accumulated Tc-99 activity per unit area of resin-gel was proportional to both the bulk solution activity and the exposure time for deployments of up to 2 weeks. The response of DGT was found to be independent of solution chemistries over the pH range 3-8 and ionic strength range 0.01-1.3 M. Seawater has pH 8 and ionic strength of similar to0.7 M; therefore, the potential of the technique for field deployment in seawater was demonstrated. Detection limits of 0.05 and 0.025 Bq L-1, for 2- and 4-week DGT deployments, respectively, were calculated for Tc-99 measurement by liquid scintillation spectrometry. Using quadrupole ICPMS to measure bound Tc-99 could reduce these detection limits to 0.125 mBq L-1 for a 4-week deployment. These detection limits are sufficiently low for monitoring contaminated environments, including the Irish Sea. This method is simpler and faster than other Tc-99 analysis methods and represents the only means of obtaining time-integrated data.