Novel speciation method based on Diffusive Gradients in Thin Films for in situ measurement of uranium in the vicinity of the former uranium mining sites

摘要

The Diffusive Gradients in Thin Films (DGT) technique using PIWBA resin (The Dow Chemical Company) was developed and validated for the measurement of uranium (U) concentration in natural and uranium mining influenced waters. The U uptake on the PIWBA resin gel was 97.3 +/- 0.4% (batch method; V-sol = 5 mL; [U] = 20 mu g L-1; 0.01 M NaNO3; pH = 7.0 +/- 0.2). The optimal eluent was found to be HNO3conc/70 degrees C with an elution efficiency of 88.9 +/- 1.4%. The laboratory DGT investigation demonstrated that the PIWBA resin gel exhibits a very good performance across a wide range of pH (3-9) and ionic strength (0.001-0.7 M NaNO3) at different time intervals. Neither effect of PO43- (up to 1.72 x 10(-4) M), nor of HCO3- (up to 8.20 x 10(-3) M) on the quantitative measurement of uranium by DGT-PIWBA method were observed. Only at very high Ca2+ (2.66 x 10(-4) M), and SO42- (5.55 x 10(-4) M) concentration, the U uptake on DGT-PIWBA was appreciably lessened. In-situ DGT field evaluation was carried out in the vicinity of three former uranium mining sites in France (Loire-Atlantique and Herault departments), which employ different water treatment technologies and have different natural geochemical characteristics. There was a similar or inferior U uptake on DGT-Chelex (R)-100 in comparison with the U accumulation on a DGT-PIWBA sampler. Most likely, the performance of Chelex (R)-100 was negatively affected by a highly complex matrix of mining waters. The high concentration and identity of co-accumulating analytes, typical for the mining environment, did not have a substantial impact on the quantitative uptake of labile U species on DGT-PIWBA.