Method of diffusive gradients in thin films (DGT) compared with other soil testing methods to predict uranium phytoavailability

摘要

The measurement of diffusive gradients in thin films (DGT) has been proposed as a surrogate for metal uptake by plants. A small-scale experiment was performed to test the predictive capacity of the DGT method with respect to uranium availability and uptake by ryegrass. Correlation analysis was performed to compare the results obtained with the DGT device with more conventional bioavailability indices: concentration of uranium in pore water or in selective extractants. Six soils with different histories of uranium contamination and with distinct soil characteristics were used for the availability tests and the uptake experiment. The four uranium bioavailability indices that we screened were highly correlated, indicating that uranium pools assessed were at least partially comparable. Uranium concentration in the pore water was a better predictor for uranium uptake by ryegrass than amount of uranium recovered following extraction with 0.11M CH3COOH or 0.4 M MgCl2. The concentration measured with DGT concentration, CDGT, was also highly correlated with plant uptake. However, the significance level was sensitive to the value of the diffusion coefficient (pH dependent or not) used to calculate CDGT. From the results obtained,we could not conclude that the DGT method would have additional value in assessing uranium bioavailability.