Degryse Fien, Smolders Erik, Oliver Ian, Zhang Hao
Laboratory for Soil and Water Management, K.U. Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium.
Environ Sci Technol. 2003 Sep 1;37(17):3958-65. doi: 10.1021/es034075p.
The technique of diffusive gradients in thin films (DGT) has been suggested to sample an available fraction of metals in soil. The objectives of this study were to compare DGT measurements with commonly measured fractions of Zn in soil, viz, the soil solution concentration and the total Zn concentration. The DGT technique was used to measure fluxes and interfacial concentrations of Zn in three series of field-contaminated soils collected in transects toward galvanized electricity pylons and in 15 soils amended with ZnCl2 at six rates. The ratio of DGT-measured concentration to pore water concentration of Zn, R, varied between 0.02 and 1.52 (mean 0.29). This ratio decreased with decreasing distribution coefficient, Kd, of Zn in the soil, which is in agreement with the predictions of the DGT-induced fluxes in soils (DIFS) model. The R values predicted with the DIFS model were generally larger than the observed values in the ZnCl2-amended soils at the higher Zn rates. A modification of the DIFS model indicated that saturation of the resin gel was approached in these soils, despite the short deployment times used (2 h). The saturation of the resin with Zn did not occur in the control soils (no Zn salt added) or the field-contaminated soils. Pore water concentration of Zn in these soils was predicted from the DGT-measured concentration and the total Zn content. Predicted values and observations were generally in good agreement. The pore water concentration was more than 5 times underpredicted for the most acid soil (pH = 3) and for six other soils, for which the underprediction was attributed to the presence of colloidal Zn in the soil solution.
薄膜扩散梯度技术（DGT）已被用于对土壤中金属的有效部分进行采样。本研究的目的是将DGT测量结果与土壤中锌的常用测量部分，即土壤溶液浓度和总锌浓度进行比较。DGT技术用于测量在向镀锌电塔方向的样带中采集的三个系列的现场污染土壤以及以六种速率用ZnCl₂改良的15种土壤中锌的通量和界面浓度。DGT测量的锌浓度与孔隙水浓度之比R在0.02至1.52之间变化（平均为0.29）。该比值随土壤中锌的分配系数Kd降低而减小，这与土壤中DGT诱导通量（DIFS）模型的预测结果一致。在较高锌添加速率下，用DIFS模型预测的R值通常大于在ZnCl₂改良土壤中的观测值。DIFS模型的修正表明，尽管使用的部署时间较短（2小时），但这些土壤中的树脂凝胶已接近饱和。在对照土壤（未添加锌盐）或现场污染土壤中未发生锌对树脂的饱和。根据DGT测量的浓度和总锌含量预测了这些土壤中锌的孔隙水浓度。预测值和观测值总体上吻合良好。对于酸性最强的土壤（pH = 3）和其他六种土壤，孔隙水浓度被低估了5倍以上，对于这些土壤，低估归因于土壤溶液中存在胶体锌。
