Montmorillonite (MMT), a natural clay mineral with high ion-exchange capacity and trace metal adsorbability, has been demonstrated to be a suitable binding phase in the diffusive gradient in thin film (DGT) technique for the determination of labile trace metals in synthetic water samples. However, in situ working performance of DGT-MMT with natural river water has not yet been investigated. The present study examined the performance of a DGT containing montmorillonite (MMT) for the in situ isolation and determination of labile Cd, Pb, Mn, and Zn fractions in Lach Tray River water, North Vietnam. The repeatability and accuracy of the DGT-MMT probe were assessed on the basis of seven measurement replicates performed on Cd2+, Pb2+, Mn2+, and Zn2+ standard solutions. Then, the DGT-MMT probes were deployed in Lach Tray River water at different sampling sites to determine the labile metal fractions present in river water. By comparing the total and dissolved metal concentrations in the river water, the distributions of the four tested trace metals were constructed. The proportions of the dissolved fractions of Cd, Pb, Mn, and Zn were 46.7–73.7%, 38.5–63.9%, 36.4–41.6%, and 49.8–67.7%, respectively. The results also showed that the high accuracy and reproducibility of the DGT-MMT data were comparable with measurements obtained by the commonly used DGT-Chelex-100 method. In comparison with the data obtained from anodic stripping voltammetry (ASV), a traditional technique for the determination of non-in situ speciation of trace metals, labile metal concentrations measured by DGT-MMT were in similar ranges. These findings indicate that naturally available montmorillonite can be used as an alternative binding material in DGT probes for the in situ determination of labile metal concentrations in natural watercourses.

中文翻译：

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评估嵌入蒙脱石的薄膜中扩散梯度测定天然河水中不稳定的 Cd、Pb、Mn 和 Zn 的性能

蒙脱石 (MMT) 是一种具有高离子交换能力和痕量金属吸附能力的天然粘土矿物，已被证明是薄膜扩散梯度 (DGT) 技术中的合适结合相，可用于测定合成水中的不稳定痕量金属样品。然而，尚未研究 DGT-MMT 与天然河水的原位工作性能。本研究检验了含有蒙脱石 (MMT) 的 DGT 在原位分离和测定越南北部 Lach Tray 河水中不稳定的 Cd、Pb、Mn 和 Zn 组分的性能。DGT-MMT 探针的可重复性和准确度基于对 Cd2+、Pb2+、Mn2+ 和 Zn2+ 标准溶液进行的七次测量重复进行评估。然后，DGT-MMT 探针部署在 Lach Tray 河水中的不同采样点，以确定河水中存在的不稳定金属成分。通过比较河水中的总金属浓度和溶解金属浓度，构建了四种测试痕量金属的分布。Cd、Pb、Mn 和 Zn 的溶解部分比例分别为 46.7-73.7%、38.5-63.9%、36.4-41.6% 和 49.8-67.7%。结果还表明，DGT-MMT 数据的高精度和可重复性与通过常用 DGT-Chelex-100 方法获得的测量结果相当。与从阳极溶出伏安法 (ASV)（一种测定痕量金属非原位形态的传统技术）获得的数据相比，通过 DGT-MMT 测量的不稳定金属浓度处于相似的范围内。