Santos Cristiane Aily, Gemeiner Hendryk, Menegário Amauri Antonio, Galceran Josep, Zanatta Melina Borges Teixeira, Chang Hung Kiang
Environmental Studies Center (CEA), São Paulo State University (UNESP), Avenida 24-A, 1515, Rio Claro, SP, 13506-900, Brazil; Department of Applied Geology and Basin Studies Laboratory (LEBAC), São Paulo State University (UNESP), Avenida 24-A, 1515, Rio Claro, SP, 13506-900, Brazil.
Environmental Studies Center (CEA), São Paulo State University (UNESP), Avenida 24-A, 1515, Rio Claro, SP, 13506-900, Brazil; Department of Applied Geology and Basin Studies Laboratory (LEBAC), São Paulo State University (UNESP), Avenida 24-A, 1515, Rio Claro, SP, 13506-900, Brazil.
Talanta. 2022 Feb 1;238(Pt 2):123044. doi: 10.1016/j.talanta.2021.123044. Epub 2021 Nov 8.
The Diffusive Gradients in Thin-films (DGT) technique represents an ideal tool for monitoring water quality of inorganic species in systems with a high flow such as rivers, streams, lakes and seas. However, in low-flow systems (non-turbulent waters), the influence of a diffusive boundary layer (DBL) formed on the surface of the DGT device has been observed, which can lead to erroneous measurements by DGT. Therefore, the use of DGT in wells for groundwater monitoring is still very limited until now. In this sense, the present study evaluates the applicability of the DGT technique in non-turbulent and low-flow water systems. We propose a new way to calculate the DBL with the objective to carry out a robust DGT analysis in environmental monitoring wells. For this purpose, DGT devices with different diffusive gel thicknesses were deployed in an experimental set-up simulating a groundwater monitoring well. A DBL thickness (for each element) was calculated from the slopes of the linear regressions between the DGT accumulated mass of metal and the deployment time (4, 8, 12, 24 and 48 h) for each of the two diffusive gel thicknesses. The mean DBL thickness (averaging the individual DBL thicknesses calculated from the slopes) was 0.06 cm. The concentrations of the analysed elements were corrected with this DBL with the result that the metal concentrations measured by DGT improved and were highly approximated to their actual total values in this non-complexing medium.
薄膜扩散梯度（DGT）技术是监测河流、溪流、湖泊和海洋等高流量系统中无机物种水质的理想工具。然而，在低流量系统（非湍流水体）中，已观察到DGT装置表面形成的扩散边界层（DBL）的影响，这可能导致DGT测量结果出现误差。因此，到目前为止，DGT在用于地下水监测的水井中的应用仍然非常有限。从这个意义上讲，本研究评估了DGT技术在非湍流和低流量水系统中的适用性。我们提出了一种计算DBL的新方法，目的是在环境监测井中进行可靠的DGT分析。为此，将具有不同扩散凝胶厚度的DGT装置部署在模拟地下水监测井的实验装置中。根据两种扩散凝胶厚度中每种的金属DGT累积质量与部署时间（4、8、12、24和48小时）之间线性回归的斜率，计算出（每种元素的）DBL厚度。平均DBL厚度（平均根据斜率计算出的各个DBL厚度）为0.06厘米。用此DBL对分析元素的浓度进行校正，结果是DGT测量的金属浓度得到改善，并在这种非络合介质中高度接近其实际总值。
