Ruđer Bošković Institute, Center for Marine and Environmental Research, Bijenička 54, Zagreb, Croatia.
Université de Toulon, Aix Marseille Université, CNRS/INSU, IRD, MIO UM 110, Mediterranean Institute of Oceanography, La Garde, France.
Sci Total Environ. 2020 Jun 15;721:137784. doi: 10.1016/j.scitotenv.2020.137784. Epub 2020 Mar 6.
Understanding the potential bioavailability of trace metals (TM) in marine systems is of prime importance to implement adapted regulations and efficiently protect our coastal and estuarine waters. In this study Diffusive Gradients in Thin films (DGT) technique with two different pore size was used to evaluate the potentially bioavailable fractions (DGT-labile) of Cd, Co, Cu, Ni, Pb and Zn at various depths of a highly stratified estuary (the Krka River estuary, Croatia) both in winter and summer. DGT-labile concentrations were compared to (1) total dissolved concentrations, (2) concentrations of labile species measured by anodic stripping voltammetry (ASV-labile) for Cu and (3) concentrations derived by chemical speciation modelling. High correlation between dissolved and DGT-labile concentrations was found for all metals, except for Zn where contamination problems prevented reliable conclusions. Percentages of DGT-labile fractions over total dissolved concentrations were (AVG ± SD): 92 ± 3%, 64 ± 2%, 23 ± 5%, 61 ± 3% and 57 ± 6% for Cd, Pb, Cu, Ni and Co, respectively. No significant difference was found between trace metal concentrations measured with an open pore and restricted pore devices, implying the predominance of kinetically labile metal complexes smaller than 1 nm. For Cu, ASV-labile and DGT labile concentrations were highly correlated (0.97) with ASV-labile concentration being around 35% lower than that of the DGT-labile. Modelling of chemical speciation reliably predicted dynamic (free, inorganic and part of organic complexes) concentration of Cd, whereas dynamic concentrations of Cu and Pb were underestimated by 32% and 65%, respectively. In view of the relative simplicity of DGT devices, they are well suited for the monitoring effort of coastal waters, informing on potentially bioavailable concentrations of TM and thereby, helping to achieve good environmental status of coastal waters, as stipulated within the EU Water Framework Directive.
了解海洋系统中痕量金属（TM）的潜在生物可利用性对于实施适应性法规和有效保护我们的沿海和河口水域至关重要。本研究使用两种不同孔径的扩散梯度薄膜（DGT）技术，在冬季和夏季，分别在高度分层的河口（克罗地亚的克尔卡河河口）的不同深度处，评估 Cd、Co、Cu、Ni、Pb 和 Zn 的潜在生物可利用部分（DGT-可利用）。将 DGT-可利用浓度与（1）总溶解浓度、（2）通过阳极溶出伏安法（ASV-可利用）测量的可利用物种浓度以及（3）通过化学形态建模得出的浓度进行比较。除 Zn 外，所有金属的溶解浓度与 DGT-可利用浓度之间均存在高度相关性，Zn 由于存在污染问题，无法得出可靠的结论。DGT-可利用分数与总溶解浓度的百分比分别为：Cd、Pb、Cu、Ni 和 Co 为 92±3%、64±2%、23±5%、61±3%和 57±6%。使用开孔和限制孔设备测量的痕量金属浓度之间没有发现显著差异，这意味着动力学上可利用的金属络合物优先存在，其粒径小于 1nm。对于 Cu，ASV-可利用浓度与 DGT 可利用浓度高度相关（0.97），ASV-可利用浓度比 DGT 可利用浓度低约 35%。化学形态建模可靠地预测了 Cd 的动态（游离、无机和部分有机络合物）浓度，而 Cu 和 Pb 的动态浓度分别低估了 32%和 65%。鉴于 DGT 设备相对简单，它们非常适合沿海水域的监测工作，可以提供 TM 的潜在生物可利用浓度信息，从而有助于实现欧盟水框架指令规定的沿海水域良好环境状况。
