Pađan Jasmin, Marcinek Saša, Cindrić Ana-Marija, Santinelli Chiara, Retelletti Brogi Simona, Radakovitch Olivier, Garnier Cédric, Omanović Dario
Rud-er Bošković Institute, Center for Marine and Environmental Research, Zagreb, Croatia.
CNR-Biophysics Institute, Pisa, Italy.
Front Chem. 2021 Feb 2;8:628749. doi: 10.3389/fchem.2020.628749. eCollection 2020.
The determination of copper (Cu) speciation and its bioavailability in natural waters is an important issue due to its specific role as an essential micronutrient but also a toxic element at elevated concentrations. Here, we report an improved anodic stripping voltammetry (ASV) method for organic Cu speciation, intended to eliminate the important problem of surface-active substances (SAS) interference on the voltammetric signal, hindering measurements in samples with high organic matter concentration. The method relies on the addition of nonionic surfactant Triton-X-100 (T-X-100) at a concentration of 1 mg L. T-X-100 competitively inhibits the adsorption of SAS on the Hg electrode, consequently 1) diminishing SAS influence during the deposition step and 2) strongly improving the shape of the stripping Cu peak by eliminating the high background current due to the adsorbed SAS, making the extraction of Cu peak intensities much more convenient. Performed tests revealed that the addition of T-X-100, in the concentration used here, does not have any influence on the determination of Cu complexation parameters and thus is considered "interference-free." The method was tested using fulvic acid as a model of natural organic matter and applied for the determination of Cu speciation in samples collected in the Arno River estuary (Italy) (in spring and summer), characterized by a high dissolved organic carbon (DOC) concentration (up to 5.2 mgC L) and anthropogenic Cu input during the tourist season (up to 48 nM of total dissolved Cu). In all the samples, two classes of ligands (denoted as L and L) were determined in concentrations ranging from 3.5 ± 2.9 to 63 ± 4 nM eq Cu for L and 17 ± 4 to 104 ± 7 nM eq Cu for L, with stability constants log = 9.6 ± 0.2-10.8 ± 0.6 and log = 8.2 ± 0.3-9.0 ± 0.3. Different linear relationships between DOC and total ligand concentrations between the two seasons suggest a higher abundance of organic ligands in the DOM pool in spring, which is linked to a higher input of terrestrial humic substances into the estuary. This implies that terrestrial humic substances represent a significant pool of Cu-binding ligands in the Arno River estuary.
由于铜（Cu）作为一种必需的微量营养素，但在高浓度时也是有毒元素，其在天然水中的形态测定及其生物有效性是一个重要问题。在此，我们报告一种改进的阳极溶出伏安法（ASV）用于有机铜形态分析，旨在消除表面活性物质（SAS）对伏安信号干扰这一重要问题，该干扰会阻碍对高有机质浓度样品的测量。该方法依赖于添加浓度为1 mg/L的非离子表面活性剂Triton-X-100（T-X-100）。T-X-100竞争性抑制SAS在汞电极上的吸附，从而1）在沉积步骤中减少SAS的影响，以及2）通过消除由于吸附的SAS导致的高背景电流，极大地改善溶出铜峰的形状，使得铜峰强度的提取更加方便。进行的测试表明，此处使用的浓度下添加T-X-100对铜络合参数的测定没有任何影响，因此被认为是“无干扰的”。该方法以富里酸作为天然有机物模型进行测试，并应用于在意大利阿诺河河口采集的样品（春季和夏季）中铜形态的测定，这些样品的特点是溶解有机碳（DOC）浓度高（高达5.2 mgC/L）以及旅游季节人为铜输入高（总溶解铜高达48 nM）。在所有样品中，测定了两类配体（表示为L₁和L₂），L₁的浓度范围为3.5±2.9至63±4 nM eq Cu，L₂的浓度范围为17±4至104±7 nM eq Cu，稳定常数logK₁ = 9.6±0.2 - 10.8±0.6以及logK₂ = 8.2±0.3 - 9.0±0.3。两个季节之间DOC与总配体浓度的不同线性关系表明春季DOM库中有机配体的丰度更高，这与陆地腐殖质向河口的更高输入有关。这意味着陆地腐殖质是阿诺河河口铜结合配体的一个重要库。
