Cornu J Y, Parat C, Schneider A, Authier L, Dauthieu M, Sappin-Didier V, Denaix L
INRA (Institut National de la Recherche Agronomique), UMR 1220 TCEM (Transfert sol-plante et Cycle des Eléments Minéraux dans les écosystèmes cultivés), 71 Avenue E. Bourlaux, F-33883 Villenave d'Ornon, France.
Chemosphere. 2009 Jul;76(4):502-8. doi: 10.1016/j.chemosphere.2009.03.016. Epub 2009 Apr 7.
Analytical techniques and speciation models have been developed to characterize the speciation of Cd in soil solution. They provide an estimate of operationally defined species of Cd that need to be compared, especially for soil solutions highly concentrated in organic matter as are the solutions collected after soil rewetting. This work deals with the comparison between the speciation of Cd measured by anodic stripping voltammetry (ASV) and ion exchange and the speciation of Cd calculated using Visual MINTEQ. The aim of this study was to quantify and explain the differences in Cd speciation observed between the three approaches. Cd speciation was assessed in soil solutions collected 4, 8, 24, 48, 96 and 144h after the rewetting of an air-dried contaminated soil. To optimize the computed speciation of Cd, other physico-chemical parameters were followed (e.g. pH, ionic strength and the concentrations of major anions, major cations and dissolved organic carbon) and a brief characterisation of dissolved organic matter (DOM) was performed. The discrepancy between model predictions and analytical measurements highlighted the need for caution in the interpretation of geochemical speciated data for Cd. The major result of this study was that a characterization of DOM based on its specific UV-absorbance at 254 nm improved the accuracy of model predictions. Another finding is that labile Cd complexes, even organic, may have been included in the electrochemically labile fraction of Cd measured by ASV.
已开发出分析技术和形态模型来表征土壤溶液中镉的形态。它们提供了对需进行比较的操作性定义的镉形态的估计，特别是对于像土壤重新湿润后收集的溶液那样富含有机物的土壤溶液。这项工作涉及通过阳极溶出伏安法（ASV）和离子交换测定的镉形态与使用Visual MINTEQ计算的镉形态之间的比较。本研究的目的是量化并解释三种方法之间观察到的镉形态差异。在风干的污染土壤重新湿润后4、8、24、48、96和144小时收集的土壤溶液中评估镉形态。为了优化计算出的镉形态，还跟踪了其他物理化学参数（例如pH、离子强度以及主要阴离子、主要阳离子和溶解有机碳的浓度），并对溶解有机物（DOM）进行了简要表征。模型预测与分析测量之间的差异突出表明，在解释镉的地球化学形态数据时需要谨慎。本研究的主要结果是，基于其在254 nm处的特定紫外吸光度对DOM进行表征提高了模型预测的准确性。另一个发现是，不稳定的镉络合物，即使是有机络合物，可能已包含在通过ASV测量的镉的电化学不稳定部分中。
