Lenoble V, Dang D H, Loustau Cazalet M, Mounier S, Pfeifer H-R, Garnier C
Laboratoire PROTEE, Université du Sud Toulon Var, BP 20132, 83957 La Garde Cedex, France.
Laboratoire PROTEE, Université du Sud Toulon Var, BP 20132, 83957 La Garde Cedex, France.
Talanta. 2015 Mar;134:530-537. doi: 10.1016/j.talanta.2014.11.053. Epub 2014 Dec 9.
Many studies have been carried out to identify dissolved organic matter-trace metals interactions, as organic matter (OM) was demonstrated to be a governing parameter of metals speciation. Concerning arsenic (As), such OM-As studies are scarce and concluded that, when As binding occurred, it was probably through cationic bridges or, in some cases, directly. Yet, analytical proofs remained complex to obtain. In this work, As binding with Suwanee River Humic Acid (SRHA), as an example of dissolved organic matter, was studied, considering both As(III) and As(V), at various pH and in absence/presence of Na and Ca. Dialysis, fluorescence measurements and PHREEQC modelling were performed to identify and characterize the mechanisms at work for the various performed experiments. It was observed that As(III) binding on SRHA occurred through direct SRHA-As(III) binding and that neither Na nor Ca presence modify this mechanism. As(V) appeared to be also bound by SRHA through direct interaction, but suffered from the competition of Na for the SRHA binding sites. Oppositely, in presence of Ca, the overall As(V)-SRHA binding was significantly enhanced, Ca acting as an efficient cationic bridge through the formation of an SRHA-Ca-As(V) ternary complex. All the obtained data were satisfactorily simulated using a unique set of binding parameters which can therefore be implemented in any speciation code to better address As behaviour in environmental conditions.
许多研究致力于确定溶解有机物与痕量金属之间的相互作用，因为有机物（OM）被证明是金属形态的一个关键参数。关于砷（As），此类有机物 - 砷的研究较少，并且得出结论，当发生砷结合时，可能是通过阳离子桥，或者在某些情况下是直接结合。然而，分析证据仍然难以获得。在这项工作中，以溶解有机物的一个例子——苏万尼河腐殖酸（SRHA）与砷的结合为研究对象，考虑了三价砷（As(III)）和五价砷（As(V)），在不同pH值以及有无钠（Na）和钙（Ca）存在的情况下进行研究。通过透析、荧光测量和PHREEQC建模来识别和表征各种实验中起作用的机制。观察到As(III)与SRHA的结合是通过直接的SRHA - As(III)结合发生的，并且钠和钙的存在都不会改变这种机制。As(V)似乎也通过直接相互作用与SRHA结合，但会受到钠对SRHA结合位点的竞争影响。相反，在有钙存在的情况下，总的As(V) - SRHA结合显著增强，钙通过形成SRHA - Ca - As(V)三元复合物起到有效的阳离子桥作用。所有获得的数据都使用一组独特的结合参数进行了令人满意的模拟，因此这些参数可以应用于任何形态代码中，以更好地描述环境条件下砷的行为。
