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首页> 外文期刊>Marine Chemistry >The speciation of lead in seawater by pseudopolarography using a vibrating silver amalgam microwire electrode
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The speciation of lead in seawater by pseudopolarography using a vibrating silver amalgam microwire electrode

机译：使用振动银汞合金微丝电极通过伪极谱法测定海水中的铅形态

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摘要

A novel electrode based on a vibrating silver amalgam microwire was used for pseudopolarography of lead (Pb) in seawater. Pseudopolarography is a method to study the stability of metal species by examination of their reduction potential. The reduction potential of kinetically irreversible species is related to the thermo-dynamic complex stability constant, whilst for labile species it is related to the conditional stability constant. The new electrode enables the speciation of Pb at picomolar level in uncontaminated seawater. The potential shift of electrochemically irreversible lead complexes was calibrated against the complex stability of several ligands in pH 8 seawater. The method was compared against the mercury drop electrode at various concentrations of lead and various deposition times, and the response was in general agreement with the theory. The method is tested on samples from oceanic (Atlantic), coastal (Irish Sea) and estuarine (Mersey) origins at Pb concentrations between 30 pM and 2 nM. The pseudopolarograms were found to resolve the speciation of lead in terms of labile and irreversibly bound Pb species. The lead in the samples was largely in the labile component of the pseudopolarograms, indicating that it was reversibly complexed with values for log α'_(pb2+L) of 2 for the oceanic sample, and of 4 for the coastal sample. A smaller fraction was resolved as stable, irreversibly bound species with values for the thermodynamic stability constant of log K_(Pb2+L) = 15-16. The speciation method was able to resolve metal species occurring at levels of only a fraction of that of the metal. Unlike copper, where organic complexation is strong and electrochemically irreversible, and able to significantly decrease its bioavailability, the Pb mostly occurs in the labile complexed fraction and is therefore readily available for geochemical scavenging or biological uptake reactions.
机译：一种基于振动银汞合金微丝的新型电极用于海水中铅（Pb）的伪极谱法。伪极谱法是一种通过检查金属还原电位来研究其稳定性的方法。动力学不可逆物种的还原电位与热力学复杂稳定常数有关，而不稳定的物种与条件稳定常数有关。新的电极可以在未污染的海水中形成皮摩尔级的铅。针对几种配体在pH 8海水中的络合稳定性，对电化学不可逆的铅络合物的电势位移进行了校准。该方法在各种铅浓度和不同沉积时间下与汞滴电极进行了比较，其响应与理论基本一致。该方法已在来自海洋（大西洋），沿海（爱尔兰海）和河口（默西）的铅浓度为30 pM至2 nM的样品上进行了测试。发现伪极谱图可解决不稳定和不可逆结合的铅物种方面的铅形态。样品中的铅主要在伪极谱图的不稳定成分中，表明与海洋样品的logα'_（pb2 + L）值分别为2和沿海样品的logα'_（pb2 + L）可逆地复杂。较小的部分被解析为稳定的，不可逆结合的物质，其热力学稳定性常数为log K_（Pb2 + L）= 15-16。物种形成方法能够分辨仅以金属的一小部分水平出现的金属物种。与铜不同的是，铜的有机络合作用强且电化学不可逆，并且能够显着降低其生物利用度，而铅大多出现在不稳定的络合馏分中，因此很容易用于地球化学清除或生物吸收反应。

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