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Abstract：
Vanadium (V), although serving as an important component of industrial activities, has bioinorganic implications to pose highly toxic hazards to humans and animals. Soils and sediments throughout the world exhibit wide ranges of vanadium concentrations. Although vanadium toxicity varies between different species, it is mainly controlled by soil redox potential (EH). Nonetheless, knowledge of the redox geochemistry of vanadium lags in comparison to what is known about other potentially toxic elements (PTEs). In particular, the redox-induced speciation and mobilization of vanadium in soils and sediments and the associated risks to the environment have not been reviewed to date. Therefore, this review aims to address 1) the content and geochemical fate of vanadium in soils and sediments, 2) its redox-induced release dynamics, 3) redox-mediated chemical reactions between vanadium and soil organic and inorganic colloidal materials in soil solution, 4) its speciation in soil solution and soil-sediments, and 5) the use of advanced geochemical and spectroscopic techniques to investigate these complex systems. Vanadium (+5) is the most mobile and toxic form of its species while being the thermodynamically stable valence state in oxic environments, while vanadium (+3) might be expected to be predominant under euxinic (anoxic and sulfidic) conditions. Vanadium can react variably in response to changing soil EH: under anoxic conditions, the mobilization of vanadium can decrease because vanadium (+5) can be reduced to relatively less soluble vanadium (+4) via inorganic reactions such as with H2S and organic matter and by metal-reducing microorganisms. On the other hand, dissolved concentrations of vanadium can increase at low EH in many soils to reveal a similar pattern to that of Fe, which may be due to the reductive dissolution of Fe(hydr)oxides and the release of the associated vanadium. Those differences in vanadium release dynamics might occur as a result of the direct impact of EH on vanadium speciation in soil solution and soil sediments, and/or because of the EH-dependent changes in soil pH, chemistry of (Fe)(hydr)oxides, and complexation with soil organic carbon. Release dynamics of vanadium in soils may also be affected positively by soil pH and the release of aromatic organic compounds. X-ray absorption spectroscopy (XAS) is a powerful tool to investigate the speciation of vanadium present in soil. X-ray absorption near edge structure (XANES) is often used to constrain the average valence state of vanadium in soils and sediments, and in limited cases extended X-ray absorption fine structure (EXAFS) analysis has been used to determine the average molecular coordination environment of vanadium in soil components. In conclusion, this review presents the state of the art about the redox geochemistry of vanadium and thus contributes to a better understanding of the speciation, potential mobilization, and environmental hazards of vanadium in the near-surface environment of uplands, wetlands, and agricultural ecosystems as affected by various colloidal particles. Further research is needed to elucidate the geochemistry and speciation of vanadium in the dissolved, colloidal, and soil sediments phases, including the determination of factors that control the redox geochemistry of vanadium.
摘要：
钒(V),虽然作为工业活动的重要组成部分，具有生物无机意义，对人类和动物造成剧毒危害。世界各地的土壤和沉积物显示出广泛的钒浓度。虽然不同物种之间的钒毒性不同，主要受土壤氧化还原电位(EH)控制。尽管如此，与已知的其他潜在有毒元素（PTE）相比，钒的氧化还原地球化学知识滞后。特别是,迄今为止，尚未审查氧化还原诱导的土壤和沉积物中钒的形态和动员以及对环境的相关风险。因此,这篇综述旨在解决1)土壤和沉积物中钒的含量和地球化学命运，2)其氧化还原诱导的释放动力学，3)钒与土壤溶液中土壤有机和无机胶体物质之间的氧化还原介导的化学反应，4)其在土壤溶液和土壤沉积物中的形态，5）使用先进的地球化学和光谱技术来研究这些复杂的系统。钒（5）是其物种中最具流动性和毒性的形式，同时在有氧环境中处于热力学稳定的价态，而钒（+3）可能预计在低氧（缺氧和硫化）条件下占主导地位。钒可以响应变化的土壤EH：在缺氧条件下，钒的动员可以减少，因为钒（5）可以通过与H2S和有机物的无机反应以及通过金属还原微生物还原为相对较少可溶性的钒（4）。另一方面,在许多土壤中，钒的溶解浓度在低EH时会增加，以揭示与Fe相似的模式。这可能是由于Fe（氢）氧化物的还原溶解和相关钒的释放。钒释放动力学的差异可能是EH对土壤溶液和土壤沉积物中钒形态的直接影响的结果。和/或由于土壤pH值的EH依赖性变化，(Fe)(氢)氧化物的化学性质，并与土壤有机碳络合。土壤中钒的释放动力学也可能受到土壤pH值和芳香有机化合物释放的积极影响。X射线吸收光谱（XAS）是研究土壤中钒形态的有力工具。X射线吸收近边缘结构（XANES）通常用于限制土壤和沉积物中钒的平均价态，在有限的情况下，扩展X射线吸收精细结构（EXAFS）分析已用于确定土壤成分中钒的平均分子配位环境。总之,这篇综述介绍了最先进的关于氧化还原地球化学的钒，从而有助于更好地理解的形态，潜在动员，和钒在高地近地表环境中的环境危害，湿地,和受各种胶体颗粒影响的农业生态系统。需要进一步的研究来阐明溶解中钒的地球化学和形态，胶体，和土壤沉积相，包括确定控制钒氧化还原地球化学的因素。
