Tantalum in the environment
Tantalum in the environment
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DOI：
10.1016/j.earscirev.2017.07.002
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发表时间：
2017-10-01
影响因子：
12.1
通讯作者：
Filella, Montserrat
中科院分区：
文献类型：
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作者：
Filella, Montserrat
在我们的现代经济中，钽已成为一种“技术关键元素”，越来越多地用于新技术。这就需要评估潜在的环境影响，而这反过来又需要了解其在环境中的浓度，并更好地了解其环境行为背后的化学过程。本综述试图总结我们目前对环境中钽的了解。环境领域对钽的关注远远落后于它在某些地球科学中的吸引力：虽然陨石和岩石中存在丰富的钽浓度值，可以很好地估计其在大陆地壳中的含量和 Nb/Ta 比率（一种宝贵的地球化学工具），但不同环境分区中钽浓度的数据却很少，特别是在自然水域中，甚至无法对海水和淡水中“溶解”钽浓度进行可靠估计。更重要的是，钽似乎主要以“颗粒”形式存在于天然水中，而不是“溶解”。土壤、沉积物和大气气溶胶中存在浓度值；这些值接近钽 UCC 值，因此表明是碎屑起源。没有任何迹象表明与人类使用该元素有关的污染影响。乍一看，钽在生物地球化学方面似乎是一种非常保守的元素，但真正了解其循环和反应性需要收集广泛且有意义的数据。这受到分析困难的阻碍，主要是：（i）“溶解”浓度远低于天然水中当前的分析能力，需要预浓缩程序，但目前无法给出一致的结果； (ii) 固体样品需要复杂的矿化程序，将钽排除在常规多元素研究之外。最后，有关钽配合物的稳定性常数（即不存在或高度不确定的值）的可靠数据很少。目前还没有关于钽与天然有机物或无机颗粒结合的吸附研究。
In our modern economy, tantalum has become a 'technology-critical element' which is increasingly used in new technologies. This has led to a need to evaluate potential environmental impacts, which, in turn, requires knowledge of its concentration in the environment along with better understanding of the chemical processes underlying its environmental behaviour. This review is an attempt to summarize our current knowledge about tantalum in the environment. The attention paid to tantalum in the environmental field lags far behind what it attracts in some geosciences: while a wealth of tantalum concentration values in meteorites and rocks is available allowing for good estimates of its content in the continental crust and of the Nb/Ta ratio (a precious geochemical tool) - data on tantalum concentrations in the different environmental compartments is scarce, particularly in natural waters where reliable estimates of 'dissolved' tantalum concentrations in seawater and freshwaters cannot even be produced. What is more, tantalum appears to be mostly present in 'particulate' form in natural waters, not 'dissolved'. Values exist for concentrations in soils, bed sediments and atmospheric aerosols; these are close to tantalum UCC values, thus pointing to a detrital origin. No signs of pollution effects linked to human use of the element are visible. At first sight, tantalum appears to be a very conservative element in biogeochemical terms but real understanding of its cycling and reactivity would require extensive and meaningful data collection. This is hindered by analytical difficulties, mainly: (i) 'dissolved' concentrations are well below current analytical capabilities in natural waters and require pre-concentration procedures that, for the moment, do not give consistent results; (ii) solid samples require complex mineralisation procedures that exclude tantalum from routine multielement studies. Lastly, there is scant reliable data on stability constants (i.e., absence or highly uncertain values) for relevant tantalum complexes. No sorption studies exist on tantalum binding by natural organic matter or inorganic particles.