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首页> 外文期刊>Environmental Science & Technology >Iron isotope fractionation during proton-promoted, ligand-controlled, and reductive dissolution of goethite
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Iron isotope fractionation during proton-promoted, ligand-controlled, and reductive dissolution of goethite

机译：针铁质质子促进，配体控制和还原性溶解过程中的铁同位素分馏

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Iron isotope fractionation during dissolution of goethite (alpha-FeOOH) was studied in laboratory batch experiments. Proton-promoted (HCl), ligand-controlled (oxalate dark), and reductive (oxalate light) dissolution mechanisms were compared in order to understand the behavior of iron isotopes during natural weathering reactions. Multicollector ICP-MS was used to measure iron isotope ratios of dissolved iron in solution. The influence of kinetic and equilibrium isotope fractionation during different time scales of dissolution was investigated. Proton-promoted dissolution did not cause iron isotope fractionation, concurrently demonstrating the isotopic homogeneity of the goethite substrate. In contrast, both ligand-controlled and reductive dissolution of goethite resulted in significant iron isotope fractionation. The kinetic isotope effect, which caused an enrichment of light isotopes in the early dissolved fractions, was modeled with an enrichment factor for the Fe-57/Fe-54 ratio of -2.6 parts per thousand between reactive surface sites and solution. Later dissolved fractions of the ligand-controlled experiments exhibit a reverse trend with a depletion of light isotopes of similar to 0.5 parts per thousand in solution. We interpret this as an equilibrium isotope effect between Fe(III)-oxalate complexes in solution and the goethite surface. In conclusion, different dissolution mechanisms cause diverse iron isotope fractionation effects and likely influence the iron isotope signature of natural soil and weathering environments.
机译：在实验室分批实验中研究了针铁矿（α-FeO​​OH）溶解过程中的铁同位素分馏。为了了解自然风化反应过程中铁同位素的行为，比较了质子促进的（HCl），配体控制的（草酸盐暗）和还原性（草酸盐光）的溶解机理。使用Multicollector ICP-MS测定溶液中溶解的铁的铁同位素比。研究了不同溶出时间尺度下动力学和平衡同位素分馏的影响。质子促进的溶出不引起铁同位素分级分离，同时证明了针铁矿基质的同位素均质性。相反，针铁矿的配体控制和还原溶解均导致铁同位素分馏显着。动力学同位素效应在早​​期溶解的馏分中引起了轻同位素的富集，其反应表面和溶液之间的Fe-57 / Fe-54比值为-2.6千分之一。后来由配体控制的实验溶解的部分表现出相反的趋势，即溶液中的光同位素耗竭量约为0.5千分之1。我们将其解释为溶液中的Fe（III）-草酸盐配合物与针铁矿表面之间的平衡同位素效应。总之，不同的溶解机制会导致不同的铁同位素分馏作用，并可能影响天然土壤和风化环境的铁同位素特征。

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