Fe(II)-Catalyzed Transformation of Organic Matter-Ferrihydrite Coprecipitates: A Closer Look Using Fe Isotopes.
Fe(II)-Catalyzed Transformation of Organic Matter-Ferrihydrite Coprecipitates: A Closer Look Using Fe Isotopes.
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DOI：
10.1021/acs.est.8b03407
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发表时间：
2018-09
影响因子：
11.4
通讯作者：
Zhe Zhou;Drew E. Latta;Nadia Noor;A. Thompson;T. Borch;M. Scherer
中科院分区：
文献类型：
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作者：
Zhe Zhou;Drew E. Latta;Nadia Noor;A. Thompson;T. Borch;M. Scherer
水铁矿是土壤和沉积物中常见的铁矿物，在Fe（II）存在下迅速转化为次生矿物。Fe（II）催化的水铁矿转化的速率和产物已被证明是显着的天然有机质（NOM）的影响。在这里，我们使用了丰富的Fe同位素实验和57 Fe穆斯堡尔谱跟踪形成的次生矿物，以及电子转移和Fe水铁矿水溶液与几种类型的NOM.Ferrihydrite共沉淀与腐殖酸反应后，主要转化为针铁矿（II）之间的混合。与此相反，共沉淀与富里酸和Suwannee河NOM（SRNOM）的水铁矿导致没有可测量的次生矿物的形成。尽管没有二次矿物转化，穆斯堡尔谱表明电子转移之间仍然发生Fe（II）和水铁矿共沉淀与富里酸和SRNOM。此外，同位素示踪实验表明，一个显着的部分结构铁的水铁矿混合水相Fe（II）（约85%）。与Fe（II）反应后，穆斯堡尔谱表明共沉淀物中结晶度、粒度或颗粒相互作用发生了一些微妙的变化。我们的观察表明，水铁矿共沉淀与富里酸和SRNOM仍然是一个高度动态相，即使没有水铁矿转化。
Ferrihydrite is a common Fe mineral in soils and sediments that rapidly transforms to secondary minerals in the presence of Fe(II). Both the rate and products of Fe(II)-catalyzed ferrihydrite transformation have been shown to be significantly influenced by natural organic matter (NOM). Here, we used enriched Fe isotope experiments and 57Fe Mössbauer spectroscopy to track the formation of secondary minerals, as well as electron transfer and Fe mixing between aqueous Fe(II) and ferrihydrite coprecipitated with several types of NOM. Ferrihydrite coprecipitated with humic acids transformed primarily to goethite after reaction with Fe(II). In contrast, ferrihydrite coprecipitated with fulvic acids and Suwannee River NOM (SRNOM) resulted in no measurable formation of secondary minerals. Despite no secondary mineral transformation, Mössbauer spectra indicated electron transfer still occurred between Fe(II) and ferrihydrite coprecipitated with fulvic acid and SRNOM. In addition, isotope tracer experiments revealed that a significant fraction of structural Fe in the ferrihydrite mixed with the aqueous phase Fe(II) (∼85%). After reaction with Fe(II), Mössbauer spectroscopy indicated some subtle changes in the crystallinity, particle size, or particle interactions in the coprecipitate. Our observations suggest that ferrihydrite coprecipitated with fulvic acid and SRNOM remains a highly dynamic phase even without ferrihydrite transformation.