Copper Redox Transformation and Complexation by Reduced and Oxidized Soil Humic Acid. 1. X-ray Absorption Spectroscopy Study
Copper Redox Transformation and Complexation by Reduced and Oxidized Soil Humic Acid. 1. X-ray Absorption Spectroscopy Study
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DOI：
10.1021/es4024089
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发表时间：
2013-10-01
影响因子：
11.4
通讯作者：
Kretzschmar, Ruben
中科院分区：
文献类型：
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作者：
Fulda, Beate;Voegelin, Andreas;Kretzschmar, Ruben
天然有机质(NOM)对土壤和水系中铜的形态和生物有效性有很大影响。在氧化还原动力学环境中，铜与NOM的氧化还原活性部分之间的电子转移反应可能引发铜(I)和铜(0)的形成。到目前为止，对铜与NOM的氧化还原作用以及铜(1)与NOM的结合还知之甚少。在这里，我们介绍了在氧化和缺氧条件下，在未经处理和电化学还原的土壤腐植酸(HA)中添加铜(II)或铜(I)时，铜的氧化还原转化的X射线吸收光谱结果。未处理和还原的HA均可介导铜的氧化还原转化。在缺氧条件下，铜(II)和铜(I)与还原的透明质酸(HA)形成主要络合，在低负荷下以铜(I)-HA的形式稳定下来，而在高负荷下会额外形成纳米铜(0)(占总铜的16-%)。与HA结合的铜(I)主要是2配位的，其次是3-4配位，至少有一个氮和/或硫配体贡献。在有氧条件下，铜(II)-HA络合物占优势，但也有少量铜以3-4倍配位的形式稳定为铜(I)-HA。结果表明，铜-透明质酸的氧化还原作用受铜(II)和铜(I)与羟基磷灰石(HA)结合的强烈影响，HA有助于稳定铜(I)的歧化反应。
Natural organic matter (NOM) exerts strong influence on copper speciation and bioavailability in soils and aquatic systems. In redox-dynamic environments, electron transfer reactions between copper and redox-active moieties of NOM may trigger Cu(I) and Cu(0) formation. To date, little is known about Cu-NOM redox interactions and Cu(1) binding to NOM. Here, we present X-ray absorption spectroscopy results on copper redox transformations upon addition of Cu(II) or Cu(I)to untreated and electrochemically reduced soil humic acid (HA) under oxic and anoxic conditions. Both untreated and reduced HA mediated copper redox transformations. Under anoxic conditions, Cu(II) and Cu(I) added to reduced HA were primarily complexed and thereby stabilized as Cu(I)-HA at low loadings, whereas high copper loadings resulted in the additional formation of Cu(0) nanoparticles (16-64% of total copper). Cu(I) bound to HA was predominantly 2-fold coordinated and to a lower extent 3- to 4-fold coordinated, with a contribution of at least one nitrogen and/or sulfur ligand group. Under oxic conditions, Cu(II)-HA complexes prevailed, but smaller fractions of copper were also stabilized as Cu(I)-HA in a 3- to 4-fold coordination. Our results show that Cu-HA redox interactions are strongly affected by binding of Cu(II) and Cu(I) to HA and that HA contributes to the stabilization of Cu(I) against disproportionation.