Organic Carbon and Reducing Conditions Lead to Cadmium Immobilization by Secondary Fe Mineral Formation in a pH-Neutral Soil
Organic Carbon and Reducing Conditions Lead to Cadmium Immobilization by Secondary Fe Mineral Formation in a pH-Neutral Soil
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DOI：
10.1021/es403438n
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发表时间：
2013-12-03
影响因子：
11.4
通讯作者：
Kappler, Andreas
中科院分区：
文献类型：
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作者：
Muehe, E. Marie;Adaktylou, Irini J.;Kappler, Andreas
镉（Cd）是环境相关的，因为它通过含镉的磷肥进入土壤，并在被作物吸收时危害人类健康。已知镉与pH中性至微酸性土壤中的Fe（III）（oxyhydr）氧化物相关联，但尚不清楚Fe（III）还原条件下Fe和Cd的相互关系如何变化。因此，我们研究了如何流动性的变化时，镉的土壤面临着有机碳输入和还原条件。使用脂肪酸谱和定量PCR，我们发现，发酵和Fe（III）还原细菌的刺激，有机碳丰富的条件下，导致显着的Fe（III）还原。Fe（III）矿物的减少是伴随着土壤pH值的增加，增加溶解无机碳，降低镉的流动性。土壤颗粒的SEM-EDX图谱表明，一小部分镉被转移到钙和硫的矿物，可能是碳酸盐和硫化物。大部分的镉，然而，与次生铁矿物相，在微生物Fe（III）矿物还原过程中形成的，主要含有铁，这表明氧化铁矿物，如磁铁矿（Fe 3 O 4）。因此，我们的数据提供了证据，证明次生Fe（II）和Fe（II）/Fe（III）混合矿物在还原条件下可以成为土壤中Cd的汇，从而降低土壤中Cd的迁移率。
Cadmium (Cd) is of environmental relevance as it enters soils via Cd-containing phosphate fertilizers and endangers human health when taken up by crops. Cd is known to associate with Fe(III) (oxyhydr)oxides in pH-neutral to slightly acidic soils, though it is not well understood how the interrelation of Fe and Cd changes under Fe(III)-reducing conditions. Therefore, we investigated how the mobility of Cd changes when a Cd-bearing soil is faced with organic carbon input and reducing conditions. Using fatty acid profiles and quantitative PCR, we found that both fermenting and Fe(III)reducing bacteria were stimulated by organic carbon-rich conditions, leading to significant Fe(III) reduction. The reduction of Fe(III) minerals was accompanied by increasing soil pH, increasing dissolved inorganic carbon, and decreasing Cd mobility. SEM-EDX mapping of soil particles showed that a minor fraction of Cd was transferred to Ca- and S-bearing minerals, probably carbonates and sulfides. Most of the Cd, however, correlated with a secondary iron mineral phase that was formed during microbial Fe(III) mineral reduction and contained mostly Fe, suggesting an iron oxide mineral such as magnetite (Fe3O4). Our data thus provide evidence that secondary Fe(II) and Fe(II)/Fe(III) mixed minerals could be a sink for Cd in soils under reducing conditions, thus decreasing the mobility of Cd in the soil.