Effect of Natural Organic Matter on the Fate of Cadmium During Microbial Ferrihydrite Reduction.
Effect of Natural Organic Matter on the Fate of Cadmium During Microbial Ferrihydrite Reduction.
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DOI：
10.1021/acs.est.0c03062
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发表时间：
2020-07
影响因子：
11.4
通讯作者：
Zhe Zhou;E. Muehe;E. Tomaszewski;E. Tomaszewski;J. Lezama-Pacheco;A. Kappler;James Byrne;James By
中科院分区：
文献类型：
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作者：
Zhe Zhou;E. Muehe;E. Tomaszewski;E. Tomaszewski;J. Lezama-Pacheco;A. Kappler;James Byrne;James By
已知天然有机物 (NOM) 会影响水铁矿的微生物还原和转化，但其对与水铁矿相关的镉 (Cd) 的影响尚不清楚。在这里，我们研究了当水铁矿在 NOM 存在下经历微生物还原时，Cd 如何重新分布。与硫还原地杆菌一起培养表明，随着 NOM 浓度（即 C/Fe 比）的增加，负载 Cd 的水铁矿的还原速度和程度均得到增强。如果没有 NOM，则仅还原 3-4% 的 Fe(III)，但由于水铁矿转化为纤铁矿，约 61% 的预吸附 Cd 被释放到溶液中。在高 C/Fe 比 (1.6) 下，超过 35% 的 Fe(III) 被还原，因为 NOM 可以通过电子穿梭和减小聚集体尺寸来促进生物还原，但只有微量的 Cd 释放到溶液中，从而降低了 Cd 毒性并延长了微生物 Fe(III) 的还原时间。使用穆斯堡尔谱和 X 射线衍射，在高 C/Fe 比下没有观察到水铁矿转变，X 射线吸收光谱表明微生物还原后 Cd-OM 键的比例增加。这项研究表明，NOM 的存在导致还原条件下 Cd 的迁移减少，这可能是通过抑制水铁矿转化并通过 Cd-OM 键重新捕获 Cd 来实现的。
Natural organic matter (NOM) is known to affect the microbial reduction and transformation of ferrihydrite, but its implication towards cadmium (Cd) associated with ferrihydrite is not well known. Here, we investigated how Cd is redistributed when ferrihydrite undergoes microbial reduction in the presence of NOM. Incubation with Geobacter sulfurreducens showed that both the rate and extent of reduction of Cd-loaded ferrihydrite were enhanced by increasing concentrations of NOM (i.e. C/Fe ratio). Without NOM, only 3-4% of Fe(III) was reduced, but around 61% of pre-adsorbed Cd was released into solution due to ferrihydrite transformation to lepidocrocite. At high C/Fe ratio (1.6), more than 35% of Fe(III) was reduced, as NOM can facilitate bio-reduction by working as an electron shuttle and decreased aggregate size, but only a negligible amount of Cd was released into solution, thus decreasing Cd toxicity and prolonging microbial Fe(III) reduction. No ferrihydrite transformation was observed at high C/Fe ratios using Mössbauer spectroscopy and X-ray diffraction, and X-ray absorption spectroscopy indicated the proportion of Cd-OM bond increased after microbial reduction. This study shows the presence of NOM leads to less mobilization of Cd under reducing condition possibly by inhibiting ferrihydrite transformation and recapturing Cd through Cd-OM bond.