Iron mineralogy and uranium-binding environment in the rhizosphere of a wetland soil.
Iron mineralogy and uranium-binding environment in the rhizosphere of a wetland soil.
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DOI：
10.1016/j.scitotenv.2016.06.120
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发表时间：
2016-11
期刊：
影响因子：
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通讯作者：
D. Kaplan;R. Kukkadapu;J. Seaman;B. Arey;A. Dohnalkova;Shea W. Buettner;Dien Li;T. Varga;K. Scheckel;P. Jaffé
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文献类型：
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作者：
D. Kaplan;R. Kukkadapu;J. Seaman;B. Arey;A. Dohnalkova;Shea W. Buettner;Dien Li;T. Varga;K. Scheckel;P. Jaffé
湿地通过一系列增强多种污染物结合过程的生物地球化学梯度来缓解地下水污染物的迁移。本研究的假设是湿地植物根系在根际(植物-土壤带)内贡献有机碳并释放O2，从而促进Fe(III)-(Oxhyr)氧化物的形成。反过来，这些铁(III)-(氧水)氧化物稳定了有机物，这些有机物共同有助于污染物的固定。对南卡罗来纳州萨凡纳河湿地污染区和非污染区采集的样品进行了矿物学和铀结合环境评价。穆斯堡尔谱分析表明，根际土壤中富含纳米针铁矿、类铁氢氧化铁纳米颗粒和赤铁矿，几乎没有Fe(II)的存在。X射线计算机断层扫描和各种显微技术显示，根斑厚达数十微米，由高度定向的铁纳米颗粒组成，表明根参与创造了有利于纳米颗粒形成的生物地球化学条件。XAS分析表明，湿地土壤中大部分U以+-6氧化态存在，且与Fe浓度在空间上的相关性不大。扫描电子显微镜/能谱分析证实，U在根斑上富集铀，并与磷结合在一起。这些发现支持了我们的假设，并表明植物可以改变有利于湿地污染物固定的矿物学条件。
Wetlands mitigate the migration of groundwater contaminants through a series of biogeochemical gradients that enhance multiple contaminant-binding processes. The hypothesis of this study was that wetland plant roots contribute organic carbon and release O2within the rhizosphere (plant-impact soil zone) that promote the formation of Fe(III)-(oxyhydr)oxides. In turn, these Fe(III)-(oxyhydr)oxides stabilize organic matter that together contribute to contaminant immobilization. Mineralogy and U binding environments of the rhizosphere were evaluated in samples collected from contaminated and non-contaminated areas of a wetland on the Savannah River Site in South Carolina. Based on Mössbauer spectroscopy, rhizosphere soil was greatly enriched with nanogoethite, ferrihydrite-like nanoparticulates, and hematite, with negligible Fe(II) present. X-ray computed tomography and various microscopy techniques showed that root plaques were tens-of-microns thick and consisted of highly oriented Fe-nanoparticles, suggesting that the roots were involved in creating the biogeochemical conditions conducive to the nanoparticle formation. XAS showed that a majority of the U in the bulk wetland soil was in the + 6 oxidation state and was not well correlated spatially to Fe concentrations. SEM/EDS confirm that U was enriched on root plaques, where it was always found in association with P. Together these findings support our hypothesis and suggest that plants can alter mineralogical conditions that may be conducive to contaminant immobilization in wetlands.