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首页> 外文期刊>Environmental Science & Technology >Treatment Of Nitric Acid-, U(vi)-, And Tc(vii)-contaminated Groundwater In Intermediate-scale Physical Models Of An In Situ Biobarrier
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Treatment Of Nitric Acid-, U(vi)-, And Tc(vii)-contaminated Groundwater In Intermediate-scale Physical Models Of An In Situ Biobarrier

机译：原位生物屏障中尺度物理模型处理硝酸，U（vi）和Tc（vii）污染的地下水

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摘要

Metal and hydrogen ion acidity and extreme nitrate concentrations at Department of Energy legacy waste sites pose challenges for successful in situ U and Tc bioimmobilization. In this study, we investigated a potential in situ biobarrier configuration designed to neutralize pH and remove nitrate and radionuclides from nitric acid-, U-, and Tc-contaminated groundwater for over 21 months. Ethanol additions to groundwater flowing through native sediment and crushed limestone effectively increased pH (from 4.7 to 6.9), promoted removal of 116 mM nitrate, increased sediment biomass, and immobilized 94% of total U. Increased groundwater pH and significant U removal was also observed in a control column that received no added ethanol. Sequential extraction and XANES analyses showed U in this sediment to be solid-associated U(VI), and EXAFS analysis results were consistent with uranyl orthophosphate (UO_2)_3(PO_4)_2·4H_2O_((s)), which may control U solubility in this system. Ratios of respiratory ubiquinones to menaquinones and copies of dissimilatory nitrite reductase genes, nirS and nirK, were at least 1 order of magnitude greater in the ethanol-stimulated system compared to the control, indicating that ethanol addition promoted growth of a largely denitrifying microbial community. Sediment 16S rRNA gene clone libraries showed that Betaproteobacteria were dominant (89%) near the source of influent acidic groundwater, whereas members of Gamma-and Alphaproteobacteria and Bacteroidetes increased along the flow path as pH increased and nitrate concentrations decreased, indicating spatial shifts in community composition as a function of pH and nitrate concentrations. Results of this study support the utility of biobarriers for treating acidic radionuclide- and nitrate-contaminated groundwater.
机译：能源部旧有废料场中的金属和氢离子酸度和极高的硝酸盐浓度为成功进行原位U和Tc生物固定化带来了挑战。在这项研究中，我们调查了潜在的原位生物屏障配置，该配置可中和pH值并在21个月内从硝酸，U和Tc污染的地下水中去除硝酸盐和放射性核素。流过天然沉积物和压碎的石灰石的地下水中添加的乙醇有效地提高了pH（从4.7至6.9），促进了116 mM硝酸盐的去除，增加了沉积物的生物量并固定了94％的总U在没有添加乙醇的对照柱中。连续萃取和XANES分析表明该沉积物中的U为固相U（VI），并且EXAFS分析结果与正磷酸铀酰（UO_2）_3（PO_4）_2·4H_2O_（s）一致，这可以控制U的溶解度在这个系统中。与对照组相比，乙醇刺激的系统中呼吸泛醌与甲基萘醌的比率以及异化亚硝酸还原酶基因nirS和nirK的拷贝至少高1个数量级，表明乙醇的加入促进了大部分反硝化微生物群落的生长。沉积物16S rRNA基因克隆文库显示，在流入酸性地下水的水源附近，β-变形杆菌是占主导地位的（89％），而随着pH的增加和硝酸盐浓度的降低，γ-和α-变形细菌和拟杆菌的成员沿着流动路径增加，表明群落的空间转移pH和硝酸盐浓度的函数。这项研究的结果支持了生物屏障在处理酸性放射性核素和硝酸盐污染的地下水中的实用性。

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