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Michael JP, Putt AD, Yang Y, Adams BG, McBride KR, Fan Y, Lowe KA, Ning D, Jagadamma S, Moon JW, Klingeman DM, Zhang P, Fu Y, Hazen TC, Zhou J. Reproducible responses of geochemical and microbial successional patterns in the subsurface to carbon source amendment. WATER RESEARCH 2024; 255:121460. [PMID: 38552495 DOI: 10.1016/j.watres.2024.121460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/24/2024]
Abstract
Carbon amendments designed to remediate environmental contamination lead to substantial perturbations when injected into the subsurface. For the remediation of uranium contamination, carbon amendments promote reducing conditions to allow microorganisms to reduce uranium to an insoluble, less mobile state. However, the reproducibility of these amendments and underlying microbial community assembly mechanisms have rarely been investigated in the field. In this study, two injections of emulsified vegetable oil were performed in 2009 and 2017 to immobilize uranium in the groundwater at Oak Ridge, TN, USA. Our objectives were to determine whether and how the injections resulted in similar abiotic and biotic responses and their underlying community assembly mechanisms. Both injections caused similar geochemical and microbial succession. Uranium, nitrate, and sulfate concentrations in the groundwater dropped following the injection, and specific microbial taxa responded at roughly the same time points in both injections, including Geobacter, Desulfovibrio, and members of the phylum Comamonadaceae, all of which are well established in uranium, nitrate, and sulfate reduction. Both injections induced a transition from relatively stochastic to more deterministic assembly of microbial taxonomic and phylogenetic community structures based on 16S rRNA gene analysis. We conclude that geochemical and microbial successions after biostimulation are reproducible, likely owing to the selection of similar phylogenetic groups in response to EVO injection.
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Affiliation(s)
- Jonathan P Michael
- Institute for Environmental Genomics, University of Oklahoma, Norman, OK, USA; School of Biological Sciences, University of Oklahoma, Norman, OK, USA
| | - Andrew D Putt
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | - Yunfeng Yang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, China
| | - Benjamin G Adams
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA
| | - Kathryn R McBride
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
| | - Yupeng Fan
- Institute for Environmental Genomics, University of Oklahoma, Norman, OK, USA; School of Biological Sciences, University of Oklahoma, Norman, OK, USA
| | - Kenneth A Lowe
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Daliang Ning
- Institute for Environmental Genomics, University of Oklahoma, Norman, OK, USA; School of Biological Sciences, University of Oklahoma, Norman, OK, USA
| | - Sindhu Jagadamma
- Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN, USA
| | - Ji Won Moon
- National Minerals Information Center, United States Geological Survey, Reston, VA, USA
| | - Dawn M Klingeman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Ping Zhang
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Ying Fu
- Institute for Environmental Genomics, University of Oklahoma, Norman, OK, USA; School of Biological Sciences, University of Oklahoma, Norman, OK, USA
| | - Terry C Hazen
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, USA; Department of Microbiology, University of Tennessee, Knoxville, TN, USA; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Department of Civil and Environmental Sciences, University of Tennessee, Knoxville, TN, USA; Institute for a Secure and Sustainable Environment, University of Tennessee, Knoxville, TN, USA
| | - Jizhong Zhou
- Institute for Environmental Genomics, University of Oklahoma, Norman, OK, USA; School of Biological Sciences, University of Oklahoma, Norman, OK, USA; School of Civil Engineering and Environmental Sciences, University of Oklahoma, Norman, OK, USA; Earth and Environmental Sciences, Lawrence Berkley National Laboratory, Berkeley, CA, USA.
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Biotic and Abiotic Biostimulation for the Reduction of Hexavalent Chromium in Contaminated Aquifers. WATER 2022. [DOI: 10.3390/w14010089] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Hexavalent chromium is a carcinogenic heavy metal that needs to be removed effectively from polluted aquifers in order to protect public health and the environment. This work aims to evaluate the reduction of Cr(VI) to Cr(III) in a contaminated aquifer through the stimulation of indigenous microbial communities with the addition of reductive agents. Soil-column experiments were conducted in the absence of oxygen and at hexavalent chromium (Cr(VI)) groundwater concentrations in the 1000–2000 μg/L range. Two carbon sources (molasses and EVO) and one iron electron donor (FeSO4·7H2O) were used as ways to stimulate the metabolism and proliferation of Cr(VI) reducing bacteria in-situ. The obtained results indicate that microbial anaerobic respiration and electron transfer can be fundamental to alleviate polluted groundwater from hazardous Cr(VI). The addition of organic electron donors increased significantly Cr(VI) reduction rates in comparison to natural soil attenuation rates. Furthermore, a combination of organic carbon and iron electron donors led to a longer life span of the remediation process and thus increased total Cr(VI) removal. This is the first study to investigate biotic and abiotic Cr(VI) removal by conducting experiments with natural soil and by applying biostimulation to modify the natural existing microbial communities.
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Pei P, Sun T, Xu Y, Sun Y. Soil aggregate-associated mercury (Hg) and organic carbon distribution and microbial community characteristics under typical farmland-use types. CHEMOSPHERE 2021; 275:129987. [PMID: 33631401 DOI: 10.1016/j.chemosphere.2021.129987] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 01/28/2021] [Accepted: 02/11/2021] [Indexed: 06/12/2023]
Abstract
In order to get insight into the distribution characteristics of mercury (Hg) and organic carbon in soil aggregates, and the diversity and composition of soil microbial community under different farmland-use types (soil form three adjacent cultivation systems, i.e., corn, vegetable, and rice fields, named as CFS, VFS, and RFS), a field investigation close to Wanshan Hg mining area was conducted. Results indicated that soil total Hg (0-20 cm) presented in decreasing order of RFS (5.27 mg kg-1) > VFS (4.32 mg kg-1) > CFS (2.21 mg kg-1), implying soils from rice field with higher ability of Hg accumulation. Soil aggregate-associated Hg and organic carbon enriched with the decrease of particle size under all farmland-use types, with the maximum at microaggregates (<0.053 mm). Due to the mass ratio of soil aggregates fraction, soil aggregate-associated Hg and organic carbon mainly distributed in >2 mm particles for RFS, whereas 0.25-2 mm particles for CFS and VFS. Furthermore, 16S rRNA results revealed the obvious differences in RFS and dry land soils (CFS and VFS), such as the observed species and unique OUTs, Shannon index, relative abundance at phylum and genus, which implied the diversity and composition of soil microbial community were greatly affected by farmland-use types. Spearman correlation and RDA results suggested farmland-use types, pH and total Hg were main drives for differences in soil microbial community. These findings provide evidence that farmland-use type is an important factor that affects soil total Hg accumulation, soil aggregate-associated Hg and organic carbon distribution, as well as the indigenous microbial community profiles.
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Affiliation(s)
- Penggang Pei
- Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs (MARA), Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China; Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China
| | - Tao Sun
- Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs (MARA), Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China; Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China
| | - Yingming Xu
- Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs (MARA), Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China; Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China
| | - Yuebing Sun
- Key Laboratory of Original Agro-Environmental Pollution Prevention and Control, Ministry of Agriculture and Rural Affairs (MARA), Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China; Tianjin Key Laboratory of Agro-Environment and Agro-Product Safety, Agro-Environmental Protection Institute, MARA, Tianjin, 300191, China.
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Ding L, Song J, Huang D, Lei J, Li X, Sun J. Simultaneous removal of nitrate and hexavalent chromium in groundwater using indigenous microorganisms enhanced by emulsified vegetable oil: Interactions and remediation threshold values. JOURNAL OF HAZARDOUS MATERIALS 2021; 406:124708. [PMID: 33296759 DOI: 10.1016/j.jhazmat.2020.124708] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 11/07/2020] [Accepted: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Combined pollution in groundwater has become increasingly serious. Adding emulsified vegetable oil to an aquifer is an effective method to remediate multiple pollutants. However, the efficiency and threshold values for the remediation of groundwater contaminated by both nitrate and hexavalent chromium (Cr(VI)) stimulated by emulsified vegetable oil remain unclear. In this study, emulsified vegetable oil was used for the first time to simultaneously remediate nitrate and Cr(VI) in groundwater. The results suggested that the addition of emulsified vegetable oil could effectively remediate nitrate and Cr(VI), and there were interplay effects between nitrate and Cr(VI). Nitrate promoted Cr(VI) removal, while Cr(VI) inhibited nitrate reduction. The remediation thresholds for nitrate and Cr(VI) alone were 1600 mg/L and 10 mg/L, respectively (emulsified vegetable oil = 7 g/L). For combined pollution, the remediation threshold values were 868.10 mg/L for nitrate and 12.43 mg/L for Cr(VI) (emulsified vegetable oil = 7 g/L). The dose of emulsified vegetable oil played an important role in the threshold value. When the concentration of emulsified vegetable oil was 10.8 g/L, the maximum threshold values were 1379.79 mg/L for nitrate and 12.67 mg/L for Cr(VI). When the pollutant concentration was below the threshold value, the contaminant could be completely removed.
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Affiliation(s)
- Linjie Ding
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China.
| | - Jibin Song
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China
| | - Dongxia Huang
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China
| | - Jiansen Lei
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China
| | - Xiang Li
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China
| | - Jianhui Sun
- Key Laboratory for Yellow River and Huai River Water Environmental and Pollution Control, Ministry of Education, Henan Key Laboratory for Environmental Pollution Control, School of Environment, Henan Normal University, Xinxiang, Henan 453007, PR China
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5
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Bagwell CE, Gillispie EC, Lawter AR, Qafoku NP. Evaluation of gaseous substrates for microbial immobilization of contaminant mixtures in unsaturated subsurface sediments. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2020; 214-215:106183. [PMID: 32063288 DOI: 10.1016/j.jenvrad.2020.106183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/24/2020] [Accepted: 01/25/2020] [Indexed: 06/10/2023]
Abstract
Extensive vadose zone metals and organic contamination remains at many former industrial and defense manufacturing sites, and effective remedial solutions are needed to slow or prevent its migration to groundwater. In this study, the application of gaseous substrates to stimulate microbial respiratory reduction of comingled radioisotopes and nitrate under unsaturated conditions was examined for possible application at the Hanford Site, a former nuclear production facility in southeastern WA, USA. First, screening studies were performed to qualitatively measure the sediment respiratory response to 14 gaseous or volatile organic substrates at two moisture contents, 4% and 8%. Volatile substrates produced the strongest respiratory response, among them were butyrate, pentane, butyl acetate. Ethane and butane were the most effective gaseous substrates but only at 8% water content. Hanford sediment from two waste sites with distinctive chemistries were wetted to 7% moisture content, packed into columns, and treated with ethane or butane. After 4 weeks, columns were then leached to quantify retardation in the mobility of aqueous contaminant concentrations compared to no gas control columns. Treatment with both gases resulted in >80% removal of Cr from the aqueous phase. However, NO3 concentration and a waste sites exposure history to NO3 had a major effect on U and Tc reduction. Incomplete nitrate reduction outcompeted U and Tc in waste site sediments having limited prior exposure to NO3. Conversely, waste site sediments co-contaminated with NO3 were able to achieve highly reduced conditions resulting in complete denitrification of NO3, and delayed leaching of U and Tc. This implied effective reduction of both contaminants to less mobile species. This study demonstrates that unsaturated vadose sediments at Hanford waste sites have the capacity for a sustained respiratory response to gaseous substrate injection, which could potentially be deployed as part of an overall strategy to reduce the flux of long-lived radionuclides to groundwater at Hanford and other legacy waste sites.
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Affiliation(s)
- Christopher E Bagwell
- Pacific Northwest National Laboratory, Earth Systems Science Division, Richland, WA, USA.
| | - Elizabeth C Gillispie
- Pacific Northwest National Laboratory, Earth Systems Science Division, Richland, WA, USA
| | - Amanda R Lawter
- Pacific Northwest National Laboratory, Earth Systems Science Division, Richland, WA, USA
| | - Nikolla P Qafoku
- Pacific Northwest National Laboratory, Earth Systems Science Division, Richland, WA, USA
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Wang L, Wang LA, Zhan X, Huang Y, Wang J, Wang X. Response mechanism of microbial community to the environmental stress caused by the different mercury concentration in soils. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 188:109906. [PMID: 31708226 DOI: 10.1016/j.ecoenv.2019.109906] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 10/23/2019] [Accepted: 10/31/2019] [Indexed: 05/12/2023]
Abstract
Despite the toxicity of mercury for mammal has been widely studied in recent years, little is known on its impact on the soil microbiome. In this paper, the effects of mercury in soils microbial communities along a gradient of contamination from no to high concentration was assessed by the richness and diversity of microbial community using high throughput sequencing method. The richness of microbial community decreased gradually with the increase of culture time, while the low and medium concentration of mercury had little effect on the evenness of soil microbial community. Proteobacteria tolerated the mercury contamination, while Acidobacteria, Planctomycetes and Chloroflexi were sensitive to mercury pollution in phylum level. Omnitrophica and Ignavibacteriae microorganisms were very sensitive to mercury contamination and dead quickly when contaminated with mercury. Mercury contamination selected two mercury tolerance genuses which were Massilia and Burkholderia in genus level and at least 22 microorganisms such as Alkanindiges, Geothrix, Polycyclovorans and Sporichthya in genus which mainly from the Acidobacteria, Proteobacteria, Bacteroides, Chloroflexi and Omnitrophica phylum were sensitive to mercury. The bacteria tolerant to mercury in soil were Massilia and Burkholderia from Betaproteobacteria and Lysobacter, Luteimonas from Gammaproteobacteria, separately, they were Gram-negative bacteria with thin cell walls and complex ingredients that responded quickly to pollution stress.
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Affiliation(s)
- Lei Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China
| | - Li-Ao Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China
| | - Xinyuan Zhan
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China
| | - Yongkui Huang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China
| | - Jia Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China
| | - Xiang Wang
- State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing, 400044, China; College of Resources and Environmental Science, Chongqing University, Chongqing, 400044, China.
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7
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Dong J, Yu J, Bao Q. Simulated reactive zone with emulsified vegetable oil for the long-term remediation of Cr(VI)-contaminated aquifer: dynamic evolution of geological parameters and groundwater microbial community. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:34392-34402. [PMID: 30306441 DOI: 10.1007/s11356-018-3386-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2018] [Accepted: 10/01/2018] [Indexed: 06/08/2023]
Abstract
Cr(VI), which is highly toxic and soluble, is one of the most challenging groundwater contaminants. Previous work has indicated that emulsified vegetable oil (EVO) is an effective in situ amendment for removing Cr(VI) from groundwater. However, the spatial and temporal changes in geological parameters and microbial community structures throughout the remediation period are poorly understood. In this study, a large laboratory-scale sand-packed chamber (reactive zone of 100 × 50 × 30 cm) was used to simulate the bioremediation of Cr(VI)-contaminated aquifer by EVO over a 512-day period. Various geological parameters and microbial communities were monitored during both the establishment and remediation stages. The results indicate that several biogeochemical reactions occurred in a specific sequence following the injection of EVO, creating an acidic and reducing environment. A shift in the community structure and a decrease in the community diversity were observed. The abundance of microbes involved in the degradation of EVO and reduction of electron acceptors significantly increased. Then, the EVO reactive zone was flushed with Cr(VI)-contaminated groundwater. Biogeochemical reactions were inhibited after the inflow of Cr(VI) and subsequently recovered a month later. The pH of the aquifer returned to the initial neutral condition (approximately 7.2). The EVO reactive zone could remediate Cr(VI)-contaminated groundwater at an efficiency exceeding 97% over 480 days. Biogeochemistry played a major role in the early period (0~75 days). In the later period (240~480 days), the remediation of Cr(VI) in the reactive zone depended mostly on bio-reduction by Cr(VI)-reducing bacteria.
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Affiliation(s)
- Jun Dong
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China
| | - Jinqiu Yu
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China
| | - Qiburi Bao
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China.
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Dong J, Ding L, Chi Z, Lei J, Su Y. Kinetics of nitrobenzene degradation coupled to indigenous microorganism dissimilatory iron reduction stimulated by emulsified vegetable oil. J Environ Sci (China) 2017; 54:206-216. [PMID: 28391930 DOI: 10.1016/j.jes.2016.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 02/17/2016] [Accepted: 02/18/2016] [Indexed: 06/07/2023]
Abstract
Widespread contamination by nitrobenzene (NB) in sediments and groundwater requires better understanding of the biogeochemical removal process of the pollutant. NB degradation, coupled with dissimilatory iron reduction, is one of the most efficient pollutant removal methods. However, research on NB degradation coupled to indigenous microorganism dissimilatory iron reduction stimulated by electron donors is still experimental. A model for remediation in an actual polluted site does not currently exist. Therefore, in this study, the dynamics was derived from the Michaelis-Menten model (when the mass ratio of emulsified vegetable oil and NB reached the critical value 91:1). The effect of SO42-, NO3-, Ca2+/Mg2+, and the grain size of aquifer media on the dynamics were studied, and the NB degradation dynamic model was then modified based on the most significant factors. Utilizing the model, the remediation time could be calculated in a contaminated site.
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Affiliation(s)
- Jun Dong
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China
| | - Linjie Ding
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China.
| | - Zifang Chi
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130021, China.
| | - Jiansen Lei
- Exploration Unit Of North China Geological Exploration Bureau, Tianjin 065201, China
| | - Yan Su
- Shenyang Academy of Environmental Sciences, Shenyang 110000, China
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Newsome L, Cleary A, Morris K, Lloyd JR. Long-Term Immobilization of Technetium via Bioremediation with Slow-Release Substrates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1595-1604. [PMID: 28051295 DOI: 10.1021/acs.est.6b04876] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Radionuclides are present in groundwater at contaminated nuclear facilities with technetium-99, one of the most mobile radionuclides encountered. In situ bioremediation via the generation of microbially reducing conditions has the potential to remove aqueous and mobile Tc(VII) from groundwater as insoluble Tc(IV). However, questions remain regarding the optimal methods of biostimulation and the stability of reduced Tc(IV) phases under oxic conditions. Here, we selected a range of slow-release electron donor/chemical reduction based substrates available for contaminated land treatment, and assessed their potential to stimulate the formation of recalcitrant Tc(IV) biominerals under conditions relevant to radioactively contaminated land. These included a slow-release polylactate substrate (HRC), a similar substrate with an additional organosulfur ester (MRC) and a substrate containing zerovalent iron and plant matter (EHC). Results showed that Tc was removed from solution in the form of poorly soluble hydrous Tc(IV)-oxides or Tc(IV)-sulfides during the development of reducing conditions. Reoxidation experiments showed that these phases were largely resistant to oxidative remobilization and were more resistant than Tc(IV) produced via biostimulation with an acetate/lactate electron donor mix in the sediments tested. The implications of the targeted formation of recalcitrant Tc(IV) phases using these proprietorial substrates in situ is discussed in the context of the long-term management of technetium at legacy nuclear sites.
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Affiliation(s)
- Laura Newsome
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Adrian Cleary
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Katherine Morris
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Jonathan R Lloyd
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
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Saunders JA, Pivetz BE, Voorhies N, Wilkin RT. Potential aquifer vulnerability in regions down-gradient from uranium in situ recovery (ISR) sites. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2016; 183:67-83. [PMID: 27576149 PMCID: PMC7316075 DOI: 10.1016/j.jenvman.2016.08.049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 08/16/2016] [Accepted: 08/19/2016] [Indexed: 05/17/2023]
Abstract
Sandstone-hosted roll-front uranium ore deposits originate when U(VI) dissolved in groundwater is reduced and precipitated as insoluble U(IV) minerals. Groundwater redox geochemistry, aqueous complexation, and solute migration are important in leaching uranium from source rocks and transporting it in low concentrations to a chemical redox interface where it is deposited in an ore zone typically containing the uranium minerals uraninite, pitchblende, and/or coffinite; various iron sulfides; native selenium; clays; and calcite. In situ recovery (ISR) of uranium ores is a process of contacting the uranium mineral deposit with leaching and oxidizing (lixiviant) fluids via injection of the lixiviant into wells drilled into the subsurface aquifer that hosts uranium ore, while other extraction wells pump the dissolved uranium after dissolution of the uranium minerals. Environmental concerns during and after ISR include water quality degradation from: 1) potential excursions of leaching solutions away from the injection zone into down-gradient, underlying, or overlying aquifers; 2) potential migration of uranium and its decay products (e.g., Ra, Rn, Pb); and, 3) potential mobilization and migration of redox-sensitive trace metals (e.g., Fe, Mn, Mo, Se, V), metalloids (e.g., As), and anions (e.g., sulfate). This review describes the geochemical processes that control roll-front uranium transport and fate in groundwater systems, identifies potential aquifer vulnerabilities to ISR operations, identifies data gaps in mitigating these vulnerabilities, and discusses the hydrogeological characterization involved in developing a monitoring program.
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Affiliation(s)
- James A Saunders
- Department of Geosciences, 210 Petrie Hall, Auburn University, AL 36849, United States
| | - Bruce E Pivetz
- CSS-Dynamac, 10301 Democracy Lane Suite 300, Fairfax, VA 22030, United States
| | - Nathan Voorhies
- Environmental Solutions and Services, Battelle, 1300 Clay St., Suite 600, Oakland, CA 94612, United States
| | - Richard T Wilkin
- U.S. Environmental Protection Agency, National Risk Management Research Laboratory, Ground Water and Ecosystems Restoration Division, 919 Kerr Research Dr., Ada, OK 74820, United States.
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Wang D, Boukhalfa H, Marina O, Ware DS, Goering TJ, Sun F, Daligault HE, Lo CC, Vuyisich M, Starkenburg SR. Biostimulation and microbial community profiling reveal insights on RDX transformation in groundwater. Microbiologyopen 2016; 6. [PMID: 27860341 PMCID: PMC5387309 DOI: 10.1002/mbo3.423] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 09/29/2016] [Accepted: 10/06/2016] [Indexed: 11/06/2022] Open
Abstract
Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) is a high explosive released to the environment as a result of weapons manufacturing and testing worldwide. At Los Alamos National Laboratory, the Technical Area (TA) 16 260 Outfall discharged high‐explosives‐bearing water from a high‐explosives‐machining facility to Cañon de Valle during 1951 through 1996. These discharges served as a primary source of high‐explosives and inorganic‐element contamination in the area. Data indicate that springs, surface water, alluvial groundwater, and perched‐intermediate groundwater contain explosive compounds, including RDX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine); HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine); and TNT (2,4,6‐trinitrotoluene). RDX has been detected in the regional aquifer in several wells, and a corrective measures evaluation is planned to identify remedial alternatives to protect the regional aquifer. Perched‐intermediate groundwater at Technical Area 16 is present at depths from 650 ft to 1200 ft bgs. In this study, we examined the microbial diversity in a monitoring well completed in perched‐intermediate groundwater contaminated by RDX, and examined the response of the microbial population to biostimulation under varying geochemical conditions. Results show that the groundwater microbiome was dominated by Actinobacteria and Proteobacteria. A total of 1,605 operational taxonomic units (OTUs) in 96 bacterial genera were identified. Rhodococcus was the most abundant genus (30.6%) and a total of 46 OTUs were annotated as Rhodococcus. One OTU comprising 25.2% of total sequences was closely related to a RDX ‐degrading strain R. erythropolis HS4. A less abundant OTU from the Pseudomonas family closely related to RDX‐degrading strain P. putida II‐B was also present. Biostimulation significantly enriched Proteobacteria but decreased/eliminated the population of Actinobacteria. Consistent with RDX degradation, the OTU closely related to the RDX‐degrading P. putida strain II‐B was specifically enriched in the RDX‐degrading samples. Analysis of the accumulation of RDX‐degradation products reveals that during active RDX degradation, there is a transient increase in the concentration of the degradation products MNX, DNX, TNX, and NDAB. The accumulation of these degradation products suggests that RDX is degraded via sequential reduction of the nitro functional groups followed by abiotic ring‐cleavage. The results suggest that strict anaerobic conditions are needed to stimulate RDX degradation under the TA‐16 site‐specific conditions.
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Affiliation(s)
- Dongping Wang
- Earth Systems Observations EES-14, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Hakim Boukhalfa
- Earth Systems Observations EES-14, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Oana Marina
- Earth Systems Observations EES-14, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Doug S Ware
- Earth Systems Observations EES-14, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Tim J Goering
- Environmental Programs ADEP, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Fengjie Sun
- School of Science and Technology, Georgia Gwinnett College, Lawrenceville, GA, USA
| | - Hajnalka E Daligault
- Bioenergy and Biome Sciences, Biology Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Chien-Chi Lo
- Bioenergy and Biome Sciences, Biology Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Momchilo Vuyisich
- Bioenergy and Biome Sciences, Biology Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
| | - Shawn R Starkenburg
- Bioenergy and Biome Sciences, Biology Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
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Deng Y, Zhang P, Qin Y, Tu Q, Yang Y, He Z, Schadt CW, Zhou J. Network succession reveals the importance of competition in response to emulsified vegetable oil amendment for uranium bioremediation. Environ Microbiol 2015; 18:205-18. [DOI: 10.1111/1462-2920.12981] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 07/08/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Ye Deng
- CAS Key Laboratory of Environmental Biotechnology; Research Center for Eco-Environmental Sciences; Chinese Academy of Sciences (CAS); Beijing China
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
| | - Ping Zhang
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
| | - Yujia Qin
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
| | - Qichao Tu
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
| | - Yunfeng Yang
- State Key Joint Laboratory of Environment Simulation and Pollution Control; School of Environment; Tsinghua University; Beijing China
| | - Zhili He
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
| | | | - Jizhong Zhou
- Institute for Environmental Genomics and Department of Microbiology and Plant Biology; University of Oklahoma; Norman OK USA
- State Key Joint Laboratory of Environment Simulation and Pollution Control; School of Environment; Tsinghua University; Beijing China
- Earth Sciences Division; Lawrence Berkeley National Laboratory; Berkeley CA USA
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Dynamic Succession of Groundwater Functional Microbial Communities in Response to Emulsified Vegetable Oil Amendment during Sustained In Situ U(VI) Reduction. Appl Environ Microbiol 2015; 81:4164-72. [PMID: 25862231 DOI: 10.1128/aem.00043-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 04/05/2015] [Indexed: 11/20/2022] Open
Abstract
A pilot-scale field experiment demonstrated that a one-time amendment of emulsified vegetable oil (EVO) reduced groundwater U(VI) concentrations for 1 year in a fast-flowing aquifer. However, little is known about how EVO amendment stimulates the functional gene composition, structure, and dynamics of groundwater microbial communities toward prolonged U(VI) reduction. In this study, we hypothesized that EVO amendment would shift the functional gene composition and structure of groundwater microbial communities and stimulate key functional genes/groups involved in EVO biodegradation and reduction of electron acceptors in the aquifer. To test these hypotheses, groundwater microbial communities after EVO amendment were analyzed using a comprehensive functional gene microarray. Our results showed that EVO amendment stimulated sequential shifts in the functional composition and structure of groundwater microbial communities. Particularly, the relative abundance of key functional genes/groups involved in EVO biodegradation and the reduction of NO3 (-), Mn(IV), Fe(III), U(VI), and SO4 (2-) significantly increased, especially during the active U(VI) reduction period. The relative abundance for some of these key functional genes/groups remained elevated over 9 months. Montel tests suggested that the dynamics in the abundance, composition, and structure of these key functional genes/groups were significantly correlated with groundwater concentrations of acetate, NO3 (-), Mn(II), Fe(II), U(VI), and SO4 (2-). Our results suggest that EVO amendment stimulated dynamic succession of key functional microbial communities. This study improves our understanding of the composition, structure, and function changes needed for groundwater microbial communities to sustain a long-term U(VI) reduction.
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Phillips DH, Watson DB. Distribution of uranium and thorium in dolomitic gravel fill and shale saprolite. JOURNAL OF HAZARDOUS MATERIALS 2015; 285:474-482. [PMID: 25544493 DOI: 10.1016/j.jhazmat.2014.11.046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 10/07/2014] [Accepted: 11/10/2014] [Indexed: 06/04/2023]
Abstract
The objectives of this study were to examine (1) the distribution of U and Th in dolomitic gravel fill and shale saprolite, and (2) the removal of uranium from acidic groundwater by dolomitic gravel through precipitation with amorphous basaluminite at the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) field site west of the Oak Ridge Y-12 National Security Complex in East Tennessee. Media reactivity and sustainability are a technical concern with the deployment of any subsurface reactive media. Because the gravel was placed in the subsurface and exposed to contaminated groundwater for over 20 years, it provided a unique opportunity to study the solid and water phase geochemical conditions within the media after this length of exposure. This study illustrates that dolomite gravel can remove U from acidic contaminated groundwater with high levels of Al(3+), Ca(2+), NO(3-), and SO4(2-) over the long term. As the groundwater flows through high pH carbonate gravel, U containing amorphous basaluminite precipitates as the pH increases. This is due to an increase in groundwater pH from 3.2 to ∼6.5 as it comes in contact with the gravel. Therefore, carbonate gravel could be considered as a possible treatment medium for removal and sequestration of U and other pH sensitive metals from acidic contaminated groundwater. Thorium concentrations are also high in the carbonate gravel. Thorium generally shows an inverse relationship with U from the surface down into the deeper saprolite. Barite precipitated in the shallow saprolite directly below the dolomitic gravel from barium present in the acidic contaminated groundwater.
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Affiliation(s)
- D H Phillips
- Environmental Engineering Research Centre, School of Planning, Architecture, and Civil Engineering, Queen's University of Belfast, Belfast BT9 5AG, Northern Ireland
| | - D B Watson
- Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, 37831 TN, USA.
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15
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Li D, Kaplan DI, Chang HS, Seaman JC, Jaffé PR, Koster van Groos P, Scheckel KG, Segre CU, Chen N, Jiang DT, Newville M, Lanzirotti A. Spectroscopic evidence of uranium immobilization in acidic wetlands by natural organic matter and plant roots. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:2823-2832. [PMID: 25634067 DOI: 10.1021/es505369g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Biogeochemistry of uranium in wetlands plays important roles in U immobilization in storage ponds of U mining and processing facilities but has not been well understood. The objective of this work was to study molecular mechanisms responsible for high U retention by Savannah River Site (SRS) wetland sediments under varying redox and acidic (pH = 2.6-5.8) conditions using U L3-edge X-ray absorption spectroscopy. Uranium in the SRS wetland sediments existed primarily as U(VI) bonded as a bidentate to carboxylic sites (U-C bond distance at ∼2.88 Å), rather than phenolic or other sites of natural organic matter (NOM). In microcosms simulating the SRS wetland processes, U immobilization on roots was 2 orders of magnitude higher than on the adjacent brown or more distant white sands in which U was U(VI). Uranium on the roots were both U(IV) and U(VI), which were bonded as a bidentate to carbon, but the U(VI) may also form a U phosphate mineral. After 140 days of air exposure, all U(IV) was reoxidized to U(VI) but remained as a bidentate bonding to carbon. This study demonstrated NOM and plant roots can highly immobilize U(VI) in the SRS acidic sediments, which has significant implication for the long-term stewardship of U-contaminated wetlands.
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Affiliation(s)
- Dien Li
- Savannah River National Laboratory, Aiken, South Carolina 29808, United States
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16
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Bao C, Wu H, Li L, Newcomer D, Long PE, Williams KH. Uranium bioreduction rates across scales: biogeochemical hot moments and hot spots during a biostimulation experiment at Rifle, Colorado. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:10116-10127. [PMID: 25079237 DOI: 10.1021/es501060d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We aim to understand the scale-dependent evolution of uranium bioreduction during a field experiment at a former uranium mill site near Rifle, Colorado. Acetate was injected to stimulate Fe-reducing bacteria (FeRB) and to immobilize aqueous U(VI) to insoluble U(IV). Bicarbonate was coinjected in half of the domain to mobilize sorbed U(VI). We used reactive transport modeling to integrate hydraulic and geochemical data and to quantify rates at the grid block (0.25 m) and experimental field scale (tens of meters). Although local rates varied by orders of magnitude in conjunction with biostimulation fronts propagating downstream, field-scale rates were dominated by those orders of magnitude higher rates at a few selected hot spots where Fe(III), U(VI), and FeRB were at their maxima in the vicinity of the injection wells. At particular locations, the hot moments with maximum rates negatively corresponded to their distance from the injection wells. Although bicarbonate injection enhanced local rates near the injection wells by a maximum of 39.4%, its effect at the field scale was limited to a maximum of 10.0%. We propose a rate-versus-measurement-length relationship (log R' = -0.63 log L - 2.20, with R' in μmol/mg cell protein/day and L in meters) for orders-of-magnitude estimation of uranium bioreduction rates across scales.
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Affiliation(s)
- Chen Bao
- John and Willie Leone Department of Energy and Mineral Engineering, ‡EMS Energy Institute, and §Earth and Environmental Systems Institute (EESI), Pennsylvania State University , University Park, Pennsylvania 16802, United States
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17
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Hiortdahl KM, Borden RC. Enhanced reductive dechlorination of tetrachloroethene dense nonaqueous phase liquid with EVO and Mg(OH)2. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 48:624-631. [PMID: 24328264 DOI: 10.1021/es4042379] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In situ treatment of dense nonaqueous phase liquids (DNAPL) by enhanced reductive dechlorination (ERD) can be limited by contaminant toxicity, low pH, and challenges in effectively delivering electron donor. Flushing emulsified vegetable oil (EVO), colloidal Mg(OH)2 buffer, and a bioaugmentation culture (BC) through a zone containing neat tetrachloroethene (PCE) was effective in reducing contaminant toxicity, limiting pH declines, and accelerating bioenhanced dissolution of the DNAPL. In the effluent of porous media columns with little fine material, PCE concentrations reached a maximum of 40-50 times PCE aqueous solubility in water, demonstrating NAPL PCE was distributed throughout the 1.5 m column length. In a column treated with only EVO+BC, reductive dechlorination was limited. However, a single injection of EVO+Mg(OH)2+BC was effective in reducing PCE to below detection for over 400 days with a large increase in Cl(-) and dichloroethene (DCE), accelerating bioenhanced DNAPL dissolution. Dechlorination rates gradually increased over time with the rate of total ethene (TE) release from the Mg(OH)2+EVO+BC column reaching 5-6 times the TE release rate from the EVO+BC column. The accelerated dechlorination was likely due to both Mg(OH)2 addition which limited pH declines from HCl, volatile fatty acids (VFAs), and inorganic carbon (IC) production, and formation of a mixed PCE-vegetable oil NAPL which provided a readily accessible electron donor, resulting in rapid PCE degradation with reduced PCE toxicity.
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Affiliation(s)
- Kirsten M Hiortdahl
- Department of Civil, Construction and Environmental Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States
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Watson DB, Wu WM, Mehlhorn T, Tang G, Earles J, Lowe K, Gihring TM, Zhang G, Phillips J, Boyanov MI, Spalding BP, Schadt C, Kemner KM, Criddle CS, Jardine PM, Brooks SC. In situ bioremediation of uranium with emulsified vegetable oil as the electron donor. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:6440-6448. [PMID: 23697787 DOI: 10.1021/es3033555] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A field test with a one-time emulsified vegetable oil (EVO) injection was conducted to assess the capacity of EVO to sustain uranium bioreduction in a high-permeability gravel layer with groundwater concentrations of (mM) U, 0.0055; Ca, 2.98; NO3(-), 0.11; HCO3(-), 5.07; and SO4(2-), 1.23. Comparison of bromide and EVO migration and distribution indicated that a majority of the injected EVO was retained in the subsurface from the injection wells to 50 m downgradient. Nitrate, uranium, and sulfate were sequentially removed from the groundwater within 1-2 weeks, accompanied by an increase in acetate, Mn, Fe, and methane concentrations. Due to the slow release and degradation of EVO with time, reducing conditions were sustained for approximately one year, and daily U discharge to a creek, located approximately 50 m from the injection wells, decreased by 80% within 100 days. Total U discharge was reduced by 50% over the one-year period. Reduction of U(VI) to U(IV) was confirmed by synchrotron analysis of recovered aquifer solids. Oxidants (e.g., dissolved oxygen, nitrate) flowing in from upgradient appeared to reoxidize and remobilize uranium after the EVO was exhausted as evidenced by a transient increase of U concentration above ambient values. Occasional (e.g., annual) EVO injection into a permeable Ca and bicarbonate-containing aquifer can sustain uranium bioreduction/immobilization and decrease U migration/discharge.
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Affiliation(s)
- David B Watson
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6038, United States.
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Tang G, Wu WM, Watson DB, Parker JC, Schadt CW, Shi X, Brooks SC. U(VI) bioreduction with emulsified vegetable oil as the electron donor--microcosm tests and model development. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:3209-3217. [PMID: 23397992 DOI: 10.1021/es304641b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We conducted microcosm tests and biogeochemical modeling to study U(VI) reduction in contaminated sediments amended with emulsified vegetable oil (EVO). Indigenous microorganisms in the sediments degraded EVO and stimulated Fe(III), U(VI), and sulfate reduction, and methanogenesis. Acetate concentration peaked in 100-120 days in the EVO microcosms versus 10-20 days in the oleate microcosms, suggesting that triglyceride hydrolysis was a rate-limiting step in EVO degradation and subsequent reactions. Acetate persisted 50 days longer in oleate- and EVO- than in ethanol-amended microcosms, indicating that acetate-utilizing methanogenesis was slower in the oleate and EVO than ethanol microcosms. We developed a comprehensive biogeochemical model to couple EVO hydrolysis, production, and oxidation of long-chain fatty acids (LCFA), glycerol, acetate, and hydrogen, reduction of Fe(III), U(VI) and sulfate, and methanogenesis with growth and decay of multiple functional microbial groups. By estimating EVO, LCFA, and glycerol degradation rate coefficients, and introducing a 100 day lag time for acetoclastic methanogenesis for oleate and EVO microcosms, the model approximately matched observed sulfate, U(VI), and acetate concentrations. Our results confirmed that EVO could stimulate U(VI) bioreduction in sediments and the slow EVO hydrolysis and acetate-utilizing methanogens growth could contribute to longer term bioreduction than simple substrates (e.g., ethanol, acetate, etc.) in the subsurface.
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Affiliation(s)
- Guoping Tang
- Environmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, MS-6038, Oak Ridge, Tennessee 37831-6038, United States.
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