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Van De Ven CJC, Laurenzi L, Arnold AC, Hallam SJ, Mayer KU. The nature of gas production patterns associated with methanol degradation in natural aquifer sediments: A microcosm study. JOURNAL OF CONTAMINANT HYDROLOGY 2022; 247:103988. [PMID: 35303484 DOI: 10.1016/j.jconhyd.2022.103988] [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: 09/21/2020] [Revised: 02/28/2022] [Accepted: 03/03/2022] [Indexed: 06/14/2023]
Abstract
With growing global use of methanol as a fuel additive and extensive use in other industrial processes, there is the potential for unintended release and spills into soils and aquifers. In these subsurface systems it is likely that methanol will be readily biodegraded; however, degradation may lead to the production of by-products, most importantly methane possibly resulting in explosion hazards and volatile fatty acids (VFAs) causing aesthetic issues for groundwater. In this study, the formation of these potentially harmful by-products due to methanol biodegradation was investigated in natural sand and silt sediments using microcosms inoculated with neat methanol (100%) ranging in concentration from 100 to 100,000 ppm. To assess the rate of degradation and by-product formation, water and headspace samples were collected and analyzed for methanol, volatile fatty acids (VFAs, including acetic, butyric, and propionic acid), cation (metal) concentrations (Al, Ca, Fe, K, Mg, Mn and Na), microbial community structure and activity, headspace pressure, gas composition (CH4, CO2, O2 and N2), and compound specific isotopes. Methanol was completely biodegraded in sand and silt up to concentrations of 1000 ppm and 10,000 ppm, respectively. Degradation was initially aerobic, consuming oxygen (O2) and producing carbon dioxide (CO2). When O2 was depleted, the microcosms became anaerobic and a lag in methanol degradation occurred (ranging from 41 to 87 days). Following this lag, methanol was preferentially degraded to acetate, coupled with CO2 reduction. Microcosms with high methanol concentrations (10,000 ppm) were driven further down the redox ladder and exhibited fermentation, leading to concurrent acetate and methane (CH4) generation. In all cases acetate was an intermediate product, further degraded to the final products of CH4 and CO2. Carbonates present in the microcosm sediments helped buffer VFA acidification and replenished CO2. Methane generation in the anaerobic microcosms was short-lived, but temporarily reached high rates up to 13 mg kg-1 day-1. Under the conditions of these experiments, methanol degradation occurred rapidly, after initial lag periods, which were a function of methanol concentration and sediment type. Our experiment also showed that methanol degradation and associated methane production can occur in a stepwise fashion.
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Affiliation(s)
- Cole J C Van De Ven
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada; Carleton University, Department of Civil & Environmental Engineering, Ottawa, ON K1S 5B6, Canada.
| | - Laura Laurenzi
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Ashley C Arnold
- Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Steven J Hallam
- Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada; Graduate Program in Bioinformatics, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Genome Sciences Centre, BC Cancer Agency, Vancouver, BC V5Z 4S6, Canada; Genome Science and Technology Program, University of British Columbia, 2329 West Mall, Vancouver, BC V6T 1Z4, Canada; Life Sciences Institute, University of British Columbia, Vancouver, BC V6T 1Z3, Canada; ECOSCOPE Training Program, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - K Ulrich Mayer
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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Han K, Hong U, Park S, Kwon S, Kim Y. In situ field method for evaluating biodegradation potential of BTEX by indigenous heterotrophic denitrifying microorganisms in a BTEX-contaminated fractured-rock aquifer. ENVIRONMENTAL TECHNOLOGY 2021; 42:1326-1335. [PMID: 31524076 DOI: 10.1080/09593330.2019.1668482] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 09/10/2019] [Indexed: 06/10/2023]
Abstract
Generally different anaerobic degradation potentials for benzene, toluene, ethylbenzene and xylene isomers (BTEX) has been reported due to site specific conditions, such as the indigenous microbial population, electron acceptors (EA) available and concentrations of each BTEX compound. It was of interest to estimate relative biodegradation potential of each BTEX compound during enhanced anaerobic bioremediation of a BTEX-contaminated aquifer. In this study, an in situ method for assessing the degradation potentials of each BTEX compound present as a mixture under NO3-injecting conditions by performing a series of single-well push-pull tests and well-to-well tests (WWTs) was developed. During the 1st and 2nd WWTs, biological heterotrophic dissimilative NO3- denitrification was confirmed by simultaneous detection of both NO2- and N2O and significant production of CO2 during the NO3- degradation. The biodegradation fractions of NO3- injected during the 1st and 2nd WWTs were 1.7% and 5.0%, respectively, with 7.18 and 8.85 mmol N/L/day of in situ zero-order denitrification rate coefficients. The concentrations of benzene, ethylbenzene, and xylenes measured were similar to values calculated when considering only dilution, but the measured concentrations of toluene were significantly lower than the values calculated were. These results indicate that in situ method presented in the study successfully evaluate anaerobic biodegradation potential of individual BTEX compounds by indigenous heterotrophic denitrifying microorganisms.
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Affiliation(s)
- Kyungjin Han
- Department of Environmental Engineering, Korea University, Sejong, Republic of Korea
| | - Uijeon Hong
- Department of Environmental Engineering, Korea University, Sejong, Republic of Korea
- KE Tech Incorporated, Daejeon, Republic of Korea
| | - Sunhwa Park
- National Institute of Environmental Research, Incheon, Republic of Korea
| | - Sooyoul Kwon
- Department of Environmental Health, Korea National Open University, Seoul, Republic of Korea
| | - Young Kim
- Department of Environmental Engineering, Korea University, Sejong, Republic of Korea
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Rama F, Ramos DT, Müller JB, Corseuil HX, Miotliński K. Flow field dynamics and high ethanol content in gasohol blends enhance BTEX migration and biodegradation in groundwater. JOURNAL OF CONTAMINANT HYDROLOGY 2019; 222:17-30. [PMID: 30797547 DOI: 10.1016/j.jconhyd.2019.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 12/21/2018] [Accepted: 01/09/2019] [Indexed: 06/09/2023]
Abstract
Gasohol spills may easily descend through the soil column down and impact sensitive receptors as contaminants dissolve into the groundwater. Gasoline formulations are commonly blended with ethanol to alleviate environmental and economic issues associated with fossil fuels. However, the amount of ethanol added to gasoline and the groundwater hydraulic regime can significantly affect BTEX plume dynamics and lifespan. In this study, two long-term (5 and 10 years) field-scale gasohol releases with ethanol contents of 85% (E85) and 24% (E24), respectively, were assessed to discern the different dynamics undergone by gasohol blends. Statistical, geochemical, microbiological and trend approaches were employed to estimate the influence of groundwater flow variations on ethanol and dissolved BTEX transport, and the associated biodegradation rates of different gasohol blend spills. Ethanol and BTEX groundwater flow were quantified in terms of breakthrough curve characteristics, plume centroid positions and spreading, source depletion and mass degradation rates. In addition, bromide migration was evaluated to address the contribution of flow-driven dissolution. Results revealed that the high amount of ethanol along with a fast and dynamic flow exerted a flushing behavior that enhanced BTEX dissolution, migration (vertical and horizontal) and concentrations in groundwater. The higher amount of ethanol in E85 enhanced BTEX dissolution (and bioavailability) relative to E24 site and led to faster biodegradation rates, which can be explained by the cosolvency effect and metabolic flux dilution. Therefore, flow field dynamics and high ethanol content in gasohol blends enhance BTEX migration and biodegradation in gasohol-contaminated sites. The balance of these factors is crucial to determine fate and transport of contaminants in field sites. These findings suggest that hydraulic regime should be spatially and temporally characterized to support decisions on appropriate monitoring plan and remedial strategies for gasohol spills.
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Affiliation(s)
- Fabrizio Rama
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Débora Toledo Ramos
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Juliana Braun Müller
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Henry Xavier Corseuil
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
| | - Konrad Miotliński
- Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
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McLeod HC, Roy JW, Slater GF, Smith JE. Anaerobic biodegradation of dissolved ethanol in a pilot-scale sand aquifer: Variability in plume (redox) biogeochemistry. JOURNAL OF CONTAMINANT HYDROLOGY 2018; 208:35-45. [PMID: 29224929 DOI: 10.1016/j.jconhyd.2017.12.002] [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: 08/25/2017] [Revised: 11/07/2017] [Accepted: 12/02/2017] [Indexed: 06/07/2023]
Abstract
The use of ethanol in alternative fuels has led to contamination of groundwater with high concentrations of this easily biodegradable organic compound. Previous laboratory and field studies have shown vigorous biodegradation of ethanol plumes, with prevalence of reducing conditions and methanogenesis. The objective of this study was to further our understanding of the dynamic biogeochemistry processes, especially dissolved gas production, that may occur in developing and aging plume cores at sites with ethanol or other organic contamination of groundwater. The experiment performed involved highly-detailed spatial and temporal monitoring of ethanol biodegradation in a 2-dimensional (175cm high×525cm long) sand aquifer tank for 330days, with a vertical shift in plume position and increased nutrient inputs occurring at ~Day 100. Rapid onset of fermentation, denitrification, sulphate-reduction and iron(III)-reduction occurred following dissolved ethanol addition, with the eventual widespread development of methanogenesis. The detailed observations also demonstrate a redox zonation that supports the plume fringe concept, secondary reactions resulting from a changing/moving plume, and time lags for the various biodegradation processes. Additional highlights include: i) the highest dissolved H2 concentrations yet reported for groundwater, possibly linked to vigorous fermentation in the absence of common terminal electron-acceptors (i.e., dissolved oxygen, nitrate, and sulphate, and iron(III)-minerals) and methanogenesis; ii) evidence of phosphorus nutrient limitation, which stalled ethanol biodegradation and perhaps delayed the onset of methanogenesis; and iii) the occurrence of dissimilatory nitrate reduction to ammonium, which has not been reported for ethanol biodegradation to date.
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Affiliation(s)
- Heather C McLeod
- School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada
| | - James W Roy
- School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada; Water Science and Technology Directorate, Environment and Climate Change Canada, Burlington, Ontario, Canada.
| | - Gregory F Slater
- School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada
| | - James E Smith
- School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada
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Bushnaf KM, Mangse G, Meynet P, Davenport RJ, Cirpka OA, Werner D. Mechanisms of distinct activated carbon and biochar amendment effects on petroleum vapour biofiltration in soil. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2017; 19:1260-1269. [PMID: 28920987 DOI: 10.1039/c7em00309a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We studied the effects of two percent by weight activated carbon versus biochar amendments in 93 cm long sand columns on the biofiltration of petroleum vapours released by a non-aqueous phase liquid (NAPL) source. Activated carbon greatly enhanced, whereas biochar slightly reduced, the biofiltration of volatile petroleum hydrocarbons (VPHs) over 430 days. Sorbent amendment benefitted the VPH biofiltration by retarding breakthrough during the biodegradation lag phase. Subsequently, sorbent amendment briefly reduced the mineralization of petroleum hydrocarbons by limiting their bioavailability. During the last and longest study period, when conditions became less supportive of microbial growth, because of inorganic nutrient scarcity, the sorbents again improved the pollution attenuation by preventing the degrading microorganisms from being overloaded with VPHs. A 16S rRNA gene based analysis showed sorbent amendment effects on soil microbial communities. Nocardioidaceae benefitted the most from petroleum hydrocarbons in activated carbon amended soil, whereas Pseudomonadacea predominated in unamended soil. Whilst the degrading microorganisms were overloaded with VPHs in the unamended soil, the reduced mobility and bioavailability of VPHs in the activated carbon amended soil led to the emergence of communities with higher specific substrate affinity, which removed bioavailable VPHs effectively at low concentrations. A numerical pollutant fate model reproduced these experimental observations by considering sorption effects on the pollutant migration and bioavailability for growth of VPH degrading biomass, which is limited by a maximum soil biomass carrying capacity. Activated carbon was a much stronger sorbent for VPHs than biochar, which explained the diverging effects of the two sorbents in this study.
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Affiliation(s)
- Khaled M Bushnaf
- Department of Earth and Environmental Sciences, El-mergab University, Khoms, Libya
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6
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Bacterial community structure within an activated sludge reactor added with phenolic compounds. Appl Microbiol Biotechnol 2016; 101:3405-3414. [DOI: 10.1007/s00253-016-8000-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 10/26/2016] [Accepted: 11/06/2016] [Indexed: 01/02/2023]
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Cápiro NL, Löffler FE, Pennell KD. Spatial and temporal dynamics of organohalide-respiring bacteria in a heterogeneous PCE-DNAPL source zone. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 182:78-90. [PMID: 26348832 DOI: 10.1016/j.jconhyd.2015.08.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 08/15/2015] [Accepted: 08/19/2015] [Indexed: 06/05/2023]
Abstract
Effective treatment of sites contaminated with dense non-aqueous phase liquids (DNAPLs) requires detailed understanding of the microbial community responses to changes in source zone strength and architecture. Changes in the spatial and temporal distributions of the organohalide-respiring Dehalococcoides mccartyi (Dhc) strains and Geobacter lovleyi strain SZ (GeoSZ) were examined in a heterogeneous tetrachloroethene- (PCE-) DNAPL source zone within a two-dimensional laboratory-scale aquifer flow cell. As part of a combined remedy approach, flushing with 2.3 pore volumes (PVs) of 4% (w/w) solution of the nonionic, biodegradable surfactant Tween® 80 removed 55% of the initial contaminant mass, and resulted in a PCE-DNAPL distribution that contained 51% discrete ganglia and 49% pools (ganglia-to-pool ratio of 1.06). Subsequent bioaugmentation with the PCE-to-ethene-dechlorinating consortium BDI-SZ resulted in cis-1,2-dichloroethene (cis-DCE) formation after 1 PV (ca. 7 days), while vinyl chloride (VC) and ethene were detected 10 PVs after bioaugmentation. Maximum ethene yields (ca. 90 μM) within DNAPL pool and ganglia regions coincided with the detection of the vcrA reductive dehalogenase (RDase) gene that exceeded the Dhc 16S rRNA genes by 2.0±1.3 and 4.0±1.7 fold in the pool and ganglia regions, respectively. Dhc and GeoSZ cell abundance increased by up to 4 orders-of-magnitude after 28 PVs of steady-state operation, with 1 to 2 orders-of-magnitude increases observed in close proximity to residual PCE-DNAPL. These observations suggest the involvement of these dechlorinators the in observed PCE dissolution enhancements of up to 2.3 and 6.0-fold within pool and ganglia regions, respectively. Analysis of the solid and aqueous samples at the conclusion of the experiment revealed that the highest VC (≥155 μM) and ethene (≥65 μM) concentrations were measured in zones where Dhc and GeoSZ were predominately attached to the solids. These findings demonstrate dynamic responses of organohalide-respiring bacteria in a heterogeneous DNAPL source zone, and emphasize the influence of source zone architecture on bioremediation performance.
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Affiliation(s)
- Natalie L Cápiro
- Department of Civil and Environmental Engineering, Tufts University, Medford, MA 02155, United States.
| | - Frank E Löffler
- Department of Microbiology, University of Tennessee, Knoxville, TN 37996, United States; Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN 37996, United States; Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN 37996, United States; University of Tennessee and Oak Ridge National Laboratory (UT-ORNL) Joint Institute for Biological Sciences (JIBS) and Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, United States
| | - Kurt D Pennell
- Department of Civil and Environmental Engineering, Tufts University, Medford, MA 02155, United States.
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Ma J, Nossa CW, Alvarez PJJ. Groundwater ecosystem resilience to organic contaminations: microbial and geochemical dynamics throughout the 5-year life cycle of a surrogate ethanol blend fuel plume. WATER RESEARCH 2015; 80:119-129. [PMID: 25996759 DOI: 10.1016/j.watres.2015.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 03/31/2015] [Accepted: 05/04/2015] [Indexed: 06/04/2023]
Abstract
The capacity of groundwater ecosystem to recover from contamination by organic chemicals is a vital concern for environmental scientists. A pilot-scale aquifer system was used to investigate the long-term dynamics of contaminants, groundwater geochemistry, and microbial community structure (by 16S rRNA gene pyrosequencing and quantitative real-time PCR) throughout the 5-year life cycle of a surrogate ethanol blend fuel plume (10% ethanol + 50 mg/L benzene + 50 mg/L toluene). Two-year continuous ethanol-blended release significantly changed the groundwater geochemistry (resulted in anaerobic, low pH, and organotrophic conditions) and increased bacterial and archaeal populations by 82- and 314-fold respectively. Various anaerobic heterotrophs (fermenters, acetogens, methanogens, and hydrocarbon degraders) were enriched. Two years after the release was shut off, all contaminants and their degradation byproducts disappeared and groundwater geochemistry completely restored to the pre-release states (aerobic, neutral pH, and oligotrophic). Bacterial and archaeal populations declined by 18- and 45-fold respectively (relative to the time of shut off). Microbial community structure reverted towards the pre-release states and alpha diversity indices rebounded, suggesting the resilience of microbial community to ethanol blend releases. We also found shifts from O2-sensitive methanogens (e.g., Methanobacterium) to methanogens that are not so sensitive to O2 (e.g., Methanosarcina and Methanocella), which is likely to contribute to the persistence of methanogens and methane generation following the source removal. Overall, the rapid disappearance of contaminants and their metabolites, rebound of geochemical footprints, and resilience of microbial community unequivocally document the natural capacity of groundwater ecosystem to attenuate and recover from a large volume of catastrophic spill of ethanol-based biofuel.
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Affiliation(s)
- Jie Ma
- State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum-Beijing, Beijing 102249, China; Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA.
| | | | - Pedro J J Alvarez
- Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA
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Ma J, Deng Y, Yuan T, Zhou J, Alvarez PJJ. Succession of microbial functional communities in response to a pilot-scale ethanol-blended fuel release throughout the plume life cycle. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2015; 198:154-160. [PMID: 25603154 DOI: 10.1016/j.envpol.2015.01.005] [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: 10/21/2014] [Revised: 01/08/2015] [Accepted: 01/10/2015] [Indexed: 06/04/2023]
Abstract
GeoChip, a comprehensive gene microarray, was used to examine changes in microbial functional gene structure throughout the 4-year life cycle of a pilot-scale ethanol blend plume, including 2-year continuous released followed by plume disappearance after source removal. Canonical correlation analysis (CCA) and Mantel tests showed that dissolved O2 (which was depleted within 5 days of initiating the release and rebounded 194 days after source removal) was the most influential environmental factor on community structure. Initially, the abundance of anaerobic BTEX degradation genes increased significantly while that of aerobic BTEX degradation genes decreased. Gene abundance for N fixation, nitrification, P utilization, sulfate reduction and S oxidation also increased, potentially changing associated biogeochemical cycle dynamics. After plume disappearance, most genes returned to pre-release abundance levels, but the final functional structure significantly differed from pre-release conditions. Overall, observed successions of functional structure reflected adaptive responses that were conducive to biodegradation of ethanol-blend releases.
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Affiliation(s)
- Jie Ma
- State Key Laboratory of Heavy Oil Processing, Beijing Key Lab of Oil & Gas Pollution Control, China University of Petroleum-Beijing, Beijing 102249, China; Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA
| | - Ye Deng
- Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China; Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019, USA
| | - Tong Yuan
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019, USA
| | - Jizhong Zhou
- Institute for Environmental Genomics, and Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019, USA; State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; Earth Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94270, USA
| | - Pedro J J Alvarez
- Department of Civil and Environmental Engineering, Rice University, Houston, TX 77005, USA.
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Ma J, Rixey WG, Alvarez PJJ. Increased fermentation activity and persistent methanogenesis in a model aquifer system following source removal of an ethanol blend release. WATER RESEARCH 2015; 68:479-486. [PMID: 25462754 DOI: 10.1016/j.watres.2014.10.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 10/06/2014] [Accepted: 10/10/2014] [Indexed: 06/04/2023]
Abstract
The increased probability of groundwater contamination by ethanol-blended fuel calls for improved understanding of how remediation efforts affect the fate and transport of constituents of concern, including the generation and fate of fermentation byproducts. A pilot-scale (8 m³) model aquifer was used to investigate changes in the concentrations of ethanol and its metabolites (methane and volatile fatty acids) after removal of the contamination source. Following the shut-off of a continuous release of a dissolved ethanol blend (10% v:v ethanol, 50 mg/L benzene, and 50 mg/L toluene), fermentation activity was surprisingly stimulated and the concentrations of ethanol metabolites increased. A microcosm experiment showed that this result was due to a decrease in the dissolved ethanol concentration below its toxicity threshold (∼2000 mg/L for this system). Methane generation (>1.5 mg/L of dissolved methane) persisted for more than 100 days after the disappearance of ethanol, despite clean air-saturated water flowing continuously through the tank at a relative high seepage velocity (0.76 m/day). Quantitative real-time PCR showed that functional genes associated with methane metabolism (mcrA for methanogenesis and pmoA for methanotrophy) also persisted in the aquifer material. Persistent methanogenesis was apparently due to the anaerobic degradation of soil-bound organic carbon (e.g., biomass grown on ethanol and other substrates). Overall, this study reflects the complex plume dynamics following source removal, and suggests that monitoring for increases in the concentration of ethanol metabolites that impact groundwater quality should be considered.
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Affiliation(s)
- Jie Ma
- Department of Civil and Environmental Engineering, Rice University, 6100 Main St., Houston, TX 77005, USA
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Firth S, Hildenbrand B, Morgan P. Ethanol effects on the fate and transport of gasoline constituents in the UK. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 485-486:705-710. [PMID: 24641979 DOI: 10.1016/j.scitotenv.2014.02.119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 11/14/2013] [Accepted: 02/27/2014] [Indexed: 06/03/2023]
Abstract
In the UK, use of ethanol in fuel as a fuel oxygenate/fuel supplement is currently limited but could rise in an effort to meet the requirements of the European "Biofuels" Directive. This Energy Institute study focussed on the risk that accidental releases of ethanol blended gasoline (EBG) (i.e. gasoline containing 10% or less of ethanol) could pose to UK groundwater resources. Ethanol is miscible and highly biodegradable. As a result it tends to be strongly attenuated in the unsaturated zone and in groundwater and so does not, in itself, pose a significant risk to groundwater resources. However, it may lead to increased persistence of other gasoline constituents, particularly through alteration of geochemical conditions as a result of intensive biodegradation activity. A semi-probabilistic modelling exercise was undertaken to better understand the risks that use of EBG could pose to UK groundwater resources. Site investigation information from over 500 filling stations was used in combination with GIS data to predict the proportion of potable water supply wells that could potentially be impacted by benzene and MtBE, and estimate the length of benzene and MtBE plumes with and without the use of ethanol in gasoline. The results show that the use of EBG is likely to have a negligible effect on MtBE plumes. Some increase in benzene plume length is predicted, most notably in fissured aquifers, but increases in plume length of greater than 30% are predicted to be rare. A corresponding slight increase in risk to licensed potable water supply wells from benzene was predicted with the use of EBG but the percentage of wells at risk was still predicted to be small (0.13%), and in the context of the conservatism within the modelling, it was concluded that widespread use of EBG is unlikely to cause an increased risk to UK water resources.
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Affiliation(s)
- Simon Firth
- Firth Consultants Ltd, Windsor House, Greville Road, Bristol, BS3 1LL, UK.
| | | | - Phil Morgan
- The Sirius Group, Red Hill House, Hope Street, Chester, CH4 8BU, UK.
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Complex resistivity signatures of ethanol biodegradation in porous media. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 153:37-50. [PMID: 23969406 DOI: 10.1016/j.jconhyd.2013.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 06/02/2023]
Abstract
Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (m(n)) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ') and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (F(app)). Unlike the control columns, a substantial decrease in σ' and increase in F(app) occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ' is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and m(n) were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ, 07102 USA.
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Li M, Mathieu J, Yang Y, Fiorenza S, Deng Y, He Z, Zhou J, Alvarez PJJ. Widespread distribution of soluble di-iron monooxygenase (SDIMO) genes in Arctic groundwater impacted by 1,4-dioxane. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:9950-9958. [PMID: 23909410 DOI: 10.1021/es402228x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Soluble di-iron monooxygenases (SDIMOs), especially group-5 SDIMOs (i.e., tetrahydrofuran and propane monooxygenases), are of significant interest due to their potential role in the initiation of 1,4-dioxane (dioxane) degradation. Functional gene array (i.e., GeoChip) analysis of Arctic groundwater exposed to dioxane since 1980s revealed that various dioxane-degrading SDIMO genes were widespread, and PCR-DGGE analysis showed that group-5 SDIMOs were present in every tested sample, including background groundwater with no known dioxane exposure history. A group-5 thmA-like gene was enriched (2.4-fold over background, p < 0.05) in source-zone samples with higher dioxane concentrations, suggesting selective pressure by dioxane. Microcosm assays with (14)C-labeled dioxane showed that the highest mineralization capacity (6.4 ± 0.1% (14)CO2 recovery during 15 days, representing over 60% of the amount degraded) corresponded to the source area, which was presumably more acclimated and contained a higher abundance of SDIMO genes. Dioxane mineralization ceased after 7 days and was resumed by adding acetate (0.24 mM) as an auxiliary substrate to replenish NADH, a key coenzyme for the functioning of monoxygenases. Acetylene inactivation tests further corroborated the vital role of monooxygenases in dioxane degradation. This is the first report of the prevalence of oxygenase genes that are likely involved in dioxane degradation and suggests their usefulness as biomarkers of dioxane natural attenuation.
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Affiliation(s)
- Mengyan Li
- Department of Civil and Environmental Engineering, Rice University, Houston, Texas, United States
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Rasa E, Bekins BA, Mackay DM, de Sieyes NR, Wilson JT, Feris KP, Wood IA, Scow KM. Impacts of an ethanol-blended fuel release on groundwater and fate of produced methane: Simulation of field observations. WATER RESOURCES RESEARCH 2013; 49:4907-4926. [PMID: 24678130 PMCID: PMC3962844 DOI: 10.1002/wrcr.20382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In a field experiment at Vandenberg Air Force Base (VAFB) designed to mimic the impact of a small-volume release of E10 (10% ethanol and 90% conventional gasoline), two plumes were created by injecting extracted groundwater spiked with benzene, toluene, and o-xylene, abbreviated BToX (No-Ethanol Lane) and BToX plus ethanol (With-Ethanol Lane) for 283 days. We developed a reactive transport model to understand processes controlling the fate of ethanol and BToX. The model was calibrated to the extensive field dataset and accounted for concentrations of sulfate, iron, acetate, and methane along with iron-reducing bacteria, sulfate-reducing bacteria, fermentative bacteria, and methanogenic archaea. The benzene plume was about 4.5 times longer in the With-Ethanol Lane than in the No-Ethanol Lane. Matching this different behavior in the two lanes required inhibiting benzene degradation in the presence of ethanol. Inclusion of iron reduction with negligible growth of iron-reducers was required to reproduce the observed constant degradation rate of benzene. Modeling suggested that vertical dispersion and diffusion of sulfate from an adjacent aquitard were important sources of sulfate in the aquifer. Matching of methane data required incorporating initial fermentation of ethanol to acetate, methane loss by outgassing, and methane oxidation coupled to sulfate and iron reduction. Simulation of microbial growth using dual Monod kinetics, and including inhibition by more favorable electron acceptors, generally resulted in reasonable yields for microbial growth of 0.01-0.05.
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Affiliation(s)
- Ehsan Rasa
- Department of Civil and Environmental Engineering, University of California-Davis, One shield Avenue, Davis, California, 95616, USA.
| | - Barbara A Bekins
- U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, California, 94025, USA.
| | - Douglas M Mackay
- Department of Land, Air, and Water Resources, University of California-Davis, One shield Avenue, Davis, California, 95616, USA.
| | - Nicholas R de Sieyes
- Department of Land, Air, and Water Resources, University of California-Davis, One shield Avenue, Davis, California, 95616, USA.
| | - John T Wilson
- U. S. Environmental Protection Agency, Ada, Oklahoma 74820, USA.
| | - Kevin P Feris
- Department of Biology, Boise State University, Boise, Idaho 83725, USA.
| | - Isaac A Wood
- CH2M-Hill consultants, 150 Spear Street, Suite 750, San Francisco, CA, 94105, USA.
| | - Kate M Scow
- Department of Land, Air, and Water Resources, University of California-Davis, One shield Avenue, Davis, California, 95616, USA.
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Ma J, Nossa CW, Xiu Z, Rixey WG, Alvarez PJJ. Adaptive microbial population shifts in response to a continuous ethanol blend release increases biodegradation potential. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2013; 178:419-425. [PMID: 23628885 DOI: 10.1016/j.envpol.2013.03.057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Revised: 03/26/2013] [Accepted: 03/28/2013] [Indexed: 06/02/2023]
Abstract
The fate of fuel releases largely depends on the poorly-understood response in microbial community structure and function. Here, we evaluate the impacts to the microbial community resulting from a pilot-scale continuous release (10 months) of a 10% v:v ethanol solution mixed with benzene and toluene (50 mg/L each). Microbial population shifts were characterized by pyrosequencing-based 16S rRNA analysis and by quantitative PCR targeting Bacteria, Archaea, and functional genes for methanogenesis (mcrA), acetogenesis (fhs) and aerobic degradation of aromatic hydrocarbons (PHE), which could occur in hypoxic micro-environments. The release stimulated microbial growth, increased species richness and diversity, and selected for genotypes involved in fermentative degradation (the relative abundance of mcrA and fhs increased 18- and 6-fold, respectively). The growth of putative hydrocarbon degraders and commensal anaerobes, and increases in microbial diversity and in degradation rates suggest an adaptive response that increases the potential for natural attenuation of ethanol blend releases.
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Affiliation(s)
- Jie Ma
- Department of Civil and Environmental Engineering, Rice University, 6100 Main St., Houston, TX 77005, USA
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Microbial processes influencing the transport, fate and groundwater impacts of fuel ethanol releases. Curr Opin Biotechnol 2013; 24:457-66. [DOI: 10.1016/j.copbio.2012.09.005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2012] [Revised: 08/30/2012] [Accepted: 09/04/2012] [Indexed: 11/20/2022]
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Complex resistivity signatures of ethanol in sand-clay mixtures. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 149:76-87. [PMID: 23603518 DOI: 10.1016/j.jconhyd.2013.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 03/17/2013] [Accepted: 03/22/2013] [Indexed: 06/02/2023]
Abstract
We performed complex resistivity (CR) measurements on laboratory columns to investigate changes in electrical properties as a result of varying ethanol (EtOH) concentration (0% to 30% v/v) in a sand-clay (bentonite) matrix. We applied Debye decomposition, a phenomenological model commonly used to fit CR data, to determine model parameters (time constant: τ, chargeability: m, and normalized chargeability: mn). The CR data showed a significant (P≤0.001) time-dependent variation in the clay driven polarization response (~12 mrad) for 0% EtOH concentration. This temporal variation probably results from the clay-water reaction kinetics trending towards equilibrium in the sand-clay-water system. The clay polarization is significantly suppressed (P≤0.001) for both measured phase (ϕ) and imaginary conductivity (σ″) with increasing EtOH concentration. Normalized chargeability consistently decreases (by up to a factor of ~2) as EtOH concentration increases from 0% to 10% and 10 to 20%, respectively. We propose that such suppression effects are associated with alterations in the electrical double layer (EDL) at the clay-fluid interface due to (a) strong EtOH adsorption on clay, and (b) complex intermolecular EtOH-water interactions and subsequent changes in ionic mobility on the surface in the EDL. Changes in the CR data following a change of the saturating fluid from EtOH 20% to plain water indicate strong hysteresis effects in the electrical response, which we attribute to persistent EtOH adsorption on clay. Our results demonstrate high sensitivity of CR measurements to clay-EtOH interactions in porous media, indicating the potential application of this technique for characterization and monitoring of ethanol contamination in sediments containing clays.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ 07102, USA.
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da Silva MLB, Gomez DE, Alvarez PJJ. Analytical model for BTEX natural attenuation in the presence of fuel ethanol and its anaerobic metabolite acetate. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 146:1-7. [PMID: 23340452 DOI: 10.1016/j.jconhyd.2012.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 12/14/2012] [Accepted: 12/19/2012] [Indexed: 06/01/2023]
Abstract
Flow-through column studies were conducted to mimic the natural attenuation of ethanol and BTEX mixtures, and to consider potential inhibitory effects of ethanol and its anaerobic metabolite acetate on BTEX biodegradation. Results were analyzed using a one-dimensional analytical model that was developed using consecutive reaction differential equations based on first-order kinetics. Decrease in pH due to acetogenesis was also modeled, using charge balance equations under CaCO(3) dissolution conditions. Delay in BTEX removal was observed and simulated in the presence of ethanol and acetate. Acetate was the major volatile fatty acid intermediate produced during anaerobic ethanol biodegradation (accounting for about 58% of the volatile fatty acid mass) as suggested by the model data fit. Acetate accumulation (up to 1.1 g/L) near the source zone contributed to a pH decrease by almost one unit. The anaerobic degradation of ethanol (2 g/L influent concentration) at the source zone produced methane at concentrations exceeding its solubility (~/=26mg/L). Overall, this simple analytical model adequately described ethanol degradation, acetate accumulation and methane production patterns, suggesting that it could be used as a screening tool to simulate lag times in BTEX biodegradation, changes in groundwater pH and methane generation following ethanol-blended fuel releases.
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Personna YR, Slater L, Ntarlagiannis D, Werkema D, Szabo Z. Electrical signatures of ethanol-liquid mixtures: implications for monitoring biofuels migration in the subsurface. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 144:99-107. [PMID: 23159764 DOI: 10.1016/j.jconhyd.2012.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 10/04/2012] [Accepted: 10/08/2012] [Indexed: 06/01/2023]
Abstract
Ethanol (EtOH), an emerging contaminant with potential direct and indirect environmental effects, poses threats to water supplies when spilled in large volumes. A series of experiments was directed at understanding the electrical geophysical signatures arising from groundwater contamination by ethanol. Conductivity measurements were performed at the laboratory scale on EtOH-water mixtures (0 to 0.97 v/v EtOH) and EtOH-salt solution mixtures (0 to 0.99 v/v EtOH) with and without a sand matrix using a conductivity probe and a four-electrode electrical measurement over the low frequency range (1-1000 Hz). A Lichtenecker-Rother (L-R) type mixing model was used to simulate electrical conductivity as a function of EtOH concentration in the mixture. For all three experimental treatments increasing EtOH concentration resulted in a decrease in measured conductivity magnitude (|σ|). The applied L-R model fitted the experimental data at concentration ≤0.4v/v EtOH, presumably due to predominant and symmetric intermolecular (EtOH-water) interaction in the mixture. The deviation of the experimental |σ| data from the model prediction at higher EtOH concentrations may be associated with hydrophobic effects of EtOH-EtOH interactions in the mixture. The |σ| data presumably reflected changes in relative strength of the three types of interactions (water-water, EtOH-water, and EtOH-EtOH) occurring simultaneously in EtOH-water mixtures as the ratio of EtOH to water changed. No evidence of measurable polarization effects at the EtOH-water and EtOH-water-mineral interfaces over the investigated frequency range was found. Our results indicate the potential for using electrical measurements to characterize and monitor EtOH spills in the subsurface.
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Affiliation(s)
- Yves Robert Personna
- Department of Earth and Environmental Sciences, Rutgers University, Newark, New Jersey 07102, USA.
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Ma J, Rixey WG, DeVaull GE, Stafford BP, Alvarez PJJ. Methane bioattenuation and implications for explosion risk reduction along the groundwater to soil surface pathway above a plume of dissolved ethanol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:6013-6019. [PMID: 22568485 DOI: 10.1021/es300715f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Fuel ethanol releases can stimulate methanogenesis in impacted aquifers, which could pose an explosion risk if methane migrates into enclosed spaces where ignitable conditions exist. To assess this potential risk, a flux chamber was emplaced on a pilot-scale aquifer exposed to continuous release (21 months) of an ethanol solution (10% v:v) that was introduced 22.5 cm below the water table. Despite methane concentrations within the ethanol plume reaching saturated levels (20-23 mg/L), the maximum methane concentration reaching the chamber (21 ppm(v)) was far below the lower explosion limit in air (50,000 ppm(v)). The low concentrations of methane observed in the chamber are attributed to methanotrophic activity, which was highest in the capillary fringe. This was indicated by methane degradation assays in microcosms prepared with soil samples from different depths, as well as by PCR measurements of pmoA, which is a widely used functional gene biomarker for methanotrophs. Simulations with the analytical vapor intrusion model "Biovapor" corroborated the low explosion risk associated with ethanol fuel releases under more generic conditions. Model simulations also indicated that depending on site-specific conditions, methane oxidation in the unsaturated zone could deplete the available oxygen and hinder aerobic benzene biodegradation, thus increasing benzene vapor intrusion potential. Overall, this study shows the importance of methanotrophic activity near the water table to attenuate methane generated from dissolved ethanol plumes and reduce its potential to migrate and accumulate at the surface.
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Affiliation(s)
- Jie Ma
- Department of Civil and Environmental Engineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
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Taylor M, Ramond JB, Tuffin M, Burton S, Eley K, Cowan D. Mechanisms and Applications of Microbial Solvent Tolerance. MICROBIOLOGY MONOGRAPHS 2012. [DOI: 10.1007/978-3-642-21467-7_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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Corseuil HX, Monier AL, Fernandes M, Schneider MR, Nunes CC, do Rosario M, Alvarez PJJ. BTEX plume dynamics following an ethanol blend release: geochemical footprint and thermodynamic constraints on natural attenuation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:3422-3429. [PMID: 21410252 DOI: 10.1021/es104055q] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this 10 year study, Brazilian gasoline (100 L, containing 24% ethanol by volume) was released to a sandy aquifer to evaluate the natural attenuation of benzene, toluene, ethylbenzene, and total xylenes (BTEX) in the presence of ethanol. Groundwater concentrations of BTEX, ethanol, and degradation products (e.g., acetate and methane) were measured over the entire plume using an array of monitoring well clusters, to quantify changes in plume mass and region of influence. Ethanol biodegradation coincided with the development of methanogenic conditions while acetate (a common anaerobic metabolite) accumulated. The benzene plume expanded beyond the 30 m long monitored area and began to recede after 2.7 years, when ethanol had disappeared. Theoretical calculations suggest that the transient accumulation of acetate (up to 166 mg L(-1)) may have hindered the thermodynamic feasibility of benzene degradation under methanogenic conditions. Yet, benzene removal proceeded relatively fast compared to literature values (and faster than the alkylbenzenes present at this site) after acetate concentrations had decreased below inhibitory levels. Thus, site investigations of ethanol blend releases should consider monitoring acetate concentrations. Overall, this study shows that inhibitory effects of ethanol and acetate are relatively short-lived, and demonstrates that monitored natural attenuation can be a viable option to deal with ethanol blend releases.
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Affiliation(s)
- Henry X Corseuil
- Universidade Federal de Santa Catarina , Departamento de Engenharia Sanitária e Ambiental, Florianópolis, Santa Catarina, Brazil
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Nelson DK, Lapara TM, Novak PJ. Effects of ethanol-based fuel contamination: microbial community changes, production of regulated compounds, and methane generation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:4525-4530. [PMID: 20481624 DOI: 10.1021/es903940q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Ethanol-based fuels are becoming more heavily used, increasing the likelihood of ethanol-based fuel spills during transportation and storage. Although ethanol is well-known to be readily biodegradable, very little is known about the effects that such a spill might have on an indigenous microbial community. Of particular concern is that ethanol contamination could stimulate the growth of organisms that can generate regulated compounds and/or produce explosive quantities of methane gas. A column-based study was performed to elucidate the potential impacts of ethanol-based fuel (E85) on the indigenous microbial community during a simulated fuel spill. A continuous dilute supply of E85 resulted in profound shifts in both the bacterial and archaeal communities. The shift was accompanied by the production of high concentrations of volatile fatty acids and butanol, a compound that is regulated in groundwater by some states. Results also indicated that a continuous feed of dilute E85 generated explosive levels of methane within one month of column operation. Quantitative PCR data showed a statistically significant increase in methanogenic populations when compared to a control column. The elevated population numbers correlated to areas of the column receiving a sustained carbon load. Toxicity data indicated that microbial growth was completely inhibited (as evidenced by absence of ethanol breakdown products) at ethanol levels above 6% (v/v). These data suggest that ethanol from ethanol-based fuel can be readily degraded, but can also produce metabolic products that are regulated as well as explosive levels of methane. The core of an E85 spill may serve as a long-term source of contamination as it cannot be degraded until significant dilution has occurred.
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Affiliation(s)
- Denice K Nelson
- Department of Civil Engineering, University of Minnesota, 500 Pillsbury Drive Southeast, Minneapolis, Minnesota, 55455, USA
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Gomez DE, Alvarez PJJ. Comparing the effects of various fuel alcohols on the natural attenuation of benzene plumes using a general substrate interaction model. JOURNAL OF CONTAMINANT HYDROLOGY 2010; 113:66-76. [PMID: 20189262 DOI: 10.1016/j.jconhyd.2010.02.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 01/26/2010] [Accepted: 02/02/2010] [Indexed: 05/28/2023]
Abstract
The effects of five fuel alcohols (methanol, ethanol, 1-propanol, iso-butanol and n-butanol) on the natural attenuation of benzene were compared using a previously developed numerical model (General Substrate Interaction Module--GSIM) and a probabilistic sensitivity analysis. Simulations with a 30 gal dissolving LNAPL (light non-aqueous phase liquid) source consisting of a range of gasoline blends (10% and 85% v:v alcohol content) suggest that all fuel alcohols can hinder the natural attenuation of benzene, due mainly to accelerated depletion of dissolved oxygen and a decrease in the specific degradation rate for benzene (due to catabolite repression and metabolic flux dilution). Simulations for blends with 10% alcohol, assuming a homogeneous sandy aquifer, inferred maximum benzene plume elongations (relative to a regular gasoline release) of 26% for ethanol, 47% for iso-butanol, 147% for methanol, 188% for 1-propanol, and 265% for n-butanol. The corresponding elongation percentages for blends with 85% alcohol were generally smaller (i.e., 25%, 54%, 135%, 163%, and 181%, respectively), reflecting a lower content of benzene in the simulated release. Benzene plume elongation and longevity were more pronounced in the presence of alcohols that biodegrade slower (e.g., propanol and n-butanol), forming longer and more persistent alcohol plumes. Conversely, ethanol and iso-butanol exhibited the lowest potential to hinder the natural attenuation of benzene, illustrating the significant effect that a small difference in chemical structure (e.g., isomers) can have on biodegradation. Overall, simulations were highly sensitive to site-specific biokinetic coefficients for alcohol degradation, which forewarns against generalizations about the level of impact of specific fuel alcohols on benzene plume dynamics.
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Affiliation(s)
- Diego E Gomez
- Department of Civil and Environmental Engineering, Rice University, MS-317, 6100 Main St., Houston, TX 77005, USA.
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