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Gharasoo M, Elsner M, Van Cappellen P, Thullner M. Pore-Scale Heterogeneities Improve the Degradation of a Self-Inhibiting Substrate: Insights from Reactive Transport Modeling. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:13008-13018. [PMID: 36069624 DOI: 10.1021/acs.est.2c01433] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In situ bioremediation is a common remediation strategy for many groundwater contaminants. It was traditionally believed that (in the absence of mixing-limitations) a better in situ bioremediation is obtained in a more homogeneous medium where the even distribution of both substrate and bacteria facilitates the access of a larger portion of the bacterial community to a higher amount of substrate. Such conclusions were driven with the typical assumption of disregarding substrate inhibitory effects on the metabolic activity of enzymes at high concentration levels. To investigate the influence of pore matrix heterogeneities on substrate inhibition, we use a numerical approach to solve reactive transport processes in the presence of pore-scale heterogeneities. To this end, a rigorous reactive pore network model is developed and used to model the reactive transport of a self-inhibiting substrate under both transient and steady-state conditions through media with various, spatially correlated, pore-size distributions. For the first time, we explore on the basis of a pore-scale model approach the link between pore-size heterogeneities and substrate inhibition. Our results show that for a self-inhibiting substrate, (1) pore-scale heterogeneities can consistently promote degradation rates at toxic levels, (2) the effect reverses when the concentrations fall to levels essential for microbial growth, and (3) an engineered combination of homogeneous and heterogeneous media can increase the overall efficiency of bioremediation.
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Affiliation(s)
- Mehdi Gharasoo
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, Leipzig 04318, Germany
- Bundesanstalt für Gewässerkunde, Abteilung Quantitative Gewässerkunde, Am Mainzer Tor 1, Koblenz 56068, Germany
- Department of Earth and Environmental Sciences, Ecohydrology Research Group, University of Waterloo, 200 University Av W, Waterloo ON N2L3G1, Canada
| | - Martin Elsner
- Technical University of Munich, Chair of Analytical Chemistry and Water Chemistry, Marchioninistr. 17, Munich 81377, Germany
| | - Philippe Van Cappellen
- Department of Earth and Environmental Sciences, Ecohydrology Research Group, University of Waterloo, 200 University Av W, Waterloo ON N2L3G1, Canada
| | - Martin Thullner
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstr. 15, Leipzig 04318, Germany
- Federal Institute for Geosciences and Natural Resources (BGR), Hannover 30655, Germany
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Madrid F, Rubio-Bellido M, Villaverde J, Tejada M, Morillo E. Natural attenuation of fluorene and pyrene in contaminated soils and assisted with hydroxypropyl-β-cyclodextrin. Effect of co-contamination. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 571:42-49. [PMID: 27454573 DOI: 10.1016/j.scitotenv.2016.07.110] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/15/2016] [Accepted: 07/15/2016] [Indexed: 06/06/2023]
Abstract
The objectives of this study were to investigate the mutual effect of the PAHs fluorene and pyrene on their respective biodegradation and dissipation processes in an agricultural soil, and to determine the effect of hydroxypropyl-β-cyclodextrin (HPBCD), used to increase the bioavailability of PAHs, on such processes. Fluorene dissipation was primarily due to abiotic processes, although a small contribution from biodegradation was also observed. Therefore, fluorene dissipation did not increase with HPBCD and its presence did not significantly alter the dehydrogenase activity. In contrast to fluorene, pyrene dissipation depended primarily on biotic factors, with endogenous soil microorganisms capable of degrading pyrene, with large increases in dehydrogenase activity. HPBCD increased biodegradation rate of pyrene. The co-contamination of soil with both PAHs did not affect fluorene evolution, but significantly inhibited pyrene biodegradation. The different abilities of soil bacterial consortia to catabolize these PAHs are discussed. Additionally, the possibility that the abiotic loss of fluorene through volatilization had a significant effect on the microbial community biodegradation of both fluorene and pyrene is examined.
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Affiliation(s)
- F Madrid
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Apdo. 1052, 41080 Seville, Spain
| | - M Rubio-Bellido
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Apdo. 1052, 41080 Seville, Spain
| | - J Villaverde
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Apdo. 1052, 41080 Seville, Spain
| | - M Tejada
- Departamento de Cristalografía, Mineralogía y Química Agrícola, Escuela Técnica Superior de Ingeniería Agronómica, Universidad de Sevilla, Ctr. Utrera km. 1, 41013 Seville, Spain
| | - E Morillo
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Apdo. 1052, 41080 Seville, Spain.
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Modrzyński JJ, Christensen JH, Mayer P, Brandt KK. Limited recovery of soil microbial activity after transient exposure to gasoline vapors. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 216:826-835. [PMID: 27376993 DOI: 10.1016/j.envpol.2016.06.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 06/22/2016] [Accepted: 06/23/2016] [Indexed: 06/06/2023]
Abstract
During gasoline spills complex mixtures of toxic volatile organic compounds (VOCs) are released to terrestrial environments. Gasoline VOCs exert baseline toxicity (narcosis) and may thus broadly affect soil biota. We assessed the functional resilience (i.e. resistance and recovery of microbial functions) in soil microbial communities transiently exposed to gasoline vapors by passive dosing via headspace for 40 days followed by a recovery phase of 84 days. Chemical exposure was characterized with GC-MS, whereas microbial activity was monitored as soil respiration (CO2 release) and soil bacterial growth ([(3)H]leucine incorporation). Microbial activity was strongly stimulated and inhibited at low and high exposure levels, respectively. Microbial growth efficiency decreased with increasing exposure, but rebounded during the recovery phase for low-dose treatments. Although benzene, toluene, ethylbenzene and xylene (BTEX) concentrations decreased by 83-97% during the recovery phase, microbial activity in high-dose treatments did not recover and numbers of viable bacteria were 3-4 orders of magnitude lower than in control soil. Re-inoculation with active soil microorganisms failed to restore microbial activity indicating residual soil toxicity, which could not be attributed to BTEX, but rather to mixture toxicity of more persistent gasoline constituents or degradation products. Our results indicate a limited potential for functional recovery of soil microbial communities after transient exposure to high, but environmentally relevant, levels of gasoline VOCs which therefore may compromise ecosystem services provided by microorganisms even after extensive soil VOC dissipation.
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Affiliation(s)
- Jakub J Modrzyński
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg, Denmark.
| | - Jan H Christensen
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg, Denmark.
| | - Philipp Mayer
- Department of Environmental Engineering, Technical University of Denmark, 2800, Kongens Lyngby, Denmark; Department of Environmental Science, Aarhus University, 4000, Roskilde, Denmark.
| | - Kristian K Brandt
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg, Denmark.
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Khan AM, Wick LY, Harms H, Thullner M. Biodegradation of vapor-phase toluene in unsaturated porous media: Column experiments. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 211:325-331. [PMID: 26774779 DOI: 10.1016/j.envpol.2016.01.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 01/05/2016] [Accepted: 01/05/2016] [Indexed: 06/05/2023]
Abstract
Biodegradation of organic chemicals in the vapor phase of soils and vertical flow filters has gained attention as promising approach to clean up volatile organic compounds (VOC). The drivers of VOC biodegradation in unsaturated systems however still remain poorly understood. Here, we analyzed the processes controlling aerobic VOC biodegradation in a laboratory setup mimicking the unsaturated zone above a shallow aquifer. The setup allowed for diffusive vapor-phase transport and biodegradation of three VOC: non-deuterated and deuterated toluene as two compounds of highly differing biodegradability but (nearly) identical physical and chemical properties, and MTBE as (at the applied experimental conditions) non-biodegradable tracer and internal control. Our results showed for toluene an effective microbial degradation within centimeter VOC transport distances despite high gas-phase diffusivity. Degradation rates were controlled by the reactivity of the compounds while oxic conditions were found everywhere in the system. This confirms hypotheses that vadose zone biodegradation rates can be extremely high and are able to prevent the outgassing of VOC to the atmosphere within a centimeter range if compound properties and site conditions allow for sufficiently high degradation rates.
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Affiliation(s)
- Ali M Khan
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Lukas Y Wick
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany.
| | - Hauke Harms
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Martin Thullner
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
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Gharasoo M, Centler F, Van Cappellen P, Wick LY, Thullner M. Kinetics of Substrate Biodegradation under the Cumulative Effects of Bioavailability and Self-Inhibition. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:5529-37. [PMID: 25839352 DOI: 10.1021/es505837v] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Microbial degradation is an important process in many environments controlling for instance the cycling of nutrients or the biodegradation of contaminants. At high substrate concentrations toxic effects may inhibit the degradation process. Bioavailability limitations of a degradable substrate can therefore either improve the overall dynamics of degradation by softening the contaminant toxicity effects to microorganisms, or slow down the biodegradation by reducing the microbial access to the substrate. Many studies on biodegradation kinetics of a self-inhibitive substrate have mainly focused on physiological responses of the bacteria to substrate concentration levels without considering the substrate bioavailability limitations rising from different geophysical and geochemical dynamics at pore-scale. In this regard, the role of bioavailability effects on the kinetics of self-inhibiting substrates is poorly understood. In this study, we theoretically analyze this role and assess the interactions between self-inhibition and mass transfer-limitations using analytical/numerical solutions, and show the findings practical relevance for a simple model scenario. Although individually self-inhibition and mass-transfer limitations negatively impact biodegradation, their combined effect may enhance biodegradation rates above a concentration threshold. To our knowledge, this is the first theoretical study describing the cumulative effects of the two mechanisms together.
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Affiliation(s)
- Mehdi Gharasoo
- †Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
- ‡Institute of Groundwater Ecology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany
| | - Florian Centler
- †Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
| | - Philippe Van Cappellen
- §Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Lukas Y Wick
- †Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
| | - Martin Thullner
- †Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
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Tejeda-Agredano MC, Mayer P, Ortega-Calvo JJ. The effect of humic acids on biodegradation of polycyclic aromatic hydrocarbons depends on the exposure regime. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2014; 184:435-442. [PMID: 24121418 DOI: 10.1016/j.envpol.2013.09.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 09/15/2013] [Accepted: 09/18/2013] [Indexed: 06/02/2023]
Abstract
Binding of polycyclic aromatic hydrocarbons (PAHs) to dissolved organic matter (DOM) can reduce the freely dissolved concentration, increase apparent solubility or enhance diffusive mass transfer. To study the effects of DOM on biodegradation, we used phenanthrene and pyrene as model PAHs, soil humic acids as model DOM and a soil Mycobacterium strain as a representative degrader organism. Humic acids enhanced the biodegradation of pyrene when present as solid crystals but not when initially dissolved or provided by partitioning from a polymer. Synchronous fluorescence spectrophotometry, scintillation counting and a microscale diffusion technique were applied in order to determine the kinetics of dissolution and diffusive mass transfer of pyrene. We suggest that humic acids can enhance or inhibit biodegradation as a result of the balance of two opposite effects, namely, solubilization of the chemicals on the one hand and inhibition of cell adhesion to the pollutant source on the other.
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Affiliation(s)
- Maria-Carmen Tejeda-Agredano
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS-CSIC), Apartado 1052, E-41080 Seville, Spain; Department of Environmental Science, Aarhus University, P.O. Box 358, 4000 Roskilde, Denmark
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