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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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2
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Khan AM, Gharasoo M, Wick LY, Thullner M. Phase-specific stable isotope fractionation effects during combined gas-liquid phase exchange and biodegradation. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 309:119737. [PMID: 35817302 DOI: 10.1016/j.envpol.2022.119737] [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: 02/24/2022] [Revised: 06/28/2022] [Accepted: 07/04/2022] [Indexed: 06/15/2023]
Abstract
Stable isotope fractionation of toluene under dynamic phase exchange was studied aiming at ascertaining the effects of gas-liquid partitioning and biodegradation of toluene stable isotope composition in liquid-air phase exchange reactors (Laper). The liquid phase consisted of a mixture of aqueous minimal media, a known amount of a mixture of deuterated (toluene-d) and non-deuterated toluene (toluene-h), and bacteria of toluene degrading strain Pseudomonas putida KT2442. During biodegradation experiments, the liquid and air-phase concentrations of both toluene isotopologues were monitored to determine the observable stable isotope fractionation in each phase. The results show a strong fractionation in both phases with apparent enrichment factors beyond -800‰. An offset was observed between enrichment factors in the liquid and the gas phase with gas-phase values showing a stronger fractionation in the gas than in the liquid phase. Numerical simulation and parameter fitting routine was used to challenge hypotheses to explain the unexpected experimental data. The numerical results showed that either a very strong, yet unlikely, fractionation of the phase exchange process or a - so far unreported - direct consumption of gas phase compounds by aqueous phase microorganisms could explain the observed fractionation effects. The observed effect can be of relevance for the analysis of volatile contaminant biodegradation using stable isotope analysis in unsaturated subsurface compartments or other environmental compartment containing a gas and a liquid phase.
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Affiliation(s)
- Ali M Khan
- Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Mehdi Gharasoo
- Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - Lukas Y Wick
- 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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Sun F, Mellage A, Gharasoo M, Melsbach A, Cao X, Zimmermann R, Griebler C, Thullner M, Cirpka OA, Elsner M. Mass-Transfer-Limited Biodegradation at Low Concentrations-Evidence from Reactive Transport Modeling of Isotope Profiles in a Bench-Scale Aquifer. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:7386-7397. [PMID: 33970610 PMCID: PMC8173607 DOI: 10.1021/acs.est.0c08566] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Organic contaminant degradation by suspended bacteria in chemostats has shown that isotope fractionation decreases dramatically when pollutant concentrations fall below the (half-saturation) Monod constant. This masked isotope fractionation implies that membrane transfer is slow relative to the enzyme turnover at μg L-1 substrate levels. Analogous evidence of mass transfer as a bottleneck for biodegradation in aquifer settings, where microbes are attached to the sediment, is lacking. A quasi-two-dimensional flow-through sediment microcosm/tank system enabled us to study the aerobic degradation of 2,6-dichlorobenzamide (BAM), while collecting sufficient samples at the outlet for compound-specific isotope analysis. By feeding an anoxic BAM solution through the center inlet port and dissolved oxygen (DO) above and below, strong transverse concentration cross-gradients of BAM and DO yielded zones of low (μg L-1) steady-state concentrations. We were able to simulate the profiles of concentrations and isotope ratios of the contaminant plume using a reactive transport model that accounted for a mass-transfer limitation into bacterial cells, where apparent isotope enrichment factors *ε decreased strongly below concentrations around 600 μg/L BAM. For the biodegradation of organic micropollutants, mass transfer into the cell emerges as a bottleneck, specifically at low (μg L-1) concentrations. Neglecting this effect when interpreting isotope ratios at field sites may lead to a significant underestimation of biodegradation.
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Affiliation(s)
- Fengchao Sun
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, Neuherberg 85764, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Marchioninistrasse 17, Munich 81377, Germany
| | - Adrian Mellage
- Center
for Applied Geoscience, University of Tübingen, Schnarrenbergstrasse 94−96, Tübingen 72076, Germany
| | - Mehdi Gharasoo
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, Neuherberg 85764, Germany
- Department
of Earth and Environmental Sciences, Ecohydrology, University of Waterloo, 200 University Avenue West, Waterloo N2L 3G1, Canada
| | - Aileen Melsbach
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, Neuherberg 85764, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Marchioninistrasse 17, Munich 81377, Germany
| | - Xin Cao
- Joint
Mass Spectrometry Centre, Comprehensive
Molecular Analytics (CMA) Cooperation Group Helmholtz Zentrum, Gmunderstrasse 37, Munich 81379, Germany
| | - Ralf Zimmermann
- Joint
Mass Spectrometry Centre, Comprehensive
Molecular Analytics (CMA) Cooperation Group Helmholtz Zentrum, Gmunderstrasse 37, Munich 81379, Germany
| | - Christian Griebler
- Department
of Functional and Evolutionary Ecology, University of Vienna, Althanstrasse 14, Vienna 1090, Austria
| | - Martin Thullner
- Department
of Environmental Microbiology, UFZ—Helmholtz
Centre for Environmental Research, Permoserstrasse 15, Leipzig 30418, Germany
| | - Olaf A. Cirpka
- Center
for Applied Geoscience, University of Tübingen, Schnarrenbergstrasse 94−96, Tübingen 72076, Germany
| | - Martin Elsner
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, Neuherberg 85764, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Marchioninistrasse 17, Munich 81377, Germany
- Phone: +49 89 2180-78232
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Sigmund G, Gharasoo M, Hüffer T, Hofmann T. Deep Learning Neural Network Approach for Predicting the Sorption of Ionizable and Polar Organic Pollutants to a Wide Range of Carbonaceous Materials. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:4583-4591. [PMID: 32124609 PMCID: PMC7205386 DOI: 10.1021/acs.est.9b06287] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 02/28/2020] [Accepted: 03/02/2020] [Indexed: 05/23/2023]
Abstract
Most contaminants of emerging concern are polar and/or ionizable organic compounds, whose removal from engineered and environmental systems is difficult. Carbonaceous sorbents include activated carbon, biochar, fullerenes, and carbon nanotubes, with applications such as drinking water filtration, wastewater treatment, and contaminant remediation. Tools for predicting sorption of many emerging contaminants to these sorbents are lacking because existing models were developed for neutral compounds. A method to select the appropriate sorbent for a given contaminant based on the ability to predict sorption is required by researchers and practitioners alike. Here, we present a widely applicable deep learning neural network approach that excellently predicted the conventionally used Freundlich isotherm fitting parameters log KF and n (R2 > 0.98 for log KF, and R2 > 0.91 for n). The neural network models are based on parameters generally available for carbonaceous sorbents and/or parameters freely available from online databases. A freely accessible graphical user interface is provided.
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Affiliation(s)
- Gabriel Sigmund
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Althanstrasse 14, 1090 Wien, Austria
- Agroscope,
Environmental Analytics, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland
- Ithaka
Institute, Ancienne Eglise
9, 1974 Arbaz, Switzerland
| | - Mehdi Gharasoo
- Department
of Earth and Environmental Sciences, Ecohydrology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
| | - Thorsten Hüffer
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Althanstrasse 14, 1090 Wien, Austria
| | - Thilo Hofmann
- Department
of Environmental Geosciences, Centre for Microbiology and Environmental
Systems Science, University of Vienna, Althanstrasse 14, 1090 Wien, Austria
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Chen S, Zhang K, Jha RK, Ma L. Impact of atrazine concentration on bioavailability and apparent isotope fractionation in Gram-negative Rhizobium sp. CX-Z. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2020; 257:113614. [PMID: 31761577 DOI: 10.1016/j.envpol.2019.113614] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2019] [Revised: 11/10/2019] [Accepted: 11/10/2019] [Indexed: 06/10/2023]
Abstract
Compound-specific stable isotope analysis of micropollutants has become an established method for the qualitative and quantitative assessment of biodegradation in the field. However, many of environmental factors may have an influence on the observed isotope fractionation. Herein, we investigate the impact of substrate concentration on the observed enrichment factor derived from Rayleigh plot of batch laboratory experiments conducted to measure the atrazine carbon isotope fractionation of Rhizobium sp. CX-Z subjected to the different initial concentration level of atrazine. The Rayleigh plot (changes in bulk concentration vs. isotopic composition) derived from batch experiments shown divergence from the linear relation towards the end of degradation, confirming bioavailability of atrazine changed along with the decay of substrate concentration, consequently, influenced the isotope fractionation and lowered the observed enrichment factor. When microbial degradation is coupled to a mass transfer step limiting the bioavailability of substrate, the observed enrichment factor displays a dependence on initial atrazine concentration. Observed enrichment factors (ε) (absolute value) derived from the low concentration (i.e. 9.5 μM) are below 3.5‰ to the value of -5.4‰ determined at high bioavailability (membrane-free cells). The observed enrichment factor depended significantly on the atrazine concentration, indicating the concentration level and the bioavailability of a substrate in realistic environments should be considered during the assessment of microbial degradation or in situ bioremediation based on compound-specific stable isotope analysis (CSIA) method.
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Affiliation(s)
- Songsong Chen
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China
| | - Kai Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China
| | - Rohit Kumar Jha
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China
| | - Limin Ma
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
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Ehrl B, Kundu K, Gharasoo M, Marozava S, Elsner M. Rate-Limiting Mass Transfer in Micropollutant Degradation Revealed by Isotope Fractionation in Chemostat. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:1197-1205. [PMID: 30514083 PMCID: PMC6365907 DOI: 10.1021/acs.est.8b05175] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 05/05/2023]
Abstract
Biodegradation of persistent micropollutants like pesticides often slows down at low concentrations (μg/L) in the environment. Mass transfer limitations or physiological adaptation are debated to be responsible. Although promising, evidence from compound-specific isotope fractionation analysis (CSIA) remains unexplored for bacteria adapted to this low concentration regime. We accomplished CSIA for degradation of a persistent pesticide, atrazine, during cultivation of Arthrobacter aurescens TC1 in chemostat under four different dilution rates leading to 82, 62, 45, and 32 μg/L residual atrazine concentrations. Isotope analysis of atrazine in chemostat experiments with whole cells revealed a drastic decrease in isotope fractionation with declining residual substrate concentration from ε(C) = -5.36 ± 0.20‰ at 82 μg/L to ε(C) = -2.32 ± 0.28‰ at 32 μg/L. At 82 μg/L ε(C) represented the full isotope effect of the enzyme reaction. At lower residual concentrations smaller ε(C) indicated that this isotope effect was masked indicating that mass transfer across the cell membrane became rate-limiting. This onset of mass transfer limitation appeared in a narrow concentration range corresponding to about 0.7 μM assimilable carbon. Concomitant changes in cell morphology highlight the opportunity to study the role of this onset of mass transfer limitation on the physiological level in cells adapted to low concentrations.
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Affiliation(s)
- Benno
N. Ehrl
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Kankana Kundu
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Mehdi Gharasoo
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Sviatlana Marozava
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
| | - Martin Elsner
- Institute
of Groundwater Ecology, Helmholtz Zentrum
München, Ingolstädter
Landstrasse 1, 85764 Neuherberg, Germany
- Chair
of Analytical Chemistry and Water Chemistry, Technical University of Munich, Marchioninistrasse 17, 81377 Munich, Germany
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