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Ballentine WM, Dorgan KM. The Meioflume: A New System for Observing the Interstitial Behavior of Meiofauna. Integr Org Biol 2024; 6:obae016. [PMID: 38883566 PMCID: PMC11177882 DOI: 10.1093/iob/obae016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 04/27/2024] [Accepted: 05/24/2024] [Indexed: 06/18/2024] Open
Abstract
Meiofauna (benthic invertebrates < 1 mm in size) facilitate sediment biogeochemical cycling, alter sediment microbial community structure, and serve as an important trophic link between benthic micro- and macrofauna, yet the behaviors that mechanistically link individuals to their ecological effects are largely unknown. Meiofauna are small and sediments are opaque, making observing the in situ activities of these animals challenging. We developed the Meioflume, a small, acrylic flow tunnel filled with grains of cryolite, a transparent sand analog, to simulate the in situ conditions experienced by meiofauna in an observable lab environment. The Meioflume has a working area (28.57 mm × 10.16 mm × 1 mm) that is small enough to quickly locate fauna and clearly observe behavior but large enough that animals are not tightly confined. When connected to a syringe press, the Meioflume can produce low velocity flows consistently and evenly across the width of its working area while retaining the contents. To demonstrate its functionality in observing the behavior of meiofauna, we placed individual meiofaunal animals (a protodrilid annelid, a harpacticoid copepod, and a platyhelminth flatworm) in Meioflumes and filmed their behavioral response to a sudden initiation of porewater flow. All animals were clearly visible within the flume and could be observed responding to the onset of flow. The design and construction of the Meioflume make it an accessible, affordable tool for researchers. This experimental system could be modified to address many questions in meiofaunal ecology, such as studying behavior in response to chemical cues, allowing us to observe meiofaunal behaviors to better understand their ecological effects.
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Affiliation(s)
- W M Ballentine
- School of Marine and Environmental Sciences, University of South Alabama, Mobile, AL 36688, USA
- Dauphin Island Sea Lab, Dauphin Island, AL 36528, USA
| | - K M Dorgan
- School of Marine and Environmental Sciences, University of South Alabama, Mobile, AL 36688, USA
- Dauphin Island Sea Lab, Dauphin Island, AL 36528, USA
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Sharma K, Palatinszky M, Nikolov G, Berry D, Shank EA. Transparent soil microcosms for live-cell imaging and non-destructive stable isotope probing of soil microorganisms. eLife 2020; 9:e56275. [PMID: 33140722 PMCID: PMC7609051 DOI: 10.7554/elife.56275] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Accepted: 10/16/2020] [Indexed: 01/02/2023] Open
Abstract
Microscale processes are critically important to soil ecology and biogeochemistry yet are difficult to study due to soil's opacity and complexity. To advance the study of soil processes, we constructed transparent soil microcosms that enable the visualization of microbes via fluorescence microscopy and the non-destructive measurement of microbial activity and carbon uptake in situ via Raman microspectroscopy. We assessed the polymer Nafion and the crystal cryolite as optically transparent soil substrates. We demonstrated that both substrates enable the growth, maintenance, and visualization of microbial cells in three dimensions over time, and are compatible with stable isotope probing using Raman. We applied this system to ascertain that after a dry-down/rewetting cycle, bacteria on and near dead fungal hyphae were more metabolically active than those far from hyphae. These data underscore the impact fungi have facilitating bacterial survival in fluctuating conditions and how these microcosms can yield insights into microscale microbial activities.
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Affiliation(s)
- Kriti Sharma
- Department of Biology, University of North CarolinaChapel HillUnited States
| | - Márton Palatinszky
- Department of Microbiology and Ecosystem Science, Centre for Microbiology and Environmental Systems Science, University of ViennaViennaAustria
| | - Georgi Nikolov
- Department of Microbiology and Ecosystem Science, Centre for Microbiology and Environmental Systems Science, University of ViennaViennaAustria
| | - David Berry
- Department of Microbiology and Ecosystem Science, Centre for Microbiology and Environmental Systems Science, University of ViennaViennaAustria
| | - Elizabeth A Shank
- Department of Biology, University of North CarolinaChapel HillUnited States
- Department of Microbiology and Immunology, University of North CarolinaChapel HillUnited States
- Program in Systems Biology, University of Massachusetts Medical SchoolWorcesterUnited States
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Yang L, Chen X, Zeng X, Radosevich M, Ripp S, Zhuang J, Sayler GS. Surface-Adsorbed Contaminants Mediate the Importance of Chemotaxis and Haptotaxis for Bacterial Transport Through Soils. Front Microbiol 2019; 10:2691. [PMID: 32038503 PMCID: PMC6988784 DOI: 10.3389/fmicb.2019.02691] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 11/06/2019] [Indexed: 12/25/2022] Open
Abstract
Chemotaxis and haptotaxis are important biological mechanisms that influence microbial movement toward concentrated chemoattractants in mobile liquids and along immobile surfaces, respectively. This study investigated their coupled effect, as induced by naphthalene (10 mg L−1), on the transport and retention of two pollutant-degrading bacteria, Pseudomonas fluorescens 5RL (Pf5RL) and Pseudomonas stutzeri DQ1 (PsDQ1), in quartz sand and natural soil. The results demonstrated that PsDQ1 was not chemotactic, whereas Pf5RL was chemotactic at 25°C but not at 4°C due to the restricted movement. In a quartz sand column, haptotaxis did not play a role in increasing the transport of Pf5RL as compared with chemotaxis. Compared with a naphthalene-free soil column, Pf5RL broke through naphthalene-presaturated soil columns to reach a stable effluent concentration 0.5 pore volumes earlier due to advective chemotaxis occurring behind the plume front in the bulk solution. Pf5RL also demonstrated greater retention (e.g., a doubled rate of attachment and a one-third smaller breakthrough percentage) due to along-surface haptotaxis and near-surface chemotaxis occurring in less mobile water near the soil surface. However, both chemotaxis and haptotaxis were weakened when Pf5RL co-transported with naphthalene due to reduced adsorption of naphthalene on the soil. This study suggests that surface adsorption of naphthalene can mediate the relative importance of advective chemotaxis (facilitating initial breakthrough), near-surface chemotaxis (increasing bacterial collision), and haptotaxis (increasing bacterial residence time).
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Affiliation(s)
- Liqiong Yang
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.,College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China
| | - Xijuan Chen
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
| | - Xiangfeng Zeng
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
| | - Mark Radosevich
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN, United States
| | - Steven Ripp
- Department of Microbiology, Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, United States
| | - Jie Zhuang
- Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.,Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN, United States.,Department of Microbiology, Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, United States
| | - Gary S Sayler
- Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, TN, United States.,Department of Microbiology, Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, United States
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Hofmann R, Grösbacher M, Griebler C. Mini Sediment Columns and Two-Dimensional Sediment Flow-Through Microcosms: Versatile Experimental Systems for Studying Biodegradation of Organic Contaminants in Groundwater Ecosystems. ACTA ACUST UNITED AC 2016. [DOI: 10.1007/8623_2016_210] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Barns GL, Thornton SF, Wilson RD. Identification of small-scale low and high permeability layers using single well forced-gradient tracer tests: fluorescent dye imaging and modelling at the laboratory-scale. JOURNAL OF CONTAMINANT HYDROLOGY 2015; 172:84-99. [PMID: 25478669 DOI: 10.1016/j.jconhyd.2014.11.005] [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: 02/16/2014] [Revised: 11/09/2014] [Accepted: 11/12/2014] [Indexed: 06/04/2023]
Abstract
Heterogeneity in aquifer permeability, which creates paths of varying mass flux and spatially complex contaminant plumes, can complicate the interpretation of contaminant fate and transport in groundwater. Identifying the location of high mass flux paths is critical for the reliable estimation of solute transport parameters and design of groundwater remediation schemes. Dipole flow tracer tests (DFTTs) and push-pull tests (PPTs) are single well forced-gradient tests which have been used at field-scale to estimate aquifer hydraulic and transport properties. In this study, the potential for PPTs and DFTTs to resolve the location of layered high- and low-permeability layers in granular porous media was investigated with a pseudo 2-D bench-scale aquifer model. Finite element fate and transport modelling was also undertaken to identify appropriate set-ups for in situ tests to determine the type, magnitude, location and extent of such layered permeability contrasts at the field-scale. The characteristics of flow patterns created during experiments were evaluated using fluorescent dye imaging and compared with the breakthrough behaviour of an inorganic conservative tracer. The experimental results show that tracer breakthrough during PPTs is not sensitive to minor permeability contrasts for conditions where there is no hydraulic gradient. In contrast, DFTTs are sensitive to the type and location of permeability contrasts in the host media and could potentially be used to establish the presence and location of high or low mass flux paths. Numerical modelling shows that the tracer peak breakthrough time and concentration in a DFTT is sensitive to the magnitude of the permeability contrast (defined as the permeability of the layer over the permeability of the bulk media) between values of 0.01-20. DFTTs are shown to be more sensitive to deducing variations in the contrast, location and size of aquifer layered permeability contrasts when a shorter central packer is used. However, larger packer sizes are more likely to be practical for field-scale applications, with fewer tests required to characterise a given aquifer section. The sensitivity of DFTTs to identify layered permeability contrasts was not affected by test flow rate.
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Affiliation(s)
- Gareth L Barns
- Groundwater Restoration and Protection Group, Department of Civil and Structural Engineering, University of Sheffield, Kroto Research Institute, Broad Lane, Sheffield, S3 7HQ, United Kingdom.
| | - Steven F Thornton
- Groundwater Restoration and Protection Group, Department of Civil and Structural Engineering, University of Sheffield, Kroto Research Institute, Broad Lane, Sheffield, S3 7HQ, United Kingdom
| | - Ryan D Wilson
- Groundwater Restoration and Protection Group, Department of Civil and Structural Engineering, University of Sheffield, Kroto Research Institute, Broad Lane, Sheffield, S3 7HQ, United Kingdom
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Pseudomonas fluorescens HK44: lessons learned from a model whole-cell bioreporter with a broad application history. SENSORS 2012; 12:1544-71. [PMID: 22438725 PMCID: PMC3304127 DOI: 10.3390/s120201544] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Revised: 01/24/2012] [Accepted: 02/03/2012] [Indexed: 11/21/2022]
Abstract
Initially described in 1990, Pseudomonas fluorescens HK44 served as the first whole-cell bioreporter genetically endowed with a bioluminescent (luxCDABE) phenotype directly linked to a catabolic (naphthalene degradative) pathway. HK44 was the first genetically engineered microorganism to be released in the field to monitor bioremediation potential. Subsequent to that release, strain HK44 had been introduced into other solids (soils, sands), liquid (water, wastewater), and volatile environments. In these matrices, it has functioned as one of the best characterized chemically-responsive environmental bioreporters and as a model organism for understanding bacterial colonization and transport, cell immobilization strategies, and the kinetics of cellular bioluminescent emission. This review summarizes the characteristics of P. fluorescens HK44 and the extensive range of its applications with special focus on the monitoring of bioremediation processes and biosensing of environmental pollution.
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Barns GL, Wilson RD, Thornton SF. Fluorescent dye imaging of the volume sampled by single well forced-gradient tracer tests evaluated in a laboratory-scale aquifer physical model. JOURNAL OF CONTAMINANT HYDROLOGY 2012; 128:58-70. [PMID: 22192345 DOI: 10.1016/j.jconhyd.2011.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 10/09/2011] [Accepted: 10/12/2011] [Indexed: 05/31/2023]
Abstract
This study presents a new method to visualise forced-gradient tracer tests in 2-D using a laboratory-scale aquifer physical model. Experiments were designed to investigate the volume of aquifer sampled in vertical dipole flow tracer tests (DFTT) and push-pull tests (PPT), using a miniature monitoring well and straddle packer arrangement equipped with solute injection and recovery chambers. These tests have previously been used to estimate bulk aquifer hydraulic and transport properties for the evaluation of natural attenuation and other remediation approaches. Experiments were performed in a silica glass bead-filled box, using a fluorescent tracer (fluorescein) to deduce conservative solute transport paths. Digital images of fluorescein transport were captured under ultraviolet light and processed to analyse tracer plume geometry and obtain point-concentration breakthrough histories. Inorganic anion mixtures were also used to obtain conventional tracer breakthrough histories. Concentration data from the conservative tracer breakthrough curves was compared with the digital images and a well characterised numerical model. The results show that the peak tracer breakthrough response in dipole flow tracer tests samples a zone of aquifer close to the well screen, while the sampling volume of push-pull tests is limited by the length of the straddle packers used. The effective sampling volume of these single well forced-gradient tests in isotropic conditions can be estimated with simple equations. The experimental approach offers the opportunity to evaluate under controlled conditions the theoretical basis, design and performance of DFTTs and PPTs in porous media in relation to measured flow and transport properties.
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Affiliation(s)
- Gareth L Barns
- Groundwater Restoration and Protection Group, Department of Civil and Structural Engineering, University of Sheffield, Kroto Research Institute, Sheffield, United Kingdom
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Bozorg A, Gates ID, Sen A. Real time monitoring of biofilm development under flow conditions in porous media. BIOFOULING 2012; 28:937-951. [PMID: 22963147 DOI: 10.1080/08927014.2012.723204] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Biofilm growth can impact the effectiveness of industrial processes that involve porous media. To better understand and characterize how biofilms develop and affect hydraulic properties in porous media, both spatial and temporal development of biofilms under flow conditions was investigated in a translucent porous medium by using Pseudomonas fluorescens HK44, a bacterial strain genetically engineered to luminesce in the presence of an induction agent. Real-time visualization of luminescent biofilm growth patterns under constant pressure conditions was captured using a CCD camera. Images obtained over 8 days revealed that variations in bioluminescence intensity could be correlated to biofilm cell density and hydraulic conductivity. These results were used to develop a real-time imaging method to study the dynamic behavior of biofilm evolution in a porous medium, thereby providing a new tool to investigate the impact of biological fouling in porous media under flow conditions.
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Affiliation(s)
- Ali Bozorg
- Department of Chemical and Petroleum Engineering, Schulich School of Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada
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Bozorg A, Sen A, Gates ID. A new approach to model the spatiotemporal development of biofilm phase in porous media. Environ Microbiol 2011; 13:3010-23. [DOI: 10.1111/j.1462-2920.2011.02578.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Werth CJ, Zhang C, Brusseau ML, Oostrom M, Baumann T. A review of non-invasive imaging methods and applications in contaminant hydrogeology research. JOURNAL OF CONTAMINANT HYDROLOGY 2010; 113:1-24. [PMID: 20163885 PMCID: PMC3864598 DOI: 10.1016/j.jconhyd.2010.01.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 01/17/2010] [Accepted: 01/19/2010] [Indexed: 05/04/2023]
Abstract
Contaminant hydrogeological processes occurring in porous media are typically not amenable to direct observation. As a result, indirect measurements (e.g., contaminant breakthrough at a fixed location) are often used to infer processes occurring at different scales, locations, or times. To overcome this limitation, non-invasive imaging methods are increasingly being used in contaminant hydrogeology research. Four of the most common methods, and the subjects of this review, are optical imaging using UV or visible light, dual-energy gamma radiation, X-ray microtomography, and magnetic resonance imaging (MRI). Non-invasive imaging techniques have provided valuable insights into a variety of complex systems and processes, including porous media characterization, multiphase fluid distribution, fluid flow, solute transport and mixing, colloidal transport and deposition, and reactions. In this paper we review the theory underlying these methods, applications of these methods to contaminant hydrogeology research, and methods' advantages and disadvantages. As expected, there is no perfect method or tool for non-invasive imaging. However, optical methods generally present the least expensive and easiest options for imaging fluid distribution, solute and fluid flow, colloid transport, and reactions in artificial two-dimensional (2D) porous media. Gamma radiation methods present the best opportunity for characterization of fluid distributions in 2D at the Darcy scale. X-ray methods present the highest resolution and flexibility for three-dimensional (3D) natural porous media characterization, and 3D characterization of fluid distributions in natural porous media. And MRI presents the best option for 3D characterization of fluid distribution, fluid flow, colloid transport, and reaction in artificial porous media. Obvious deficiencies ripe for method development are the ability to image transient processes such as fluid flow and colloid transport in natural porous media in three dimensions, the ability to image many reactions of environmental interest in artificial and natural porous media, and the ability to image selected processes over a range of scales in artificial and natural porous media.
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Affiliation(s)
- Charles J Werth
- Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 N. Mathews Ave., Urbana, IL 61801, USA.
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Bauer RD, Rolle M, Bauer S, Eberhardt C, Grathwohl P, Kolditz O, Meckenstock RU, Griebler C. Enhanced biodegradation by hydraulic heterogeneities in petroleum hydrocarbon plumes. JOURNAL OF CONTAMINANT HYDROLOGY 2009; 105:56-68. [PMID: 19095328 DOI: 10.1016/j.jconhyd.2008.11.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 10/20/2008] [Accepted: 11/04/2008] [Indexed: 05/27/2023]
Abstract
In case of dissolved electron donors and acceptors, natural attenuation of organic contaminant plumes in aquifers is governed by hydrodynamic mixing and microbial activity. Main objectives of this work were (i) to determine whether aerobic and anaerobic biodegradation in porous sediments is controlled by transverse dispersion, (ii) to elucidate the effect of sediment heterogeneity on mixing and biodegradation, and (iii) to search for degradation-limiting factors. Comparative experiments were conducted in two-dimensional sediment microcosms. Aerobic toluene and later ethylbenzene degradation by Pseudomonas putida strain F1 was initially followed in a plume developing from oxic to anoxic conditions and later under steady-state mixing-controlled conditions. Competitive anaerobic degradation was then initiated by introduction of the denitrifying strain Aromatoleum aromaticum EbN1. In homogeneous sand, aerobic toluene degradation was clearly controlled by dispersive mixing. Similarly, under denitrifying conditions, microbial activity was located at the plume's fringes. Sediment heterogeneity caused flow focusing and improved the mixing of reactants. Independent from the electron accepting process, net biodegradation was always higher in the heterogeneous setting with a calculated efficiency plus of 23-100% as compared to the homogeneous setup. Flow and reactive transport model simulations were performed in order to interpret and evaluate the experimental results.
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Affiliation(s)
- Robert D Bauer
- Helmholtz Zentrum Muenchen - German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany
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Rees HC, Oswald SE, Banwart SA, Pickup RW, Lerner DN. Biodegradation processes in a laboratory-scale groundwater contaminant plume assessed by fluorescence imaging and microbial analysis. Appl Environ Microbiol 2007; 73:3865-76. [PMID: 17468279 PMCID: PMC1932726 DOI: 10.1128/aem.02933-06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 04/19/2007] [Indexed: 11/20/2022] Open
Abstract
Flow reactors containing quartz sand colonized with biofilm were set up as physical model aquifers to allow degrading plumes of acetate or phenol to be formed from a point source. A noninvasive fluorescent tracer technique was combined with chemical and biological sampling in order to quantify transport and biodegradation processes. Chemical analysis of samples showed a substantial decrease in carbon concentration between the injection and outflow resulting primarily from dilution but also from biodegradation. Two-dimensional imaging of the aqueous oxygen [O2(aq)] concentration field quantified the depletion of O2(aq) within the contaminant plume and provided evidence for microbial respiration associated with biodegradation of the carbon source. Combined microbiological, chemical, and O2(aq) imaging data indicated that biodegradation was greatest at the plume fringe. DNA profiles of bacterial communities were assessed by temperature gradient gel electrophoresis, which revealed that diversity was limited and that community changes observed depended on the carbon source used. Spatial variation in activity within the plume could be quantitatively accounted for by the changes observed in active cell numbers rather than differences in community structure, the total biomass present, or the increased enzyme activity of individual cells. Numerical simulations and comparisons with the experimental data were used to test conceptual models of plume processes. Results demonstrated that plume behavior was best described by growth and decay of active biomass as a single functional group of organisms represented by active cell counts.
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Affiliation(s)
- Helen C Rees
- Department of Civil and Structural Engineering, Kroto Research Institute, University of Sheffield, United Kingdom.
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Bridge JW, Banwart SA, Heathwaite AL. Noninvasive quantitative measurement of colloid transport in mesoscale porous media using time lapse fluorescence imaging. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:5930-6. [PMID: 17051781 DOI: 10.1021/es060373l] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
We demonstrate noninvasive quantitative imaging of colloid and solute transport at millimeter to decimeter (meso-) scale. Ultraviolet (UV) excited fluorescent solute and colloid tracers were independently measured simultaneously during co-advection through saturated quartz sand. Pulse-input experiments were conducted at constant flow rates and ionic strengths 10(-3), 10(-2) and 10(-1) M NaCl. Tracers were 1.9 microm carboxylate latex microspheres and disodium fluorescein. Spatial moments analysis was used to quantify relative changes in mass distribution of the colloid and solute tracers over time. The solute advected through the sand at a constant velocity proportional to flow rate and was described well by a conservative transport model (CXTFIT). In unfavorable deposition conditions increasing ionic strength produced significant reduction in colloid center of mass transport velocity over time. Velocity trends correlated with the increasing fraction of colloid mass retained along the flowpath. Attachment efficiencies (defined by colloid filtration theory) calculated from nondestructive retained mass data were 0.013 +/- 0.03, 0.09 +/- 0.02, and 0.22 +/- 0.05 at 10(-3), 10(-2), and 10(-1) M ionic strength, respectively, which compared well with previously published data from breakthrough curves and destructive sampling. Mesoscale imaging of colloid mass dynamics can quantify key deposition and transport parameters based on noninvasive, nondestructive, spatially high-resolution data.
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Affiliation(s)
- Jonathan W Bridge
- Groundwater Protection and Restoration Group, Department of Civil and Structural Engineering, Kroto Research Institute, University of Sheffield, UK.
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Zhang P, Wang Y. Epi-fluorescence imaging of colloid transport in porous media at decimeter scales. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:6064-9. [PMID: 17051801 DOI: 10.1021/es061104y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
A noninvasive epi-fluorescence imaging technique was developed for real-time observation of colloid transport in porous media at decimeter scales. Fluorescent latex microspheres and translucent quartz sand were used as a model colloid-porous medium system. Various calibrations were performed for accurate conversion of fluorescence intensities to microsphere concentrations. Fluorescence intensities were found to linearly increase with microsphere concentrations (5 x 10(5)-5 x 10(8) spheres/mL in saturated sand) and with camera exposure time. Fluorescence intensities also increased with sand thickness (saturated with microsphere solution), indicating that the fluorescence signals detected by the imaging system were integrated signals from the entire thickness (10 mm) of the sand. A set of microsphere transport experiments was conducted to demonstrate the versatility of the imaging system. Excellent mass recoveries (93-103%) were achieved in all transport experiments, demonstrating the robustness of the imaging system for quantitative study of colloid transport. The system allowed the change of flow velocity, ionic strength, and flow direction within one transport experiment and the real-time, quantitative monitoring of the movement of microspheres in packed sand, greatly reducing the time and effort needed for similar work with traditional column experiments.
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Affiliation(s)
- Pengfei Zhang
- Department of Earth & Atmospheric Sciences, City College of New York, New York 10031, USA.
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