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Spanik S, Rrokaj E, Mondal PK, Sleep BE. Favorable and unfavorable attachment of colloids in a discrete sandstone fracture. JOURNAL OF CONTAMINANT HYDROLOGY 2021; 243:103919. [PMID: 34763243 DOI: 10.1016/j.jconhyd.2021.103919] [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: 07/15/2021] [Revised: 10/15/2021] [Accepted: 11/01/2021] [Indexed: 06/13/2023]
Abstract
The transport of cationic amine-modified latex (AML) and anionic carboxylate-modified latex (CML) microspheres through a discrete sandstone fracture with mineralogical heterogeneity and roughness was studied. Two microsphere sizes (200 nm and 1000 nm), two ionic strengths (5 mM and 10 mM), and two specific discharges (0.35 mm.s-1 and 0.70 mm.s-1) were tested to observe the impact on transport under favorable and unfavorable conditions. The difference in retention between AML (net favorable) and CML (net unfavorable) microsphere attachment was 25% for the 200 nm microspheres and 13% for the 1000 nm microspheres. Less than 50% of the AML microspheres were retained in the fracture, postulated to be due to the effects of mineralogical heterogeneity and fracture surface roughness. The effect of an increase in ionic strength in increasing retention was significant for unfavorable attachment, but was not significant for favorable attachment conditions. The effect of specific discharge was minor for all but the 200 nm CML microspheres at 10 mM ionic strength. When flushing the fracture first with cationic microspheres, then with anionic microspheres, the recovery of anionic microspheres resembled favorable attachment presumably due to interaction with cationic microspheres that remained attached to the sandstone surface. Colloid breakthrough curves could be fit well with a two site attachment model, with reversible and irreversible sites.
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Affiliation(s)
- Sean Spanik
- Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada
| | - Ertiana Rrokaj
- Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada
| | - Pulin K Mondal
- Lassonde School of Engineering, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - Brent E Sleep
- Department of Civil & Mineral Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada.
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2
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Numerical simulation of reactive particle transport in a randomly-orientated rough fracture with reversible and irreversible surface attachments. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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3
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Yosri A, Dickson-Anderson S, Siam A, El-Dakhakhni W. Analytical description of colloid behavior in single fractures under irreversible deposition. J Colloid Interface Sci 2021; 589:597-604. [PMID: 33515975 DOI: 10.1016/j.jcis.2020.12.089] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 12/21/2020] [Accepted: 12/22/2020] [Indexed: 11/28/2022]
Abstract
OBJECTIVES Irreversible colloid deposition in groundwater-saturated fractures is typically modeled using a lumped deposition coefficient (κ) that reflects the system physiochemical conditions. A mathematical relationship between this coefficient and the physicochemical conditions controlling deposition has not yet been defined in the literature; thus, κ is typically fitted using experimental observations. This research develops, for the first time, an analytical relationship between κ and the fraction of colloids retained in single fractures (Fr). This relationship could be subsequently integrated with available models relating Fr to the system's physicochemical properties to develop an explicit mathematical relationship between κ and these properties. METHOD The Fr-κ analytical relationship was developed through conceptualizing irreversible deposition as first-order decay, as both lead to permanent mass loss, and coupling this with the advection-dispersion equation. The model estimates of colloid deposition were compared to observations from laboratory-scale colloid tracer experiments. A variance-based global sensitivity analysis was applied to identify the parameters controlling deposition. FINDINGS The analytical relationship efficiently replicated the experimental observations, and the global sensitivity analysis revealed that colloid deposition variability is controlled by fracture length, aperture size, and deposition coefficient; this supports the accepted understanding that colloid deposition is controlled by the system's physicochemical properties.
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Affiliation(s)
- Ahmed Yosri
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada.
| | | | - Ahmad Siam
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada.
| | - Wael El-Dakhakhni
- Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S4L7, Canada.
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4
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Meng X, Yang D. Pore-network modeling of particle dispersion in porous media. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.123768] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Donath A, Kantzas A, Bryant S. Opportunities for Particles and Particle Suspensions to Experience Enhanced Transport in Porous Media: A Review. Transp Porous Media 2019. [DOI: 10.1007/s11242-019-01256-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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6
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Neukum C. Transport of silver nanoparticles in single fractured sandstone. JOURNAL OF CONTAMINANT HYDROLOGY 2018; 209:61-67. [PMID: 29396180 DOI: 10.1016/j.jconhyd.2018.01.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 12/15/2017] [Accepted: 01/18/2018] [Indexed: 06/07/2023]
Abstract
Silver nanoparticles (Ag-NP) are used in various consumer products and are one of the most prevalent metallic nanoparticle in commodities and are released into the environment. Transport behavior of Ag-NP in groundwater is one important aspect for the assessment of environmental impact and protection of drinking water resources in particular. Ag-NP transport processes in saturated single-fractured sandstones using triaxial flow cell experiments with different kind of sandstones is investigated. Ag-NP concentration and size are analyzed using flow field-flow fractionation and coupled SEM-EDX analysis. Results indicate that Ag-NP are more mobile and show generally lower attachment on rock surface compared to experiments in undisturbed sandstone matrix and partially fractured sandstones. Ag-NP transport is controlled by the characteristics of matrix porosity, time depending blocking of attachment sites and solute chemistry. Where Ag-NP attachment occur, it is heterogeneously distributed on the fracture surface.
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Affiliation(s)
- Christoph Neukum
- Federal Institute for Geoscience and Natural Resources, Stilleweg 2, 30655 Hanover, Germany.
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Babakhani P, Bridge J, Doong RA, Phenrat T. Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review. Adv Colloid Interface Sci 2017. [PMID: 28641812 DOI: 10.1016/j.cis.2017.06.002] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case.
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Meng X, Yang D. Determination of dynamic dispersion coefficients for passive and reactive particles flowing in a circular tube. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Cianflone SPL, Dickson SE, Mumford KG. On the Importance of Gravity in DNAPL Invasion of Saturated Horizontal Fractures. GROUND WATER 2017; 55:27-37. [PMID: 27404732 DOI: 10.1111/gwat.12441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 06/08/2016] [Indexed: 06/06/2023]
Abstract
Invasion percolation (IP) models of dense non-aqueous phase liquid (DNAPL) invasion into saturated horizontal fractures typically neglect viscous and gravity forces, as it is assumed that capillarity dominates in many situations. An IP model simulating DNAPL invasion into saturated horizontal fractures was modified to include gravity as a local effect. The model was optimized using a genetic algorithm, and demonstrated that the inclusion of gravity is important for replicating the architecture of the DNAPL invasion pattern. The optimized gravity-included simulation showed the DNAPL invasion pattern to be significantly more representative of the experimentally observed pattern (80% accuracy) than did the optimized gravity-neglected simulation (70% accuracy). Additional simulations of DNAPL invasion in 360 randomly generated fractures were compared with and without gravity forces. These simulations showed that with increasing fracture roughness, the minimum difference between simulations with and without gravity increases to 35% for a standard deviation of the mid-aperture elevation field (SDz ) of 10 mm. Even for low roughness (SDz = 0.1 mm), the difference was as high as 30%. Furthermore, a scaled Bond Number is defined which includes data regarding DNAPL type, media type and statistical characteristics of the fracture. The value of this scaled Bond Number can be used to determine the conditions under which gravity should be considered when simulating DNAPL invasion in a macroscopically horizontal fracture. Finally, a set of equations defining the minimum and maximum absolute percentage difference between gravity-included and gravity-neglected simulations is presented based on the fracture and DNAPL characteristics.
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Affiliation(s)
- Sean P L Cianflone
- Department of Civil Engineering, McMaster University, 1280 Main St. West, Hamilton, Ontario L8S 4L7, Canada
| | | | - Kevin G Mumford
- Department of Civil Engineering, Queen's University, 99 University Ave, Kingston, Ontario K7L 3N6, Canada
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10
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Meng X, Yang D. Determination of dynamic dispersion coefficient for particles flowing in a parallel-plate fracture. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2016.08.019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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11
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Rodrigues SN, Dickson SE. The Effect of Matrix Properties and Preferential Pathways on the Transport of Escherichia coli RS2-GFP in Single, Saturated, Variable-Aperture Fractures. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2015; 49:8425-8431. [PMID: 26089105 DOI: 10.1021/acs.est.5b01578] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Fractured aquifers are a relatively under-studied area of groundwater science particularly because of the heterogeneities present in fractures which make it difficult to understand and predict the transport and retention of contaminants. This research was designed to elucidate some of the factors that contribute to particle transport and retention in fractures using solute and particle tracers in a natural rock fracture and a transparent epoxy replica of that same fracture. Significantly less attachment was observed from the tracer experiments conducted in the replica fracture illustrating the large effect that matrix properties have on transport and retention of particles in fractures. The E. coli RS2-GFP tracer experiments conducted in the replica fracture show that increasing specific discharge results in increasing recovery; however, there is a critical specific discharge at which particle recovery seems to steady or slightly decrease. Images were collected of the E. coli RS2-GFP transport through the epoxy replica fracture, which capture for the first time the preferential pathways of E. coli in fractures, and also demonstrate a slight broadening of the dominant preferential pathway under increasing flow conditions. These results are instructive to the development and improvement of predictive models for particle transport in fractured aquifers.
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Affiliation(s)
- S N Rodrigues
- McMaster University, 1280 Main St. W., Hamilton, Ontario L8S 4L7, Canada
| | - S E Dickson
- McMaster University, 1280 Main St. W., Hamilton, Ontario L8S 4L7, Canada
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12
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Boschan A, Aguirre MA, Gauthier G. Suspension flow: do particles act as mixers? SOFT MATTER 2015; 11:3367-3372. [PMID: 25809584 DOI: 10.1039/c4sm02909g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Recently, Roht et al. [J. Contam. Hydrol., 2013, 145, 10-16] observed that the presence of suspended non-Brownian macroscopic particles decreased the dispersivity of a passive solute, for a pressure-driven flow in a narrow parallel-plate channel at low Reynolds numbers. This result contradicts the idea that the streamline distortion caused by the random diffusive motion of the particles increases the dispersion and mixing of the solute. Therefore, to estimate the influence of this motion on the dispersivity of the solute, and investigate the origin of the reported decrease, we experimentally studied the probability density function (pdf) of the particle velocities, and spatio-temporal correlations, in the same experimental configuration. We observed that, as the mean suspension velocity exceeds a critical value, the pdf of the streamwise velocity of the particles markedly changes from a symmetric distribution to an asymmetric one strongly skewed to high velocities and with a peak of the most probable velocity close to the maximum velocity. The latter observations and the analysis of the suspension microstructure indicate that the observed decrease in the dispersivity of the solute is due to particle migration to the mid-plane of the channel, and consequent flattening of the velocity profile. Moreover, we estimated the contribution of particle diffusive motion to the solute dispersivity to be three orders of magnitude smaller than the reported decrease, and thus negligible. Solute dispersion is then much more affected by how particles modify the flow velocity profile across the channel than by their random diffusive motion.
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Affiliation(s)
- A Boschan
- Grupo de Medios Porosos, Facultad de Ingeniería, Universidad de Buenos Aires, Argentina.
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Insights into transport velocity of colloid-associated plutonium relative to tritium in porous media. Sci Rep 2014; 4:5037. [PMID: 24849695 PMCID: PMC4052758 DOI: 10.1038/srep05037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Accepted: 05/02/2014] [Indexed: 11/08/2022] Open
Abstract
Although faster transport velocities of colloid-associated actinides, bacteria, and virus than nonreactive solutes have been observed in laboratory and field experiments, some questions still need to be answered. To accurately determine the relative velocity (UPu/UT) of 239Pu and tritium representative of the bulk water, a conceptual model of electrostatic interactions coupled with the parabolic water velocity profile in pore channels is developed. Based on the expression for UPu/UT derived from this model, we study the effects of water flow rates and ionic strengths on the UPu/UT. Also, the velocity relationship between Pu, tritium and Sr2+ is explored. The results show that UPu/UT increased fairly linearly with decreasing water flow rates; UPu/UT declined approximately exponentially with increasing Na+ concentrations; the charge properties of colloid-associated Pu (negative), tritium (neutral) and Sr2+ (positive) had a close association with their transport velocities as UPu : UT : USr2+ = 1.41 : 1 : 0.579.
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Albarran N, Missana T, Alonso U, García-Gutiérrez M, López T. Analysis of latex, gold and smectite colloid transport and retention in artificial fractures in crystalline rock. Colloids Surf A Physicochem Eng Asp 2013. [DOI: 10.1016/j.colsurfa.2013.02.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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15
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Weisbrod N, Meron H, Walker S, Gitis V. Virus transport in a discrete fracture. WATER RESEARCH 2013; 47:1888-1898. [PMID: 23379972 DOI: 10.1016/j.watres.2013.01.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 01/04/2013] [Accepted: 01/06/2013] [Indexed: 06/01/2023]
Abstract
Tracer experiments were carried out in a naturally discrete-fractured chalk core with solute tracers Li(+) and Br(-), and colloidal tracers of two origins-bacteriophages (MS2, ϕX174 and T4) and fluorescent latex microspheres. The colloidal tracers were either ∼20 nm (MS2, ϕX174 and microspheres) or ∼200 nm (T4 and microspheres) in size. Both solute and colloidal tracers were injected at a constant flux at the fracture inlet and collected at the outlet to evaluate the form of their breakthrough curves (BTCs). The BTCs of all tracers were compared and analyzed. The BTC analysis displayed significant differences in recovery as a function of tracer size and type. Even within the same colloid size, transport of the microspheres and bacteriophages was dissimilar, likely due to minor differences in density, surface chemistry and shape. More pronounced peaks and recoveries were observed with ∼200 nm compared to ∼20 nm microspheres and phages. Arrival time at the outlet was also size-dependent, with larger microspheres and phages having longer residence times than smaller ones, and solutes being 5-15 times slower than colloids of both sizes. The observed differences were explained by a combination of size and electrostatic interactions that facilitates entrance and transport within the pores in the chalk matrix. Overall, our results clearly demonstrate that fractures are favorable carriers for viruses of different sizes with different surface properties. The viruses' properties were also shown to govern their transport through the fractures.
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Affiliation(s)
- Noam Weisbrod
- Department of Environmental Hydrology & Microbiology, Zuckerberg Institute for Water Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, PO Box 192, Midreshet Ben Gurion 84990, Israel.
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Roht YL, Boschan A, Ippolito I, Chertcoff R. Experimental study of solute dispersion in macroscopic suspension flow. JOURNAL OF CONTAMINANT HYDROLOGY 2013; 145:10-16. [PMID: 23266561 DOI: 10.1016/j.jconhyd.2012.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/05/2012] [Accepted: 11/08/2012] [Indexed: 06/01/2023]
Abstract
We experimentally investigate the influence of suspended neutrally-buoyant particles on the dispersion of a passive solute in pressure-driven axial flow in a constant aperture fracture (parallel plates configuration). A dye is employed as solute in order to measure its local concentration by means of a light transmission technique. In the experiments a dyed particle suspension displaces a transparent one at constant flow rate, for volume fractions φ ranging from 0 to 0.25 and for solute Péclet numbers (Pe(s)) between 35 and 476 (mean flow velocities U between 0.004 and 0.0544 cm/s). The local time variation of the solute concentration in the measurement zone was well-fitted by the solution of the advection-dispersion equation, and a longitudinal dispersion coefficient D for the solute was measured. For Pe(s)<300, the values of D for flow with particles (φ>0) and without particles (φ=0) are equal within the measurement error. For Pe(s)>300, D decreases for φ>0 compared to φ=0. The magnitude of the reduction increases as φ increases, and also as Pe(s) increases. This decrease of D in the presence of suspended macroscopic particles is analyzed in the light of theoretical, numerical and experimental results from other authors that studied suspension flow in similar geometries.
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Affiliation(s)
- Y L Roht
- Grupo de Medios Porosos, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, 1063, Buenos Aires, Argentina
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Rodrigues SN, Dickson SE, Qu J. Colloid retention mechanisms in single, saturated, variable-aperture fractures. WATER RESEARCH 2013; 47:31-42. [PMID: 23127622 DOI: 10.1016/j.watres.2012.08.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2012] [Revised: 08/09/2012] [Accepted: 08/22/2012] [Indexed: 06/01/2023]
Abstract
The characterization of fractured aquifers is commonly limited to the methodologies developed for unconsolidated porous media aquifers, which results in many uncertainties. Recent work indicates that fractured rocks remove more particulates than they are conventionally credited for. This research was designed to quantify the number of Escherichia coli RS2-GFP retained in single, saturated, variable-aperture fractures extracted from the natural environment. Conservative solute and E. coli RS2-GFP tracer experiments were used to elucidate the relationships between dominant retention mechanisms, aperture field characteristics, and flow rate. A non-destructive method of determining a surrogate measure of a coefficient of variation (COV(S)) for each fracture was used to better understand the transport behaviour of E. coli RS2-GFP. The results from this research all point to the importance of aperture field characterization in understanding the fate and transport of contaminants in fractured aquifers. The mean aperture was a very important characteristic in determining particulate recovery, so were matrix properties, COV(s), and flow rate. It was also determined that attachment is a much more significant retention mechanism than straining under the conditions employed in this research. Finally, it was demonstrated that the dominant retention mechanism in a fracture varies depending on the specific discharge. An improved understanding of the mechanisms that influence the fate and transport of contaminants through fractures will lead to the development of better tools and methodologies for the characterization of fractured aquifers, as well as the ability to manipulate the relevant mechanisms to increase or decrease retention, depending on the application.
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