Numerical study on kinetic/equilibrium behaviour of dissolution of toluene under variable subsurface conditions

doi:10.1080/19648189.2014.922902

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Numerical study on kinetic/equilibrium behaviour of dissolution of toluene under variable subsurface conditions

Journal Article•DOI•

Numerical study on kinetic/equilibrium behaviour of dissolution of toluene under variable subsurface conditions

M. Vasudevan¹, G. Suresh Kumar¹, Indumathi M. Nambi¹•Institutions (1)

Indian Institute of Technology Madras¹

21 Jul 2014-European Journal of Environmental and Civil Engineering (Taylor & Francis)-Vol. 18, Iss: 9, pp 1070-1093

TL;DR: In this article, numerically simulating dissolution and transport of toluene under the effect of sorption and biodegradation to understand their synergistic influence during the tailing phase, the authors found that influence of soil grain size and porosity are most significant in calculating the extent of mass transfer limitation.

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Abstract: Estimating the extent of kinetic/equilibrium behaviour of dissolution is essential for selecting remediation strategy for highly soluble aromatic constituents of petroleum present in the subsurface. Present study aims at numerically simulating dissolution and transport of toluene under the effect of sorption and biodegradation to understand their synergistic influence during the tailing phase. Subsurface conditions influencing mass transfer such as porous media properties, flow velocity and volumetric residual saturation of toluene entrapped in the pore space are varied and their impacts are assessed. The numerical results in terms of dimensionless numbers suggest that influence of soil grain size and porosity are most significant in calculating the extent of mass transfer limitation. Increases in the volumetric residual saturation results in prolonged near-equilibrium condition for dissolution especially for fine-grained porous media. Tailing is found to be prolonged for sand with low saturations and hig...

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Journal Article•DOI•

Assessment of LNAPL in Subsurface under Fluctuating Groundwater Table Using 2D Sand Tank Experiments

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Pankaj Kumar Gupta¹, Basant Yadav², Brijesh Kumar Yadav¹•Institutions (2)

Indian Institute of Technology Roorkee¹, Cranfield University²

01 Sep 2019-Journal of Environmental Engineering

TL;DR: In this article, the fate and transport of toluene, a light nonaqueous-phase liquids (LNAPLs) in the subsurface region under dynamic groundwater table conditions were investigated.

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Abstract: The focus of this study was to investigate the fate and transport of toluene, a light nonaqueous-phase liquids (LNAPLs) in the subsurface region under dynamic groundwater table conditions. ...

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39 citations

Cites background from "Numerical study on kinetic/equilibr..."

...Dynamic 77 nature of groundwater table causes significant spreading of pooled LNAPL in smear zone, 78 which considerably increases the LNAPL-water interphase area and resulted in accelerated 79 dissolution (Mobile et al. 2012; Vasudevan et al. 2014)....
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...This in turn significantly 332 increases dissolved phase concentration load to receiving groundwater and vapor 333 contamination to unsaturated pore air (Dobson et al. 2007; Vasudevan et al. 2014)....
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Journal Article•DOI•

Evaluating the reliability of equilibrium dissolution assumption from residual gasoline in contact with water saturated sands.

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Greg Lekmine¹, Kaveh Sookhak Lari², Kaveh Sookhak Lari¹, C.D. Johnston¹, C.D. Johnston³, Trevor P. Bastow¹, John L. Rayner¹, Greg B. Davis³, Greg B. Davis¹ - Show less +5 more•Institutions (3)

Commonwealth Scientific and Industrial Research Organisation¹, Edith Cowan University², University of Western Australia³

01 Jan 2017-Journal of Contaminant Hydrology

TL;DR: Results compared to previous numerical studies suggest the presence of small scale dissolution fingering created perpendicular to the horizontal dissolution front, mainly triggered by heterogeneities in the medium structure and the local NAPL residual saturation.

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26 citations

Cites background from "Numerical study on kinetic/equilibr..."

...Petroleum hydrocarbon dissolution is often described in terms of mass transfer at the NAPL/water interface assuming local equilibrium (Seagren et al., 1999; Sulaymon and Gzar, 2011) or rate limited mass transfer (Miller et al., 1990; Imhoff et al., 1994; Vasudevan et al., 2014)....
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Journal Article•DOI•

Pollution Load on Indian Soil-Water Systems and Associated Health Hazards: A Review

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Pankaj Kumar Gupta¹•Institutions (1)

University of Waterloo¹

01 May 2020-Journal of Environmental Engineering

TL;DR: In this paper, the authors proposed that India's soil-water systems provide a vital source of freshwater and sustain the drinking water supply for the world's second-largest population, however, groundwater within the large geogra...

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Abstract: India’s soil-water systems provide a vital source of freshwater and sustain the drinking water supply for the world’s second-largest population. However, groundwater within the large geogra...

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24 citations

Journal Article•DOI•

Three-Dimensional Laboratory Experiments on Fate and Transport of LNAPL under Varying Groundwater Flow Conditions

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Pankaj Kumar Gupta¹, Brijesh Kumar Yadav²•Institutions (2)

University of Waterloo¹, Indian Institute of Technology Roorkee²

01 Apr 2020-Journal of Environmental Engineering

TL;DR: Variations in groundwater flow regimes due to direct draining/pumping and surrounding climatic variabilities may significantly affect the spatial and temporal distribution of hydrocarbon co-... as mentioned in this paper.

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Abstract: Variations in groundwater flow regimes due to direct draining/pumping and surrounding climatic variabilities may significantly affect the spatial and temporal distribution of hydrocarbon co...

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24 citations

Journal Article•DOI•

A critical review of the influence of groundwater level fluctuations and temperature on LNAPL contaminations in the context of climate change

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Amélie Cavelan¹, Fabrice Golfier¹, Stéfan Colombano, Hossein Davarzani, Jacques Deparis, Pierre Faure¹ - Show less +2 more•Institutions (1)

University of Lorraine¹

01 Feb 2022-Science of The Total Environment

TL;DR: In this article, the authors synthesize and discuss the possible effects of the increase in temperature and groundwater level fluctuations on the behavior of light nonaqueous phase liquid and its components in a climate change context.

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15 citations

References

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Journal Article•DOI•

The influence of mass transfer characteristics and porous media heterogeneity on nonaqueous phase dissolution

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Alex S. Mayer¹, Cass T. Miller•Institutions (1)

Michigan Technological University¹

01 Jun 1996-Water Resources Research

TL;DR: In this article, a multiphase flow and species transport model was developed and applied to the case of nonaqueous phase liquid (NAPL) emplacement and dissolution in both homogeneous and heterogeneous porous media systems.

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Abstract: A two-dimensional multiphase flow and species transport model was developed and applied to the case of nonaqueous phase liquid (NAPL) emplacement and dissolution in both homogeneous and heterogeneous porous media systems. Simulations were performed to observe dissolution rate variations and the degree of NAPL-aqueous phase nonequilibrium as a function of two aqueous phase velocities and five forms of the NAPL-aqueous phase mass transfer formulation. An integrated form of the Damkohler number was introduced to analyze the degree of NAPL-aqueous phase nonequilibrium. Mass removal rates for homogeneous media were insensitive to the form of the NAPL-aqueous phase mass transfer formulation, yielding results similar to a local equilibrium approach for all but one mass transfer formulation. This latter formulation was most sensitive to NAPL saturation and yielded significant nonequilibrium behavior, which was manifested as a decrease in NAPL dissolution rates as the NAPL volume fraction decreased. Variations in mass elution rates between homogeneous and heterogeneous media were observed, with more significant variations found for variances in porous media properties than for horizontal correlation lengths. In heterogeneous media, decreases in dissolution rates were attributed to the existence of relatively immobile regions of NAPL with saturations greater than the residual saturation of the media, so-called NAPL pools. These results illustrate the importance of the statistical characteristics of heterogeneous porous media on NAPL distribution and dissolution processes.

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150 citations

"Numerical study on kinetic/equilibr..." refers background in this paper

...…which is being represented as a function of flow and NAPL properties for single compound from residually entrapped porous system with/without considering the effect of heterogeneity (Imhoff et al., 1994; Mayer & Miller, 1996; Nambi & Powers, 2003; Powers et al., 1994; Schaerlaekens et al., 2000)....
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...Damkohler number Da ¼ KnwLVp represents the ratio of hydraulic residence time to the mass transfer reaction time, in other words, it is the ratio of reaction rate to advection rate which is a fraction approach to analyse equilibrium conditions for homogeneous systems (Mayer & Miller, 1996)....
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...…by using empirical mass transfer relations, thereby enabling to link with the macro-scale Darcy flux (Chu, Kitanidis, & McCarty, 2007; Geller & Hunt, 1993; Imhoff, Jaffe, & Pinder, 1994; Kim and Chrysikopoulos, 1999; Liu, Tindall, Friedel, & Zhang, 2007; Mayer & Miller, 1996; Nambi & Powers, 2003)....
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Journal Article•DOI•

Rate-Limited Sorption and Nonequilibrium Transport of Organic Chemicals in Low Organic Carbon Aquifer Materials

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Mark L. Brusseau, Thomas Ostenfeld Larsen, Thomas Højlund Christensen

01 Jun 1991-Water Resources Research

TL;DR: In this article, the rate-limited sorption and nonequilibrium transport of several hydrophobic organic chemicals in three low-organic carbon aquifer materials was investigated using miscible displacement experiments performed at two pore water velocities and with very low solution-phase concentrations.

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Abstract: The rate-limited sorption and nonequilibrium transport of several hydrophobic organic chemicals in three low-organic carbon (<0.025%) aquifer materials was investigated. Results of miscible displacement experiments performed at two pore water velocities and with very low solution-phase concentrations (30–60 μg L−1) were analyzed using a first-order mass transfer nonequilibrium model, as well as a model employing the local equilibrium assumption. Results of the analyses revealed sorption to be significantly rate limited, possibly by a diffusion-limited mechanism. The impact of rate-limited sorption on transport was dependent upon pore water velocity. The experiments performed at a faster velocity (∼1 cm/h) could be successfully simulated only with the nonequilibrium model, whereas the equilibrium model was adequate for the slower-velocity (∼0.2 cm/h) experiments. Comparison of experimental results to those reported in the literature revealed that time scale has a significant impact on the degree of nonequilibrium observed in, and on the values of rate constants determined from, experiments. Regression equations were developed for the two kinetics-associated parameters contained in the nonequilibrium model: first-order mass transfer constant and fraction of instantaneous sorption.

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147 citations

Additional excerpts

...…al. (2003); Wang (2004) Soil bulk density, ρb (g/m 3) 1.6e6 1.4e6 1.27e6 Couto and Malta (2008); Nourmoradi et al. (2013) Mean particle size, dp (m) 3.2e−4 3.2e−5 3.2e−6 Brusseau, Larsen, and Christensen (1991) Fraction of organic carbon, foc (–) .001 .01 .05 Di Toro and De Rosa (1996) F ig ur e 6....
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Journal Article•DOI•

Kinetics of aerobic biodegradation of benzene and toluene in sandy aquifer material.

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Pedro J. J. Alvarez¹, Paul J. Anid¹, Timothy M. Vogel¹•Institutions (1)

University of Michigan¹

01 Jan 1991-Biodegradation

TL;DR: Monod's equation adequately described aerobic biodegradation rates of benzene and toluene by the microbial population of a sandy aquifer when these compounds were initially present at concentrations lower than 100 mg/l each.

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Abstract: Monod's equation adequately described aerobic biodegradation rates of benzene and toluene by the microbial population of a sandy aquifer when these compounds were initially present at concentrations lower than 100 mg/l each. Concentrations higher than 100 mg/l were inhibitory, and no benzene or toluene degradation was observed when these compounds were initially present at 250 mg/l each. The Monod coefficients were calculated as k = 8.3 g-benzene/g-cells/day and Ks = 12.2 mg/l for benzene, and k = 9.9 g-toluene/g-cells/day and Ks = 17.4 mg/l for toluene. Specific first-order coefficients would be 0.68 l/mg.day for benzene and 0.57 l.mg.day for toluene.

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131 citations

Journal Article•DOI•

Effect of groundwater flow dimensionality on mass transfer from entrapped nonaqueous phase liquid contaminants

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Tarek Saba, Tissa H. Illangasekare

01 Apr 2000-Water Resources Research

TL;DR: In this paper, experiments in two-dimensional flow fields were used to evaluate the effects of flow dimensionality on NAPL dissolution, and regression analysis, matching experimental observations to simulated predictions, provided parameter values for a proposed phenomenological model of dissolution in 2D flow fields.

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Abstract: Mass transfer from entrapped nonaqueous phase liquids (NAPLs) at subsurface locations of environmental contamination typically takes place in three-dimensional groundwater flow fields. Yet most laboratory studies of NAPLs dissolution have been one-dimensional, eliminating more realistic conditions such as the heterogeneous distribution of entrapped NAPL ganglia and the potential for flow bypassing due to reduced water permeability in contaminated zones. In this study, experiments in two-dimensional flow fields were used to evaluate the effects of flow dimensionality on NAPL dissolution. Modifications of the transport code MT3D provided the capability to simulate NAPL dissolution. Regression analysis, matching experimental observations to simulated predictions, provided parameter values for a proposed phenomenological model of dissolution in two-dimensional flow fields. The proposed model predicted lower NAPL dissolution rates relative to models developed on the basis of published one-dimensional experimental measurements. The results indicate potential for significant errors using the one-dimensionally based models for NAPL dissolution in field applications.

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128 citations

"Numerical study on kinetic/equilibr..." refers background in this paper

...…transfer of organic compounds is closely related to their relative hydrophobic nature, distribution of the non-aqueous phase mass within the aquifer pore volume, prevailing flow and other geo-chemical properties of the porous medium (Saba & Illangasekare, 2000; Soga, Page, & Illangasekare, 2004)....
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Journal Article•DOI•

Mass transfer correlations for nonaqueous phase liquid dissolution from regions with high initial saturations

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Indumathi M. Nambi¹, Indumathi M. Nambi², Susan E. Powers¹•Institutions (2)

Clarkson University¹, University of Illinois at Urbana–Champaign²

01 Feb 2003-Water Resources Research

TL;DR: In this paper, a new mass transfer correlation was developed using NAPL dissolution data from a small 2D experimental cell that contained a well-characterized heterogeneous distribution of grain sizes.

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Abstract: [1] The application of existing correlations for nonaqueous phase liquid (NAPL) dissolution, which were developed in small, one-dimensional columns, to larger-scale, heterogeneous or multidimensional systems has shown the predicted dissolution behavior depends greatly on the correlation used. Variation among existing correlations is due to the system scale, NAPL-water interfacial area, and the nature of mass transfer or hydrodynamic mechanisms that are lumped in the correlation. In this paper, new mass transfer correlation is developed using NAPL dissolution data from a small 2-D experimental cell that contained a well-characterized heterogeneous distribution of grain sizes. The new correlation can be used for quantifying NAPL dissolution rates over a wide range of NAPL saturations and aqueous phase velocities within the NAPL source zone. When incorporated in a finite difference transport model, the correlation provides reasonably good predictions for systems with initially high NAPL saturations that are then reduced through the dissolution process. It is shown that NAPL dissolution is slower in this case due to the larger amorphous blobs that result from preferential flow and dissolution pathways. These large blobs have significantly less surface area in comparison with small discrete blobs that result from capillary entrapment. In comparison with other published dissolution correlations, the slower mass transfer rate is characterized with a significantly higher exponent on the NAPL saturation term.

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106 citations

"Numerical study on kinetic/equilibr..." refers background or methods in this paper

...…which is being represented as a function of flow and NAPL properties for single compound from residually entrapped porous system with/without considering the effect of heterogeneity (Imhoff et al., 1994; Mayer & Miller, 1996; Nambi & Powers, 2003; Powers et al., 1994; Schaerlaekens et al., 2000)....
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...Similarly, correlation developed by Nambi and Powers (2003) is well suited for heterogeneous laboratory scale systems for a wide range of NAPL saturation and Reynolds number, especially with high initial NAPL saturation....
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...…by using empirical mass transfer relations, thereby enabling to link with the macro-scale Darcy flux (Chu, Kitanidis, & McCarty, 2007; Geller & Hunt, 1993; Imhoff, Jaffe, & Pinder, 1994; Kim and Chrysikopoulos, 1999; Liu, Tindall, Friedel, & Zhang, 2007; Mayer & Miller, 1996; Nambi & Powers, 2003)....
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...…the non-equilibrium nature of dissolution mass transfer, a first-order driving force model is employed here with a lumped mass transfer coefficient inclusive of the surface area parameter and a concentration gradient term (Nambi & Powers, 2003; Powers et al., 1994) as given in Equation (2)....
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