Title: Journal of Contaminant Hydrology

Title: Journal of Contaminant Hydrology

ISO Abbreviated Title: J. Contam. Hydrol.

JCR Abbreviated Title: J Contam Hydrol

ISSN: 0169-7722

Issues/Year: 16

Journal Country/Territory: Netherlands

Language: English

Publisher: Elsevier Science BV

Publisher Address: PO Box 211, 1000 AE Amsterdam, Netherlands

Subject Categories:

Environmental Sciences: Impact factor 1.351, 31/126 (1999), Impact Factor 1.284, 31/127 (2000)

Geosciences, Interdisciplinary: Impact Factor

Water Resources: Impact factor 1.284, 3/47 (2000)

Barber II, L.B., Thurman, E.M. and Runnells, D.D. (1992), Geochemical heterogeneity in a sand and gravel aquifer: Effect of sediment mineralogy and particle-size on the sorption of chlorobenzenes. Journal of Contaminant Hydrology, 9 (1-2), 35-54.

Full Text: J\J Con Hyd9, 35.pdf

Abstract: The effect of particle size, mineralogy and sediment organic carbon (SOC) on sorption of tetrachlorobenzene and pentachlorobenzene was evaluated using batch-isotherm experiments on sediment particle-size and mineralogical fractions from a sand and gravel aquifer, Cape Cod, Massachusetts. Concentration of SOC and sorption of chlorobenzenes increase with decreasing particle size. For a given particle size, the magnetic fraction has a higher SOC content and sorption capacity than the bulk or non-magnetic fractions. Sorption appears to be controlled by the magnetic minerals, which comprise only 5-25% of the bulk sediment. Although SOC content of the bulk sediment is < 0.1%, the observed sorption of chlorobenzenes is consistent with a partition mechanism and is adequately predicted by models relating sorption to the octanol/water partition coefficient of the solute and SOC content. A conceptual model based on preferential association of dissolved organic matter with positively-charged mineral surfaces is proposed to describe micro-scale, intergranular variability in sorption properties of the aquifer sediments.

Keywords: Hydrophobic Organic-Compounds, Solute Transport, Humic Substances, Spatial Variability, Natural Sediments, Water, Adsorption, Soil, Pollutants, Groundwater

Gutierrez, M. and Fuentes, H.R. (1993), Modeling adsorption in multicomponent systems using a Freundlich-type isotherm. Journal of Contaminant Hydrology, 14 (3-4), 247-260.

Full Text: J\J Con Hyd14, 247.pdf

Abstract: The suitability of a Freundlich-type isotherm, the Sheindorf-Rebuhn-Sheintuch (SRS) equation, to represent the competitive adsorption of Sr, Cs and Co in Ca-montmorillonite suspensions was investigated. Experimental adsorption data were obtained for systems containing these cations as single-component, binary and ternary mixtures. The competition coefficients alpha(ij), which were obtained based on the experimental adsorption data for bicomponent systems, can be viewed as a way to quantify competitive interactions. The competition coefficients obtained for the cations under consideration indicate that their competitive interactions are of similar magnitude, with the cation least affected by competitive effects being Cs, while the adsorption of Co was more significantly affected by the presence of Cs, and Sr by the presence of Co. After alpha(ij)-values were substituted in the SRS equation, the adsorption of systems of three or more components could be predicted. To validate the SRS equation, the adsorption values predicted by this equation for the ternary mixture Sr-Cs-Co were compared to values determined experimentally. The SRS equation successfully modeled adsorption for the range of concentrations that followed Freundlich behavior.

Keywords: Competitive Adsorption, Sorption, Strontium, Cesium, Soils

Holm, T.R. and Zhu, X.F. (1994), Sorption by kaolinite of Cd²⁺, Pb²⁺ and Cu²⁺ from landfill leachate-contaminated groundwater. Journal of Contaminant Hydrology, 16 (3), 271-287.

Full Text: J\J Con Hyd16, 271.pdf

Abstract: Sorption of Cd²⁺, Pb²⁺ and Cu²⁺ to kaolinite from landfill leachate-contaminated groundwater, artificial groundwater (same major-ion concentrations as groundwater) and NaNO₃ (same ionic strength as the groundwater) was studied. Complexation of Cu²⁺ and Cd²⁺ by dissolved organic matter (DOM) in the groundwater was also studied. There was less sorption of all three metals from groundwater than from NaNO₃ for large pH ranges. Sorption of Cd²⁺ and Pb²⁺ seemed to be due to a combination of ion exchange and surface complexation. This hypothesis was supported by agreement between an ion exchange/surface complexation model and the sorption data. There was less Cu²⁺ sorption from groundwater than from NaNO₃ for pH-values > 5, but Cu²⁺ sorption from artificial groundwater was the same as from NaNO₃. Sorption of Cu²⁺ was apparently by surface complexation only. For fixed pH and variable total Cu, there was less Cu²⁺ Sorption from groundwater than from NaNO₃, which is consistent with the formation of nonsorbing soluble complexes with DOM. A soluble complexation/surface complexation model reproduced the trends in the data, which supports the hypothesis of nonsorbing Cu complex formation.

Keywords: Natural Organic-Matter, Humic Substances, Complex-Formation, Hydrous Oxides, Soil Solutions, Trace-Metals, Cadmium, Surface, Adsorption, Copper

Fuller, C.C., Davis, J.A., Coston, J.A. and Dixon, E. (1996), Characterization of metal adsorption variability in a sand and gravel aquifer, Cape Cod, Massachusetts, USA. Journal of Contaminant Hydrology, 22 (3-4), 165-187.

Full Text: J\J Con Hyd22, 165.pdf

Abstract: Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb²⁺) and zinc (Zn²⁺) adsorption at constant chemical conditions (pH 5.3) varied by a factor of 2 and 4, respectively. Pb²⁺ and Zn²⁺ were adsorbed primarily by Fe- and Al-oxide coatings on quartz-grain surfaces. Per unit surface area, both Pb²⁺ and Zn²⁺ adsorption were significantly correlated with the amount of Feand Al that dissolved from the aquifer material in a partial chemical extraction. The variability in conditional binding constants for Pb²⁺ and Zn²⁺ adsorption (log K-ADS) derived from a simple non-electrostatic surface complexation model were also predicted by extracted Feand Al normalized to surface area. Because the abundance of Fe- and Al-oxide coatings that dominate adsorption does not vary inversely with grain size by a simple linear relationship, only a weak, negative correlation was found between the spatial variability of Pb²⁺ adsorption and grain size in this aquifer. The correlation between Zn²⁺ adsorption and grain size was not significant. Partial chemical extractions combined with surface-area measurements have potential use for estimating metal adsorption variability in other sand and gravel aquifers of negligible carbonate and organic carbon content.

Choi, J.W. and Oscarson, D.W. (1996), Diffusive transport through compacted Na- and Ca-bentonite. Journal of Contaminant Hydrology, 22 (3-4), 189-202.

Full Text: J\J Con Hyd22, 189.pdf

Abstract: Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb²⁺) and zinc (Zn²⁺) adsorption at constant chemical conditions (pH 5.3) varied by a factor of 2 and 4, respectively. Pb²⁺ and Zn²⁺ were adsorbed primarily by Fe- and Al-oxide coatings on quartz-grain surfaces. Per unit surface area, both Pb²⁺ and Zn²⁺ adsorption were significantly correlated with the amount of Fe and Al that dissolved from the aquifer material in a partial chemical extraction. The variability in conditional binding constants for Pb²⁺ and Zn²⁺ adsorption (log K_ADS) derived from a simple non-electrostatic surface complexation model were also predicted by extracted Fe and Al normalized to surface area. Because the abundance of Fe- and Al-oxide coatings that dominate adsorption does not vary inversely with grain size by a simple linear relationship, only a weak, negative correlation was found between the spatial variability of Pb²⁺ adsorption and grain size in this aquifer. The correlation between Zn²⁺ adsorption and grain size was not significant. Partial chemical extractions combined with surface-area measurements have potential use for estimating metal adsorption variability in other sand and gravel aquifers of negligible carbonate and organic carbon content.

Wang, W.Z., Brusseau, M.L. and Artiola, J.F. (1997), The use of calcium to facilitate desorption and removal of cadmium and nickel in subsurface soils. Journal of Contaminant Hydrology, 25 (3-4), 325-336.

Full Text: J\J Con Hyd25, 325.pdf

Abstract: The transport and elution behavior of Cd and Ni in the presence of Ca in subsurface soils was investigated using batch and miscible-displacement experiments. The adsorption of Cd and Ni by the soils was dramatically decreased and their transpor through the soils was significantly enhanced in the presence of Ca. These effects were attributed to the competition between Ca and these metals for exchange sites on the soil surfaces. The volume of CaCl₂ solution required to remove a certain % of Cd decreased with increasing concentration of CaCl₂. However, the concentration of CaCl₂ used to flush the soil did not significantly affect the final % of Cd removed, which was 90%. The position of the Cd elution peak varied with Ca concentration due to the nonlinear sorption behavior of Ca. (C) 1997 Elsevier Science B.V.

Keywords: Ionic-Strength, Sorption, Adsorption, Copper, pH, Complexation, Metals, Zinc, Calcium, Cadmium, Nickel, Adsorption, Desorption, Non-Linear, Removal, Metal-Contaminated, Soils

? Huang, W.L., Yu, H. and Weber, Jr., W.J. (1998), Hysteresis in the sorption and desorption of hydrophobic organic contaminants by soils and sediments. 1. A comparative analysis of experimental protocols. Journal of Contaminant Hydrology, 31 (1-2), 129-148.

Full Text: 1998\J Con Hyd31, 129.pdf

Abstract: Sorption and desorption equilibria were measured for an organic contaminant probe, phenanthrene, and five EPA reference soils and sediments to evaluate the existence and extent of apparent isotherm hysteresis. Three different experimental protocols were tested to assess their relative potentials for introduction of artifact. The results reveal that: i) all systems studied exhibit apparent sorption-desorption hysteresis, ii) the three protocols tested yield significantly different degrees of apparent hysteresis, iii) principal sources of artifact are solute losses to reactor components and failure to achieve equilibrium sorption conditions, iv) isotherm nonlinearity elevates the potential for introduction of artifacts in the quantification of desorption hysteresis, and v) Little if any ‘solids effect’ was observed. A single-cycle decant-refill batch reactor technique employing sealed and resealed glass ampules was found to involve minimal potential for introduction of artifacts. The general suitability of the procedure is confirmed in additional studies described in the companion paper of this two-part series. (C) 1998 Elsevier Science B.V.

Keywords: Adsorption-Desorption, Chemicals, Desorption, Desorption Hysteresis, Distributed Reactivity Model, Experimental Artifacts, Hydrophobic Organic Contaminants, Insecticides, Partitioning Behavior, Phenanthrene, Pollutants, Polychlorinated-Biphenyls, Polycyclic Aromatic-Hydrocarbons, Solids, Sorption, Water Systems

? Weber, Jr., W.J., Huang, W.L. and Yu, H. (1998), Hysteresis in the sorption and desorption of hydrophobic organic contaminants by soils and sediments. 2. Effects of soil organic matter heterogeneity. Journal of Contaminant Hydrology, 31 (1-2), 149-165.

Full Text: 1998\J Con Hyd31, 149.pdf

Abstract: Sorption and desorption equilibria were measured for phenanthrene and 12 different soil and sediment samples using an experimental protocol described in the companion paper of this two-part series. Ten of the 12 sorbents studied were found to exhibit statistically significant sorption-desorption hysteresis, with those containing diagenetically-altered soil organic matter (kerogens) doing so to greater extents than those containing geologically-younger humic soil organic matter. Correlations between the extent of hysteresis and the characteristics of C-13-NMR spectra indicate that particle-scale soil organic matter heterogeneity significantly affects this phenomenon. The experimental observations are mechanistically consistent with a conceptual model based on polymer sorption theory, the Dual Reactive Domain Model (DRDM). The work reinforces the general suitability of the DRDM for characterizing sorption-desorption interactions between hydrophobic organic contaminants and soils and sediments. (C) 1998 Elsevier Science B.V.

Keywords: Adsorption, Aquifer Material, Atrazine, Covalent Binding, Desorption, Desorption Hysteresis, Distributed Reactivity Model, Fulvic-Acid, Herbicides, Humic Substances, Hydrophobic Organic Contaminants, Mechanisms, Naphthalene, Organic Matter, Phenanthrene, Soil Heterogeneity, Sorption

? Johnson, W.P., Cabral, K., Lion, L.W. and Corapcioglu, Y.M. (1998), Reconciliation of expressions for the modified retardation factor and incorporation of non-linear contaminant sorption to the stationary phase. Journal of Contaminant Hydrology, 32 (3-4), 247-266.

Full Text: 1998\J Con Hyd32, 247.pdf

Abstract: The retardation factor describes the average velocity of a sorbing contaminant in groundwater relative to the average velocity of groundwater. The modified retardation factor (R’ or R*) describes the average velocity of a sorbing contaminant relative to groundwater in the presence of a carrier that binds the contaminant and facilitates its transport. Dissolved organic matter and particulate colloids are examples of potential facilitating carriers. The modified retardation factor R’ concerns the case when sorption of the carrier itself to the stationary phase is negligible, whereas R* accounts for significant sorption of a facilitating carrier to the stationary phase, and so represents a magnitude less than R, but greater than R’. A well-cited expression for R* is shown to differ in form and behavior relative to a lesser known expression for R*, and the bounds of applicability of these expressions are examined. The lesser-known expression for R* is shown to be more broadly applicable in its ability to describe situations where carrier sorption to the stationary phase is significant, and even rivals or exceeds that of the contaminant. The well-known expression for R* is shown to be not applicable to situations involving significant sorption of the carrier. The derivation of the expression for R* presented in this paper is given by two separate methods used to develop the previously published expressions, in order to relate the presented and previously published expression to each other. The expression is extended to include non-linear contaminant sorption to the stationary phase, and predictions from this expression are compared to a set of experimental data. (C) 1998 Elsevier Science B.V. All rights reserved.

Keywords: Accounts, Aquifer Material, Behavior, Carbon, Colloids, Groundwater, Humic Substances, Macromolecules, Matter, Modified, Natural Organic-Matter, Organic, Organic Matter, Paper, Particulate, Phenanthrene, Polycyclic Aromatic-Hydrocarbons, Porous-Media, Predictions, Retardation Factor, Sandy Aquifer, Sorption, Transport

Johnson, C.A., Richner, G.A., Vitvar, T., Schittli, N. and Eberhard, M. (1998), Hydrological and geochemical factors affecting leachate composition in municipal solid waste incinerator bottom ash. Part I: The hydrology of Landfill Lostorf, Switzerland. Journal of Contaminant Hydrology, 33 (3-4), 361-376.

Full Text: J\J Con Hyd33, 361.pdf

Abstract: The objective of the investigation of the municipal solid waste incinerator (MSWI) bottom ash landfill, Landfill Lostorf, was to determine the residence time of water in the landfill and the flow paths through the landfill. Over a period of 22 months, measurements of rainfall, landfill discharge and leachate electrical conductivity were recorded and tracer experiments made. Over the yearly period 1995, approximately 50% of the incident rainfall was measured in the discharge. An analysis of single rain events showed that in winter, 90-100% of rainfall was expressed in the landfill discharge, whereas in summer months, the value was between 9 and 40% depending on the intensity of the rain event. The response to rainfall was rapid. Within 30-100 h, approximately 50% of water discharged in response to a rain event had left the landfill. The discharge was less’ than 4 l/min for approximately 50% of the measurement periods. Qualitative tracer studies with fluorescein, pyranine and iodide clearly showed the existence of preferential flow paths. This was further substantiated by quantitative tracer studies of single rain events using O-18/O-16 ratios and electrical conductivity measurements. The proportion of rainwater passing directly through the landfill was found to be between 20 and 80% in summer months and around 10% in winter months. The difference has been ascribed to the water content in the landfill. The average residence time of the water within the landfill has been estimated to be roughly 3 years and this water is the predominant component in the discharge over a yearly period. (C) 1998 Elsevier Science B.V. All rights reserved.

Keywords: Waste Disposal, Landfill, Hydrology, Oxygen Isotope, Tracers, Water

Pang, L.P. and Close, M.E. (1999), Non-equilibrium transport of Cd in alluvial gravels. Journal of Contaminant Hydrology, 36 (1-2), 185-206.

Full Text: J\J Con Hyd36, 185.pdf

Abstract: The transport of Cd in alluvial gravels was investigated using batch tests and miscible displacement experiments with large and small columns. Batch tests indicates that Cd adsorption fitted the Freundlich isotherm reasonably well and was highly nonlinear. The sorption of Cd under batch conditions was essentially complete within a few minutes, followed by a time-dependent slow sorption in weeks. A large column (200 cm long, 19 cm diameter) was injected with pulse solutions containing Cd, Br, Cl, and rhodamine WT at pore-water velocities of 20 and 61 m/day, while the small column (18 cm long, 10 cm diameter) was injected with Br and Cd pulses at pore-water velocities of 18 and 58 m/day. Breakthrough curves (BTCs) of Cd were highly asymmetric while those of other solutes were essentially symmetric, suggesting the presence of a non-equilibrium component for the Cd transport. This was further evidenced by decreases in Cd concentrations when flow was interrupted. Under all conditions investigated, asymmetry in Cd BTCs essentially resulted from chemical non-equilibrium as physical non-equilibrium was not present. Both equilibrium and non-equilibrium models, as incorporated in CXTFIT, were used to describe observed BTCs of Cd. Dispersivity was obtained from the nonreactive solute Br data, and it was then held constant for the other solutes. The retardation factor (R) values were estimated based on results from batch tests and the time moment method. For comparison purposes, the R values of the Cd data were also simulated from the two-site models. The values of the partitioning coefficient (beta) and the mass transfer coefficient (omega) were estimated from two-region/site models. Modelling results suggest that (1) Cd transport was mainly controlled by rate-limited sorption, (2) the scale effect on Cd transport was minor for the reasonably well sorted material investigated, with a slight increase in the degree of equilibrium in the large column. Small columns may be used to obtain fast experimental results for homogeneous medium. However, if heterogeneity and preferential flow is important, larger columns are recommended. (3) it was evidenced that the degree of chemical non-equilibrium increased with increasing pore-water velocities, however the change was not major for the flow rates investigated (18-61 m/day), and (4) equilibrium models could provide apparently good fits to skewed BTCs by overestimating dispersivity, which incorporates all the effects from the dispersion and diffusion within both mobile and immobile liquid phases and/or type-1 and type-2 sorption sites. Comparatively, non-equilibrium models described the Cd data better and provided a more correct explanation for the spreading and asymmetry of the Cd BTC. (C) 1999 Elsevier Science B.V. All rights reserved.

Keywords: Non-Equilibrium Transport, Cxtfit, Cadmium, Alluvial Gravels, Pore-Water Velocity, Nonequilibrium Transport, Organic-Chemicals, Aquifer Materials, Solute Transport, Rhodamine WT, Sorption, Soil, Adsorption, Cadmium

Morrissey, F.A. and Grismer, M.E. (1999), Kinetics of volatile organic compound sorption/desorption on clay minerals. Journal of Contaminant Hydrology, 36 (3-4), 291-312.

Keywords: Clay Minerals, Volatile Organic Compounds, Sorption

Kedziorek, M.A.M. and Bourg, A.C.M. (2000), Solubilization of lead and cadmium during the percolation of EDTA through a soil polluted by smelting activities. Journal of Contaminant Hydrology, 40 (4), 381-392.

Full Text: J\J Con Hyd40, 381.pdf

Abstract: EDTA was percolated in laboratory columns through a soil polluted by heavy metals to investigate the efficiency of and processes involved in soil decontamination by chemical extraction. At high EDTA concentration (10^-2 M), elution of Pb and Cd was very efficient for one pore volume, after which it decreased to almost zero due to depletion of available Pb and Cd and to competition with Ca and Fe slowly solubilized during the passage of the EDTA front. Clogging occurred after the end of the EDTA plateau. At lower EDTA concentrations (10^-3 and 10^-4 M), elution was less efficient, but extraction decreased little with the volume percolated, moreover no Ca above background values was dissolved. The optimum EDTA concentration for heavy metal extraction ranges between 10^-2 and 10^-3 M, The higher the concentration, the greater the extraction efficiency, but as the EDTA concentration is increased there is an optimum point at which clogging takes place and permeability decreases. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Heavy Metals, Soil Pollution, Edta, Solubilization, Organic-Acids

Warwick, P.W., Hall, A., Pashley, V., Bryan, N.D. and Griffin, D. (2000), Modelling the effect of humic substances on the transport of europium through porous media: A comparison of equilibrium and equilibrium/kinetic models. Journal of Contaminant Hydrology, 42 (1), 19-34.

Full Text: J\J Con Hyd42, 19.pdf

Abstract: A series of column experiments have been performed, which demonstrate the effect of humic substances on the transport of europium through a sand column. Two approaches have been used to model the results: an approach based on a assumption of local chemical equilibrium, and one which accounts for kinetically hindered reactions. A significant improvement in fit is observed upon the inclusion of kinetics. The model explains the observed behaviour of the europium in terms of two distinct humic bound fractions. One which is exchangeably bound, and interacts with the surface of the column packing, and another, kinetically hindered, which does not.

Keywords: Natural Organic-Matter, Metal-Ion Binding, Fulvic-Acid, Adsorption, Complexation, Speciation, Cadmium, Humic Substances, Natural Organic Matter, Contaminant Transport, Radionuclides, Waste Disposal

Bayard, R., Barna, L., Mahjoub, B. and Gourdon, R. (2000), Influence of the presence of PAHs and coal tar on naphthalene sorption in soils. Journal of Contaminant Hydrology, 46 (1-2), 61-80.

Full Text: J\J Con Hyd46, 61.pdf

Abstract: The mobility of the most water-soluble polynuclear aromatic hydrocarbons (PAHs) such as naphthalene in contaminated soils from manufactured gas plant (MGP) sites or other similar sites is influenced not, only by the naturally occurring soil organic matter (SOM) but also, and in many cases mostly, by the nature and concentration of coal tar. xenobiotic organic matter (XOM) and other PAH molecules present in the medium under various physical states. The objective of the present study was to quantify the effects of these factors using batch experiments, in order to simulate naphthalene transport in soil-tar-water systems using column experiments. Naphthalene sorption was studied in the presence of (i) solid coal tar particles, (II) phenanthrene supplied as pure crystals, in the aqueous solution or already sorbed onto the soil, (iii) fluoranthene as pure crystals, and (iv) an aqueous solution of organic molecules extracted from a liquid tar. All experiments were conducted under abiotic conditions using short naphthalene/sorbent contact times of 24-60 h. Although these tests do not reflect true equilibrium conditions which usually rake more time to establish, they were used to segregate relatively rapid sorption phenomena (“pseudo equilibrium”) from slow sorption and other aging phenomena. For longer contact times, published data have shown that experimental biases due to progressive changes in the characteristics of the soil and the solution may drastically modify the affinity of the solutes for the soil. Slow diffusion in the microporosity and in dense organic phases may also become significant over the long term, along with some irreversible aging phenomena which have not been addressed in this work.

Results showed that pAHs had no effect on naphthalene sorption when present in the aqueous solution ol as pure crystals, due to their low solubility in water. Adsorbed phenanthrene was found to reduce naphthalene adsorption only when present at relatively high concentrations (about 120 mg/kg) in the soil. In contrast, experiments carried out with coal tar particles revealed a significant effect. Naphthalene sorption appeared to be proportional to the amount of coal tar added to the sand or soil, and a much higher affinity of naphthalene for XOM (K-oc above 2000 cm³/g) than SOM (K-oc around 300 cm³/g) was observed. Naphthalene transport in the columns of sand or soil spiked with coal tar particles was simulated very satisfactorily with a dual double-domain model. Around 90% of naphthalene retention by coal tar was found to occur within the organic phase, suggesting a phase partition process which may be explained by the amorphous nature of the XOM and its extreme affinity fur naphthalene. For SOM, however, which is present as porous microaggregates of clay and humic substances, with less affinity for naphthalene, only 1/3 of naphthalene retention was found to occur within the organic phase, underlining the significant role of surface adsorption in the short term behavior of naphthalene in soil. For longer contact times, the model simulations proposed in the present study should be coupled to slow sorption, aging and biodegradation models to describe long-term behavior of naphthalene in soil-tar-water systems. (C) 2000 Elsevier Science B.V. All rights reserved.

Keywords: Naphthalene, Adsorption, Partition, Soil, Modeling, Coal Tar, Distributed Reactivity Model, Organic-Chemicals, Natural Sediments, Hydrocarbons, Adsorption, Water, Equilibrium, Pollutants, Transport, Systems

? Bourg, I.C., Bourg, A.C.M. and Sposito, G. (2003), Modeling diffusion and adsorption in compacted bentonite: A critical review. Journal of Contaminant Hydrology, 61 (1-4), 293-302.

Full Text: 2003\J Con Hyd61, 293.pdf

Abstract: The current way of describing diffusive transport through compacted clays is a simple diffusion model coupled to a linear adsorption coefficient (K-d). To fit the observed results of cation diffusion, this model is usually extended with an adjustable “surface diffusion” coefficient. Description of the negative adsorption of anions calls for a further adjustment through the use of an “effective porosity”. The final model thus includes many fitting parameters. This is inconvenient where predictive modeling is called for (e.g., for waste confinement using compacted clay liners). The diffusion/adsorption models in current use have been derived from the common hydrogeological equation of advection/dispersion/adsorption. However, certain simplifications were also borrowed without questioning their applicability to the case of compacted clays. Among these simplifications, the assumption that the volume of the adsorbed phase is negligible should be discussed. We propose a modified diffusion/adsorption model that accounts for the volume of the adsorbed phase. It suggests that diffusion through highly compacted clay takes place through the interlayers (i.e., in the adsorbed phase). Quantitative prediction of the diffusive flux will necessitate more detailed descriptions of surface reactivity and of the mobility of interlayer species. (C) 2002 Elsevier Science B.V. All rights reserved.

Keywords: Adsorption, Bentonite, Cesium Ions, Charge, Clay, Clay-Minerals, Diffusion, Diffusion And Adsorption, Mechanism, Mechanisms, Membranes, Mobility, Model, Modeling, Models, Ray-Absorption Spectroscopy, Review, Science, Smectite, Sodium Montmorillonite, Sorption, Volume, Water

? Riva, M., Sánchez-Vila, X., Guadagnini, A., De Simoni, M. and Willmann, M. (2006), Travel time and trajectory moments of conservative solutes in two-dimensional convergent flows. Journal of Contaminant Hydrology, 82 (1-2), 23-43.

Full Text: 2006\J Con Hyd82, 23.pdf

Abstract: We address advective transport of a solute traveling toward a single pumping well in a two-dimensional randomly heterogeneous aquifer. The two random variables of interest are the trajectory followed by an individual particle from the injection point to the well location and the particle travel time under steady-state conditions. Our main objective is to derive the predictors of trajectory and travel time and the associated uncertainty, in terms of their first two statistical moments (mean and variance). We consider a solute that undergoes mass transfer between a mobile and an immobile zone. Based on Lawrence et al. [Lawrence, A.E., Sánchez-Vila, X., Rubin, Y., 2002. Conditional moments of the breakthrough curves of kinetically sorbing solute in heterogeneous porous media using multirate mass transfer models for sorption and desorption. Water Resour. Res. 38 (11), 1248, doi:10.1029/2001WR001006.], travel time moments can be written in terms of those of a conservative solute times a deterministic quantity. Moreover, the moments of solute particles trajectory do not depend on mass transfer processes. The resulting mean and variance of travel time and trajectory for a conservative species can be written as functions of the first, second moments and cross-moments of trajectory and velocity components. The equations are developed from a consistent second order expansion in σY (standard deviation of the natural logarithm of hydraulic conductivity). Our solution can be completely integrated with the moment equations of groundwater flow of Guadagnini and Neuman [Guadagnini, A., Neuman, S.P., 1999a. Nonlocal and localized analyses of conditional mean steady state flow in bounded, randomly non uniform domains 1. Theory and computational approach. Water Resour. Res. 35(10), 2999–3018.,Guadagnini, A., Neuman, S.P., 1999b. Nonlocal and localized analyses of conditional mean steady state flow in bounded, randomly non uniform domains 2. Computational examples. Water Resour. Res. 35(10), 3019–3039.], it is free of distributional assumptions regarding the log conductivity field, and formally includes conditioning. We present analytical expressions for the unconditional case by making use of the results of Riva et al. [Riva, M., Guadagnini, A., Neuman, S.P., Franzetti, S., 2001. Radial flow in a bounded randomly heterogeneous aquifer. Transport in Porous Media 45, 139–193.]. The quality of the solution is supported by numerical Monte Carlo simulations. Potential uses of this work include the determination of aquifer reclamation time by means of a single pumping well, and the demarcation of the region potentially affected by the presence of a contaminant in the proximity of a well, whenever the aquifer is very thin and Dupuit–Forchheimer assumption holds.

Keywords: Groundwater Flow and Transport, Porous Media, Travel Time, Statistical Moments, Model Uncertainty

? Radu, T., Kumar, A., Clement, T.P., Jeppu, G. and Barnett, M.O. (2008), Development of a scalable model for predicting coupled with oxidation and adsorption arsenic transport reactions. Journal of Contaminant Hydrology, 95 (1-2), 30-41.

Full Text: 2008\J Con Hyd95, 30.pdf

Abstract: Understanding the fundamentals of arsenic adsorption and oxidation reactions is critical for predicting its transport dynamics in groundwater systems. We completed batch experiments to study the interactions of arsenic with a common MnO_2(S) mineral, pyrolusite. The reaction kinetics and adsorption isotherm developed from the batch experiments were integrated into a scalable reactive transport model to facilitate column-scale transport predictions. We then completed a set of column experiments to test the predictive capability of the reactive transport model. Our batch results indicated that the commonly used pseudo-first order kinetics for As(III) oxidation reaction neglects the scaling effects with respect to the MnO_2(S) concentration. A second order kinetic equation that explicitly includes MnO_2(S) concentration dependence is a more appropriate kinetic model to describe arsenic oxidation by MnO_2(S) minerals. The arsenic adsorption reaction follows the Langmuir isotherm with the adsorption capacity of 0.053 mol of As(V)/g of MnO_2(S) at the tested conditions. The knowledge gained from the batch experiments was used to develop a conceptual model for describing arsenic reactive transport at a column scale. The proposed conceptual model was integrated within a reactive transport code that accurately predicted the breakthrough profiles observed in multiple column experiments. The kinetic and adsorption process details obtained from the batch experiments were valuable data for scaling to predict the column-scale reactive transport of arsenic in MnO_2(S)-containing sand columns. (c) 2007 Elsevier B.V. All rights reserved.

Keywords: Adsorption, Adsorption Isotherm, Arsenic, As(III), Bangladesh, Chemistry, Column Experiments, Contaminant Transport, Dioxides, Ground Water Modeling, Groundwater, Isotherm, Kinetic, Kinetics, Langmuir, Langmuir Isotherm, Manganese Oxides, Numerical Modeling, Oxidation, Reaction Kinetics, Reactive Transport, Removal, Sand, Scaling, Surfaces, Synthetic Birnessite, Transport

? Malusis, M.A., Maneval, J.E., Barben, E.J., Shackelford, C.D. and Daniels, E.R. (2010), Influence of adsorption on phenol transport through soil-bentonite vertical barriers amended with activated carbon. Journal of Contaminant Hydrology, 116 (1-4), 58-72.

Full Text: 2010\J Con Hyd116, 58.pdf

Abstract: The potential for enhanced containment of phenol by soil-bentonite (SB) vertical barriers amended with activated carbon (AC) was investigated Results of batch equilibrium adsorption tests on model SB backfills amended with 0-10 wt% granular AC (GAC) or powdered AC (PAC) illustrate that the backfills exhibited nonlinear adsorption behavior that was described well by both the Freundlich and Toth adsorption models. The AC amended backfills exhibited enhanced phenol adsorption relative to unamended backfill due to hydrophobic partitioning to the AC Adsorption capacity increased with increasing AC content but was insensitive to AC type (GAC versus PAC) Results of numerical transport simulations based on the measured adsorption behavior show that the Toth model yielded similar or lower phenol breakthrough times than the Freundlich model for the range of source concentrations (C-o) considered in the simulations (0 1-10 mg/L) Breakthrough time decreased with increasing C-o but increased with increasing AC content Predicted breakthrough times for an SB vertical barrier amended with 2-10 wt% AC increased by several orders of magnitude relative to the theoretical case of a nonreactive (non-adsorbing) barrier. The findings suggest that AC may be a highly effective adsorption amendment for sustaining the containment performance of SB vertical barriers (C) 2010 Elsevier BV All rights reserved.

Keywords: Activated Carbon, Adsorption, Adsorption Behavior, Adsorption Capacity, Barrier, Barriers, Batch, Behavior, Breakthrough, Capacity, Carbon, Co, Component Systems, Containment Barriers, Cutoff Wall, Cutoff Walls, Dye Adsorption, Equilibrium, Freundlich, Freundlich Model, GAC, Hydrophobic, Isotherm, Landfill Liners, Model, Models, Nonlinear Adsorption, Organic Contaminant Transport, PAC, Performance, Phenol, Porous-Media, Potential, Retardation, Rights, Slurry Walls, Soil-Bentonite Vertical Barrier, Sorption, Source, Transport, Vertical