Transport Of Naphthalene Research Articles

Harnessing Maxwell’s demon to establish a macroscale concentration gradient

Maxwell’s demon describes a thought experiment in which a ‘demon’ regulates the flow of particles between two adjoining spaces, establishing a potential gradient without appearing to do work. This seeming paradox led to the understanding that sorting entails thermodynamic work, a foundational concept of information theory. In the past centuries, many systems analogous to Maxwell’s demon have been introduced in the form of molecular information, molecular pumps and ratchets. Here we report a functional example of a Maxwell’s demon that pumps material over centimetres, whereas previous examples operated on a molecular scale. In our system, this demon drives directional transport of o-fluoroazobenzene between the arms of a U-tube apparatus upon light irradiation, transiting through an aqueous membrane containing a coordination cage. The concentration gradient thus obtained is further harnessed to drive naphthalene transport in the opposite direction.

Adsorption and desorption of gaseous naphthalene on carbonaceous sorbents: Insights into advantageous pore sizes and morphologies

Capturing and recovering naphthalene as a profitable chemical from hot flue gas are of significance in terms of environmental protection with economic benefits, for which the adsorption technology using high-performance sorbents provides the key step for success in practical applications. Carbonaceous materials with hydrophobic natures have been shown to render high affinities with non-polar naphthalene, but remain challenging due to difficulties in tackling the trade-off between adsorption and desorption. This work reports a systematic investigation with deeper insights into adsorption equilibria, kinetics and regenerabilities of gaseous naphthalene on typical carbonaceous sorbents originated from different texture properties, including ordered mesoporous carbons (CMK-3, CMK-5 and FDU-15), carbon nanotubes (SWCNT and MWCNT) and a coconut-shell-based activated carbon (AC). The adsorption isotherm and breakthrough curves at wide feed concentration ranges and temperature programmed desorption curves for each sorbent were obtained along with series of theoretical model fitting. FDU-15 and CMK-5 were demonstrated as superior sorbents with high maximum adsorption capacities (1.13 and 1.735 mmol/g) and low desorption activation energy (62.66 and 72.68 kJ/mol), respectively exhibiting advantages of the 3-dimensional diffusion-controlled desorption upon a hexagonal pore arrangement and the efficient adsorption upon a reasonable mesopore-micropore hierarchical structure, in contrast to poor kinetics on pure microporosity (AC) and 1-dimensional topologies (CNTs). Deeper insights into the morphology-affinity relationship revealed advantageous naphthalene transport behaviors over 3-dimensional ordered mesoporosities with appropriate coexisting microporosities and narrower primary size (2–5 nm) or diverse forms of mesopore, which contribute toward reaching comprehensive balances of sorption performances.

Numerical investigation of naphthalene deposition dynamics during CO2 leakage

An important leakage risk associated with CO2 geological sequestration is the potential transport and fate of organic contaminants due to the CO2 leakage. In this paper, a precipitation and deposition dynamic model was constructed using COMSOL to evaluate the potential impacts of organic contaminants in response to the leakage of CO2 and brine into a shallow aquifer. The Span-Wagner equation and Peng-Robinson equations were adopted to estimate the partitioning behavior of organic contaminants. Numerical simulations with naphthalene as a representative contaminant show that the dissolved component is transported with the equilibrium concentrations at the thermodynamic conditions built by the fluid phase, while the precipitated solid particles are either transported with carrier fluid or deposited in the leakage pathway according to the deposition dynamic model. The sharp decrease of solubility promotes the precipitation impetus while the deposition rate mainly depends upon the leakage velocity and pore structure. Local blockage may occur due to the accumulation of deposited particles, and the potential location is most likely to be near the outlet of the leakage pathway in current scenario. Sensitivity analyses indicate that pressure difference and temperature buildup would influence both the leakage velocity and deposition dynamics, while the pore structure of leakage pathway, represented by porosity and permeability, will affect the leakage characteristic so as to the deposition rate. The presented models are generic in nature for naphthalene transport, demonstrating a methodology that can explore the generation of a potential third organic phase in contaminant transport for risk assessments.

Migration of Naphthalene through Low Organic Content Sandy Soil Columns: Comparison of Unsaturated and Saturated Conditions

ABSTRACTThe transient transport of naphthalene through low organic matter content soil columns was investigated in different water-saturation and flow conditions. Some parameters were tested as flow rate, column height, and water saturation conditions. The soil was a clayed sandy soil from the Algerian coast near Boumerdes. The organic carbon content was 0.13% and the main mineral components were quartz (88%), clays minerals (7%) and calcite (3%). The height of the packing of the soil column (5.1 cm in diameter) varied from 15 to 40 cm. Simultaneous step injections of inert tracer (calcium chloride) and naphthalene at 10 mg L−1 were performed. Tracer and naphthalene breakthrough curves (BTCs) were measured continuously by conductimetry and UV – 220 nm, respectively. The BTCs were simulated using the classical mixing cells in series with exchange model (MCE). In unsaturated conditions the comparison of the mean residence time of tracer BTCs with the geometrical pore volume gave us access to average water saturation along the column as a function of height. The higher the soil bed was, the higher the mean water saturation. The comparison of naphthalene distribution coefficients (Kd) in different flow conditions with the theoretical value from the Karickhoff law showed that in saturated conditions the obtained value was close to the theoretical one. In unsaturated conditions, the measured naphthalene Kd's were much lower than the theoretical value and correlated to the water saturation.

Advection and retardation of non-polar contaminants in compacted clay barrier material with organoclay amendment

Compacted clay liners (CCLs) are widely used as hydraulic barriers in landfills, underground storage tanks, vertical cutoff walls and surface impoundments. Most commonly, the breakthrough of contaminant flows in CCLs takes a long time due to the reduced advection rate; however, the attenuation of non-polar fluid or organic contaminants in CCLs is relatively low because of the non-reactive nature of most CCL materials. Surfactant-modified bentonites are promising barrier amendments as they are coated with organic surfactant and are capable of uptaking the non-polar species from the aqueous phase. In this study, laboratory tests were carried out to evaluate the swelling, permeability and contaminant retention of compacted silty clay amended with an organoclay (hexadecyltrimethylammonium (HDTMA) modified bentonite) against both gasoline and organic solution. The swelling properties and the hydraulic conductivities of compacted soils with varying liquids were evaluated and the transport of naphthalene, a representative of polycyclic aromatic hydrocarbons (PAHs) and a possible component of NAPLs, in organobentonite-amended silty clay was examined through batch sorption and column tests. The results indicated that the addition of 10% HDTMA bentonite to compacted silty clay slightly increased the permeability of the mixture to water. However, higher swelling tendency and lower permeability to gasoline were also observed. With 5% of HDTMA bentonite amendment, the compacted silty clay soil had a much stronger retardation capacity for naphthalene.

Laboratory-scale in situ bioremediation in heterogeneous porous media: Biokinetics-limited scenario

Subsurface heterogeneities influence interfacial mass-transfer processes and affect the application of in situ bioremediation by impacting the availability of substrates to the microorganisms. However, for difficult-to-degrade compounds, and/or cases with inhibitory biodegradation conditions, slow biokinetics may also limit the overall bioremediation rate, or be as limiting as mass-transfer processes. In this work, a quantitative framework based on a set of dimensionless coefficients was used to capture the effects of the competing interfacial and biokinetic processes and define the overall rate-limiting process. An integrated numerical modeling and experimental approach was used to evaluate application of the quantitative framework for a scenario in which slow-biokinetics limited the overall bioremediation rate of a polycyclic aromatic hydrocarbon (naphthalene). Numerical modeling was conducted to simulate the groundwater flow and naphthalene transport and verify the system parameters, which were used in the quantitative framework application. The experiments examined the movement and biodegradation of naphthalene in a saturated, heterogeneous intermediate-scale flow cell with two layers of contrasting hydraulic conductivities. These experiments were conducted in two phases: Phase I, simulating an inhibited slow biodegradation; and Phase II, simulating an engineered bioremediation, with system perturbations selected to enhance the slow biodegradation rate. In Phase II, two engineered perturbations to the system were selected to examine their ability to enhance in situ biodegradation. In the first perturbation, nitrogen and phosphorus in excess of the required stoichiometric amounts were spiked into the influent solution to mimic a common remedial action taken in the field. The results showed that this perturbation had a moderate positive impact, consistent with slow biokinetics being the overall rate-limiting process. However, the second perturbation, which was to alleviate inhibition and increase the biodegradation rate, enhanced the overall biotransformation rate to a greater degree.

A three-dimensional numerical model for linking community-wide vapour risks

A three-dimensional (3D) numerical model that couples contaminant transport in the saturated zone to vapour transport in the vadose zone and vapour intrusion into buildings was developed. Coupling these processes allows the simulation of vapour intrusion, arising from volatilization at the water table, associated with temporally and spatially variable groundwater plumes. In particular, the model was designed to permit, for the first time, 3D simulations of risk at receptors located in the wider community (i.e., kilometre scale) surrounding a contaminated site. The model can account for heterogeneous distributions of permeability, fraction organic carbon, sorption and biodegradation in the vadose and saturated zones. The model formulation, based upon integration of a number of widely accepted models, is presented along with verification and benchmarking tests. In addition, a number of exploratory simulations of benzene and naphthalene transport in a 1000 m long domain (aquifer cross-section: 500 m×14 m) are presented, which employed conservative assumptions consistent with the development of regulatory guidance. Under these conservative conditions, these simulations demonstrated, for example, that whether houses in the community were predicted to be impacted by groundwater and indoor air concentrations exceeding regulatory standards strongly depended on their distance downgradient from the source and lateral distance from the plume centreline. In addition, this study reveals that the degree of reduction in source concentration (i.e., remediation) required to achieve compliance with standards is less if the risk receptor is in the wider community than at the site boundary. However, these example scenarios suggest that, even considering community receptors, sources with initially high concentrations still required substantial remediation (i.e., >99% reductions in source concentration). Overall, this work provides insights and a new tool for considering the relationships between contaminated site source zones and community-wide risk assessment that allows for development of policies and technical approaches for contaminated site management. It is anticipated that this coupled model not only will allow significant convenience, for example in running suites of Monte Carlo simulations for complex scenarios, but will also allow the investigation of vapour intrusion under conditions where soil gas concentrations may change over the same timescale as an evolving plume.

Uptake and Elimination of Naphthalene from Liver, Lung, and Muscle Tissue in the Leopard frog (Rana pipiens)

The effects of a 0–12-hour naphthalene exposure on pulmonary CO2 excretion and bioaccumulation in the leopard frog, Rana pipiens, were investigated. The data showed that naphthalene transport occurred from the aqueous phase into the frog tissue. The first-order rate constant (k in day−1) for the entry of naphthalene from the water into the frog was 0.079 ± 0.007 (k ± 95% C.I.). Bioaccumulation of naphthalene was measured in liver, lung, and thigh muscle tissue. Exposure to naphthalene caused a significant reduction in pulmonary CO2 excretion, particularly following the first 30 minutes of exposure. Pulmonary CO2 excretion returned to baseline levels after 8 hours of exposure, indicating that some degree of acclimation had occurred. Depuration experiments were used to monitor recovery from naphthalene exposure. Recovery of CO2 excretion was evident following 2 hours of depuration and complete elimination of naphthalene from tissues occurred after 3 hours. The data indicate that accumulated polycyclic aromatic hydrocarbons (PAHs) may alter normal physiologic functions such as gas exchange. Since amphibians, such as frogs, are one of the first organisms to come into contact with contaminated water and sediments, the information in this study suggests that this species may be used to assess bioaccumulation and toxicity of PAHs in ecosystems.

Study of C60 transport in porous media and the effect of sorbed C60 on naphthalene transport

In this study, the transport of water-stable “nano-C60 particles” (a term used to refer to underivatized C60 crystalline nanoparticles, stable in water for months) through a soil column (packed with Lula soil, 0.27% organic carbon) was investigated for the first time. Nano-C60 particle breakthrough experiments were conducted at different flow rates, while other column operating parameters remained fixed through all the experiments. Nano-C60 particles were observed to be more mobile at higher flow velocity: at the flow velocity of 0.38 m/d, the maximum percent of nano-C60 breakthrough (C/C0) was 47%; at the flow velocity of 3.8 m/d, the plateau value of nano-C60 breakthrough was 60%; and at the flow velocity of 11.4 m/d, the plateau value of nano-C60 breakthrough was almost 80%. At the low flow velocity (0.38 m/d), which is typical of groundwater flow, nano-C60 particles showed very limited mobility: after about 57 pore volumes, they deposited to the soil column so rapidly that virtually no nano-C60 was detected in the effluent. This observed “favorable deposition” (attachment efficiency α = 1) was probably due to “filter ripening.” Also the release of nano-C60 particles after flow interruption was observed. The transport of naphthalene through the same soil column containing 0.18% nano-C60 particles deposited was measured. A retardation factor of about 13 was observed, possibly suggesting that sorbed nano-C60 particles in the soil column sorbed naphthalene similar to soil organic carbon. An asymmetric naphthalene breakthrough curve was observed, which is possibly due to “sorption nonequilibrium.”

Real-Time, in Situ Monitoring of Bioactive Zone Dynamics in Heterogeneous Systems

Successful implementation of in situ bioremediation is contingent upon understanding how physicochemical and microbial factors affect the formation and dynamics of microbially active regions known as bioactive zones (BAZs). This study demonstrates how a novel fiber optic detection system can be used to test hypotheses concerning real-time, in situ BAZ formation and dynamics. This study focuses on naphthalene transport in saturated porous media containing defined physicochemical and microbial heterogeneities. Biological activity was measured using a lux reporter bacterium, Pseudomonas putida RB1353, that bioluminesces during naphthalene catabolism. Results show that the presence of defined heterogeneities drives the development of BAZs at material-property interfaces where the confluence of naphthalene, dissolved oxygen, and sufficient microbial density is optimal. Thus, despite successful transport of P. putida RB1353 into a sterile low-permeability region containing substrate, BAZ formation in this region was limited by local physicochemical conditions (e.g., naphthalene and dissolved oxygen bioavailability). In another instance, transport of P. putida RB1353 occurred against advective flow, resulting in BAZ formation upgradient of inoculated regions. Defined systems such as this can be used as a basis for predicting localization of activity in complex subsurface systems.

Sorption and Transport of Naphthalene and Phenanthrene in Silica Sand in the Presence of Rhamnolipid Biosurfactant

Sorption and transport of naphthalene and phenanthrene in silica sand in the presence of rhamnolipid biosurfactant were investigated by batch and column experiments. Naphthalene and phenanthrene had linear sorption isotherms on silica sand with partition coefficients decreasing with increasing rhamnolipid biosurfactant concentrations until the critical micellar concentration (CMC). After the CMC was reached, naphthalene and phenanthrene partition coefficients on silica sand increased with the increase of rhamnolipid biosurfactant concentrations. It was believed that micelles were formed when rhamnolipid biosurfactant was supplied at concentrations higher than the CMC, to which naphthalene and phenanthrene had higher affinity than silica sand. In column experiments, both naphthalene and phenanthrene had early breakthroughs in the presence of rhamnolipid biosurfactant than in its absence. Estimated naphthalene and phenanthrene retardation using naphthalene and phenanthrene batch sorption data was consistent with column experimental observations. Nevertheless, naphthalene and phenanthrene recovery decreased in answer to the presence of rhamnolipid biosurfactant at concentrations greater than the CMC, which was attributed to the entrapment of naphthalene and phenanthrene associated rhamnolipid biosurfactant micelles.

Comparison of Naphthalene Diffusion and Nonequilibrium Adsorption-Desorption Experiments

Diffusion of hydrophobic organic compounds (HOC) is a key process controlling transport of contaminants in soils. However, the separate effects of sorption and diffusion on net (effective) HOC diffusion are not fully understood. In this study, effective diffusion of naphthalene in five unsaturated soils was evaluated by: (i) naphthalene adsorption-desorption experiments (batch method), (ii) naphthalene effective diffusion experiments (half-cell method), and (iii) trace-gas diffusivity experiments (chamber method). There was no soil type effect on gas diffusivity in repacked unsaturated soil, but a pronounced soil type effect on naphthalene sorption behavior. Varying degree of adsorption nonlinearity (Freundlich n' a ) and apparent adsorption-desorption nonsingularity (ω) and w increased with decreasing n' a were observed. In the half-cell experiments, gas diffusion was the governing naphthalene transport mechanism. Three effective diffusion coefficients were calculated from the half-cell experiments, based on concentration profile from either the whole (D eff ) cell, the source (desorption) half-cell (D eff,D ), or the recipient (adsorption) half-cell (D eff,A ). Generally, the observed D eff decreased with naphthalene-soil contact time, because of aging effects. The D eff , D eff,A , and D eff,D values (half-cell method) could only to some extend be estimated from Freundlich isotherm parameters (batch method). A suggested index of effective diffusion nonsingularity, H = D eff,D /D eff,A , showed that H was correlated with w and inversely correlated with n' a . Thus, the sorption nonlinearity (n' s ) was found to provide good indications of degree of nonsingularity in both HOC adsorption-desorption and effective diffusion. The combination of batch and half-cell experiments generally gave useful insight towards understanding and predicting the influence of sorption nonlinearity and nonequilibrium on HOC diffusion.

Comparison of Naphthalene Diffusion and Nonequilibrium Adsorption-Desorption Experiments

Diffusion of hydrophobic organic compounds (HOC) is a key process controlling transport of contaminants in soils. However, the separate effects of sorption and diffusion on net (effective) HOC diffusion are not fully understood. In this study, effective diffusion of naphthalene in five unsaturated soils was evaluated by: (i) naphthalene adsorption-desorption experiments (batch method), (ii) naphthalene effective diffusion experiments (half-cell method), and (iii) trace-gas diffusivity experiments (chamber method). There was no soil type effect on gas diffusivity in repacked unsaturated soil, but a pronounced soil type effect on naphthalene sorption behavior. Varying degree of adsorption nonlinearity (Freundlich n′a) and apparent adsorption-desorption nonsingularity (ω) and ω increased with decreasing n′a were observed. In the half-cell experiments, gas diffusion was the governing naphthalene transport mechanism. Three effective diffusion coefficients were calculated from the half-cell experiments, based on concentration profile from either the whole (Deff) cell, the source (desorption) half-cell (Deff,D), or the recipient (adsorption) half-cell (Deff,A). Generally, the observed Deff decreased with naphthalene-soil contact time, because of aging effects. The Deff, Deff,A, and Deff,D values (half-cell method) could only to some extend be estimated from Freundlich isotherm parameters (batch method). A suggested index of effective diffusion nonsingularity, H = Deff,D/Deff,A, showed that H was correlated with ω and inversely correlated with n′a Thus, the sorption nonlinearity (n′a) was found to provide good indications of degree of nonsingularity in both HOC adsorption-desorption and effective diffusion. The combination of batch and half-cell experiments generally gave useful insight towards understanding and predicting the influence of sorption nonlinearity and nonequilibrium on HOC diffusion.

Sorption and transport behavior of naphthalene in an aggregated soil.

Soil solution chemistry influences the sorption and transport behavior of hydrophobic organic compounds (HOCs) in soil. We used both batch and column studies to investigate the influence of ionic strengths (0.03 and 1.5 M) and flow velocities (12 and 24 cm h-1) on sorption and transport of naphthalene (NAP) in aggregated soil. Sorption parameters such as the Freundlich coefficient (Kf) and exponent (n) calculated from batch studies and column experiments were also compared. Retardation of NAP transport was greater at higher solution ionic strength, which may be attributed to greater sorption affinity due to enhanced aggregation of the sorbent. The effect of ionic strength on sorption of NAP observed in the batch study was consistent with the results from the column study. The Kf and n values obtained from the batch study for the two ionic strengths ranged from 7.8 to 13.7 and 0.68 to 0.80, respectively, whereas the Kf and n values obtained from the column study ranged from 7.9 to 9.9 and 0.73 to 0.85, respectively. The effluent breakthrough curve (BTC) of NAP at a flow rate of 24 cm h-1 showed significant chemical and physical nonequilibrium behavior, implying that a considerable amount of sorption in aggregated soil was time dependent when flow was relatively fast. The BTCs calculated with the parameters determined from batch studies compared poorly with the measured BTCs. The potential for nonequilibrium transport should be incorporated in models used for predicting the fate and transport of HOCs. Furthermore, caution is required when extrapolating the results from batch studies, especially for aggregated soils.

Influence of the presence of PAHs and coal tar on naphthalene sorption in soils

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 take 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 or 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 cm 3/g) than SOM ( K oc around 300 cm 3/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 for 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.

Membrane transport of naphthalene and dodecane in jet fuel mixtures

Jet fuels are formulated with numerous aliphatic and aromatic components that are thought to cause dermal irritation in air force personnel. However, diffusion of these components in such a complex mixture is not well understood. The purpose of this study is to evaluate the physicochemical properties of these mixtures in the context of how they influence partitioning, diffusion, and absorption of aromatic (14C-naphthalene) and aliphatic (14C-dodecane) markers in porcine skin and silastic membranes in vitro. In these 5-h flowthrough diffusion studies, Jet-A, JP-8, and JP-8(100) fuels, and weathered JP-8 (JP-8 (Puddle)) were tested. In both membrane systems and across all jet fuels tested, naphthalene absorption (1.29-1.84% dose) was significantly greater than dodecane absorption (0.14-0.28% dose). However, significantly more dodecane than naphthalene was observed in the stratum corneum (SC; 4.23-7.23% dose vs. 1.88-4.08% dose) and silastic membranes (59.2-81.7% dose vs. 30.5-36.7% dose). Naphthalene was least likely to be retained on the skin surface compared to dodecane, while this trend was reversed in silastic membranes. In porcine skin. weathered JP-8 significantly increased dodecane absorption, permeability (0.19×10−4 cm/h), and diffusivity, and also naphthalene deposition in the SC compared to other jet fuels. In contrast, weathered JP-8 appears to decrease naphthalene flux (1.56 μg/cm2/h) and permeability (1.14×10−4 cm/h) in skin. There were no differences among the three jet fuels in terms of their ability to influence naphthalene or dodecane disposition in skin and, generally, no significant differences among the four jet fuel mixtures were observed in silastic membranes. In conclusion, these transport studies suggest that absorption and deposition of naphthalene and dodecane are different when dosed in various jet fuel mixtures, and disposition in weathered jet fuel is significantly different from that in commercial and military fuels. These interactions may not only be related to the unique chemistry of these components, but also specific membrane interactions in the SC and viable epidermis.

Independent prediction of naphthalene transport and biodegradation in soil with a mathematical model.

Experiments were performed to test the ability of a mathematical model to predict naphthalene transport and biodegradation. Pseudomonas putida G7, a model bacterial strain capable of degrading naphthalene, was added to a column packed with the soil that had been pre-equilibrated with naphthalene. Model prediction for transport and degradation were based on predetermined parameters that described naphthalene desorption kinetics and the utilization of naphthalene by the test bacterium. However, initial prediction for naphthalene biodegradation was high, and the formation of cell aggregates is advanced as a plausible explanation. Access of substrate to cells in the interior of an aggregate would be restricted. When the numerical simulation was conducted with a factor to account for cell aggregation, it successfully described the experimental data. Thus, with a single adjustable parameter (an average effectiveness factor), the model predicted macroscopic responses of naphthalene in soil-columns where naphthalene was subject to transport and biodegradation.

The First International Conference on the Environmental Health and Safety of Jet Fuel

The First International Conference on the Environmental Health and Safety of Jet Fuel

Evaluation of sorption models in the simulation of naphthalene transport through saturated soils : Liu, K H; Enfield, C G; Mravik, S C Ground WaterV29, N5, Sept–Oct 1991, P685–692

Evaluation of sorption models in the simulation of naphthalene transport through saturated soils : Liu, K H; Enfield, C G; Mravik, S C Ground WaterV29, N5, Sept–Oct 1991, P685–692

Evaluation of Sorption Models in the Simulation of Naphthalene Transport Through Saturated Soils

AbstractTo show the effect of sorption model selection, the one‐dimensional transport of naphthalene in two saturated porous media was simulated using numerical models, which included the processes of dispersion, advection, and sorption. Three vdifferent models describing the sorption process: (1) a local equilibrium model, (2) a first‐order kinetic sorption model, and (3) a two‐site model (a combination of equilibrium and kinetic sorption model), were examined. In addition, this study considered two types of boundary conditions: constant concentration and constant flux boundary conditions. Simulations were made for data of naphthalene transport through a laboratory soil column packed with Lincoln or Eustis soil series. Numerical simulation results show that the selection of the sorption model had significant effects on the numerical solutions. The numerical solution obtained using either the local equilibrium model or the first‐order kinetic sorption model described the experimental data very well from the Lincoln soil column. In contrast, the numerical solution obtained using the two‐site model described the experimental data for the Eustis soil better than either the equilibrium or kinetic models. Different boundary conditions had little influence on the numerical solutions. Different amounts of organic carbon in the Eustis (0.66%) and Lincoln (0.036%) soils are thought to cause the differences in breakthrough curves and the response to the sorption processes.