河流-地下水系统有机污染物对流弥散吸附与生物降解的数学模型及有限差分求解

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: Groundwater resources and other important resources indispensable for human production and life play a very important role. This paper takes organic pollutants in river-groundwater system as the research object, establishes the model of convection and dispersion through mass conservation and mass transfer equation, and analyzes the adsorption based on Langmuir model and Freundlich model to study the migration and transformation mechanism of organic pollutants in river-groundwater systems, and the effect of biodegradation on the transformation of organic pollutants is also analyzed by Monod model.

To study the status and influencing factors of groundwater organic pollution around the Bosten Lake area (Kaidu River-Kongque River Basin), Xinjiang, China, the pollution index method was applied to 82 groundwater samples and 15 lake water samples for comprehensive pollution evaluation. Results showed that the detection rates of organic pollutants in groundwater and lake water samples in the study area are 24.4% and 6.7%, respectively, but all the water samples have concentrations of organic pollutants less than the standard water quality limits. There are 11 unpolluted groundwater samples, 8 mildly polluted groundwater samples and one mid-polluted groundwater sample, accounting for 13.4%, 9.8% and 1.2% of total groundwater samples, respectively. The detection points of groundwater organic pollutants in the study area are mainly distributed in the piedmont plain area in the northern Yanqi Basin, the Yanqi County and the northwestern plain area of Bosten Lake. Some points sporadically distributed in the urban area in Korla. Groundwater organic pollution around the Bosten Lake area is mainly affected by industrial pollution, agricultural pollution, domestic pollution, vadose zone lithology, surface water quality and land utilization type.

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As a precondition for groundwater remediation, pollution investigation of landfills requires enhanced accuracy and deeper understanding. Limited by the complexity of leachate and the inherent characteristics of each method, the application of a single method still has difficulty in comprehensively and accurately identifying groundwater pollution from landfills. To compensate for the limitations of a single method and enhance the accuracy, this study integrated survey, high-density resistivity exploration (HDR), and comprehensive analyses to develop a methodology. Using this methodology, the pollution area was identified to range from the landfill to Huang Jing River. The area from the landfill to 100 m downstream was identified as the core pollution area. The main inorganic chemical processes in polluted groundwater include the adsorption of K+, the exchange of Ca2+ and Mg2+ in the aquifer by Na+ and K+ in the groundwater, and the supersaturation and precipitation of Ca2+ and Mg2+. The transformation of organic pollutants included the dispersion and migration of refractory humic acids and the decomposition of degradable matter into humic substances, proteins, and tryptophan. Among the various methods, HDR performed excellently in rapidly identifying the polluted area. Cl− and the contribution ratio (Ylandfill) of the leachate to the chemical composition of groundwater were the best indicators for defining the maximum pollution boundary.

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A series of problems emerge gradually with the utilization of groundwater. Just as river wa‐ ters have been over-used and polluted in many parts of the world, so have groundwater. The organic solvents and dioxins pollution of Love Canal occurred in 1978 is one of the most wide‐ ly known examples, which contributes high rates of cancer and an alarming number of birth defects. Similar things occur frequently in recent decades. Governance of groundwater is so ur‐ gent a major matter of peace and prosperity. After years of researches, the nature and pollu‐ tion mechanism of the contaminants in the groundwater have already got comprehended.

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Volatile organic compounds (VOCs) pollution in groundwater is a significant global concern. In this study, 26 groundwater samples were collected from the unconfined aquifers in Huazhou District, northwestern China, to assess their distribution characteristics, influencing factors, and ecological risks across various geomorphological settings. The findings revealed 35 VOCs in collected groundwater samples, with aromatic hydrocarbons having the highest detection rate (100%), and the VOCs distribution exhibited significant spatial variations, with the highest VOCs concentration near a chemical plant on the inclined pluvial plain. The lithology and groundwater flow influenced the vertical and lateral transport of VOCs, with concentrations decreasing as the aquifer permeability decreases along the groundwater flow from the inclined pluvial plain to the river. The Mantel test was used to analyze the correlation between VOCs and environmental factors, geochemical analyses indicated that nitrate (NO3-) and sulfate (SO42-) served as electron acceptors in the anaerobic biodegradation of organic pollutants, with bicarbonate (HCO3-) levels increasing as a result of this biodegradation. Additionally, the curved streamline searchlight shaped model (CS-SLM) was applied to identify the primary land use types affecting VOCs content, construction land and cropland were primary land use types affecting VOCs distribution. Finally, the ecological risk assessment indicated the highest risk quotient (RQ) for styrene (0.21), suggesting a manageable risk level. The study emphasizes the complexity of VOCs contamination in groundwater, providing a foundation for targeted mitigation strategies.

Persistent Organic Pollutants (POPs) may exert adverse effects on human and ecosystem health. However, as an ecologically fragile zone with strong interaction between river and groundwater, the POPs pollution in the riparian zone has received little attention. The goal of this research is to examine the concentrations, spatial distribution, potential ecological risks, and biological effects of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the riparian groundwater of the Beiluo River, China. The results showed that the pollution level and ecological risk of OCPs in riparian groundwater of the Beiluo River were higher than PCBs. The presence of PCBs (Penta-CBs, Hexa-CBs) and CHLs, respectively, may have reduced the richness of bacteria (Firmicutes) and fungi (Ascomycota). Furthermore, the richness and Shannon's diversity index of algae (Chrysophyceae and Bacillariophyta) decreased, which could be linked to the presence of OCPs (DDTs, CHLs, DRINs), and PCBs (Penta-CBs, Hepta-CBs), while for metazoans (Arthropoda) the tendency was reversed, presumably as a result of SULPHs pollution. In the network analysis, core species belonging to bacteria (Proteobacteria), fungi (Ascomycota), and algae (Bacillariophyta) played essential roles in maintaining community function. Burkholderiaceae and Bradyrhizobium can be considered biological indicators of PCBs pollution in the Beiluo River. Note that the core species of interaction network, playing a fundamental role in community interactions, are strongly affected by POPs pollutants. This work provides insights into the functions of multitrophic biological communities in maintaining the stability of riparian ecosystems through the response of core species to riparian groundwater POPs contamination.

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Numerical models are commonly used to support the management of diffuse pollution sources in large agricultural landscapes. This paper investigates the suitability of a three-dimensional groundwater streamline-based nonpoint source (NPS) assessment tool for agricultural aquifers. The streamline approach is built on the assumption of steady-state groundwater flow and neglects the effect of transverse dispersion but offers considerable computational efficiency. To test the practical applicability of these assumptions, two groundwater transport models were developed using the standard three-dimensional advection–dispersion equation (ADE): one with steady-state flow and the other with transient flow conditions. The streamline approach was compared with both ADE models, under various nitrate management practice scenarios. The results show that the streamline approach predictions are comparable to the steady-state ADE, but both steady-state methods tend to overestimate the concentrations across wells by up to 10% compared to the transient ADE. The prediction of long-term attenuation of nitrate under alternative land management scenarios is identical between the streamline and the transient ADE results.

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Abstract.Groundwater transport within a fractured aquifer with a fractal nature exhibiting self-similarity cannot be accurately simulated by the classical Fickian advection-dispersion transport equation without a detailed characterisation of the fracture network and heterogeneity of the system. Because the information to characterise such a system to an appropriate level of detail is often not available, most applications fail to accurately simulate the observed contaminant transport. In response to the current limitations of transport modelling using the advection-dispersion equation, especially in fractured media, a fractal advection-dispersion groundwater transport equation is developed. Fractal differentiation is discussed in terms of the fractal derivative and the fractal integral. The fractal derivative is commonly applied and known, yet the fractal integral is developed in this paper along with the appropriate theorem and proof. The numerical approximation of the fractal derivative and integral are given, where Simpson’s 3/8Rule and Boole’s Rule for numerical integration are applied for the fractal integral, and the forward and Crank-Nicolson finite difference schemes are applied for the fractal derivative. Upon the given foundation, the fractal advection-dispersion transport equation is formulated to develop a new groundwater transport model. The qualitative properties of the fractal advection-dispersion equation are investigated to determine boundedness, existence and uniqueness of the solution. To validate the developed fractal advection-dispersion equation, a numerical simulation is performed with different fractal dimensions to demonstrate the applicability of the model to fractal groundwater systems. The numerical simulations found that anomalous diffusion could be better modelled by incorporating a fractal dimension, especially where limited information is available on preferential pathways.

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This work examines the effect of asymptotic dispersion for different contaminants, like heavy metals, biological, and radiological types, in heterogeneous groundwater systems. The migration of contaminants within groundwater systems is controlled by advection, dispersion, and sorption phenomena, and these mechanisms are mathematically modeled using the Advection-Dispersion Equation (ADE). Using the Thomas algorithm, a numerical simulation with the Peaceman - Rachford Alternating Direction Implicit (PR-ADI) scheme is applied to solve the ADE under the directional injection boundary (axial input sources). The study on asymptotic dispersion coefficients revealed a broader plume evolution. Non-linear sorption models depended on the saturation limit, and various parameters revealed physically relevant results. The iso-concentration figures depict flow patterns for diverse directional hydrological inflows, supporting stability interpretations. This study introduces a computational approach for modeling contaminant transport in groundwater systems, emphasizing asymptotic field conditions that introduce heterogeneity, coupled with nonlinear sorption effects on the plume morphology. The results highlight how plume morphology responds to variable dispersion and velocity, offering guidance for field-scale aquifer analysis and water quality management. The study is also aligned with Sustainable Development Goal 6 - Clean water and sanitation.

The fractional advection–dispersion equation is used in groundwater hydrology for modeling the movements of contaminants/solute particles along with flowing groundwater at the seepage velocity in porous media. This model is used for the prediction of the transport of nonreactive dissolved contaminants in groundwater. This paper establishes the existence and the uniqueness of solutions represented as fractional bi-variate power series of some initial-value problems and boundary-value problems for the fractional advection–dispersion equation. Moreover, a method to approximate the solutions using fractional polynomials in two variables and to evaluate the errors in a suitable rectangle is designed. Illustrative examples showing the applicability of the theoretical results are presented.

This study derives an analytical solution of a one-dimensional (1D) advection-dispersion equation (ADE) for solute transport with two contaminant sources that takes into account the source term. For a heterogeneous medium, groundwater velocity is considered as a linear function while the dispersion as a nth-power of linear function of space and analytical solutions are obtained for and . The solution in a heterogeneous finite domain with unsteady coefficients is obtained using the Generalized Integral Transform Technique (GITT) with a new regular Sturm-Liouville Problem (SLP). The solutions are validated with the numerical solutions obtained using MATLAB pedpe solver and the existing solution from the proposed solutions. We exanimated the influence of the source term, the heterogeneity parameters and the unsteady coefficient on the solute concentration distribution. The results show that the source term produces a solute build-up while the heterogeneity level decreases the concentration level in the medium. As an illustration, model predictions are used to estimate the time histories of the radiological doses of uranium at different distances from the sources boundary in order to understand the potential radiological impact on the general public.

In this study, we solve the fractional advection–dispersion equation (FADE) by applying the Laplace transform decomposition method (LTDM) and the variational iteration transform method (VITM). The Atangana–Baleanu (AB) sense is used to describe the fractional derivative. This equation is utilized to determine solute transport in groundwater and soils. The FADE is converted into a system of non-linear algebraic equations whose solution leads to the approximate solution for this equation using the techniques presented. The proposed approximate method’s convergence is examined. The suggested method’s applicability is demonstrated by testing it on several illustrative examples. The series solutions to the specified issues are obtained, and they contain components that converge more quickly to the precise solutions. The actual and estimated results are demonstrated in graphs and tables to be quite similar, demonstrating the usefulness of the proposed strategy. The innovation of the current work is in the application of an effective method that requires less calculation and achieves a greater level of accuracy. Furthermore, the proposed approaches may be implemented to prove their utility in tackling fractional-order problems in science and engineering.

The anomalous transport of particles within non-linear systems cannot be captured accurately with the classical advection-dispersion equation, due to its inability to incorporate non-linearity of geological formations in the mathematical formulation. Fortunately, fractional differential operators have been recognised as appropriate mathematical tools to describe such natural phenomena. The classical advection-dispersion equation is adapted to a fractional model by replacing the time differential operator by a time fractional derivative to include the power-law waiting time distribution. The advection component is adapted by replacing the local differential by a fractional space derivative to account for mean-square displacement from normal to super-advection. Due to the complexity of this new model, new numerical schemes are suggested, including an upwind Crank-Nicholson and weighted upwind-downwind scheme. Both numerical schemes are used to solve the modified fractional advection-dispersion model and the conditions of their stability established.

New tracer methodologies using stable and radioactive noble gases allow robustly quantifying the velocity of groundwater movement on time scales from years up to 1 million years and more. However, there is a misunderstanding about what the meaning of such a “Tracer Age” actually is. This work investigates the variation of environmental Tracer Ages for 3 H, 3 H– 3 He, 39 Ar, 14 C, 81 Kr, 36 Cl and 4 He relative to other measures of groundwater age such as the Mean Residence Time (MRT) and the advective groundwater velocity. It uses the one-dimensional advection-dispersion assumption, applying different ratios between advection and dispersion (Peclet numbers). As the age increases, Tracer Ages for radioactive tracers first follow the MRT and then approach the age derived from advective groundwater velocity. This is important, since for small Peclet numbers the difference between “Advective Age” and MRT can be up to a factor of 60. The findings open the new possibility of quantifying longitudinal dispersion, one of the most elusive groundwater solute transport parameters. Dispersion to present was determined from field tracer tests or contaminant plumes, with typical transport distances of a few tens to a few hundred metres, rarely to kilometres. Multi-tracer studies suggest the possibility to quantify the Peclet number of groundwater solute transport on time scales of centuries to many millennia from multi-tracer studies. Two studies from the literature are used to demonstrate the case. This also sheds a new light on signal preservation in the groundwater record in general, as used by earlier paleoclimate studies in groundwater.

Pollution is one of the hard challenges that face our societies in the current era. Water pollution is specifically a threatening one as it affects the main source of life causing damage to humans and the environment. We recall that water pollution is defined by the contamination of natural water bodies by chemical, physical, radioactive or pathogenic microbial substances. Thus, remediation of pollution of water resources is of high demand. A mathematically simple way to model this situation is to use the Advection-Dispersion Equation (ADE). The ADE describes the solute transport due to the combined effects of dispersion and groundwater flow in porous media (Bear and Verruijt, 1987). Also, the ADE is employed in chemical engineering (Bérard et al., 2020) and in modelling various situations, including radionuclide releases (Esmail et al., 2020), secondary migration of hydrocarbons (Borazjani et al., 2019), the dispersion of air pollutants in a finite media (Sylvain et al., 2021), petroleum contamination (Berlin and Suresh, 2019), among many others. It is obvious that a dimensionless solution accounting for different cases is of great value. ARTICLE INFO ABSTRACT

This study integrated groundwater quality assessment with Darcy-based mass-flux analysis and the Advection– Dispersion Model (ADM) to investigate contaminant transport in the shallow, unconfined aquifer of Akaba-Attisa in the Niger Delta, Nigeria. Groundwater samples were collected from three boreholes (A–C) aligned along the inferred flow direction and analyzed for physicochemical parameters, major ions, nutrients, and trace metals using standard WHO and NSDWQ protocols. Numerical modelling was applied to quantify groundwater flow, contaminant fluxes, and dominant transport mechanisms. Results indicate a Ca–Mg–HCO₃ groundwater facies with increasing mineralisation and nitrate contamination toward the mid-gradient well (B), identified as the plume core. Computed groundwater velocity (0.37 m/day) reflects a slow but persistent flow regime typical of shallow aquifers. Darcy-based mass flux calculations show that conservative solutes such as nitrate, TDS, chloride, bicarbonate, and hardness exhibit the highest fluxes, with a consistent hierarchy of B less then C greater than A. ADM results further confirm that advective fluxes exceed dispersive fluxes by more than an order of magnitude for most parameters, supported by Peclet numbers greater than unity, indicating advection-dominated transport. Sensitivity analysis demonstrates that reasonable uncertainty in hydraulic conductivity, porosity, and dispersion coefficients does not alter the dominance of advection or the observed plume structure. Public health evaluation reveals nitrate exceedances at downgradient wells, implying sustained advective delivery and elevated chronic exposure risk. The combined Darcy– ADM framework provides a robust basis for linking groundwater flow dynamics with contaminant migration and health risk, offering a valuable tool for groundwater protection and management in shallow aquifer systems.

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The study was designed to investigate the analytical simulation of two dimensional advection dispersion equation of contaminant transport. The steady state flow condition of the contaminant transport where inorganic contaminants in aqueous waste solutions are disposed of at the land surface where it would migrate through the verdoze zone to underground water is considered. We solved the two dimensional advection dispersion equation analytically which is solute transport model without sorption or degradation using change of variable method. We critically reviewed two dimensional equations depicting the transport of contaminant in groundwater and investigate with the help of graphical representation the effect of Peclet number on the concentration of contaminant and established real life interpretation of contaminant transport. Two cases were considered, when Peclet number is less than one and when Peclet number is greater than one. The result obtained revealed that the contaminant concentration increases along x direction and decreases along y direction for both values of peclet number greater than one and less than one. The study has contributed to knowledge through the method utilized to achieve the model analytical solution and the Physical interpretation of Peclet number. From the analysis, we recommend for further studies on the contaminant transport which also depends on the available data, that the extension of advection –dispersion model to three dimensions and comparison of travel time of contaminant transport solution to Kinetic or multi-component mode. Keywords: Contaminant, Seepage Velocity, Aquifer, Advection-dispersion Equation, change of variable methods

Subsurface fluid flow and solute transport through porous geological formations form the foundation of hydrogeology, environmental engineering, and energy resource management. This manuscript presents a mathematical exposition of the governing equations, analytical formulations, and computational models describing fluid and contaminant migration in groundwater systems. In addition to characterizing natural flow behavior, special emphasis is placed on the mechanisms responsible for groundwater contamination, including the movement of pollutants from industrial discharge, agricultural leachates, and subsurface waste repositories. We explore the interplay between pore-scale heterogeneity, continuum-scale flow laws, and transport mechanisms such as advection, dispersion, diffusion, and reactive interactions that govern contaminant fate. Furthermore, the discussion extends to the mathematical modeling of remediation strategies— such as pump-and-treat, in-situ bioremediation, and permeable reactive barriers—and their effectiveness under varying hydrogeological conditions. The synthesis connects classical Darcy theory with modern multi-scale, stochastic, and data- driven frameworks, offering insights into contamination prediction, risk assessment, remediation optimization, and sustainable groundwater utilization.

Abstract To improve and develop green adsorbent with high pollutant removal ability to produce clean water from wastewater, the surface of nanocomposite (zeolitic imidazolate framework (ZIF-8) as a metal-organic framework (MOF) with graphene oxide (GO) hybrid) was functionalized using 3-aminopropyl trimethoxy silane (APTMS). To identify and characterization the synthesized materials (ZIF-8, GO , ZG (ZIF-8/GO), and ZGA (ZIF-8/GO/APTMS)), Raman, FTIR, XRD, TGA and TEM analyzes were performed. Acid blue 92 (Ab92) dye was used as a contaminant to remove from the aqueous environment. Effective parameters on the adsorption process, such as the effect of contaminant concentration, dosage, contact time, and pH, were investigated. The results showed that Ab92 removal confirms the Langmuir isotherm and the pseudo-second-order kinetic. The maximum adsorption capacity for Ab92 dye was 371.8 mg/g. According to the results, ZGA nanocomposite is an acceptable adsorbent for removing Ab92 dye from the effluent.

In this laboratory batch adsorption study, the raw pine tree leaf biomass solid waste adsorbent material was used for the removal of methylene blue (MB) dye from water at different physicochemical process conditions. The characteristics of adsorbents were determined for particle size, surface area, the existence of functional group identification, and the morphology of the adsorbent surface. The adsorption was performed at different process conditions, which include solution pH, dye concentrations, adsorbent doses, and temperature, respectively. In this study, it was found that MB dye adsorption increased with increases in solution pH and adsorbate MB dye concentration but decreased with adsorbent doses and temperature at fixed process conditions. The Langmuir isotherm model was best fitted with the experimental equilibrium data, with a higher linear regression coefficient (R2) value of 99.9% among the two widely used Langmuir and Freundlich adsorption isotherm model equations. The maximum Langmuir monolayer adsorption capacity of raw pine leaf was found to be 36.88 mg/g, which was comparable with other reported adsorbent capacities towards methylene blue (MB) dye adsorption. The value of the separation factor, RL, from the Langmuir isotherm model equation gives an indication of favorable adsorption. Thermodynamic parameters such as standard Gibbs free energy change (ΔG0), standard enthalpy change (ΔH0), and standard entropy change (ΔS0) indicated that the methylene blue (MB) dye adsorption by pine tree leaf biomass was spontaneous and exothermic in nature and that the mechanism of adsorption was mainly physical adsorption. Finally, limitations and future studies are also discussed here. The outcome of this batch adsorption study may result in the valorization of locally available large pine tree leaf residue waste, which could be used in water purification.

Al-doped carbon nanotubes (Al-doped CNTs) were prepared as a multifunctional integrated material of adsorbent and coagulant aid for organic pollutant removal from aqueous solution. It was observed that aluminum species were dispersed homogeneously on the surface of CNTs, and mainly anchored onto defect structures of the CNTs. The introduction of aluminium efficiently improved adsorption ability for methyl orange (MO) onto the CNTs, and maximum adsorption capacity calculated from the Langmuir isotherm model can reach 69.7mg/g. The MO adsorption kinetics can be better described by the pseudo-second-order and pore diffusion kinetic models, and the diffusion of MO anions into pores of the Al-doped CNT adsorbent should be the rate-determining step. Thermodynamic analyses indicated that the adsorption of MO onto Al-CNTs-2.0 was endothermic and spontaneous. Moreover, adsorption capacity for MO on the Al-doped CNTs was evidently dependent on the CNT dose, solution pH and adsorbent dose. From the perspective of low-cost and multifunctional, suspension obtained during the Al-doped CNT adsorbent preparation, was tested as coagulant to remove humic acid (HA). A significant observation is that the suspension exhibited an excellent coagulation performance for HA, because abundant aluminous polymer and Al-doped CNTs existed in the suspension.

This study presents a sustainable approach to activated carbon production from olive stones in comparison to commercial ones, using various activating agents such as H3PO4, KOH, and ZnCl2, for enhancing the adsorption properties and versatile adsorption capability to remove a range of pollutants including copper ion, methylene blue, and 2,4-Dichlorophenoxyacetic acid from aqueous solutions. The performances of activated carbons across varying conditions such as pollutant concentrations, temperatures, pH levels, and adsorbent amounts were tested. Increased initial pollutant concentrations correlated with higher adsorption capacities. Maximum adsorption capacities were achieved at pH levels of 5, 10, and 2 for Cu, MB, and 2,4-D, respectively. For KOSAC, Cu removal rose from 27 % to 52 %, for ZOSAC, MB removal increased from 39 % to 65 %, and for ZOSAC, 2,4-D removal surged from 33 % to 99 % at varying adsorbent amounts. Model validation was carried out utilizing the kinetic models (PFO, PSO) and isotherm models (Langmuir, Redlich-Peterson). The PFO kinetic model and Langmuir isotherm model proved more suitability for Cu adsorption, whereas PFO and PSO kinetic models, along with Redlich-Peterson isotherm models, were more prominent for MB and 2,4-D adsorption. Thermodynamic analysis revealed that the adsorption of Cu and 2,4-D was exothermic, while MB adsorption was endothermic. By optimization of experimental conditions, the maximum adsorption capacities were attained at 30.34 °C and 297.65 mg L−1 for KOSAC-Cu, 48.62 °C and 269.37 mg L−1 for ZOSAC-MB, and 30.31 °C and 299.02 mg L−1 for ZOSAC-2,4-D sorption. This research highlights ZOSAC's potential as a cost-effective, eco-friendly solution for water treatment, contributing to environmental sustainability and economical feasibility.

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Abstract Removing aniline pollutants from organic waste-liquid rapidly and effectively has become an environmental problem owing to the high toxicity of aniline. Traditional aniline-separation methods have been limited by the complex techniques and high economic cost. In this study, green renewable Choline chloride (choline-salt, [N1,1,1C2OH]Cl) were used as new adsorbents for the removal of aniline by forming choline-based deep eutectic solvents (Choline-DESs) and displayed an excellent aniline removal efficiency. The mechanism of this separation technique is to remove aniline by forming a choline salt-aniline DES. The efficiency of [N1,1,1C2OH]Cl in removing aniline after regeneration and reuse five times was maintained. The adsorption capacity of [N1,1,1C2OH]Cl for aniline was observed at different temperatures (25–50 °C) and the adsorption process was spontaneous and endothermic. The amount of aniline adsorption was modelled by the adsorption isotherm and thermodynamics. The Freundlich model showed that the adsorption mechanism between aniline and choline-salt is controlled by entropy rather than a change in enthalpy. The data indicated that the Choline-DESs have much higher adsorption capacity (>278.5 mg/g) than conventional adsorbents. The high adsorption capacity, simple synthesis technique, and excellent reusability make choline-salt an attractive adsorbent for the removal of aniline from organic waste-liquid.

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Arsenic, a widespread toxic metalloid in groundwater, derives both from natural geological environment and industrial discharge, is extensively detected to be coexisting with organic contaminants, such as 2,4,6-trichlorophenol (TCP), a prior concerned pollutant. During biological remediation of groundwater, arsenic potentially intervenes microbial behaviors. This study found an opposite interference of arsenic in its two different valences (III and V) on the degradation of TCP by the functional bacteria, Sphingomonas fennica K101. As(III) inhibited TCP degradation in a concentration-dependent manner (from 0.1-10 mg/L), with a maximum inhibition rate of 35.5%, whereas As(V) exhibited promoting effects by 13.8% and 33.2% at 1 mg/L and 10 mg/L, respectively. Employing field emission transmission electron microscopy, quantum chemical calculations, fourier-transform ion cyclotron resonance mass spectrometry and metabolomic analysis, we unveil distinct interactions between cell membranes and arsenic in two valence states. Exposure to As(III) led to significant accumulation of As(III) in the cytoplasm, followed by interaction with intracellular ferritin (ferritin heavy chain 1), releasing iron ions and generating ROS. Subsequently, it induced ferroptosis and disrupted bacterial basal metabolism, thereby inhibiting TCP biodegradation. Oppositely, As(V) bound to a critical component sphingosine and triggered sphingosine polymerization, increasing membrane permeability, which was evidenced by measuring lactate dehydrogenase release. This process facilitated TCP transmembrane permeation by reducing membrane or extracellular secretion resistance. As(V) concurrently upregulated energy metabolism and accelerated TCP degradation. Our study elucidates the influence of prevalent arsenic on biodegradation efficacy, particularly amidst changing redox conditions associated with varying arsenic valences.

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Biodegradation of pollutants in the environment is directly affected by microbial communities and pollutant mixture at the site. Lab experiments using bacterial consortia and substrate mixtures are required to increase our understanding of these processes in the environment. One of the deficiencies of working with environmental cultures is the inability to culture and identify the active strains while knowing they are representative of the original environment. In the present study, we tested the aerobic microbial degradation of two brominated flame retardants, tribromo-neopentyl alcohol (TBNPA) and dibromo neopentyl glycol (DBNPG), by an assembled bacterial consortium of four strains. The four strains were isolated and plate-cultured from a consortium enriched from the impacted groundwater underlying the Neot Hovav industrial area (Negev, Israel), in which TBNPA and DBNPG are abundant pollutants. Total degradation (3–7 days) occurred only when the four-strain consortium was incubated together (25 °C; pH −7.2) with an additional carbon source, as both compounds were not utilized as such. Bacterial growth was found to be the limiting factor. A dual carbon–bromine isotope analysis was used to corroborate the claim that the isolated strains were responsible for the degradation in the original enriched consortium, thus ensuring that the isolated four-strain microbial consortium is representative of the actual environmental enrichment.

Bioremediation of soil and groundwater contaminated by persistent organic pollutants (e.g., chlorinated organics) using functional bacteria faces inherent challenges, such as competition from indigenous microorganisms (exogenous bacteria is difficult to establish microbial niches in soil) and poor pollutant accessibility. This study developed an integrated strategy that combines Biochar-Microbe-Hydrogel (BMH) matrix with Cyclic Hydraulic Leaching (CHL) for the concurrent bioremediation of soil-groundwater. The BMH is active gel beads encapsulated functional bacteria in porous biochar with hydrogel. The lab-scale soil column experiments demonstrated a 91.4 % removal efficiency for 2,4,6-trichloropherol (TCP) from a high contaminated soil concentration of 667 mg·kg-1, substantially outperforming the controls (53.9 %). The water flow by cyclic leaching promoted the elution of TCP from soil, followed by its re-adsorption and subsequent biodegradation in the BMH matrix. The constant proliferated bacteria (in this study we used Sphingomonas fennica as TCP degrading bacteria) migrated through biochar channels, constructing its niches along soil profile. This study also observed that the bacteria S. fennica competed with native soil microorganisms for niches in its high-density existence, but a shift toward cooperation was found at its low microbial abundance. This study provides an integrated bioremediation solution of soil and groundwater (BMHCHL) that is highly prospective for achieving effective field application.

Stable isotope tools are increasingly applied for in-depth evaluation of biodegradation of organic pollutants at contaminated field sites. They can be divided into three methods i) determination of changes in natural abundance of stable isotopes using compound-specific stable isotope analysis (CSIA), ii) detection of incorporation of stable-isotope label from a stable-isotope labelled target compound into degradation and/or mineralisation products and iii) determination of stable-isotope label incorporation into biomarkers using stable isotope probing (SIP). Stable isotope tools have been applied as key monitoring tools for multiple-line-of-evidence-approaches (MLEA) for sensitive evaluation of pollutant biodegradation. This review highlights the application of CSIA, SIP and MLEA including stable isotope tools for assessing natural and stimulated biodegradation of organic pollutants in field studies dealing with soil and groundwater contaminations.

The γ isomer of hexachlorocyclohexane (HCH), also known as lindane, is a carcinogenic persistent organic pollutant. Lindane was used worldwide as an agricultural insecticide. Legacy soil and groundwater contamination with lindane and other HCH isomers is still a big concern. The biotic reductive dechlorination of HCH to nondesirable and toxic lower chlorinated compounds such as monochlorobenzene (MCB) and benzene, among others, has been broadly documented. Here, we demonstrate that complete biodegradation of lindane to nontoxic end products is attainable using a sequential treatment approach with three mixed anaerobic microbial cultures referred to as culture I, II, and III. Biaugmentation with culture I achieved dechlorination of lindane to MCB and benzene. Culture II was able to dechlorinate MCB to benzene, and finally, culture III carried out methanogenic benzene degradation. Distinct Dehalobacter populations, corresponding to different 16S rRNA amplicon sequence variants in culture I and culture II, were responsible for lindane and MCB dechlorination, respectively. This study continues to highlight key roles of Dehalobacter as chlorobenzene- and HCH -respiring bacteria and demonstrates that sequential treatment with specialized anaerobic cultures may be explored at field sites in order to address legacy soil and groundwater contamination with HCH.

Biodegradation—the breakdown of organic matter by microorganisms—is an important groundwater process that occurs naturally and is especially important for the in situ cleanup of contaminated groundwater. Pollutant biodegradation follows well-established principles that are summarized in this book. The first principle is that the microorganisms must grow and sustain themselves by oxidizing an electron-donor substrate (food) and transferring the electrons to an electron-acceptor substrate (respiration). This electron flow generates energy that the microorganisms use to fuel biomass synthesis. Most pollutants are either an electron acceptor or an electron donor, which means that their biotransformation can grow and sustain the microorganisms. Accordingly, it is critical to understand whether a pollutant is an electron donor or electron acceptor. This book systematically describes the biodegradation mechanisms for common organic pollutants in groundwater: The author identifies if the pollutant behaves as an electron donor or acceptor, and points out when special activation reactions are necessary to initiate biodegradation and put the pollutant into a chemical form that allows it to be an energy-yielding electron donor or acceptor. Special attention is given to organics derived from petroleum and those that have chlorine, fluorine, and nitro substituents.

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To minimize groundwater pollution and suggest appropriate remedial actions, sound numerical models must be developed to predict the fate, transport and biodegradation of pollutants in partially treated or untreated industrial wastewater. Phenol is an aromatic organic compound produced on a large scale and is also released as major organic pollutant from several industrial wastewater (pharmaceutical, petroleum, coal refineries etc.,). Biodegradation of phenol in soil is generally rapid especially in presence of nutrients and acclimated microbes which are discharged along with the partially treated wastewater. A numerical model has been developed to predict the fate of phenol from industrial wastewater discharged on to a porous unsaturated soil media. The transport processes of advection, dispersion, and biodegradation process using Haldane growth and inhibition have been incorporated in the numerical model. The results suggest that acclimated microbes in the wastewater has a potential to degrade phenol up to 1500 mg/L at a bacterial concentration of 0.1 mg/L and soil depth of 50 cm. The results also show that phenols desorb at a depth of 100cm from 12th day and are simultaneously acted upon by the increased microbial concentration. In essence, high microbial concentration significantly decreases the phenol movement in the unsaturated zone, particularly at a larger depth and at higher time levels which eventually affects the groundwater quality.

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2,6-Dichlorobenzamide (BAM) is an omnipresent micropollutant in European groundwaters. Aminobacter niigataensis MSH1 is a prime candidate for biologically treating BAM-contaminated groundwater since this organism is capable of utilizing BAM as a carbon and energy source. However, detailed information on the BAM degradation kinetics by MSH1 at trace concentrations is lacking, while this knowledge is required for predicting and optimizing the degradation process. Contaminating assimilable organic carbon (AOC) in media makes the biodegradation experiment a mixed-substrate assay and hampers exploration of pollutant degradation at trace concentrations. In this study, we examined how the BAM concentration affects MSH1 growth and BAM substrate utilization kinetics in a AOC-restricted background to avoid mixed-substrate conditions. Conventional Monod kinetic models were unable to predict kinetic parameters at low concentrations from kinetics determined at high concentrations. Growth yields on BAM were concentration-dependent and decreased substantially at trace concentrations; i.e., growth of MSH1 diminished until undetectable levels at BAM concentrations below 217 μg-C/L. Nevertheless, BAM degradation continued. Decreasing growth yields at lower BAM concentrations might relate to physiological adaptations to low substrate availability or decreased expression of downstream steps of the BAM catabolic pathway beyond 2,6-dichlorobenzoic acid (2,6-DCBA) that ultimately leads to Krebs cycle intermediates for growth and energy conservation.

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The simulation of coupled groundwater flow-contaminant transport equation can be conducted numerically. The Finite-Difference Method (FDM) through Alternating Direction Implicit (ADI) Scheme will be applied in this research. The ADI scheme is chosen because the FDM in two-dimensional form. The ADI scheme recognized to solve two-dimensional PDE (Partial Differential Equation) due the Crank-Nicholson has matrix dimension problem and other problem from another scheme of FDM. This research will use ADI scheme to transform the groundwater flow and contaminant transport equation become the discrete form. The model algorithm translated into VBA (Visual Basic Algorithm) code and the physical parameter determined hypothetically. The result of model simulation describes that the ADI scheme can be applied to solve coupled groundwater flow-contaminant transport equation. The result can be stated as stable because it reached the steady condition after 60 days of simulation.

Many developing countries, and some developed countries, experience groundwater pollution. This problem is increasing in all areas of the world including Lebanon. Many factors have contributed to the groundwater pollution problem in Lebanon, some unique to the area (e.g., refugees, reliance on private wells) and others similar to those around the world (e.g., climate change, increased use of fertilizers). Efforts are being made to identify the contributing factors and find solutions. This study attempts to determine the nitrate contaminant transport to a contaminated public well in Chadra, Lebanon. MODFLOW software, a U.S. Geological Survey modular finite-difference flow model, is used to model the polluted well with its surrounding pollutant sources. Samples are collected from the well and tested in the laboratory using ASTM standard methods. A 3D model of the well was created and used to study the effect of porosity, time and well abstraction rate on the contaminant's path. Findings showed that the distance is inversely proportional to porosity and proportional to time and abstraction rate. Moreover, the software model results matched testing outcome of the nitrate concentration detected in the subject well.

Groundwater quality is one of water resource problem. This problem is driven by contaminant transport phenomena and can be described as a mathematical model. Contaminant transports equation usually is composed by advection and dispersion flux. In the porous medium or aquifer, contaminant meet tortuosity effect, therefore hydrodynamic dispersion must be considered as the development of dispersion flux. This paper explains the mathematical model of groundwater contaminant on fully saturated condition. It starts from governing equation of contaminant transport. Advection flux is based on groundwater velocity. In steady state condition, groundwater velocity can be determined as certain value. In another hand, in the transient condition, groundwater velocity must be determined based on the solution of groundwater flow model. Dispersion flux is calculated through first Fick’s law and this component is distinguished into two parts follow mechanical dispersion and molecular diffusion. Mechanical dispersion affected by groundwater velocity and dispersivity. Contaminant transport equation is solved numerically using Finite Difference Method (FDM). This final model is validated theoretically and then this model is simulated into transient condition. The result of the simulation is described and explained graphically. Based on this research, the result of FDM model has similar physical behavior to FEM model from CTRAN example.

Groundwater quality has recently received a lot of concern as a water resource problem. Contaminant’s transport is best described by a mathematical model. In this paper, we study the contaminant transport phenomenon using an advection-diffusion equation. The contaminant transport equation is solved numerically, we apply the finite volume method. Here we use Adams-Bashforth Difference to extrapolate advective terms from previous time step in an explicit manner and handles diffusive terms implicitly using Crank-Nicolson second order scheme. Our numerical model is validated by comparing the numerical results with the existing analytical solution. Further, we conclude that the methods can best approximate the exact solution when using a small Courant number and spatial grid partition.

Traditional numerical models have been widely employed to simulate the transport of multispecies reactive contaminants in groundwater systems; however, their high computational cost limits their applicability in real-time or large-scale scenarios. Recent advances in artificial intelligence (AI) offer promising alternatives, particularly data-driven machine learning techniques, for accelerating such simulations. This study presents the development of a surrogate model based on artificial neural networks (ANNs) to simulate the transport and decay of interacting multispecies contaminants in groundwater. High-fidelity training datasets are generated through finite difference-based reactive transport simulations across a wide range of environmental and geochemical conditions. The ANN model is trained to learn the complex nonlinear relationships governing the multispecies transport and transformation processes. Model validation reveals that the ANN surrogate accurately reproduces the spatial–temporal concentration profiles of both original and degradation species, capturing key dynamic behaviors with high precision. Notably, the ANN model achieves up to a 100-fold reduction in computational time compared to traditional analytical or semi-analytical solutions. These results highlight the ANN’s potential as an efficient and accurate surrogate modeling tool for groundwater contamination assessment, offering a valuable advancement for decision-making in environmental risk analysis and remediation planning.

The transport characteristics of organic contaminants are significantly affected by nonlinear consolidation and thermal‐diffusion behaviors. However, there is currently a lack of associated theoretical research on this topic. This study develops a coupled model for one‐dimensional (1D) nonlinear consolidation and organic contaminant transport in GM/GCL/CCL (geomembrane [GM], geosynthetic clay liner [GCL], and compacted clay liner [CCL]) composite liner considering the nonisothermal distribution condition. In particular, the influences of temperature on the parameters are incorporated, and the corresponding finite difference solutions are obtained. Furthermore, the rationality of the proposed theoretical model is effectively verified by conducting comparative analysis under different circumstances. Following this, the transport behaviors are investigated based on the defined breakthrough time tb${t_b}$ . Compared with the isothermal distribution state (temperature difference ΔT=0K$\Delta T\ = \ 0\ {\rm{K}}$ ), the tb${t_b}$ at ΔT$\Delta T$ equal to 10, 20, 30, and 40 K decreases by 25.4%, 41.3%, 52.2%, and 60.1%, respectively. The effect of thermal‐diffusion on the transport process is notable when the Soret coefficient ST${S_T}$ ranges between 0.01 and 0.05K−1$0.05\ {{\rm{K}}^{ - 1}}$ . Moreover, compared with the case of no consolidation (loading rate Qu=0kPa/year${Q_u} = \ 0\ {\rm{kPa}}/{\rm{year}}$ ), the tb${t_b}$ at Qu${Q_u}$ equal to 50, 100, 150, and 200kPa/year$200{\rm{\ kPa}}/{\rm{year}}$ increases by 27.1%, 49.9%, 68.1%, and 83.9%, respectively. As the diffusion coefficient Dm,R${D_{m,R}}$ in GM changes from 0.1×10−13$0.1 \times {10^{ - 13}}$ to 1.0×10−13m2/s$1.0 \times {10^{ - 13}}\ {{\rm{m}}^2}/{\rm{s}}$ , Dm,R${D_{m,R}}$ is observed to have a marked effect on the transport behavior.

A precise forecast of contaminant and solute transport has an inevitable role in the management of water resources. In accordance with this purpose, in this paper, a novel one-dimensional numerical model for the transport of a decay chain through homogeneous porous media is proposed. To develop the suggested model, two different schemes of the finite difference method, namely the Lax-Wendroff scheme and Fourth-Order scheme, are used. The verification and validation of the established model are examined by the analytical results of three multi-species solute dispersion problems with three- and four-chain members. The total mean square error, L2- and L∞-norms are applied to assess the results. Although analyses show that both schemes provided reliable results, the numerical results of the Lax-Wendroff scheme are more accurate.

PurposeThe purpose of this study is to introduce a new numerical scheme with no stability condition and high-order accuracy for the solution of two-dimensional coupled groundwater flow and transport simulation problems with regular and irregular geometries and compare the results with widely acceptable programs such as Modular Three-Dimensional Finite-Difference Ground-Water Flow Model (MODFLOW) and Modular Three-Dimensional Multispecies Transport Model (MT3DMS).Design/methodology/approachThe newly proposed numerical scheme is based on the method of lines (MOL) approach and uses high-order approximations both in space and time. Quintic B-spline (QBS) functions are used in space to transform partial differential equations, representing the relevant physical phenomena in the system of ordinary differential equations. Then this system is solved with the DOPRI5 algorithm that requires no stability condition. The obtained results are compared with the results of the MODFLOW and MT3DMS programs to verify the accuracy of the proposed scheme.FindingsThe results indicate that the proposed numerical scheme can successfully simulate the two-dimensional coupled groundwater flow and transport problems with complex geometry and parameter structures. All the results are in good agreement with the reference solutions.Originality/valueTo the best of the authors' knowledge, the QBS-DOPRI5 method is used for the first time for solving two-dimensional coupled groundwater flow and transport problems with complex geometries and can be extended to high-dimensional problems. In the future, considering the success of the proposed numerical scheme, it can be used successfully for the identification of groundwater contaminant source characteristics.

Managing the waste material unscientifically is causing a lot of direct and indirect environmental problems.Due to increase in the hydro-environmental pollution on the earth, the reactive- advective -dispersion phenomenon whichdescribes the reactive solute transport in the medium has got significant attention world over. Various analytical andnumerical methods are available to analyze this phenomenon under different initial boundary conditions. The objectiveof this study is to model the contaminant transport of the metal ions i.e. copper and zinc through the black cotton soilusing finite layer and finite difference methods viz: Backward Time Centered Scheme (BTCS), Upwind and CrankNicolson implicit schemes. The column experiments were conducted with constant and decreasing concentrations fromthe contaminant sources. The experimental results were modeled with the finite layer method using POLLUTE softwareand the finite difference method with Excel spreadsheet solution. It was found that more accurate values of the transportparameters i.e. dispersion coefficient and the distribution coefficient were obtained with finite layer method and finitedifference method using Crank-Nicolson scheme. A new Excel spreadsheet solution for the reactive-advective- dispersionphenomenon was developed by incorporating the retardation factor in the non-reactive method proposed by Karahan in2006. The dispersion coefficient of copper ions was observed to be lower than that of zinc ions while the distributioncoefficient of copper ions was found to be higher than that of zinc ions and the metal ion retention sequence was foundto be Cu > Zn in the black cotton soil.

Vertical cutoff walls are among the most effective in situ barrier systems employed to regulate the horizontal transport of contaminants into the soil and groundwater. This study presents a two-dimensional finite-difference model to simulate contaminant transport through a cutoff wall system incorporating layered buffer and aquifer zones. The buffer and aquifer zones are each assumed to comprise three distinct soil layers, characterized by low-, medium-, and high-permeability soils. Six scenarios, representing different configurations of these layers, are analyzed to assess their influence on the cutoff wall performance. The investigation further considers the effects of uniform and nonuniform contaminant concentration distributions with depth, temporal variations, and contaminant biodegradation within the cutoff wall. The results indicate that the performance of the cutoff wall is significantly influenced by the characteristics of the layered buffer and aquifer zones, as well as the distribution and biodegradation of the contaminant. The earliest contaminant breakthrough occurs when the uppermost soil layer exhibits high permeability, resulting in breakthrough times of 63 years for uniform contaminant distribution and 76 years for nonuniform contaminant distribution. Moreover, biodegradation effects become critical for accurate performance evaluation when the contaminant half-life is less than 200 years. Overall, the proposed model provides a realistic and comprehensive framework for analyzing contaminant transport behavior in layered cutoff wall systems.

Abstract Contaminant transport in fractured formations is strongly affected by the presence of fracture skin in the rock matrix. A triple continuum solute transport model is developed, incorporating the fracture skin as the third continuum, besides the fracture and the rock matrix, to describe the colloid facilitated contaminant transport in fractured formations. Sorption of the contaminant onto suspended and deposited colloids is assumed to follow a modified Freundlich reversible equilibrium isotherm. The resulting set of governing partial differential equations is solved using a fully implicit finite difference method. The distribution coefficient for contaminant sorption onto the deposited colloids and isotherm fitting parameter for contaminant sorption onto the deposited colloids are shown to be the most critical colloid related parameter affecting the contaminant transport in fractured media in presence of colloids. Furthermore, it is demonstrated that contaminant migration in fractured media is greatly affected by the presence of previously deposited colloids on fracture surfaces.

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We consider a problem of vertical percolation (bottom-up) of a mixture portion through a porous medium array under constant pressure drop. Contaminant transport is modeled within the MIM (mobile/immobile media) approach. Sorption processes are described by a nonlinear MIM model accounting for the limit of contaminant deposition on pore walls. Filtration is modeled using the Darcy–Boussinesq approximation, which enables the inclusion of gravity effects and consequently the development of concentration convection. The permeability-porosity dependence is given by the Kozeny-Carman relation. The basic non-convective state was obtained analytically. The convection onset problem was solved numerically using the finite difference method. The field of concentration and stream function perturbations were obtained, as well as the average instantaneous concentration profile along the flow direction at different time moments. It is demonstrated how the growth of the Darcy–Rayleigh number affects the solution injection and breakthrough times, as well as the breakthrough curve.

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In this paper, the two-dimensional saturated soil adsorption and desorption of contaminant transport model was considered, and it is discreted by the Crank-Nicolson difference scheme method. The benzene contaminant in the original organic chemical cesspool was determined, and the transportation of benzene contaminant is simulated by Matlab software. Simulation results show that the benzene concentration in the sewage pool reduced to 1.15mg/kg, where can be used for various soil types by the migration effect of the soil after a decade. This established model and simulation methods can be used for estimating other existing benzene contaminated soil pollution.

The calculation of radionuclide transport in the subsurface is an important part of analyses to evaluate safety of nuclear waste disposal sites. Such calculations often emphasize on the solute breakthrough in space and time. In this context, unfractured low-permeability porous media represent effective radionuclide retention because diffusion becomes the dominant mode of transport. Under such conditions and for safe containment, diffusion is desired to be smallest, optimally in combination with large retardation by e.g. sorption. The present study investigates timescales and solute breakthrough distances for selected radionuclides in low-permeability porous media. The used mathematical model is the solute transport equation incorporating the processes of diffusion, sorption, and decay. Firstly, published physical through-diffusion experiments are recalculated in order to validate the transport parameters using a numerical simulator. Secondly, timescales and distances of radionuclide breakthrough are calculated using an analytical model. The simulation results indicate that solute breakthrough converges at a certain distance as decay becomes the dominant process limiting transport. For example, the migration of 36\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{36}$$\end{document}Cl in Opalinus Clay converges at a solute breakthrough distance of approximately 162 m for timescales beyond 10 Mio years. Based on the results, an expression based on the 2nd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$2{\text {nd}}$$\end{document} Damköhler number is introduced and its accuracy is demonstrated. With this simple equation, maximum solute breakthrough distances can be calculated based solely on the input of a dimensionsless number, the effective diffusion coefficient, the effective porosity or capacity factor, and the physical half-life. That expression is accurate (R2=1.00\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R^2=1.00$$\end{document}) for non-sorbing radionuclides acting as inert tracers. For sorbing radionuclides, that equation deviates more from simulation results (R2=0.77\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R^2=0.77$$\end{document}). Results of the present study contribute to long term safety analyses of nuclear waste disposal sites.

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Abstract. We present a method to simulate fluid flow with reactive solute transport in structured, partially saturated soils using a Lagrangian perspective. In this context, we extend the scope of the Lagrangian Soil Water and Solute Transport Model (LAST) (Sternagel et al., 2019) by implementing vertically variable, non-linear sorption and first-order degradation processes during transport of reactive substances through a partially saturated soil matrix and macropores. For sorption, we develop an explicit mass transfer approach based on Freundlich isotherms because the common method of using a retardation factor is not applicable in the particle-based approach of LAST. The reactive transport method is tested against data of plot- and field-scale irrigation experiments with the herbicides isoproturon and flufenacet at different flow conditions over various periods. Simulations with HYDRUS 1-D serve as an additional benchmark. At the plot scale, both models show equal performance at a matrix-flow-dominated site, but LAST better matches indicators of preferential flow at a macropore-flow-dominated site. Furthermore, LAST successfully simulates the effects of adsorption and degradation on the breakthrough behaviour of flufenacet with preferential leaching and remobilization. The results demonstrate the feasibility of the method to simulate reactive solute transport in a Lagrangian framework and highlight the advantage of the particle-based approach and the structural macropore domain to simulate solute transport as well as to cope with preferential bypassing of topsoil and subsequent re-infiltration into the subsoil matrix.

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ABSTRACT This paper presents the triple advective–dispersive transport equations considering equilibrium sorption and first-order degradation rate coefficients. Centered implicit finite-difference method has been used to develop the numerical model for reactive solute transport through triple-permeability medium. A study has been carried out to investigate the behavior of breakthrough curves and temporal moments in the presence of mass transfer coefficients. Multi-peaked breakthrough curves have been observed for total and effluent solute concentration at large travel distance due to fast and slow flow in porous medium. In the presence of higher value of mass transfer coefficient, the magnitude of mean arrival time and second moment remains same for solutes in three regions of triple media. Higher value of first-order decay rate coefficient leads to reduce the magnitude of mean arrival time and second time moment for effluent concentration. However, higher value of retardation factor leads to increase the magnitude of mean arrival time and second moment for effluent concentration due to sorption of reactive plume in soil media.

This study presents a numerical solution of time and space fractional advection–dispersion equation (FADE) using the explicit Euler method, combined with the standard Grünwald formula and the Caputo fractional time derivative. The research aims to contribute to a better understanding and optimization of pollutant retention in subsurface environments, accounting for Freundlich parameters. The FADE model demonstrated a greater capacity for solute mass retention. Additionally, in a saturated porous medium, solute movement is more effectively influenced by the absorption parameter associated with the retardation factor. In other words, this parameter has a notable impact on pollutant dispersion in porous media. This work emphasizes the importance of accurately characterizing these parameters to optimize pollutant retention and better understand transport mechanisms in complex porous media. FADE improves the modeling of solute mass retention in saturated porous media. Freundlich parameters strongly influence solute dispersion and movement in saturated environments. Accurate characterization of Freundlich and retardation parameters optimizes pollutant retention and transport. FADE improves the modeling of solute mass retention in saturated porous media. Freundlich parameters strongly influence solute dispersion and movement in saturated environments. Accurate characterization of Freundlich and retardation parameters optimizes pollutant retention and transport.

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This study evaluated the sorption and transport potential of seven phototransformation products of 17α-trenbolone, 17β-trenbolone, trendione, and altrenogest, along with the parent trienone steroids in batch and column soil-water systems. In batch systems, the target solutes exhibited linear isotherms, with values for sorption coefficients (log Koc) of parent steroids (2.46-2.76) higher than those for photoproducts (1.92-2.57). In column systems, the estimated retardation factors (Rsol) for parents (2.7-5.1) were ∼2-5 times higher than those for photoproducts (0.84-1.7). The log Koc (R2 = 0.75) and Rsol (R2 = 0.89-0.98) were well correlated with measured log Kow values, indicating that hydrophobic partitioning governed the soil-solute interaction of these biologically potent compounds in soil-water systems. These data indicated that photoproducts exhibited reduced sorption affinity and increased transport potential relative to more hydrophobic parent structures. In agroecosystems, traditional runoff management practices would be expected to exhibit reduced treatment effectiveness for photoproducts relative to the parent compounds of commonly used trienone steroids.

Rice hush ash (RHA) and ordinary Portland cement (OPC) were used to stabilize a lead-contaminated soil. The effects of RHA content on the permeability, diffusion and sorption of lead ions for stabilized soil are presented. Test results indicate that replacement of OPC with RHA can increase significantly the short-term permeability of stabilized soil, but its effect on the long-term permeability is negligible. Furthermore, the retardation factor of lead ions increases substantially with increasing RHA content. As a result, the apparent diffusion coefficient decreases significantly by replacing OPC with RHA. Thus, a binder system with RHA could be a better option to reduce the long-term leachability of lead than the one using OPC alone.

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Riverbank filtration system is considered one of the economic and sustainable solutions to river water pollution especially in tropical countries such as Malaysia. In this work, an analytical model is developed to simulate the contaminant attenuation in riverbank filtration systems by using the separation of variables method. The basic aim of the model is to understand the role of microbial activity that occurs in riverbed sediments on reducing the concentration of the contaminant in the aquifer and changing the water characteristics. Graphically, it is found that the model can simulate the infiltration process of polluted river water effectively. Also, the analytical model results, as well as experimental data, show that nitrate (18.6 and 34.1 mg-NO3/L) and sulphate (20.9 – 22.1 mg-SO4/L) can be consumed by bacteria in the first 0.5 m of the aquifer, and reduced by more than 95% for both compounds. The model is applied for the first riverbank filtration system in Malaysia. Sensitivity analysis results highlight the importance of dissolved organic matter (DOM) concentration (ranged from 1.0 to 12.4 mg/L) for RBF efficacy in which a higher concentration of DOM leads to faster consumption of pollutants.

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Extracting water from pumping well near to river in riverbank filtration systems leads to the natural treatment for surface water. To increase the system efficiency, the well should be located at a distance from the river in which the well can produce high percentage of river water that satisfies the requirements of water quality. In case the well is located between river and a contaminant source, its location should be relocated to a suitable place between the two sources. In this article, an analytical solution is produced to specify the suitable distance of pumping well and polluted river in a riverbank filtration systems if there is a contaminant source to the present well. The analytical solution is obtained by using Green’s function. This approach is chosen because of its simplicity for solving multidimensional problems, and its flexibility to deal with arbitrary initial and boundary conditions. The model is compared with numerical one obtained by using MODFLOW software. The results indicate that the location obtained from proposed model is suitable for use to determine the well location. Additionally, the results show that increasing either the pumping rate or initial contaminant concentration leads to an increment to the distance between river well.

Abstract. Riverbank filtration (RBF), a managed aquifer recharge (MAR) technique utilised at the river–groundwater interface, can enhance groundwater quantity and quality, thus improving water supply security. However, it demands targeted local and regional monitoring strategies to understand how recharge efficiency and water quality benefits may vary with seasonal and short-term, event-based river flow fluctuations, upstream contaminant inputs, and site-specific aquifer heterogeneity. We evaluated river water–groundwater mixing and groundwater residence times to enhance the knowledge of aquifer recharge dynamics at the RBF site near Tarnów, Poland, serving as a critical drinking water source in this region. By coupling environmental tracers (stable water isotopes, chloride concentration, water temperature and specific electrical conductance) with high-resolution hydrological, meteorological and groundwater abstraction records, we show that RBF is the dominant recharge mechanism for the system that constitutes over 90 % of year-round yield from the production wells near the riverbank. Based on this example, we present a transferable and practical methodology for managing RBF systems efficiently: a multi-tracer, Ensemble End-Member Mixing Analysis (EEMMA) based workflow that covers at least one hydrological year, checks for local biases, and combines discrete water samples with continuous monitoring of physicochemical and hydrometeorological data, thus providing a robust and cost-effective template for recharge-source assessment. Such a framework determines both quantitative and qualitative status of abstracted groundwater and facilitates proactive responses to upstream pollution events and/or rapid hydrological shifts, which are crucial for sustainable water resource management internationally.

Riverbank filtration (RBF) technology has been applied and investigated worldwide for water supplies due to its sustainable water quantity guarantee and reliable quality improvement. In this work, the development history, application status, research progress, and technical overview of RBF are reviewed and summarized. RBF usually uses rivers, lakes, and groundwater as raw water, with a few cases using seawater. Nitrogen removal in RBF systems primarily occurs through key geochemical processes such as adsorption, denitrification, organic nitrogen mineralization, and dissimilatory nitrate reduction to ammonium (DNRA). For the attenuation of emerging contaminants in groundwater environments, key processes such as filtration, adsorption, and biotransformation play a crucial role, and microorganisms are essential. Based on a discussion of the advantages and disadvantages, we proposed the research prospects of RBF. To further enhance the water-supply safety and security with RBF, the mechanisms of surface water and groundwater interaction, pollutant removal, and blockage; the impact of capturing surface water on the stability of river ecosystems; and the coupling and synergistic effect of RBF with other water treatment technologies should be deeply investigated.

Tropical agriculture requires sustainable irrigation solutions that balance water availability with quality and environmental protection. This review synthesizes current knowledge on riverbank filtration (RBF)—a nature-based technology for improving agricultural water quality—with objectives to elucidate design principles, water quality performance, and operational challenges specific to tropical contexts. Through systematic analysis of 128 peer-reviewed articles across topics including RBF hydrogeology, contaminant removal mechanisms, sediment transport, pathogen reduction, site selection criteria, and monitoring strategies, this work consolidates interdisciplinary evidence on RBF effectiveness for irrigation water supply. The Roldanillo–Unión–Toro (RUT) district in Valle del Cauca, Colombia, serves as a case study illustrating RBF application to sediment-rich, pathogen-prone rivers typical of tropical agricultural regions. While RBF is established for drinking water supply in temperate zones, its adaptation to tropical irrigation remains underexplored. This review identifies critical hydrogeological, environmental, and operational considerations for implementing RBF systems in tropical agricultural settings characterized by high water demand, seasonal variability, and challenging water quality conditions. Key findings are synthesized into a practitioner-oriented framework—covering site selection, design optimization, and adaptive management—intended to guide deployment of RBF for irrigation in tropical agricultural settings.

Riverbank filtration system is a technique used for surface water treatment that is based on biological activities to attenuate the contamination in water through its movement from the river to the adjacent pumping well. Hydraulic conductivity is a critical parameter that affects the efficiency of riverbank filtration systems. In this study, an analytical model, using Green’s function approach, is developed to investigate the effect of hydraulic conductivity on contaminant transport and RBF system efficiency. The model is applied at the RBF site in Malaysia. The outcomes show that increasing the hydraulic conductivity values results in lowering the quality of the pumped water produced from the well, in which the contamination area around the well increase. Additionally, the distance from well to the river that should be considered when establishing a new RBF site is significantly affected by the hydraulic conductivity value.

The aims of this study are to (1) determine the BDOC in Elbe River water to compare with data from former studies, (2) to check the impact of changes in river water temperature (10, 20, and 25 °C). Four columns were filled with vulcanite pumice stone (for minimizing adsorption capacity), each of them having a separate reservoir feed with filtered Elbe River water. The ultraviolet absorption at 254 nm (UV254) was determined. DOC concentration was measured after 7, 10, and 14 days. Results represent that the main DOC degradation happens within an effective contact time of 5–7 days. Temperature increasing from 10 to 20 °C, raised the DOC degradation from 19 to 23%. By increasing the temperature to 25 °C, a higher DOC removal was observed than at 10 and 20 °C. This was expected due to higher biological activity at higher temperatures (BDOC increased from 23 to 26%). An increase in temperature by 15 Kelvin signified 30% more UV254 removal, expressing the effect of temperature variation on the attenuation of organic compounds. The difference in UV254 reduction at 25 °C compared to 20 °C was lower. A comparison with old data sets of last 22 years for Elbe River water at 20 °C shows that UV254 reduction (~ 27%) slightly increased but DOC biodegradation rate slightly decreased from ~ 27 to ~ 23%.

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Riverbank filtration (RBF) is a natural technology that is used for river water treatment. This research seeks to investigate the effect of pumping rate on the transport of colloids in RBF. However, this work considered Dissolved Organic Matter (DOM) as a nutrient for bacteria. The mathematical model consists of groundwater flow equation and colloids concentration equations. The equations were solved analytically using parameter expanding method and Eigen function expansion techniques. The results obtained are presented graphically and discussed. It was observed that increase in pumping rate value enhance both the hydraulic head and concentration of colloids which slightly reduces the quality of pumped water from RBF. Keywords: Riverbank filtration, analytical model, colloids, hydraulic head and pumping rat

Riverbank filtration (RBF) is used worldwide to produce high quality drinking water. With river water often contaminated by micropollutants (MPs) from various sources, this study addresses the occurrence and fate of such MPs at three different RBF sites with oxic alluvial sediments and short travel times to the drinking water well down to hours. A broad range of MPs with various physico-chemical properties were analysed with detection limits in the low ng L−1 range using solid phase extraction followed by liquid chromatography coupled to tandem high resolution mass spectrometry. Out of the 526 MPs targeted, a total of 123 different MPs were detected above the limit of quantification at the three different RBF sites. Of the 75–96 MPs detected in each river, 43–59% were attenuated during RBF. The remaining total concentrations of the MPs in the raw drinking water accounted to 0.6–1.6 μgL−1 with only a few compounds exceeding 0.1 μgL−1, an often used threshold value. The attenuation was most pronounced in the first meters of infiltration with a full elimination of 17 compounds at all three sites. However, a mixing with groundwater related to regional groundwater flow complicated the characterisation of natural attenuation potentials along the transects. Additional non-target screening at one site revealed similar trends for further non-target components. Overall, a risk assessment of the target and estimated non-target compound concentrations finally indicated during the sampling period no health risk of the drinking water according to current guidelines. Our results demonstrate that monitoring of contamination sources within a catchment and the affected water quality remains important in such vulnerable systems with partially short residence times.

AbstractA risk assessment model was developed and combined with hydrogeological data to determine the permissible limit of fecal coliform in water during riverbank filtration (RBF). It combined an ...

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Organic micropollutants (OMPs) in wastewater treatment plant (WWTP) effluent pose persistent risks to aquatic ecosystems and drinking water sources. Riverbank filtration (RBF) is a nature-based treatment process, yet the compartment-specific roles of riverbed sediment and downstream soil in OMP attenuation remain poorly resolved under wastewater-impacted conditions. Here, we combined targeted chemical analysis, OMP property compilation, shotgun metagenomics, EnviPath-based biotransformation annotation, and exploratory network analysis to investigate OMP attenuation in a laboratory-scale RBF system treating real WWTP effluent for 10 months. Nineteen OMPs were monitored along a sequential sediment-soil filtration pathway. Sediment preferentially attenuated hydrophilic or charged compounds, including lidocaine, amantadine, and sotalol, whereas soil contributed more strongly to the attenuation of naproxen, atenolol, and losartan. Metagenomic profiling revealed distinct microbial communities and functional gene repertoires between sediment and soil after long-term operation. Sediment harbored higher relative abundances of genes associated with oxidative xenobiotic transformation, including cytochrome P450-related enzymes, demethylases, dehydrogenases, oxidases, and aromatic compound degradation pathways. An exploratory Spearman network further identified associations among microbial genera, EnviPath-annotated candidate biotransformation genes, and OMP removal rates, including 17 KO-OMP links supported by both correlation and pathway annotation. These findings indicate that sediment and soil develop complementary microbial functional potentials that may support compound-specific OMP attenuation. This study provides a mechanistic basis for optimizing sediment-soil configurations in wastewater-impacted RBF systems and for improving nature-based barriers against diverse OMP mixtures.

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<p>Reactive transport in porous media involves a complex interplay of multiple processes relative to flow of water and gases, transport of elements, chemical reactions and microbial activities. In surface-groundwater interfaces, the role of the capillary fringe is of particular interest as water table variations can strongly impact the transfer of gases (e.g. oxygen), the evolution of redox conditions and the evolution/adaptation of bacterial/microbial populations that control biodegradation pathways of contaminants. Although the understanding of individual processes is advanced, their interactions are not yet fully understood challenging the development of efficient reactive transport models (RTM) for predictive applications. In this context, the combination of microbial approaches with isotope measurements and modelling may be useful to understand reactive transport of halogenated pollutants in hydrogeological dynamic systems, to improve processes representation in RTMs, and to reduce model equifinality. Dichloromethane (DCM) is a toxic and volatile halogenated compound frequently detected in multi-contaminated aquifers. Although mechanisms of DCM microbial degradation under both aerobic and anaerobic conditions have been described, little is known about the relationships between the hydrogeochemical variations caused by water table fluctuations, as well as their effects on the diversity and distribution of bacterial communities and degradation pathways.<br>&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; In this study, two laboratory aquifers fed by contaminated groundwater from the industrial site Thermeroil (France) were designed to collect water samples at high-resolution to investigate the reactive transport of DCM in porous media under steady and dynamic hydrogeological conditions. The effect of water table variations on hydrochemical, microbial and isotopic composition (&#948;¹³C and &#948;³⁷Cl) was examined to derive DCM mass removal and potential changes in degradation pathways. For the latter, Compound-Stable Isotope Analysis (CSIA) has been used as a tool to evaluate natural degradation of halogenated hydrocarbons. A RTM model (CubicM) is currently being developed to include dual-element CSIA and biological processes - such as growth, decay, attachment, detachment or dormancy &#8211; and relate changes in redox conditions with the evolution of DCM degrading populations. A two-phase flow model (i.e. water and gas) has been developed to account for the volatilization and the associated transport processes of halogenated volatile compounds in porous media. Currently, the model is tested on the experimental results to assist in the interpretation of DCM dissipation and the observed biogeochemical and microbial processes to determine the best-suited formalism to address the effect of water table fluctuations on DCM reactive transport in porous media. Such model will enable to assess natural attenuation of DCM at contaminated sites accounting for dynamic hydrogeological conditions.</p>

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<p>The vadose zone hosts a wide range of various microorganisms which provide different soil ecosystem services from nutrient cycling to biodegradation of harmful chemical substances. The efficiency of such in-situ biodegradation is influenced by different biotic and abiotic factors ranging from physical properties of the soil to the redox conditions controlled by the activity of the involved chemical compounds. One important feature of the soil system is the dynamical and simultaneous interplay of these factors, boosting or deteriorating the residing microbial community&#8217;s abundance and/or activity and hence shaping biodegradation of vadose zone contaminants. Physical properties of porous media &#8211; e.g. the pore geometry, pore size distribution, connectivity as well as the water content &#8211; play a major role in enhancing or restricting the bioavailable concentration of contaminants and other reaction partners. Pore-scale phenomena have been shown to be considerably affecting the macro-scale processes, therefore a quantitative bottom-top approach of these mechanisms in situ is adamant. Hence it is of paramount importance to understand the effect of soil physical properties on microbial activity and biodegradation of carbon compounds in soil.</p><p>Pore scale reactive transport processes have a complex, nonlinear dependency on the aforementioned factors, which severely challenges the experimental and/or numerical investigation of biodegradation at in in-situ conditions. However, the recent technological advances, specifically the imaging techniques, have made it easier to study biological and microbial evolution in porous media, but there is still a need for putting all these information together. For this purpose, numerical methods would offer the possibility of simulating a variable/controllable water saturation conditions and considering water/air dynamics and advective and diffusive micro-scale transport of all components in both, air and water phase, in porous medium structures directly obtained from CT scanned samples. Up to now, such pore-sale model approaches considering also the fate of biogeochemically reactive compounds are scarce. In this work we propose a novel reactive transport modelling technique combining the pore-scale numerical characterization of water flow and solute transport in unsaturated porous media and of biogeochemical process. For a variably saturated porous system, the presented model approach is solving the Navier Stokes equation and scalar transport equations for any arbitrary geometry and is simulating the dynamics of biogeochemical processes with any degree of complexity. Simulations are compared to experimental data to assess the effect of soil physical properties on the transport and degradation of contaminants in soil.</p>

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