Transport Of Organic Contaminants Research Articles

Atmospheric Transport of Semivolatile Organic Contaminants across an Urban-Alpine Boundary.

Current understanding of atmospheric transport of semivolatile organic contaminants (SVOCs) in alpine areas is limited due to complex meteorology and topography. Salt Lake City, Utah borders protected wilderness areas in the Wasatch Mountains, exhibiting a useful model system in which an urban source of SVOCs, including polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), is located directly adjacent to an alpine sink. Our objective was to investigate the impacts of topographical features on the transport and deposition of SVOCs across an urban-alpine boundary. To do so, we measured PAHs and PCBs in soils along a transect starting at the urban-mountain interface and extending into an alpine wilderness, crossing several prominent ridgelines. Concentrations of PAHs and PCBs in soils were heavily influenced by soil organic carbon content, air temperature, and proximity to the urban boundary. However, the role of source proximity was only revealed after normalizing concentrations in soil to organic carbon content and air temperature. Further, we present evidence of SVOC emission/deposition cycles driven by diurnal alpine winds that do not extend past topographical features. Our results illustrate the roles of multiple competing processes on SVOC transport in alpine systems and their importance at an urban-alpine boundary.

Enhancing nutrient water recovery: An integrated electrodialysis – Forward osmosis approach for reduced energy consumption and membrane fouling

The concept of combining electrodialysis (ED) and forward osmosis (FO) was previously introduced and proven effective in recovering nutrients and clean water from anaerobic effluents to produce safe liquid fertilizer. In this study, a novel and improved EDFO configuration (iEDFO) was proposed by merging the ED diluate with the FO feed solution and the ED concentrate with the FO draw solution, thus overcoming concentration limitations and fouling challenges inherent in traditional ED processes. Experimental results demonstrated significant improvements in performance, including up to 54 % and 43 % reductions in operation time and 21 % and 25 % energy savings for synthetic and real liquid digestate, respectively. These enhancements were attributed to altered ionic composition within the ED process, leading to higher, more stable current density and reduced ion back diffusion. Unlike conventional ED-only systems, the iEDFO configuration enabled continuous operation without requiring larger membrane areas or variable operational conditions. Additionally, the iEDFO configuration benefited from (1) reduced membrane fouling, and (2) decreased transport of organic contaminants across the anion exchange membranes (AEMs) into the ED concentrate product. Overall, the iEDFO system provides significant advantages in efficiency, energy savings, and operational stability, making it a highly effective and sustainable solution for resource recovery from liquid waste.

Vapor-phase transport of per and polyfluoroalkyl substances: Processes, modeling, and implications

An increasing number of studies have demonstrated the presence of per and polyfluoroalkyl substances (PFAS) in the vapor phase. It is therefore important to consider the potential for vapor-phase transport of PFAS in soil and the vadose zone and to investigate the processes impacting the retention and transport of volatile PFAS in soil. It is also critically important to evaluate existing models and develop new models as needed for their application to PFAS vapor-phase transport. The objectives of the present work were to provide an overview of vapor-phase transport processes and modeling, with a specific focus on their relevance for PFAS, and to discuss implications for mass discharge to groundwater, vapor intrusion, and soil vapor extraction. Decades of research have been devoted to the retention and transport of legacy volatile organic contaminants in the vadose zone. This work provides an abundant source of information concerning the many factors and processes of relevance, and insights into the development and application of mathematical modeling. However, given the unique properties of PFAS, there is a need to conduct research to investigate vapor-phase transport of PFAS and to develop PFAS-specific models. We highlight with illustrative examples that vapor-phase transport can be significantly more rapid than aqueous-phase advective transport, which can result in enhanced mass discharge to groundwater.

Molecular Fingerprinting of the Biodegradation of Petroleum Organic Pollutants in Groundwater and under Site-Specific Environmental Impacts

A quantitative and qualitative assessment using molecular markers derived from compound-specific indices for indicating groundwater impacted by petroleum spills in an oil field was recently undertaken and demonstrated serious contamination, with both high total petroleum hydrocarbons (TPH) (3.68–7.32 mg/L) and hazardous compounds in the groundwater. A petroleum source was identified, and the analysis revealed a decreasing trend of fresh petroleum input, along with groundwater advection and an increasing trend of biodegradation potential at locations farther from the source. This was confirmed via microbial analysis with both biodegrading microorganisms and diversity indices (Shannon, Simpson, and Pielou) and the principal component analysis (PCA) modeling approach, which classified the field samples into three types according to the distribution correlations between different organic compounds. Biodegradation was believed to be the dominant sink of hydrocarbons due to the increasing Pr/C17 and Ph/C18 values with seasonal changes. Raised temperatures activated the microbial degradation process; specifically, low-weight hydrocarbons degraded more rapidly than high-weight hydrocarbons, resulting in the accumulation of an unresolved complex mixture of bioproducts at locations that were farther away. Spatially, the Pr/C17 and Ph/C18 values increased from the upstream to the downstream areas, showing substantial biodegradation. The relationships between the molecular markers and chemical indices were quantified via canonical correlation analysis (CCA) to visually explain the interactive reaction processes. It was also demonstrated that the biodegradation of petroleum organics can be characterized by the consumption of dissolved oxygen and a decreasing Pr/Ph ratio, due to system reduction. These results demonstrate that compound-specific molecular markers, coupled with biochemical parameters, can effectively support a better understanding and effective fingerprinting of the fate and transport of petroleum organic contaminants, thus offering valuable technical support for a cost-effective remediation strategy.

Experimental research on the transport-transformation of organic contaminants under the influence of multi-field coupling at a site scale

Organic-contaminated shallow aquifers have become a global concern of groundwater contamination, yet little is known about the coupled effects of hydrodynamic-thermal-chemical-microbial (HTCM) multi-field on organic contaminant transport and transformation over a short time in aquifers. Therefore, this study proposed a quick and efficient field experimental method for the transport-transformation of contaminants under multi-field coupling to explore the relationship between organic contaminants (total petroleum hydrocarbon (TPH), polycyclic aromatic hydrocarbons (PAHs), benzene-toluene-ethylbenzene-xylene (BTEX) and phthalates acid esters (PAEs)) and multi-field factors. The results showed that hydrodynamics (affecting pH, p < 0.001) and temperature (affecting dissolved oxygen, pH and HCO3-, p < 0.05) mainly affected the organic contaminants indirectly by influencing the hydrochemistry to regulate redox conditions in the aquifer. The main degradation reactions of the petroleum hydrocarbons (TPH, PAHs and BTEX) and PAEs in the aquifer were sulfate reduction and nitrate reduction, respectively. Furthermore, the organic contamination was directly influenced by microbial communities, whose spatial patterns were shaped by the combined effects of the spatial pattern of hydrochemistry (induced by the organic contamination pressure) and other multi-field factors. Overall, our findings imply that the spatiotemporal patterns of organic contaminants are synergistically regulated by HTCM, with distinct mechanisms for petroleum hydrocarbons and PAEs.

A Critical Review of the Modelling Tools for the Reactive Transport of Organic Contaminants

The pollution of groundwater and soil by hydrocarbons is a significant and growing global problem. Efforts to mitigate and minimise pollution risks are often based on modelling. Modelling-based solutions for prediction and control play a critical role in preserving dwindling water resources and facilitating remediation. The objectives of this article are to: (i) to provide a concise overview of the mechanisms that influence the migration of hydrocarbons in groundwater and to improve the understanding of the processes that affect contamination levels, (ii) to compile the most commonly used models to simulate the migration and fate of hydrocarbons in the subsurface; and (iii) to evaluate these solutions in terms of their functionality, limitations, and requirements. The aim of this article is to enable potential users to make an informed decision regarding the modelling approaches (deterministic, stochastic, and hybrid) and to match their expectations with the characteristics of the models. The review of 11 1D screening models, 18 deterministic models, 7 stochastic tools, and machine learning experiments aimed at modelling hydrocarbon migration in the subsurface should provide a solid basis for understanding the capabilities of each method and their potential applications.

Daughter oil droplet entrainment by oil-coated bubble bursting

Compound bubbles with a liquid coating in another continuous immiscible bulk phase are ubiquitous in a wide range of natural and industrial processes. Their formation, rise and ultimate bursting at the air–liquid interface play crucial roles in the transport and fate of natural organic matter and contaminants. However, the dynamics of compound bubbles has not received considerable attention until recently. Here, inspired by our previous work (Yang et al., Nat. Phys., vol. 19, 2023, pp. 884–890), we investigate the entrainment of daughter oil droplets in bulk water produced by a bursting oil-coated bubble. We document that the size of the entrained daughter oil droplet is affected by the oil coating fraction and the bulk liquid properties. We rationalize this observation by balancing the viscous force exerted by the extensional flow produced by bubble bursting with the capillary force resisting the deformation of the oil coating, and considering the subsequent end-pinching process which finally entrains the daughter oil droplets. We propose a scaling analysis for the daughter oil droplet size that well captures the experimental results for a wide range of oil coating fractions and Ohnesorge numbers of the bulk liquid. In addition, we discuss the non-monotonic variation of daughter droplet size with the Ohnesorge number, and show the eventual absence of daughter droplets because of the strong viscous effect in the high-Ohnesorge-number regime. Our findings may advance the fundamental understanding of compound bubble bursting and provide guidance and modelling constraints for bubble-mediated contaminant transport in liquids.

In the presence of the other: How glyphosate and peptide molecules alter the dynamics of sorption on goethite

The interactions with soil mineral surfaces are among the factors that determine the mobility and bioavailability of organic contaminants and of nutrients present in dissolved organic matter (DOM) in soil and aquatic environments. While most studies focus on high molar mass organic matter fractions (e.g., humic and fulvic acids), very few studies investigate the impact of DOM constituents in competitive sorption. Here we assess the sorption behavior of a heavily used herbicide (i.e., glyphosate) and a component of DOM (i.e., a peptide) at the water/goethite interface, inclusive of potential glyphosate-peptide interactions. We used in-situ ATR-FTIR (attenuated total reflectance Fourier-transform infrared) spectroscopy to study sorption kinetics and mechanisms of interaction as well as conformational changes to the secondary structure of the peptide. NMR (nuclear magnetic resonance) spectroscopy was used to assess the level of interaction between glyphosate and the peptide and changes to the peptide' secondary structure in solution. For the first time, we illustrate competition for sorption sites results in co-sorption of glyphosate and peptide molecules that affects the extent, kinetics, and mechanism of interaction of each with the surface. In the presence of the peptide, the formation of outer-sphere glyphosate-goethite complexes is favored albeit inner-sphere glyphosate-goethite bonds (i.e., POFe) are still formed. The presence of glyphosate induces secondary structural shifts of the sorbed peptide that maximizes the formation of H-bonds with the goethite surface. However, glyphosate and the peptide do not seem to interact with one another in solution nor at the goethite surface upon sorption. The results of this work highlight potential consequences of competition for sorption sites, for example the transport of organic contaminants and nutrient-rich (i.e., nitrogen) DOM components in relevant environmental systems. Predicting the rate and extent with which organic pollutants are removed from solution by a given solid is also one of the most critical factors for the design of effective sorption systems in engineering applications.

Analytical model for organic contaminant transport in a cut-off wall and aquifer dual-domain system considering barrier arrangements

This paper presents an analytical study of organic contaminants transport in a cut-off wall and aquifer dual-domain system, considering the effects of the inlet boundary conditions and cut-off structural arrangements. The comprehensive sensitivity analysis of parameters focusing on the breakthrough time, attenuation time and cumulative concentration are presented using the Monte Carlo simulation and Sobol global method. The simplified constant inlet boundary condition can lead to an excessively conservative prediction of the contaminant breakthrough compared to the ‘finite mass’ and ‘decaying source’ boundary conditions. The cut-off wall hydraulic performance can be enhanced by reducing the contaminant's head loss, shape factor, half-life and cut-off wall hydraulic conductivity while increasing the retardation factor. The contaminant's half-life can largely influence the maximum contaminant concentration, attenuation time and breakthrough time. For example, the maximum contaminant concentrations for T1/2 = 1.4 years and T1/2 = 100 years are 13 and 123 times greater than that for T1/2 = 0.1 year, respectively. The influence of the variation of shape factor on the breakthrough curve should be taken into consideration. Altering the structural arrangement of the cut-off wall to accommodate a smaller shape factor increases the contaminant breakthrough time. The proposed solution allows the analysis of a cut-off wall and aquifer system with different inlet boundary conditions and structural arrangements of the cut-off wall.

Predicting PFAS and Hydrophilic Trace Organic Contaminant Transport in Black Carbon-Amended Engineered Media Filters for Improved Stormwater Runoff Treatment.

Improved stormwater treatment is needed to prevent toxic and mobile contaminant transport into receiving waters and allow beneficial use of stormwater runoff. In particular, safe capture of stormwater runoff to augment drinking water supplies is contingent upon removing dissolved trace organic contaminants (TrOCs) not captured by conventional stormwater control measures. This study builds upon a prior laboratory-based column study investigating biochar and regenerated activated carbon (RAC) amendment for removing hydrophilic trace organic contaminants (HiTrOCs) and poly- and perfluoroalkyl substances (PFASs) from stormwater runoff. A robust contaminant transport model framework incorporating time-dependent flow and influent concentration is developed and validated to predict HiTrOC and PFAS transport in biochar- and RAC-amended stormwater filters. Specifically, parameters fit using a sorption-retarded intraparticle pore diffusion transport model were validated using data further along the depth of the column and compared to equilibrium batch isotherms. The transport model and fitted parameters were then used to estimate the lifetime of a hypothetical stormwater filter in Seal Beach, CA, to be 35 ± 6 years for biochar- and 51 ± 17 years for RAC-amended filters, under ideal conditions with no filter clogging. This work offers insights on the kinetics of HiTrOC and PFAS transport within biochar and RAC filters and on the impact of filter design on contaminant removal performance and longevity.

Analytical Model for the Design of Permeable Reactive Barriers Considering Solute Transport in a Dual-Domain System

A permeable reactive barrier (PRB) is an effective groundwater in situ remediation technology, and the design methods used for PRBs are significant in ensuring that they meet remediation goals. Steady-state analytical solutions are an effective tool to provide conservative and simple design methods. A steady-state analytical solution is proposed to describe organic contaminant transport through the PRB and aquifer in a PRB and cut-off wall system. The proposed analytical solution may serve as an effective tool to provide conservative and simple design methods. The shape factor (S) is introduced at the PRB-aquifer interface to investigate the effects of a PRB’s layout forms on its performance. The results show that the relative contaminant concentration at the point of compliance for a PRB with S=8 is 11 orders of magnitude larger than that without considering the shape factor. Effects of degradation, dispersion, and advection on PRB design are subjected to dimensionless analysis. Dimensionless analysis shows that degradation plays a key role in decreasing contaminant concentration in the PRB. In addition, increasing advection may promote contaminant transport from the source to the aquifer. Simplified solutions to estimate PRB thickness and source remediation time are derived for the practical design and performance evaluation of the PRB system.

Determination of organic contaminants in L'Albufera Natural Park using microporous polyethylene tube passive samplers: An environmental risk assessment

L'Albufera Natural Park (Valencia, Spain) is a protected wetland of international significance that provides critical habitats to endemic and threatened bird and plant species. This study aims to use multiple cross-validation techniques to generate an accurate estimation of the environmental risk of organic contaminants (OCs) in an internationally important coastal wetland, to identify compounds of concern and their potential sources and risk factors. Microporous polyethylene tube (MPT) passive samplers were deployed at 12 locations across L'Albufera Natural Park with concurrent grab samples collected. A subset of MPT samplers were also analysed by an additional laboratory in Australia to widen the range of contaminants and assess interlaboratory reproducibility of results. Forty-three pesticides, 20 pharmaceuticals and personal care products (PPCPs), 20 per-and polyfluoroalkyl substances (PFAS) and 4 organophosphorus flame retardants (OPFRs) were detected in the MPT samplers. The fungicides tebuconazole and difenoconazole were detected at the highest concentrations in passive samplers (maximum concentrations, 153 ng sampler−1 and 106 ng sampler−1, respectively). Several other pesticides were detected in all locations (mean concentrations >1 ng sampler−1). The compounds fenamiphos, propyzamide, difenoconazole, propiconazole, metsulfuron methyl, sodium bis (perfluorohexyl) phosphinate (6:6 PFPiA), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), 6:2 fluorotelomersulfonate (6:2 FTS), citalopram desmethyl and citalopram were reported in the wetland for the first time. Spatial distribution analysis revealed higher pesticide concentrations in the North of L'Albufera. A risk quotient (RQ) analysis showed that ibuprofen is of concern in the area. Overall, the MPT sampling approach is promising as a risk assessment tool for better understanding the transport and fate of OCs in protected areas.

Finite-difference model for two-dimensional transport of degradable organic contaminants in a buffer layer-cutoff wall-aquifer system accounting for the consolidation behavior

Consolidation changes the geotechnical properties of a cutoff wall with depth. However, current research in transport theory fails to account for this factor. In this paper, a model for two-dimensional transport of degradable organic contaminants in a buffer layer-cutoff wall-aquifer system is developed, which takes the impacts of consolidation behavior into account for the first time. The finite-difference approach is employed to address this model, and its reasonableness is exhibited by the comparative analyses of three-different scenarios. Following this, a case-study on the barrier performance shows that accounting for the cutoff wall’s consolidation behavior prolongs the defined breakthrough time tb compared to when it is neglected. When a change in the cutoff wall consolidation parameter increases the horizontal and vertical effective stresses, its anti-fouling effectiveness is enhanced. Moreover, reducing the depth of the maximum inflow boundary concentration and increasing the concentration distribution range result in a decrease in tb. When the degradation half-life ≤ 400 years, the degradation effect should be considered to provide an accurate assessment of the cutoff wall’s longevity. For the “enclosure” cutoff walls, the appropriate thicknesses of the buffer layer and the cutoff wall can be determined based on the site environment and the construction cost.

Transport of Organic Contaminants in Composite Vertical Cut-Off Wall with Defective HDPE Geomembrane.

Soil-bentonite vertical cut-off wall is an emergency technique used for contaminant control in geo-environmental engineering, high-density polyethylene (HDPE) geomembrane (GM) with an extremely low-permeability coefficient is expected to enhance the contaminant barrier effect of the vertical cut-off wall. To evaluate the barrier performance of the composite barrier composed of GM and soil-bentonite mixture towards organic contaminant, while also quantitively revealing the impact of GM defects and placement, a one-dimensional transport model for organic contaminants in composite barrier is solved under semi-infinite boundary conditions. The proposed transport model is validated by numerical simulations using COMSOL Multiphysics 5.4, and the effects of GM defect rate, placement within the composite isolation wall, and contact level with soil-bentonite on contaminant transport behavior are further studied. The results show that as the average frequency of GM defects increases from 2.5 to 50 holes per hectare, the breakthrough time of organic contaminants through composite barrier decreases by almost 70%. Poor contact level between GM and soil-bentonite mixture may reduce the breakthrough time of the composite cut-off wall by 65%. Although the selection of GM placement has limited impact on the transient flux of contaminants, it does affect the total flux of contaminants over a certain period of time. The effects of permeability coefficient, effective diffusion coefficient, distribution coefficient, and hydraulic head of the composite cut-off wall can be considered by the proposed analytical solution, which would provide guidance and reference for the design and service performance evaluation of the composite cut-off wall.

A mobile-immobile model for contaminant transport through GCL/AL composite liner: analytical solutions.

The current study focuses on developing alternative formulations (mobile-immobile model) of transient analytical modelling for organic contaminant transport in a composite of geosynthetic clay (GCL) and attenuation layer (AL) system. The Laplace transform method is adopted to derive the solution. The proposed analytical frameworks are validated by two set of benchmarks. The varied examples of organic contaminant transport in the composite liner are evaluated by the proposed solution to discuss the effects of soil properties, flow conditions, adsorption, and mass transfer in mobile and immobile zones on the overall transport of contaminants. Finally, an example case is presented to show the application prospect of the proposed model. The result demonstrated that mass transfer between mobile and immobile may increase the breakthrough time by a factor of 2. This indicates that heterogeneities of clay are a non-negligible part for the performance assessment of the liner system. Péclet number in GCL ([Formula: see text]) is used to investigate the relative importance of advection and diffusion mechanisms. Increasing [Formula: see text] from 0.1 to 1 can lead to an increase of the breakthrough time by a factor of 15. The analytical solutions presented here may also serve as the basic benchmark test tool for alternative numerical studies of contaminants transport in heterogeneous media.

Transport and removal of stormwater vehicle-related mobile organic contaminants in geomedia-amended sand columns

Green infrastructure drainage systems are innovative treatment units that capture and treat stormwater. Unfortunately, highly polar contaminants remain challenging to remove in conventional biofilters. To overcome treatment limitations, we assessed the transport and removal of stormwater vehicle-related organic contaminants with persistent, mobile, and toxic (in short: PMTs) properties, such as 1H-benzotriazole, NN'-diphenylguanidine, and hexamethoxymethylmelamine (PMT precursor), using batch experiments and continuous-flow sand columns amended with pyrogenic carbonaceous materials, like granulated activated carbon (GAC) or wheat-straw derived biochar. Our results indicated that all investigated contaminants were subjected to nonequilibrium interactions in sand-only and geomedia-amended columns, with kinetic effects upon transport. Experimental breakthrough curves could be well described by a one-site kinetic transport model assuming saturation of sorption sites, which we inferred could occur due to dissolved organic matter fouling. Furthermore, from both batch and column experiments, we found that GAC could remove contaminants significantly better than biochar with higher sorption capacity and faster sorption kinetics. Hexamethoxymethylmelamine, with the lowest organic carbon-water partition coefficient (KOC) and largest molecular volume among target chemicals, exhibited the lowest affinity in both carbonaceous adsorbents based on estimated sorption parameters. Results suggest that sorption of investigated PMTs was likely driven by steric and hydrophobic effects, and coulombic and other weak intermolecular forces (e.g., London–van der Waals, H-bonding). Results from extrapolating our data to a 1-m depth geomedia-amended sand filter suggested that GAC and biochar could enhance the removal of organic contaminants in biofilters and last for more than one decade. Overall, our work is the first to study treatment alternatives for NN'-diphenylguanidine and hexamethoxymethylmelamine, and contributes to better PMT contaminant removal strategies in environmental applications.

Effect of retardation and capillarity on organic contaminant diffusion through an unsaturated composite liner: An analytical approach

AbstractIn unsaturated composite liners, the heterogeneous distribution of water content and capillarity are common phenomena with remarkable influence on the transport parameters. This study presents an analytical solution to assess the effect of unsaturation‐dependent retardation and capillarity on the organic contaminant diffusion through an unsaturated composite liner. The solution is obtained by the generalized integral transform technique and is verified against other analytical and numerical solutions. Particular attention is paid to the potential errors in predicting organic contaminant transport caused by unsaturation‐independent retardation factor assumption. The results show that neglecting saturation‐dependent retardation may cause considerable errors. The considerations of capillary fringe and degradation also have significant effects on the errors. In addition, a simplified solution based on a new averaged retardation factor is proposed and its performance is evaluated.

Particle-associated organic contaminant and cytotoxicity transport in a river during storm events

Storm events lead to mobilization of particles as well as organic contaminants that can pose a risk to river ecosystems. Assessment of total loads of particle-bound and dissolved contaminants in rivers is challenging, especially during rain events since multiple, often unknown contamination sources may be triggered, among them tributaries, combined sewer overflows, direct soil and road runoff, and the riverbed sediment. We investigated whether cytotoxicity (i.e., reduction of the cell viability of human cell lines) could be used as a proxy for the total chemical mixture to assess the transport of organic contaminant mixtures either in particle-associated form or in the aqueous phase. Time-proportional composite samples were collected in the Ammer River (Southwestern Germany) during two storm events in June 2021. All samples were screened for 127 organic contaminants and cytotoxicity in the water and particle phase separately. In total, 56 organic compounds were found, of which 14 and 34 were detected only in the water and particle extracts, respectively, and eight compounds were present in both phases. Thermodynamic equilibrium between the aqueous phase and suspended solids was observed for four compounds namely triphenyl phosphate, octocrylene, galaxolide, and p-chlorocresol. Substances that were not in equilibrium were mainly constituents of plastics and tire rubber, and their high concentrations in the particle phase were probably due to extractions from the particles themselves. Linear correlations between TSS and total compound concentrations were found for 17 PAHs and two musk fragrances, suggesting stable particle loadings and aqueous concentrations over the course of the rain event, most likely due to particle delivery from a particle source with a constant degree of contamination. The total cytotoxicity of water plus particles in the river correlated linearly with TSS during storm events. Inflowing water and particles from all sources appeared to be integrated, such that the total cytotoxicity of all contaminants per mass of particles and volume of water in the river was stable throughout storm events. From this relationship, a threshold of 0.5 g L-1 TSS was derived, above which particle-facilitated transport exceeded dissolved cumulative contaminant transport in the Ammer River, indicating the relevance of particle-facilitated contaminant transport.

Coupled model for one‐dimensional nonlinear consolidation and organic contaminant transport in a triple‐layer composite liner considering the nonisothermal distribution condition

AbstractThe 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 . Compared with the isothermal distribution state (temperature difference ), the at 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 ranges between 0.01 and . Moreover, compared with the case of no consolidation (loading rate ), the at equal to 50, 100, 150, and increases by 27.1%, 49.9%, 68.1%, and 83.9%, respectively. As the diffusion coefficient in GM changes from to , is observed to have a marked effect on the transport behavior.

Transport and fate of textile wastewater contaminants into soil

&lt;p&gt;Soil was familiar earlier in the context of agriculture and food production, but industrialization contaminated soils around the world in last two centuries. Most of the contamination is due to the consequence of improper discharge of industrial wastewater and one such situation is witnessed in the agricultural land nearby textile hub of Tiruppur, Tamil Nadu in Southern India. It is essential to identify the contaminants depth in soil system before propose any in-situ remediation technique. There is no study reported so far to understand the transport and fate of organic and inorganic contaminants of textile wastewater in soil system. This paper investigates the transport and fate of textile wastewater in soil column of 32 cm height and 8 cm diameter. Detailed investigation demonstrates the removal of color 15-84%, organic contaminants 4-51% and inorganic contaminants 11-36% from wastewater after its transport into the soil. The reduced level of calcium, magnesium and potassium ions in soil and corresponding increase in wastewater reveals anion and cation exchange between wastewater and soil. Thus the results confirm the accumulation of residual textile dyes and inorganic salts in the soil and it is huge in surface soil of 0-15 cm depth, further it requires immediate restoration.&lt;/p&gt;&#x0D;