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Numerical investigation of the effect of geosynthetic clay liner chemical incompatibility on flow and contaminant transport through a defective composite liner

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第7期24卷 557-568页

作者： Shiyuan YAO Yuchao LI Shan TONG Guannian CHEN Yunmin CHEN MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Department of Civil EngineeringZhejiang UniversityHangzhou 310058 China School of Civil&Environmental Engineering and Geography Science Ningbo UniversityNingbo 315211China Ningbo ZCONE High-tech Co. Ltd.Ningbo 315000China

A composite liner consisting of a geomembrane(GMB)and a geosynthetic clay liner(GCL)can be compromised by inorganic contaminants because of a defective GMB.When the composite liner with defective GMB is exposed to aggressive leachate conditions,the neglect of the chemical incompatibility of the GCL can potentially result in an underestimation of the leakage rate and flux through the composite liner.This paper proposed a numerical investigation on the effect of chemical incompatibility of GCL on the barrier performance of the composite liner with hole defect.Four cases with leachate solutions having varied cation valencies and ionic strengths were analyzed,in which the hydraulic conductivity of GCL was concentrationdependent.Both the effect of the chemical incompatibility of GCL and the mechanisms were analyzed.The incompatibility of GCL resulted in significant increases in leakage rate and flux through the composite liner by factors of up to 4.9 and 5.0,respectively.The incompatibility-affected area in GCL is located within 0.1 m from the center of the hole in the GMB.The coupled increase in the hydraulic conductivity of GCL and pore water concentration impacts the flux and leakage in a short period of time.With GCL chemical incompatibility considered,advection may dominate the contaminant transport through GCL.

关键词： Geosvnthetic clay liner(GCL) Chemical incompatibility Leakage contaminant transport Hvdraulic conductivity

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contaminant transport in heterogeneous aquifers: A critical review of mechanisms and numerical methods of non-Fickian dispersion

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Science China Earth Sciences 2021年第8期64卷 1224-1241页

作者： Zhilin GUO Rui MA Yong ZHANG Chunmiao ZHENG State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control School of Environmental Science and EngineeringSouthern University of Science and TechnologyShenzhen 518055China School of Environmental Studies China University of GeosciencesWuhan 430074China Department of Geological Sciences University of AlabamaTuscaloosa AL 35487USA

Natural aquifers usually exhibit complex physical and chemical heterogeneities,which are key factors complicating kinetic processes,such as contaminant transport and transformation,posing a great challenge in the remediation of contaminated groundwater.Aquifer heterogeneity usually leads to a distinct feature,the so-called“anomalous transport”in groundwater,which deviates from the phenomenon described by the classical advection-dispersion equation(ADE)based on Fick’s Law.Anomalous transport,also known as non-Fickian dispersion or“anomalous dispersion”in a broad sense,can explain the hydrogeological mechanism that leads to the temporally continuous deterioration of water quality and rapid spatial expansion of pollutant plumes.contaminants enter and then are retained in the low-permeability matrix from the high-permeability zone via molecular diffusion,chemical adsorption,and other mass exchange effects.This process can be reversed when the concentration of pollutants in high-permeability zones is relatively low.The contaminants slowly return to the high-permeability zones through reverse molecular diffusion,resulting in sub-dispersive anomalous transport leading to the chronic gradual deterioration of water quality.Meanwhile,some contaminants are rapidly transported along the interconnected preferential flow paths,resulting in super-dispersive anomalous transport,which leads to the rapid spread of contaminants.Aquifer heterogeneity is also an important factor that constrains the efficacy of groundwater remediation,while the development,application,and evaluation of groundwater remediation technologies are usually based on the Fickian dispersion process predicted by the ADE equation.Comprehensive studies of the impacts of non-Fickian dispersion on contaminant transport and remediation are still needed.This article reviews the non-Fickian dispersion phenomenon caused by the heterogeneity of geological media,summarizes the processes and current understanding of contaminant migration and transformation in highly heter

关键词： Aquifer heterogeneity contaminant transport Contamination remediation Non-Fickian dispersion Anomalous transport Small-scale preferential flow paths

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Analytical solutions of three-dimensional contaminant transport in uniform flow field in porous media:A library

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Frontiers of Environmental Science & Engineering 2009年第1期3卷 112-128页

作者： Hongtao WANG Huayong WU Department of Environmental Science and Engineering Tsinghua UniversityBeijing 100084China

The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport in uniform flow field in porous media with the first-order decay,linear sorption,and zero-order production.The library is constructed using Green's function method(GFM)in combination with available solutions.The library covers a wide range of solutions for various conditions.The aquifer can be vertically finite,semi-infinitive or infinitive,and laterally semi-infinitive or infinitive.The geometry of the sources can be of point,line,plane or volumetric body;and the source release can be continuous,instantaneous,or by following a given function over time.Dimensionless forms of the solutions are also proposed.A computer code FlowCAS is developed to calculate the solutions.Calculated results demonstrate the correctness of the presented solutions.The library is widely applicable to solve contaminant transport problems of one-or multiple-dimensions in uniform flow fields.

关键词： solution library contaminant transport analytical solution dispersion and advection porous media type curve Green’s function method(GFM)

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FLUID-SOLID COUPLING MATHEMATICAL MODEL OF contaminant transport IN UNSATURATED ZONE AND ITS ASYMPTOTICAL SOLUTION

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Applied Mathematics and Mechanics(English Edition) 2003年第12期24卷 1475-1485页

作者：薛强梁冰刘晓丽李宏艳 Department of Mechanics Engineering and Science Liaoning Technical University Institute of Environmental Sciences Beijing Normal University

The process of contaminant transport is a problem of multicomponent and multiphase flow in unsaturated zone. Under the presupposition that gas existence affects water transport, a coupled mathematical model of contaminant transport in unsaturated zone has been established based on fluid_solid interaction mechanics theory. The asymptotical solutions to the nonlinear coupling mathematical model were accomplished by the perturbation and integral transformation method. The distribution law of pore pressure, pore water velocity and contaminant concentration in unsaturated zone has been presented under the conditions of with coupling and without coupling gas phase. An example problem was used to provide a quantitative verification and validation of the model. The asymptotical solution was compared with Faust model solution. The comparison results show reasonable agreement between asymptotical solution and Faust solution, and the gas effect and media deformation has a large impact on the contaminant transport. The theoretical basis is provided for forecasting contaminant transport and the determination of the relationship among pressure_saturation_permeability in laboratory.

关键词： contaminant transport unsaturated zone numerical model fluid-solid coupling interaction asymptotical solution

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transport of a volatile contaminant in a free-surface wetland flow

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Frontiers of Earth Science 2014年第1期8卷 115-122页

作者： Jue YUAN Li ZENG Yijun ZHAO Yihong WU Ping JI Bin CHEN State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research Beijing 100038 China State Key Laboratory of Water Environment Simulation Schoolof Environment Beijing Normal University Beijing 100875 China

Presented in this paper is an analytical study of a pulsed volatile contaminant emission into a free-surface wetland flow. A simplified model is given for contaminant transport under the combined action of advection, mass dispersion, apparent reaction, and volatilization at the free water surface. The effect of periodic apparent reaction on contaminant transport is separated from the hydraulic effect via an extended transformation, with a limiting case covering the known transformation for constant apparent reaction rate. The analytical solutions of zeroth and first order concentration moments are rigorously derived and illustrated. It was found that the amount of contaminant decreases from the bottom bed to the free-surface under volatilization, and the total amount of contaminant decays with time. It was also found that the moving speed of the mass center of the whole contaminant cloud increases, as the ratio of volatilization coefficient to vertical effective mass dispersivity increases.

关键词： contaminant transport volatilization reaction wetland hydraulics

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Source emissions and climate change impacts on the multimedia transport and fate of persistent organic pollutants,Chaohu watershed,eastern China

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Journal of Environmental Sciences 2021年第11期33卷 15-25页

作者： Xianghui Cao Shouliang Huo Hanxiao Zhang Jiaqi Zheng Zhuoshi He Chunzi Ma Shuai Song State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental ScienceBeijing 100012China Beijing Normal University Beijing 100874China State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China

Emission intensity and climate change control the transport flux and fate of persistent organic pollutants(POPs)inmultiple environmental compartments.This study applied amultimedia model(BETR model)to explore alternations in the spatio-temporal trends of concentrations and transport flux of benzopyrene(BaP),phenanthrene(Phe),perfluorooctane sulfonates(PFOS)and polychlorinated biphenyls(PCBs)in the Chaohu watershed,located in the lower reaches of the Yangtze River,China in response to changes in source emissions and climate.The potential historic and future risks of these pollutants also were assessed.The results suggest that current trends in concentrations and transport were similar to that of their emissions between 2005 and 2018.During the next 100 years,temporal trends and spatial patterns were not predicted to change significantly,which is consistent with climate change.Based on sensitivity and correlation analyses,climate change had significant effects on multi-media concentrations and transport fluxes of BaP,Phe,PFOS and PCBs,and rainfall intensity was the predominant controlling factor.Risk quotients(RQs)of BaP and Phe-in soil increased from 0.42 to 0.95 and 0.06 to 0.35,respectively,from 2005 to 2090,indicating potential risks.The RQs of the other examined contaminants exhibited little potential risk in soil,water,or sediment.Based on spatial patterns,it was inferred that the ecosystem around Lake Chaohu is the most at risk.The study provides insights needed for local pollution control of POPs in the Chaohu watershed.In addition,the developed approach can be applied to other watersheds world-wide.

关键词： Climate change POP emissions Multimedia model contaminant transport Risk assessment

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Analysis for remedial alternatives of unregulated municipal solid waste landfills leachate-contaminated groundwater

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Frontiers of Earth Science 2013年第3期7卷 310-319页

作者： Da AN Yonghai JIANG Beidou XI Zhifei MA Yu YANG Queping YANG Mingxiao LI Jinbao ZHANG Shunguo BAI Lei JIANG School of Environment Beijing Normal University Beijing 100875 China State Key Laboratory of Environmental Criteria and Risk Assessment Chinese Research Academy of Environmental Sciences Beijing 100012 China

A groundwater flow and solute transport model was developed using Visual Modflow for forecasting contaminant transport and assessing effects of remedial alternatives based on a case study of an unregulated landfill leachate-contaminated groundwater in eastern China. The results showed that arsenic plume was to reach the pumping well in the downstream farmland after eight years, and the longest lateral and longitudinal distance of arsenic plume was to reach 200 m and 260 m, respectively. But the area of high concentration region of arsenic plume was not to obviously increase from eight years to ten years and the plume was to spread to the downstream river and the farmland region after 20 years; while the landfill＇s ground was hardened, the plume was not to reach the downstream farmland region after eight years; when the pumping well was installed in the plume downstream and discharge rate was 200m3/d, the plume was to be effectively restrained; for leakage-proof barriers, it might effectively protect the groundwater of sensitive objects within an extent time range. But for the continuous point source, the plume was still to circle the leakage-proof barrier; when discharge rate of drainage ditches was 170.26 m3/d, the plume was effectively controlled; the comprehensive method combining ground-harden with drainage ditches could get the best effect in controlling contaminant diffusion, and the discharge rate was to be reduced to 111.43 m3/d. Therefore, the comprehensive remedial alternative combining ground-harden with drainage ditch will be recommended for preventing ground-water contamination when leachate leakage has happened in unregulated landfills.

关键词： unregulated landfill groundwater numerical simulation contaminant transport arsenic remedial alternative

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Heavy metal content in relation to particle size and organic content of surficial sediments in Miami River and transport potential

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International Journal of Sediment Research 2016年第4期31卷 324-329页

作者： Berrin Tansel Syed Rafiuddin Department of Civil and Environmental Engineering Florida International University College of Engineering and Computing

transport of contaminants in Miami River(Florida,USA) sediments with river currents is a concern due to their potential impact in areas that are away from the potential sources.Accumulation profiles of five metals(As,Cd,Hg,Zn,Pb) in the surficial sediments of the Miami River were evaluated in relation to grain size(from less than 0.075 mm to 6.3 mm) and organic content.Surficial sediment samples were collected along the river basin as well as in bay waters.Fine sediments(transported with the river currents.The levels of heavy metal in fine sediments(< 0.425 mm) along the river bed showed that fine particles had tendency to be mobilized and accumulate at locations where the rivers currents are low and carried out to the bay.

关键词： Particle size Metals Miami River contaminant transport Sediments Sediment transport

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STREAM-SUBSURFACE EXCHANGE, SUSPENDED SEDIMENT transport, AND THE COUPLED transport OF COLLOIDS AND contaminantS IN SEDIMENT BEDS

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International Journal of Sediment Research 2003年第2期 199-207页

作者： Jianhong REN Aaron I. PACKMAN Department of Civil and Environmental Engineering Northwestern University Evanston IL USA

Recent interest in the role of sediments in contaminant transport and stream ecology has motivated additional study of both stream-subsurface exchange flows and suspended sediment transport, deposition, and resuspension. Detailed consideration of the hydrodynamic coupling of stream and pore water flows indicates that there will often be a considerable exchange flux between streams and porous stream beds. As a result, suspended sediments are readily carried from the stream into the subsurface where they can deposit due to physico-chemical interactions with the bed sediments. These processes can greatly influence the transport of fine sediments in streams, and also have important implications for the transport and fate of contaminants. Stream-subsurface exchange allows contaminants to interact with streambed sediments, and contaminants such as metals can sorb to colloidal phases, so that contaminant fate also depends to a large extent on the fate of the suspended sediments. Various degrees of interaction between colloids, contaminants, and stream bed sediments can result in a wide range of transport behavior. In addition, contaminant-particle and particle-particle interactions both depend on the background water chemistry (e.g., pH and ionic strength). Fundamental understanding of the underlying processes allows prediction of the coupled transport of suspended sediments and contaminants. These problems have been analyzed by combining fundamental fluid mechanics with appropriate chemical or physico-chemical interactions between contaminants, colloids, and bed sediments. Long-term modeling of fine sediment and contaminant transport in streams will require consideration of dynamic interactions between stream-subsurface exchange hydrodynamics and fine particle transport.

关键词： Stream hydraulics Suspended sediment transport contaminant transport Hyporheic exchange

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