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学者姓名：严华祥
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Abstract ：
The pollution from landfills due to the leakage of leachate is an important source of groundwater contamination. The service life of geomembrane and high-permeability leachate collection system, which play a crucial role in the long-term effectiveness of landfill liner systems, can be greatly shortened due to the complex environmental conditions of landfills. The one-dimensional analytical model of contaminant transport in geomembrane and compacted clay composite liners considering the service life of geomembrane and leachate collection system is presented. Influences of the service life of geomembrane on contaminants transport are described by changing boundary conditions. Effects of the service life of leachate collection system are achieved by the fluctuated leachate head. An investigation into the influence of geomembrane and leachate collection system service life on the breakthrough of the composite liner is presented. An empirical formula for the prediction of breakthrough time considering the service life of geomembrane and leachate collection system is proposed, which may provide the reference for the preliminary design of composite liners. The proposed solution can capture the field observed data well. Both the total flux and concentration are underestimated by about three orders of magnitude and 47.5%, respectively, compared to the model that doesn't consider the service life of geomembrane.
Keyword ：
Analytical Model Analytical Model Breakthrough Time Breakthrough Time Composite Liner Composite Liner Contaminant Transport Contaminant Transport Leachate Collection System Leachate Collection System Service Life Service Life
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| GB/T 7714 | Xie, Haijian , Cai, Peifu , Yan, Huaxiang et al. Analytical Model for Contaminant Transport in Composite Liners Considering the Longevity of Barrier Components [J]. | WATER AIR AND SOIL POLLUTION , 2025 , 236 (1) . |
| MLA | Xie, Haijian et al. "Analytical Model for Contaminant Transport in Composite Liners Considering the Longevity of Barrier Components" . | WATER AIR AND SOIL POLLUTION 236 . 1 (2025) . |
| APA | Xie, Haijian , Cai, Peifu , Yan, Huaxiang , Ding, Hao , Li, Congcong . Analytical Model for Contaminant Transport in Composite Liners Considering the Longevity of Barrier Components . | WATER AIR AND SOIL POLLUTION , 2025 , 236 (1) . |
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Recent advancements in landfill designs integrate vegetated covers as a sustainable layer to mitigate methane emissions. In this study, we developed a comprehensive analytical model incorporating diffusion, advection, oxidation, and root effects on methane and oxygen transport through landfill green covers. Root characteristics, including architecture, gas conductivity, depth, and density, were found to be influential parameters on methane oxidation and emission in vegetated covers. For example, at 0.4-m root depth, exponential versus uniform root distribution yields a 0.1221 difference in methane concentration for a root density of 105 m/m3. Roots with 3x10-5 m air/m root gas conductivity achieved 13.3% methane oxidation efficiency. Increasing root depth and density extended the aerobic zone, but CH4 oxidation efficiency declined beyond the root density of 104 m/m3. We showed that vegetation cover elevates methane emission control, potentially meeting emission standards [e.g., carbon farming initiative (CFI)] with root densities exceeding 104 m/m3. The balance between atmospheric oxygen and soil methane affects oxidation, with higher air transport (lambda=3x10-4 m air/m root) resulting in 1.8% less methane oxidized. Overall, root-methane dynamics analysis should be optimized for efficient methane mitigation and control through landfill green cover systems.
Keyword ：
Analytical model Analytical model Landfill Landfill Methane Methane Oxidation Oxidation Vegetated covers Vegetated covers
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| GB/T 7714 | Xie, Haijian , Chen, Xiaobin , Shi, Yanghui et al. Methane Dynamics in Landfill Vegetated Covers: Steady-State Model for Oxidation and Diffusion [J]. | JOURNAL OF ENVIRONMENTAL ENGINEERING , 2025 , 151 (1) . |
| MLA | Xie, Haijian et al. "Methane Dynamics in Landfill Vegetated Covers: Steady-State Model for Oxidation and Diffusion" . | JOURNAL OF ENVIRONMENTAL ENGINEERING 151 . 1 (2025) . |
| APA | Xie, Haijian , Chen, Xiaobin , Shi, Yanghui , Rajabi, Hamid , Yan, Huaxiang . Methane Dynamics in Landfill Vegetated Covers: Steady-State Model for Oxidation and Diffusion . | JOURNAL OF ENVIRONMENTAL ENGINEERING , 2025 , 151 (1) . |
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The leachate collection system (LCS) is an important component of the barrier system of landfills. LCS in China is subjected to serious clogging due to the more degradable organics and water in the municipal solid wastes (MSWs). To evaluate the service life of LCS, a reactive transport model is developed to simulate the biogeochemical clogging in LCS. The hydrolysis reactions of degradable components and the kinetic calcium leaching process are taken into account to calculate the generation of VFAs and Ca2+ in MSW. The ionization equilibrium of volatile fatty acids (VFAs), dissolution equilibrium of calcium carbonate, and the kinetic biodegradation reactions of VFAs are considered to simulate the pH variation, calcium carbonate precipitation, and biofilm growth during clogging. By comparing with the laboratory experiment data, the proposed numerical model shows the ability to accurately predict the decrease of the porosity in LCS. Parameter analysis indicates that the decrease of the mass fraction of degradable components in MSW, leachate irrigation rate, and calcium ion leaching rate can significantly extend the service life of LCS. The proposed reactive transport model can be the methodological support for the design and service life prediction of leachate collection systems in landfills.
Keyword ：
Clogging Clogging Groundwater pollution Groundwater pollution Landfill Landfill Leachate collection system Leachate collection system Reactive transport modeling Reactive transport modeling
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| GB/T 7714 | Cai, Peifu , Xie, Haijian , Yan, Huaxiang . Reactive transport modeling of clogging in landfill leachate collection system [J]. | COMPUTERS AND GEOTECHNICS , 2025 , 180 . |
| MLA | Cai, Peifu et al. "Reactive transport modeling of clogging in landfill leachate collection system" . | COMPUTERS AND GEOTECHNICS 180 (2025) . |
| APA | Cai, Peifu , Xie, Haijian , Yan, Huaxiang . Reactive transport modeling of clogging in landfill leachate collection system . | COMPUTERS AND GEOTECHNICS , 2025 , 180 . |
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Permeable reactive barriers (PRBs) show great potential for remediating groundwater polluted by leachate from municipal solid waste landfills (MSWLs). In this study, we conducted a series of batch tests to investigate the effects of environmental factors (e.g., temperature, pollutant concentration, and pH in groundwater) and the composition of PRB materials (i.e., Fe and zeolite) on fulvic acid (FA) removal and also simulated PRB filled with different composition to investigate its effectiveness. The response surface method (RSM) was applied to optimize experimental conditions for single- and double-stage adsorption/desorption processes. Experimental findings demonstrated that an adsorbent mixture of 2.900 g Fe and 1.505 g zeolite achieved the highest adsorption efficiency of 67.22 % among four tested combinations. The double-stage adsorption process significantly enhances the FA removal efficiency compared to the single-stage process. Field-scale simulations indicated that the 1.0-m thick PRB developed in this study may achieve an FA adsorption efficiency of 67.31 %. Moreover, the implementation of PRB may lead to a significant reduction in downstream FA concentrations, with a decrease of 40.90 % compared to cases where only cut-off walls are employed. Therefore, the proposed Fe-Zeolite PRB system may serve as an alternative method to remedy polluted groundwater by landfill leachate.
Keyword ：
Adsorption Adsorption Artificial zeolite Artificial zeolite Municipal solid waste landfill Municipal solid waste landfill Permeable reactive barrier Permeable reactive barrier Pollutant transport Pollutant transport Zero-valent iron Zero-valent iron
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| GB/T 7714 | Xie, Haijian , Chen, Yang , Chen, Xiaobin et al. Fulvic acid removal from landfill contaminated groundwater by a permeable reactive barrier: From laboratory to field-scale analyses [J]. | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING , 2024 , 12 (6) . |
| MLA | Xie, Haijian et al. "Fulvic acid removal from landfill contaminated groundwater by a permeable reactive barrier: From laboratory to field-scale analyses" . | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING 12 . 6 (2024) . |
| APA | Xie, Haijian , Chen, Yang , Chen, Xiaobin , Yan, Huaxiang . Fulvic acid removal from landfill contaminated groundwater by a permeable reactive barrier: From laboratory to field-scale analyses . | JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING , 2024 , 12 (6) . |
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Landfills emissions, ranking as the third-largest anthropogenic source of methane in the atmosphere, pose environmental challenges and threaten public health. The pivotal role of clay as a mitigating agent for methane emission within landfill cover systems cannot be overstated; however, our understanding of methane escape from fractured clay remains limited. This study aims to address the existing gaps by proposing a robust analytical model of methane transport in both fractures and clay matrix. Our investigation also includes a dimensionless analysis to govern the relative significance of diffusion and advection in methane emission from fractured clay, systematically reviewing factors such as the degree of water saturation (Sr) and fracture width. The methane concentration profiles in cracked clay demonstrated escalating sensitivity to P & eacute;clet (Pe) numbers, especially when advection dominates transport. Our findings also highlight the prevalence of preferential methane flow with increasing Sr in the clay matrix. The flux of methane emission from fractures at Sr = 0.8 was 130 times greater than that from intact clay. However, the study necessitates considering methane emission from clay matrix, particularly in dry clay conditions (Sr = 0.2 and 0.4). The accumulated methane emission flux from intact clay, more than that emitted from fractures by about 2.5 times at Sr = 0.2, was 1.3 x 10-5 g/m/s. The findings significantly advance the understanding of gas transport in fractured geomaterials, revealing the effect of water saturation and crack width on methane emissions from fractures. Overall, the outcomes emphasize the inclusion importance of methane emission from cracked clay in the design of gas barriers.
Keyword ：
analytical model analytical model clay barrier clay barrier fracture fracture landfill cover landfill cover methane emission methane emission
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| GB/T 7714 | Wang, Qiao , Zha, Fusheng , Rajabi, Hamid et al. Decoding Methane Flow in Fractured Clay: A Semi-Analytical Model With Matrix Diffusion and Advection [J]. | INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS , 2024 , 48 (18) : 4443-4456 . |
| MLA | Wang, Qiao et al. "Decoding Methane Flow in Fractured Clay: A Semi-Analytical Model With Matrix Diffusion and Advection" . | INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS 48 . 18 (2024) : 4443-4456 . |
| APA | Wang, Qiao , Zha, Fusheng , Rajabi, Hamid , Xu, Long , Yan, Huaxiang . Decoding Methane Flow in Fractured Clay: A Semi-Analytical Model With Matrix Diffusion and Advection . | INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS , 2024 , 48 (18) , 4443-4456 . |
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The cut-off wall is an effective countermeasure to prevent contaminant transport from a contaminated site. However, the aquitard beneath the cut-off wall may serve as a preferential path, leading to an earlier breakthrough of contaminants in the cut-off wall system. In this study, we present a 2-D analytical model for characterizing the contaminant transport in the cut-off wall and aquitard system. The Green function method and discretization method are used to investigate contaminant migration in a semi-infinite domain. We show that the one-dimensional cut-off wall model may be insufficient to predict contaminant transport when the aquitard hydraulic conductivity (k2) k 2 ) exceeds 5 x 10-10 m/s. The contaminant mass outflow from the aquitard for the case with k2 2 = 2 x 10-9-9 m/s may account for 53 % of the total contaminant mass outflow. Increasing k2 2 from 5 x 10-10 m/s to 5 x 10-9-9 m/s leads to a 2.9-fold increase of cumulative mass outflow. An approximate fitting formula is proposed to calculate the required minimum thickness of cut-off wall under different type of aquitards. The thicker cut-off wall is required to ensure the cumulative mass outflow will not exceed the allowable value when k2 2 is relatively high (e.g., 1 x 10-9-9 m/s).
Keyword ：
Analytical model Analytical model Aquifer Aquifer Aquitard Aquitard Contaminant transport Contaminant transport Cut-off wall Cut-off wall Groundwater Groundwater
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| GB/T 7714 | Xie, Haijian , Wang, Ao , Shi, Yanghui et al. Analytical model for two-dimensional contaminant transport in a cut-off wall and aquitard system [J]. | JOURNAL OF HYDROLOGY , 2024 , 643 . |
| MLA | Xie, Haijian et al. "Analytical model for two-dimensional contaminant transport in a cut-off wall and aquitard system" . | JOURNAL OF HYDROLOGY 643 (2024) . |
| APA | Xie, Haijian , Wang, Ao , Shi, Yanghui , Yan, Huaxiang . Analytical model for two-dimensional contaminant transport in a cut-off wall and aquitard system . | JOURNAL OF HYDROLOGY , 2024 , 643 . |
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In recent years, heavy metal contamination of soils has become a major concern in China due to the potential risks involved. To assess environmental pollution and human health risks in a typical heavy metal polluted site in Jiangxi Province, a thorough evaluation of the distribution, pollution levels, and sources of heavy metals in soils of the Yangmeijiang River watershed was conducted in this study. Positive matrix factorization and Monte Carlo simulation were used to evaluate the ecological and human health risks of heavy metals. The research findings indicate that heavy metal pollution was the most severe at the depth of 20-40 cm in soils, with local heavy metal pollution resulting from mining and sewage irrigation. The high-risk area accounted for 91.11% of the total area. However, the pollution level decreased with time due to sampling effects, rainfall, and control measures. Leaf-vegetables and rice were primarily polluted by Cd and Pb. The main four sources of heavy metals in soils were traffic emission, metal smelting, agricultural activities and natural sources, mining extraction, and electroplating industries. Heavy metals with the highest ecological risk and health risk are Cd and As, respectively. The non-carcinogenic and carcinogenic risks of children were 7.0 and 1.7 times higher than those of adults, respectively. Therefore, children are more likely to be influenced by heavy metals compared to adults. The results obtained by the risk assessments may contribute to the identification of specific sources of heavy metals (e.g., traffic emissions, metal smelting, mining excavation, and electroplating industries). Additionally, the environmental impacts and biotoxicity associated with various heavy metals (e.g., Cd and As) can also be reflected. These outcomes may serve as a scientific basis for the pollution monitoring and remediation in the mining-affected areas.
Keyword ：
Heavy metals Heavy metals Monte Carlo simulation Monte Carlo simulation Pollution Pollution Positive matrix factorization Positive matrix factorization Risk assessment Risk assessment Soil Soil
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| GB/T 7714 | Xie, Haijian , Shi, Yanghui , Wang, Liang et al. Source and risk assessment of heavy metals in mining-affected areas in Jiangxi Province, China, based on Monte Carlo simulation [J]. | ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH , 2024 . |
| MLA | Xie, Haijian et al. "Source and risk assessment of heavy metals in mining-affected areas in Jiangxi Province, China, based on Monte Carlo simulation" . | ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH (2024) . |
| APA | Xie, Haijian , Shi, Yanghui , Wang, Liang , Yan, Huaxiang , Ci, Manting , Wang, Ziheng et al. Source and risk assessment of heavy metals in mining-affected areas in Jiangxi Province, China, based on Monte Carlo simulation . | ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH , 2024 . |
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Fractured porous media with primary and secondary fractures play a key role in the propagation of wormholes. In this study, we present a nonlocal reactive flow framework, which is based on peridynamic (PD) theory, for modelling acid injected into fractured porous media. The normalised damage index and the fracture bond damage index ratio are proposed to investigate the influence of fractures on the wormhole patterns and optimal injection rate. The results of matrix acidification in fractured porous media with different fracture apertures demonstrate that the PD reactive flow model can predict acid transport in fractures and capture complex porosity evaluation processes. The parallel fractures more easily become the dominant wormhole propagation paths, whereas more branches connected to the perpendicular fractures are observed. A series of 2D radial reactive flows with different fracture propagation rates is conducted. The optimum injection rate decreases as the fracture propagation rate increases. When acid is injected at the optimum injection rate, the pore volume of acid to breakthrough (decreases to lower than 1.24) and acid leak-off are minimal (the fracture bond damage index ratio increases to higher than 44.8%). These findings may contribute to the understanding of wormholing in fractured porous media, with implications for reactive flow-related processes such as CO2 sequestration, karst system formation, and carbonate reservoir stimulation.
Keyword ：
Fractures Fractures Peridynamics Peridynamics Porous media Porous media Reactive flow Reactive flow Wormholes Wormholes
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| GB/T 7714 | Cai, Peifu , Yan, Huaxiang , Wang, Hao et al. Wormholing in fractured porous media: Nonlocal reactive flow modelling based on peridynamic theory [J]. | COMPUTERS AND GEOTECHNICS , 2024 , 176 . |
| MLA | Cai, Peifu et al. "Wormholing in fractured porous media: Nonlocal reactive flow modelling based on peridynamic theory" . | COMPUTERS AND GEOTECHNICS 176 (2024) . |
| APA | Cai, Peifu , Yan, Huaxiang , Wang, Hao , Li, Congcong , Wang, Qiao . Wormholing in fractured porous media: Nonlocal reactive flow modelling based on peridynamic theory . | COMPUTERS AND GEOTECHNICS , 2024 , 176 . |
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