A semi-analytical model for methane transport and oxidation in a soil cover

Leachate head in municipal solid waste (MSW) landfills can be very high (e.g., >10 m) in some Chinese landfills and can continuously change during the service life of the landfill. Variations of leachate head can induce time-dependent seepage velocity changes in the liner, which may lead to a change of transport mechanisms of contaminants. An analytical model for contaminant transport through clay liner system considering the effects of leachate head variations is presented. The analytical solution is obtained using the recursive method and the Green's function approach. The proposed analytical solution is verified by numerical results. The model is then applied to investigate the effects of variable leachate head on the transport of contaminants. The results indicated that timedependent advection arising from leachate head variations may play a significant part when investigating contaminant transport through a clay liner. The contaminant concentrations at the bottom of the liner predicted by using fixed leachate head may be underestimated compared to the case with variable leachate heads. The bottom concentration of Pb 2+ at t = 50 years for the case with H D = 60 m can be 6.6 times larger than that of the case with fixed leachate head. The mechanisms of contaminant transfer may change from a diffusion-dominated process to an advection-dominated process. For example, the molecular diffusion is the dominant process in Event 1 (e.g., t < 5 years with Peclet number < 1) while advection induced by the variations of leachate head may play a more important role for contaminant transport when t > 5 years. Increasing leachate head can result in an earlier breakthrough time and steady state for contaminant transport. The breakthrough time of DCM for the case with H D = 60 m can be 1.6 times lower than that for the case with fixed leachate head. Considering the effects of leachate head variations may be critical to design a more stable and reliable landfill liner.

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“…For the top boundary, contaminant concentration was assumed to be constant 27

\begin{equation}{c_s}\left( {0,t} \right) = {c_0}\end{equation}

…”

Section: Mathematical Modelmentioning

confidence: 99%

An analytical model for contaminant transport in landfill liner with fluctuating leachate head

Xie

Thomas

et al. 2022

Num Anal Meth Geomechanics

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Decoding Methane Flow in Fractured Clay: A Semi‐Analytical Model With Matrix Diffusion and Advection

Wang,

Zha,

Rajabi

et al. 2024

Num Anal Meth Geomechanics

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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 Péclet (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 × 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.

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Impact of degraded solid waste utilization as a daily cover for landfill on the formation of methane and leachate

Warmadewanthi

Chrystiadini

Kurniawan

et al. 2021

Bioresource Technology Reports

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A semi-analytical model for methane transport and oxidation in a soil cover

Cited by 12 publications

References 34 publications

An analytical model for contaminant transport in landfill liner with fluctuating leachate head

An analytical model for contaminant transport in landfill liner with fluctuating leachate head

Decoding Methane Flow in Fractured Clay: A Semi‐Analytical Model With Matrix Diffusion and Advection

Impact of degraded solid waste utilization as a daily cover for landfill on the formation of methane and leachate

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