A mathematical model for the transport of heavy metal contaminants (HMCs) in a triple-layer composite liner with defective geomembrane under the non-isothermal condition is developed in this study, where the GMB/GCL/CCL (geomembrane, geosynthetic clay liner and compacted clay liner) composite liner is adopted as an example and the Langmuir adsorption model is incorporated. The proposed model is solved by the finite difference approach, and its correctness is validated by comparison with the experimental results, an existing analytical solution and another numerical method. Later, the transport behaviours of HMCs are explored with the established model. Compared with the isothermal condition, the non-isothermal condition enlarges the transport flux, but also reduces the concentration of HMCs. The relative concentration based on the Langmuir adsorption model is higher than that based on the linear adsorption model, which is related to the decrease of the retardation factor under the Langmuir adsorption model. Furthermore, the parametric study shows that when the leachate head h_t is between 1.0 and 3.0 m, the defined breakthrough time t_b increases by about 1.57 a with the increase of GCL thickness l_g by 1 cm, and the t_b increases by about 9.07 a with the increase of CCL thickness l_c by 0.1 m.

中文翻译：

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非等温条件下复合衬里重金属污染物的输送

本研究开发了非等温条件下具有缺陷土工膜的三层复合衬里中重金属污染物 (HMC) 传输的数学模型，其中 GMB/GCL/CCL（土工膜、土工合成粘土衬里和压实以粘土衬垫)复合衬垫为例，并引入Langmuir吸附模型。所提出的模型采用有限差分法求解，并通过与实验结果、现有解析解和另一种数值方法的比较验证了其正确性。随后，利用已建立的模型探索 HMC 的传输行为。与等温条件相比，非等温条件增大了输运通量，但也降低了HMCs的浓度。基于Langmuir吸附模型的相对浓度高于基于线性吸附模型的相对浓度，这与Langmuir吸附模型下阻滞因子的减小有关。此外，参数研究表明，当渗滤液头h _t在1.0~3.0 m之间，定义突破时间t _{b随着GCL厚度}l _g增加1 cm增加约1.57 a，t b_{随着CCL厚度}l _c增加增加约9.07 a 0.1 米。