Xie Haijian, Zuo Xinru, Chen Yunmin, Yan Huaxiang, Ni Junjun
MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China.
Environ Sci Pollut Res Int. 2022 Oct;29(49):74225-74241. doi: 10.1007/s11356-022-20951-2. Epub 2022 May 30.
The quantitative assessment of landfill gas emissions is essential to assess the performance of the landfill cover and gas collection system. The relative error of the measured surface emission of landfill gas may be induced by the static flux chamber technique. This study aims to quantify effects of the size of the chamber, the insertion depth, pressure differential on the relative errors by using an integrated approach of in situ tests, and numerical modeling. A field experiment study of landfill gas emission is conducted by using a static chamber at one landfill site in Xi'an, Northwest China. Additionally, a two-dimensional axisymmetric numerical model for multi-component gas transport in the soil and the static chamber is developed based on the dusty-gas model (DGM). The proposed model is validated by the field data obtained in this study and a set of experimental data in the literature. The results show that DGM model has a better capacity to predict gas transport under a wider range of permeability compared to Blanc's method. This is due to the fact that DGM model can explain the interaction among gases (e.g., CH, CO, O, and N) and the Knudsen diffusion process while these mechanisms are not included in Blanc's model. Increasing the size and the insertion depth of static chambers can reduce the relative error for the flux of CH and CO. For example, increasing the height of chambers from 0.55 to 1.1 m can decrease relative errors of CH and CO flux by 17% and 18%, respectively. Moreover, we find that gas emission fluxes for the case with positive pressure differential (∆P) are greater than that of the case without considering pressure fluctuations. The Monte Carlo method was adopted to carry out the statistical analysis for quantifying the range of relative errors. The agreement of the measured field data and predicted results demonstrated that the proposed model has the capacity to quantify the emission of landfill gas from the landfill cover systems.
填埋气排放的定量评估对于评估填埋场覆盖层和气体收集系统的性能至关重要。静态通量箱技术可能会导致填埋气实测地表排放的相对误差。本研究旨在通过现场测试和数值模拟相结合的方法，量化箱体尺寸、插入深度、压差对相对误差的影响。在中国西北部西安的一个填埋场，使用静态箱进行了填埋气排放的现场试验研究。此外，基于含尘气体模型（DGM）建立了土壤和静态箱中多组分气体传输的二维轴对称数值模型。所提出的模型通过本研究获得的现场数据和文献中的一组实验数据进行了验证。结果表明，与布兰克方法相比，DGM模型在更广泛的渗透率范围内具有更好的气体传输预测能力。这是因为DGM模型可以解释气体之间的相互作用（如CH、CO、O和N）以及克努森扩散过程，而这些机制在布兰克模型中并未包含。增加静态箱的尺寸和插入深度可以降低CH和CO通量的相对误差。例如，将箱体高度从0.55米增加到1.1米，CH和CO通量的相对误差可分别降低17%和18%。此外，我们发现正压差（∆P）情况下的气体排放通量大于不考虑压力波动情况下的通量。采用蒙特卡罗方法进行统计分析以量化相对误差范围。实测现场数据与预测结果的一致性表明，所提出的模型有能力量化填埋场覆盖系统的填埋气排放量。
