Predicting the migration behavior of volatile organic compounds (VOCs) vapor is essential for the remediation of subsurface contamination such as soil vapor extraction. Previous analytical prediction models of VOCs migration are mostly limited to constant-concentration nonpoint sources in homogeneous soil. Thus, this study presents a novel analytical model for two-dimensional transport of VOCs vapor subjected to multiple time-dependent point sources involving transient diffusion, sorption and degradation in layered unsaturated soils. Two representative time-dependent sources, i.e., an instantaneous source and a finite pulse source, are used to describe the short-term and long-term leakage. Results reveal that soil heterogeneity can cause pollution accumulation, especially in low-diffusivity capillary fringe. The assumption of an equivalent plane source from multiple point sources would significantly overestimate the vapor concentration and the contaminated range. The previous single point source model is no longer inapplicable when the relative distance and/or the release interval between sources is small, giving a strong interaction between multiple sources. Moreover, a faster vapor degradation rate or a higher groundwater level will reduce the area of vapor plume linearly. Hence, close attention should be paid to the time-variation characteristics of multiple sources, the vapor degradation and the groundwater level fluctuation in practice to facilitate soil remediation. The proposed model is a promising tool for addressing the above issue.

预测挥发性有机化合物 (VOC) 蒸气的迁移行为对于修复地下污染（例如土壤蒸气提取）至关重要。以前的 VOC 迁移分析预测模型主要限于均质土壤中的恒定浓度非点源。因此，本研究提出了一种新的分析模型，用于在层状非饱和土壤中受到多个瞬态扩散、吸附和降解等时间相关点源的 VOC 蒸汽二维传输。两个有代表性的瞬态源，即瞬时源和有限脉冲源，用于描述短期和长期泄漏。结果表明，土壤异质性会导致污染积累，尤其是在低扩散率的毛细管边缘。来自多个点源的等效平面源的假设将大大高估蒸汽浓度和污染范围。当源之间的相对距离和/或释放间隔较小时，先前的单点源模型不再不适用，给出了多个源之间的强相互作用。此外，更快的蒸汽降解率或更高的地下水位将线性减少蒸汽羽流的面积。因此，在实践中应密切关注多源的时变特征、水汽降解和地下水位波动，以促进土壤修复。所提出的模型是解决上述问题的有前途的工具。