水平渗透性反应屏障在污染场地VOC蒸气管控中的应用及分析

Application and analysis of horizontal permeable reaction barrier in risk mitigation of VOC vapor in contaminated sites

水平渗透性反应屏障(HPRB)是一种针对包气带中挥发性有机化合物(VOC)蒸气的被动修复技术,具有运行无耗能的优点,能够作为大范围VOC污染场地长效风险管控措施。本文提出了VOC蒸气在含HPRB的层状土中迁移的一维瞬态半解析模型,采用Laplace变换得到Laplace域下的通解后,采用Talbot数值方法实现Laplace逆变换得到时间域下的VOC蒸气迁移的半解析解。解析模型计算结果和数值模型的结果吻合良好。算例结果表明,HPRB更适用于原位土体扩散系数较低的污染场地;HPRB埋深过大不利于VOC蒸气的去除;增加HPRB厚度能有效去除场地中的VOC蒸气;污染源质量浓度衰减系数增加会降低场地中VOC蒸气峰值质量浓度,不考虑污染源质量浓度衰减会导致HPRB的设计过于保守。最后提出了HPRB埋深和厚度的设计思路。

The horizontal permeable reaction barrier(HPRB)is a passive remediation technology for the volatile organic compound(VOC)vapor in the vadose zone.It has the advantage of consuming less energy during the operation.And it can be used as a long-term risk control measure for the large-scale VOC contaminated sites.A transient analytical model is proposed in this study to simulate the VOC vapor migration in the layered soil containing a layer of the HPRB.The Laplace transformation is adopted to derive the general solution in the Laplace domain,and then the Laplace inversion of the numerical Talbot method is adopted to derive the semi-analytical solution of the VOC vapor migration.It is found that the HPRB is more suitable for the contaminated sites with low effective diffusivity soil.The large depth of the HPRB is not conducive to the removal of the VOC vapor.The increase of thickness of the HPRB enhances the removal of the VOC vapor.The increase of the source concentration decay rate can reduce the peak value of the VOC concentration in the contaminated sites.The neglect of the source decay can lead to the excessively conservative design of the HPRB.Finally,the design procedure of the depth and thickness of the HPRB is proposed.