甲苯在北京褐潮土中的运移分布及其STOMP模拟研究

针对我国日益严峻的土壤突发泄漏事故等环境问题,采用二维土槽装置模拟非水相液体(甲苯)发生瞬时泄漏后,其在北京褐潮土中的运移及分布规律,并采用STOMP模型对其进行了模拟.结果表明,泄漏9 h后,含量>1 g.kg-1和>20 g.kg-1的甲苯污染羽横向与垂向距离比分别约为2.3和3.这是由于北京褐潮土的渗透性能较差(渗透系数为0.12 cm.h-1),因此对甲苯的入渗过程有较强的阻滞作用,导致甲苯运移方式主要以水平扩散为主,垂向迁移能力较小.采用STOMP模型对非均质性土层结构(北京褐潮土-砂土和砂土-北京褐潮土2种结构)中的甲苯运移模拟结果表明,由于砂土渗透系数(29.70cm.h-1)远大于北京褐潮土,因此土层分界面的相对渗透率突变是影响甲苯重新分布的主要因素之一.本研究可为非水相液体污染物发生突发泄漏后,及时获取其在土壤中的分布情况提供理论支持.

Research on the Characteristic of Toluene Migration and Distribution in Fluvo-Aquic Soil and Its Simulation Using STOMP Model

Frequently accidental spill of hazard materials into soil environment posed significant threats to human health and natural environment in China. In this paper, simulated nonaqueous phase liquid (NAPLs) toluene sudden spill in fluvo-aquic soil was performed in a two-dimensional tank to investigate the migration and distribution characteristics of toluene as well as its simulation through STOMP model. Visual observation showed that the horizontal expansion of toluene with concentration>1 g·kg^-1 and>20 g·kg^-1 were approximate 2.3 and 3 times the length of the corresponding vertical transportation, respectively. The result revealed that toluene exerted a preferential tendency to lateral spread compared to the vertical migration trends, which may contribute to the impeding effect as a result of the low permeable capacity of soil (permeability coefficient was 0.12 cm·h^-1). The behavior and fate of toluene in heterogeneous soil layers (combined fluvo-aquic-sand and sand-fluvo-aquic soil layers, respectively) after spill were simulated using STOMP model and the results indicated that the significant difference in relative permeability of interface layer, due to the much higher value of permeability coefficient of sand (29.70 cm·h^-1) than that of fluvo-aquic soil, played an important role on the redistribution of toluene after its spill into the heterogeneous soil layers. For practical purposes, the results of this study may be beneficial to identify the distribution property of NAPLs in time after its release into the soil environment.