一种用于突发性场地污染模拟的解析模型

摘要

In order to immediately and effectively deal with kinds of accidental pollution, it is necessary to develop a convenient and practical mathematical model which can be used for most kinds of contaminant at an contaminated site. Free infiltration model and rainfall infiltration model for contaminant transport were established based on the generalization of contaminant migration in unsaturated and saturated zones after the pollution accident, and the corresponding analytic solutions were obtained. Considering the infiltration downward of contaminant in unsaturated zone by gravity, a one-dimension vertical infiltration model for contaminant transport was established under no rainfall condition. Considering the convection, diffusion, volatilization, biodegradation, adsorption and root uptake in the process of contaminant migration in contaminated site (unsaturated zone), a sectional two-dimension solute transport model for unsaturated zone and a planar two-dimension solute transport model for saturated zone were established under rainfall condition. The hypothesis of the model included that the distribution of rainfall was uniform; soil texture, hydraulic property and kind of organic matter were uniform within each zone; the action between contaminant and porous medium was linear sorption; the root uptake obeyed the first order kinetics. According to the analytic solutions of the established model, the simulation case was performed. The simulation results showed that the application was wide; the simulation was effective. The model could predict the degradation and migration of contaminant in unsaturated zone and saturated zone* and the time required for contaminant to migrate into saturated zone.%为了及时有效地应对各种突发性环境污染事故,有必要开发一种简单实用、适于各类型污染物的场地污染数学模型.通过污染事故发生后污染物在包气带、饱和带迁移转化的概化,建立了污染物运移的自由入渗模型以及降雨入渗模型并给出各自相应的解析解.无降雨时,考虑污染物在重力作用下随包气带向下渗透的作用,建立一维垂直入渗模型.有降雨时,考虑污染场地(包气带)中污染物迁移和转化的对流作用、扩散作用及挥发、生物降解、吸附、根系吸收等作用,建立包气带剖面二维溶质运移模型和饱和带平面二维溶质运移数学模型.建模过程中,假定降雨量的平均分布及土壤质地、水力参数以及有机物成分、种类均相同,同时假定污染物与多孔介质间的作用为线性吸附,植物根系对污染物的吸附遵循一级动力学.基于模型的解析解,实现案例的模拟计算.模拟结果表明:该模型具有适用范围广、模拟高效快捷等优点,能够较准确预测污染发生后污染物在土壤中的动向、到达饱和带的时间以及饱和带中污染物的迁移情况.