温度梯度下土壤渗流与污染物迁移的数值模拟

发布时间：2018-03-05 10:23

本文选题：非饱和土壤　切入点：温度梯度　出处：《扬州大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来全国环境问题日益突出,土壤污染作为环境问题重要方面,已引起业内人士的广泛重视,并逐渐成为环境治理的一项重要内容。研究土壤污染机理,探讨土壤污染过程中不同因素的影响规律,对于土壤污染的治理至关重要。实际的土壤污染过程同时包含水体渗流、溶质迁移、热量传递、生物化学反应等多个方面,而目前绝大多数研究对于土壤溶质迁移的研究并未考虑传热传质的耦合作用对土壤溶质迁移的影响。因此,本文基于土壤中的水体渗流、溶质迁移、热量传递过程,对污染物在土壤中的迁移规律进行研究。本文利用土壤-水特性软件SPAW得到了土壤水分特征曲线及非饱和渗透系数曲线,并结合Van Genuchten数学模型,确定了饱和含水率、残余含水率、土壤容重及饱和渗透系数等土壤特征参数；本文以饱和-非饱和土壤为研究对象,基于多孔介质传热、传质及渗流理论,建立了土壤中水体渗流-溶质迁移-热量传递耦合模型并验证了模型的合理性。采用该模型对单污染源污染物在土壤中的迁移过程进行了非稳态数值模拟,研究了不同入渗速度、初始含水率及土壤类型对土壤温度及污染物浓度的分布规律的影响,结果表明：入渗速度越大,可以促进土壤中热量的扩散和对流,增强溶质的对流作用和弥散作用,且越接近土壤地表,土壤温度及污染物迁移受渗流影响越显著；孔隙率一定的条件下,随着含水率的增大,土壤的导热系数与污染物的扩散速率增大,土壤温升与污染物迁移加快；土壤初始含水量与渗透系数均对土壤温升速率产生影响,而污染物的迁移主要受渗透系数影响。为了研究多个污染源间的相互影响,对多个污染源迁移的模型进行了数值模拟,探讨了入渗速度、初始含水率、污染物浓度及空间分布对饱和-非饱和土壤中污染物迁移规律的影响。结果表明：随着入渗速度及初始含水率的增加,多个污染源之间的相互影响更明显,污染物迁移范围与迁移速率增大；在稳定渗流过程中,污染源在土壤中的迁移受上层污染源和两侧污染源所影响,土壤中污染物的浓度分布与污染源浓度密切相关；随着污染源间距的增大,污染物扩散范围加大,污染源间的相互影响变小,土壤中污染物的浓度增加幅度变小,土壤中污染物的浓度分布与污染源空间分布密切相关。本文的研究目的旨在研究传热传质耦合作用下的溶质迁移机制,以期为土壤污染治理措施和环境评估提供必要的理论指导与技术支持。
[Abstract]:In recent years, environmental problems in China have become increasingly prominent. Soil pollution, as an important aspect of environmental problems, has attracted extensive attention of the industry, and has gradually become an important part of environmental control. It is very important to study the influence law of different factors in the process of soil pollution. The actual process of soil pollution includes water seepage, solute migration, heat transfer, biochemical reaction and so on. However, most studies on soil solute transport have not considered the effect of heat and mass transfer coupling on soil solute transport. In this paper, the characteristic curve of soil moisture and the curve of unsaturated permeability coefficient were obtained by using soil-water characteristic software SPAW, and the saturated water content was determined by combining with the mathematical model of Van Genuchten. Residual moisture content, soil bulk density and saturated permeability coefficient are studied in this paper, based on the theory of heat transfer, mass transfer and seepage in porous media. The coupling model of seepage, solute transport and heat transfer in soil was established and the rationality of the model was verified. The model was used to simulate the transport process of pollutants from single pollution source in soil. The effects of different infiltration speed, initial moisture content and soil type on the distribution of soil temperature and pollutant concentration were studied. The results showed that the higher the infiltration rate, the better the heat diffusion and convection in the soil. The convection and dispersion of solute are enhanced, and the closer the soil surface is to the soil surface, the more the soil temperature and pollutant migration are affected by percolation. Soil thermal conductivity and pollutant diffusion rate increased, soil temperature rise and pollutant migration accelerated, initial soil moisture content and permeability coefficient affected soil temperature rise rate. The transport of pollutants is mainly affected by the permeability coefficient. In order to study the interaction between multiple pollution sources, the model of multiple pollution sources migration is numerically simulated, and the infiltration speed and initial moisture content are discussed. The effects of pollutant concentration and spatial distribution on pollutant migration in saturated-unsaturated soil were studied. The results showed that the interaction between multiple pollution sources was more obvious with the increase of infiltration speed and initial moisture content. In the process of steady seepage, the transport of pollution source in soil is affected by the upper pollution source and the pollution source on both sides, and the concentration distribution of pollutants in soil is closely related to the pollution source concentration. With the increase of the distance between pollution sources, the range of pollutant diffusion increases, the interaction between pollution sources becomes smaller, and the concentration of pollutants in soil becomes smaller. The concentration distribution of pollutants in soil is closely related to the spatial distribution of pollution sources. The purpose of this study is to study the mechanism of solute transport under the coupling of heat and mass transfer. In order to provide necessary theoretical guidance and technical support for soil pollution control measures and environmental assessment.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53;S152.7

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