本文選題：非飽和土壤　切入點(diǎn)：溫度梯度　出處：《揚(yáng)州大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：近年來全國環(huán)境問題日益突出,土壤污染作為環(huán)境問題重要方面,已引起業(yè)內(nèi)人士的廣泛重視,并逐漸成為環(huán)境治理的一項(xiàng)重要內(nèi)容。研究土壤污染機(jī)理,探討土壤污染過程中不同因素的影響規(guī)律,對于土壤污染的治理至關(guān)重要。實(shí)際的土壤污染過程同時包含水體滲流、溶質(zhì)遷移、熱量傳遞、生物化學(xué)反應(yīng)等多個方面,而目前絕大多數(shù)研究對于土壤溶質(zhì)遷移的研究并未考慮傳熱傳質(zhì)的耦合作用對土壤溶質(zhì)遷移的影響。因此,本文基于土壤中的水體滲流、溶質(zhì)遷移、熱量傳遞過程,對污染物在土壤中的遷移規(guī)律進(jìn)行研究。本文利用土壤-水特性軟件SPAW得到了土壤水分特征曲線及非飽和滲透系數(shù)曲線,并結(jié)合Van Genuchten數(shù)學(xué)模型,確定了飽和含水率、殘余含水率、土壤容重及飽和滲透系數(shù)等土壤特征參數(shù)；本文以飽和-非飽和土壤為研究對象,基于多孔介質(zhì)傳熱、傳質(zhì)及滲流理論,建立了土壤中水體滲流-溶質(zhì)遷移-熱量傳遞耦合模型并驗(yàn)證了模型的合理性。采用該模型對單污染源污染物在土壤中的遷移過程進(jìn)行了非穩(wěn)態(tài)數(shù)值模擬,研究了不同入滲速度、初始含水率及土壤類型對土壤溫度及污染物濃度的分布規(guī)律的影響,結(jié)果表明：入滲速度越大,可以促進(jìn)土壤中熱量的擴(kuò)散和對流,增強(qiáng)溶質(zhì)的對流作用和彌散作用,且越接近土壤地表,土壤溫度及污染物遷移受滲流影響越顯著；孔隙率一定的條件下,隨著含水率的增大,土壤的導(dǎo)熱系數(shù)與污染物的擴(kuò)散速率增大,土壤溫升與污染物遷移加快；土壤初始含水量與滲透系數(shù)均對土壤溫升速率產(chǎn)生影響,而污染物的遷移主要受滲透系數(shù)影響。為了研究多個污染源間的相互影響,對多個污染源遷移的模型進(jìn)行了數(shù)值模擬,探討了入滲速度、初始含水率、污染物濃度及空間分布對飽和-非飽和土壤中污染物遷移規(guī)律的影響。結(jié)果表明：隨著入滲速度及初始含水率的增加,多個污染源之間的相互影響更明顯,污染物遷移范圍與遷移速率增大；在穩(wěn)定滲流過程中,污染源在土壤中的遷移受上層污染源和兩側(cè)污染源所影響,土壤中污染物的濃度分布與污染源濃度密切相關(guān)；隨著污染源間距的增大,污染物擴(kuò)散范圍加大,污染源間的相互影響變小,土壤中污染物的濃度增加幅度變小,土壤中污染物的濃度分布與污染源空間分布密切相關(guān)。本文的研究目的旨在研究傳熱傳質(zhì)耦合作用下的溶質(zhì)遷移機(jī)制,以期為土壤污染治理措施和環(huán)境評估提供必要的理論指導(dǎo)與技術(shù)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.
【學(xué)位授予單位】：揚(yáng)州大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：X53;S152.7

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