环境污染物在土壤介质中迁移行为研究

中文摘要I摘要随着工业化，城市化，和社会经济的迅速发展，工业废弃污染物和城市生活垃圾等污染物均直接或间接通过大气、水体和生物排入土壤,造成土壤环境日渐恶化。土壤污染不同于大气污染和水体污染，污染物质在大气和水体中，一般都比在土壤中更容易迁移，这使得污染物质在土壤中并不像在大气和水体中那样容易扩散和稀释，因此容易在土壤中不断积累而超标，同时也使土壤污染具有很强的地域性。因此研究污染物质在土壤介质中的迁移行为和机理对环境评估具有重要意义。本文主要研究流体中携带的污染物在土壤环境中的迁移行为和分布规律，以及影响污染物在土壤中迁移行为的各种主要因素。本文首先分析了污染物在土壤介质中的迁移机理，得出污染物在土壤中浓度随时空分布的变化是受到土壤环境中多种因素包括各种化学、生物和物理过程共同影响的结果。这些因素包括：土壤孔隙的含水率、土壤质地构造、平均孔隙水流速、水动力弥散系数、土壤的供水方式和强度、土壤的温度、污染源的类型和释放方式、吸附解吸和挥发、衰变及降解、以及研究区域的初始边界条件等。然后结合对流弥散模型方程（CDE），建立土壤污染物在土壤介质中传输的通用的三维基本模型，定量模拟仿真土壤污染物在土壤-水环境中的迁移行为，建立土柱淋溶实验对污染物的迁移过程进行实验室模拟，获得了示踪溶质的穿透曲线，得到了达西流速，水动力弥散系数，迟滞因子等重要参数的值。最后通过MATLAB计算软件，结合所建立的综合模型和通过穿透曲线获得的参数，对各种情况下的污染物溶质迁移进行实际数值模拟仿真计算，结果较为满意。模拟仿真结果表明：土壤的容重、土壤含水率、吸附配系数、对流速度、水动力弥散速度、吸附降解、污染源排放方式、边界条件等因素不同程度的影响着污染物在土壤中的迁移过程。其中对流是影响污染物迁移传输的动力和主要因素，在迁移的整个过程中起最主要的作用；降解会减少污染物的总量，吸附会导致污染物的滞后迁移。污染源的增多，增加了污染物的总量。边界条件的存在对污染物的迁移也有着一定程度的影响。通过对模型的数值计算，掌握污染物在土壤中迁移规律(即其浓度随不同时间、空间的变化状况)。在发生土壤污染事件的时候，可以通过数值模拟研究预测其污染方向、范围和程度以及变化趋势，制定相应的控制措施，提出避免、消除和减轻土壤侵蚀和污染的防治对策，以及对已污染的土壤采取一定的治理净化措施，为土壤污染物的分析、决策、预测、评估提供科学实际的理论依据和方针。关键词：污染物，土柱实验，迁移模型，数值仿真重庆大学硕士学位论文II英文摘要IIIABSTRACTWiththefastdevelopmentofindustrialization,urbanizationandsocialeconomy,abundantindustrialpollutantandhouseholdgarbageweredischargedintosoilthroughtheair,waterandbiologydirectlyorindirectly,whichcausesthesoilenvironmentmoreandmoreworse.Soilpollutionwasdifferentfromairpollutionandwaterpollution,themigrationvelocityofpollutantsinsoilwasfasterthaninairandwater,inorderthatthediffusionanddilutionofpollutantsinsoilwasdifficult,andpollutantsaccumulationandoverweight,sothesoilpollutionhasastrongregionalism.Hence,ithasveryimportantsignificancetomasterthemigrationbehaviorandmechanismofpollutantsinsoilforenvironmentalassessment.Themainlystudyofthispaperwasthemigrationbehaviorandregularityofdistributionofthefluidcarryingpollutantsinsoilenvironment,andvariousmainfactorswhichinfluencethemigrationbehaviorofpollutantsinsoil.Firstly,themechanismofmigrationofpollutantsinsoilwasanalyzed,wecanobtainthatthevariationofconcentrationdistributionofpollutantsinsoilisaffectedbyvariousfactorsincludingvariouschemical,biologicalandphysicalprocess.Suchasthesoilmoisturecontent,thesoiltexturestructure,theaverageporewatervelocity,thehydrodynamicdispersioncoefficient,theintensityandpatternsofsoilwater,thesoiltemperature,thetypeofpollutionsourcesandemissionpatterns,theadsorptionanddesorption,thevolatilization,thedecayanddegradation,theinitialboundaryconditionsofthestudyareaandsoon.Andthencombiningwiththeconvectiondispersionequation(CDE),thegeneral3Dbasicmigrationmodelsofsoilpollutantsinsoilwereestablished.Themigrationbehaviorofsoilpollutantsinsoil-waterenvironmentwassimulatedquantitatively.Andthenthemigrationprocessofpollutantswassimulatedthroughthecolumnexperimentinlaboratory,thebreakthroughcurveoftracersoluteandtheDarcyflowvelocity,hydrodynamicdispersioncoefficient,retardationfactorandotherimportantparametervalueswereobtained.FinallythepollutantmigrationprocessonpracticalundervariouscircumstanceswassimulatedthroughMATLABsoftware,combinedwiththeestablisheduniversalmodelandtheobtainedparametersthroughbreakthroughcurve,andobtainedsatisfactoryresults.Thesimulationdatashowthatmanyfactorswhichcontainthesoilbulkdensity,thesoilmoisturecontent,theabsorbeddistributioncoefficients,theconvectionvelocity,the重庆大学硕士学位论文IVhydrodynamicdispersioncoefficient,theabsorptionanddegradation,thetypeofpollutionsourcesandemissionpatterns,theinitialboundaryconditionshavedifferentdegreeeffectonthemigrationprocessofpollutantinsoil.Themigrationofpollutantinsoilismainlydominatedbyconvectionwhichisthedrivingforceandthemajorfactorthatinfluencesthepollutanttransportation.Degradationwillreducethetotalamountofpollutionwhileabsorptionleadstothemigrationlagofpollutant.Theamountofthepollutantwillrisesastheincreaseofpollutionsources,theBoundaryconditionsalsohaveacertaindegreeofinfluenceonpollutantmigration.Throughnumericalcomputationofmodels,wecangraspthemigrationdisciplineofpollutantsinsoil(i.e.itsconcentrationvariationalongwiththevariationoftime,space).Whenthesoilpollutionincidentshappen,wecanpredictitspollutiondirection,thescopeandextentandchangetrendthroughnumericalsimulations,thenformulatethecorrespondingcontrolmeasuresandputforwardtopreventioncountermeasurestoavoid,eliminateandreducesoilerosionandpollutionaswellasadoptacertaingovernanceandpurificationmeasuresforcontaminatedsoil,andprovidescientificpracticaltheoreticalbasisandguidelinesforanalysis,decision,forecastingandassessmentofsoilpollutantsKeywords:Soilpollutants,columnexperiment,migrationmodel,NumericalSimulation目录V目录中文摘要..........................................................................................................................................I英文摘要.......................................................................................................................................III1绪论.........................................................................................................................................11.1土壤污染的概况和研究现状及趋势.......................