【作者】 丁辉；

【导师】 李鑫钢；

【作者基本信息】 天津大学 ， 化学工程， 2005， 博士

【摘要】 我国众多河流蓄集大量持久性有机污染物,但目前关于河流持久性有机污染物(POPs)归趋行为的系统研究较为缺乏。本文以大沽排污河为例,系统研究了POPs的河流环境迁移行为。采集自天津大沽排污河的底泥样品进行了特征分析:全河段底泥TOC含量较高,平均值约为8%,利于吸附POPs;Malven Mastersizer激光粒度仪测定了大沽排污河悬浮物和沉积物的粒径分布,结果表明主要以粉砂为主,占60%左右,其次为黏土,占30%左右,大沽排污河底泥颗粒属于细颗粒;悬浮物样品和表层沉积物样品经X射线衍射分析表明,石英和伊利石是大沽排污河底泥悬浮物及沉积物矿物的主要成分,两者之和分别占75.5%和62.2%;环境扫描电子显微镜结果表明,河流底泥悬浮物和沉积物的形态没有本质差别。调查了大沽排污河底泥OCPs类POPs的分布特征:GC-MS定性、GC-ECD定量分析了底泥及水体中的POPs,结果表明,大沽排污河POPs污染较为严重,2005年表层底泥中的HCHs和DDTs的平均浓度分别为113.73ng/g、40.86 ng/g。大沽排污河底泥OCPs中HCB浓度明显高于其它OCPs浓度,HCB浓度范围17.5~1315ng/g,平均240 ng/g,是大沽排污河首要POPs。底泥悬浮是水体POPs主要来源。研究了与POPs归趋密切相关的底泥悬浮、吸附-解吸、悬浮物沉降环境行为过程:使用水力槽试验装置研究了堆积密度和剪应力对侵蚀速率的影响,并回归出侵蚀速率与堆积密度和剪应力的关系式;实验研究表明HCB在悬浮底泥的解吸规律符合快、慢2段一级动力学模型,并建立了POPs快、慢两段吸附-解吸数学模型,揭示了各相污染物浓度随时间的变化关系。悬浮颗粒物浓度是影响平衡时间的主要因素,得出了平衡分配系数与悬浮底泥浓度成幂函数关系式;实验得到底泥群体沉降速度与按照底泥中值粒径得出的单颗粒在清水中沉降速度近似相等。对于含沙浓度较低的河流,浓度对沉速的影响不显著。基于河流污染物运动理论,并结合大沽排污河污染物悬浮、沉积、吸附-解吸运动规律得到了能够揭示POPs迁移、转化的数学模型,并得到符合实测的数值解,计算出POPs的入海通量约为4.32 Kg/d,模型能够很好的预测河流POPs的归趋,为环境管理部门决策做出了技术支持。更多还原

【Abstract】 Rivers have been severely polluted with high loads of persistent organic pollutants(POPs) in our country. But the research about the fate and transport of POPs in river is less systematically studied, presently. The environmental transport of POPs in Dagu Drainage River(DDR) selected as a typical example is reasonedly investigated in this article.Characteristics of sediment from DDR in Tianjin are analyzed. The mean value of TOC in sediments is as high as 8%, which is in favor of sorption POPs. The particle sizes of both suspended sediment and bottom sediment are mensurated by Malven Mastersizer. Silt accounts for about 60% in mass, while clay is about 10%. Particles of sediments belong to fine granule. Suspended sediment and bottom sediment mensurated by XRD mainly consist of quartz and illite, both account for 75.5% and 62.2%, respectively. The conformation of suspended sediment is very similar to bottom sediment from SEM photo.The distribution of POPs in sediments from DDR is investigated. OCPs are analyzed by GC-MS qualitatively and GC-ECD quantificationally. The result shows that DDR is severely polluted with POPs. Mean concentrations of OCPs in surface sediments are 113.73ng/g for HCHs and 40.86ng/g for DDTs, respectively, in 2005. Concentrations of HCB residues in surface sediments are higher than other OCPs residues. Concentrations of HCB range from 17.50 ng/g to 1315ng/g (mean 240 ng/g). Obviously, HCB is chief POPs in sediments from DDR. Sediments suspended from bottom are mainly source bringing POPs into river water.Sediment erosion, sorption-desorption, sedimentation environmental behaviors that closely relate to the fate and transport of POPs are investigated. Effects of bulk density and shear stress on erosion rate are researched by hydrodynamic equipment. The erosion rate formula as function of bulk density and shear stress is regressed. Experimental data of HCB desorption were simulated better by fast-slow two stage first-order kinetics model and dynamic parameters of HCB desorption were also calculated. Sorption-desorption mathematic model is built that can illustrate variation of POPs concentrations in different media with time. The concentration of suspended sediment is main factor deciding the balance time. Through the experimental data regression, the power function about Kp and SPM is regressed. Mass settling velocity of suspended sediment through experiment is similar to the calculated value withmean particle size by one particle settling in fresh water. For rivers with lower concentration of suspended sediment, effect of concentration on settling velocity is inapparent.Based on theories of pollutants movement in river and integrated with sediment erosion, sedimentation, sorption-desorption processes, the fate and transport of POPs mathematic model is built. The calibration model is used to simulate the transport of POPs in the DDR. POPs flux into bohai gulf is 4.32 Kg/d after calculation. The model prediction results will be a powerful tool for the environmental management.更多还原