水体泥沙污染物起动再悬浮释放的物理过程和影响因素  

Physical processes and influencing factors of contaminants release due to resuspended sediments in water environment

作　　者：朱红伟[1] 王道增[1] 樊靖郁[1] 钟宝昌[1] 

机构地区：[1]上海大学上海市应用数学和力学研究所,上海200072

出　　处：《中国科学：物理学、力学、天文学》2015年第10期18-28,共11页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金资助项目(批准号:11032007;11502138)

摘　　要：水流流动、泥沙运动与污染物迁移转化之间存在较强的相互作用,形成了一个彼此紧密联系的综合环境系统.复杂水动力条件使得沉积底泥和悬浮泥沙对水环境的影响体现为一种动态耦合的综合效应.采用室内水槽实验研究了污染物通过底泥的静态扩散释放、泥沙起动再悬浮释放以及随悬浮泥沙的紊动释放3种主要方式进入水体的物理过程.结果表明,底泥沉积物可以依据颗粒特征分为泥质和沙质两种不同的底质;颗粒粒径、孔隙率和初始污染物浓度是决定底泥-水界面污染物静态释放特性的主要因素,并由此建立了沉积物中污染物总量的衰减公式,其衰减时间与污染层厚度、密度以及污染物分配系数正相关.泥沙污染物起动再悬浮释放过程大致上可以分为起动初期,悬浮沉降交替期和悬浮沉降平衡期3个阶段,在后两个阶段水体中污染物固液分配比值先增加后减小.基于质量守恒推导了底泥再悬浮污染物释放量的经验公式,和实验结果对比表明污染物的吸附解吸性质一定程度缓解了其释放的速率.水体中污染物的浓度分布和水流流速分布以及悬浮泥沙浓度分布密切相关,呈现出一致的变化规律.泥沙污染物的分布随着流速的增加在水体垂向上差异也变大,而水体的含沙量越大,泥沙污染物的分布反而越趋向于均匀.Strong interaction exists in water flow, sediment movement and pollutants migration, resulting in an integrated environmental system of close contact with each other. Impact of sediment and suspended sediment on the water environment appears a combined dynamic coupling effect by complex hydrodynamic conditions. Three main ways of the pollutants entering water are studied by flume experiments. These three physical processes may be the static diffusion through sediment-water interface, the release due to sediment resuspension and the release of suspended sediment by turbulence. The results show that the sediment can be divided into two distinct muddy and sandy matters based on surface characteristics. Sediment grain size, porosity and initial contaminant amount are the main factors to determine static release of contaminants at the sediment-water interface. The pollutant quantity attenuation formula in sediment was established thereby, indicating that the contaminated attenuation time are proportional to the sediment thickness, density and distribution coefficient. The contaminant release process due to suspended sediment can be broadly divided into three stages： the initial stage, the alternating stage between suspension and settlement and the balance stage. The ratio of the solid/liquid distribution in the water body increases firstly and then decreases in the later two stages. Pollutants emission amount equations is derived based on the mass conservation law, and its contract with experimental results shows that the nature of the adsorption and desorption of contaminants to some extent alleviate the rate of its release. Water pollutant concentration distribution and velocity distribution as well as suspended sediment concentration distribution are closely related, showing the same variation. Vertical distribution difference of sediment contaminants becomes larger with the increase of flow velocity. The larger the initial sediment concentration is, the more uniform the distribution of sediment contaminants tend

关 键 词：底泥 污染物 静态扩散 再悬浮释放 紊动扩散 

分 类 号：X143[环境科学与工程—环境科学]