城市地区应急污染物扩散的模拟  

Simulation of emerging pollutant diffusion in urban area

作　　者：花杰[1] 刘红年[1] 张宁[1] 

机构地区：[1]南京大学大气科学学院,南京210093

出　　处：《安全与环境学报》2010年第4期50-55,共6页Journal of Safety and Environment

基　　金：自然科学基金项目(40775014);国家重点基础研究发展规划(973)项目(2006CB400506;2010CB428501)

摘　　要：将城市边界层模式(CBLM)和随机游动扩散模式连接,组成城市地区应急污染物扩散模式,利用该模式模拟瞬时源(35t氯气)泄漏后污染物在城市地区的扩散特征。通过平地、3种理想城市建筑和实际南京城市建筑条件下风场和污染物扩散模拟结果的比较,分析了建筑高度和密度对城市风场及污染物扩散的影响。此外,结合美国环保署的毒物浓度伤害准则AEGLs评估了城市地区氯气泄漏后危险区域的变化特征等。结果表明,污染物质量浓度在地面随时间逐渐减小,质量浓度最大值在泄漏后10～60min从约139mg/m^3降低到1mg/m^3,外围最小值也从约10mg/m^3降低到0.1mg/m^3。且质量浓度中心随气流向下游移动,在一定时刻内,水平分布尺度逐渐增大。由于建筑拖曳力影响,模拟区域风速变慢,污染物在模拟区域停留时间延长,质量浓度中心值衰减减缓,扩散面积衰减减缓;且建筑高度越高,建筑密度越大,以上特征越明显。污染物在实际扩散中,扩散特征随着建筑条件的变化而不断变化。在所设置的气象条件及事故发生条件下,事故发生30min后可解除重伤区警报,事故发生1h后可解除危险区警报。An urban emerging pollutant diffusion model is developed by combining the CBLM model and random walk diffusion model. Simulation of the pollutant diffusion characteristics after the instantaneous leak of 35 000 kg chlorine is proposed in this paper. Through the comparison of different simulation results of wind field and pollutant diffusion under the conditions of flatlands, three types of idealized urban buildings and a real building of Naujing, we have analyzed the influences of height and ratio of the buildings on the wind velocity, wind direction, turbulence energy and diffusion characteristics. In addition, based un Acute Exposure Guideline Levels （AEGLs） presented by U.S. Environmental Protection Agency, we have evaluated the feature variation of the hazard area after the chlorine leak took place. The results indicate that during the diffusion process, the surface pollutant concentration decreases with time. From 10 minutes to 60 minutes after the leak, the maximum concentration of chlorine decreases from 139 mg/m3 to 1 mg/m3 and the outer minimum concentration deereases from approximately 10 mg/m3 to 0.1 mg/m3. The concentration center density moves in the wind direction, and within certain duration, the horizontal scale becomes larger. Furthermore, the wind velocity decreases because of the building＇ s dragging force which has caused the pollutants stay longer in the model domain, both center concentration and diffusion range decrease more slowly. It is noteworthy that these characteristics become more obvious when in- creasing the building＇ s height and density. In the practical diffusion process, the diffusion characteristics change with the variation of the building condition. For the given condition of climate and accident occurring proposed in this paper and according to AEGLs as well, the alarm of disabling area can be relieved in 30 minutes ＇after the accident. The alarm of hazard area can be relieved in 1 hour after the accident.

关 键 词：大气科学 污染扩散 瞬时源 随机游动 城市建筑 

分 类 号：X16[环境科学与工程—环境科学]