城市下垫面影响空气污染的机制分析  

Mechanism analysis of the impact of urban underlying surface on air pollution

作　　者：羊腾跃 刘红年[1] 王学远[1] 胡非[2] YANG Tengyue;LIU Hongnian;WANG Xueyuan;HU Fei(School of Atmospheric Science,Nanjing University,Nanjing 210023,China;Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]南京大学大气科学学院,南京210023 [2]中国科学院大气物理研究所,北京100029

出　　处：《气象科学》2021年第6期780-790,共11页Journal of the Meteorological Sciences

基　　金：国家自然科学基金资助项目(41975004);国家重点研发计划项目(2017YFC0209600)。

摘　　要：本文采用RBLM-chem模式,利用杭州市高分辨率城市建筑等资料,定量分析城市动力效应、热力效应以及城市植被、人为热对SO_(2)、NO_(2)、O_(3)、PM_(2.5)等主要污染物浓度的影响。结果表明,城市化过程使得大部分城区温度上升约1℃,相对湿度下降约6%,风速下降约0.8 m·s^(-1),湍流动能增强约0.03 m^(2)·s^(-2)。城市动力效应主要通过降低城市风速,使得城区污染物浓度升高,SO_(2)浓度有近5μg·m^(-3)的上升,PM_(2.5)、O_(3)浓度也有近15μg·m^(-3)的上升。城市热力效应主要通过热岛环流使城区污染物向上输送,令地面污染物浓度降低,在城市大部分区域PM_(2.5)都有大约10μg·m^(-3)的浓度下降。城市动力效应大于热力效应,城市的总体作用是使污染物浓度升高。城市下垫面使污染物浓度上升的另外一个机制是代替了自然有植被的下垫面,使污染物干沉降速度下降,但这一作用小于动力学效应。另一方面,人为热对城市主要污染物浓度都起着减小的作用,其中SO_(2)、NO_(2)、O_(3)、PM_(2.5)浓度降幅分别在2.5、3.0、6.0、10.0μg·m^(-3)左右。城市植被可以显著增加污染物干沉降速度,使主要污染物SO_(2)、NO_(2)、O_(3)和PM_(2.5)的干沉降速度分别上升0.1、0.1、0.03、0.06 m·s^(-1)左右,相应地使上述污染物浓度分别下降2.5、6.0、4.0、6.0μg·m^(-3)左右。In this paper,RBLM Chem model was used to quantitatively analyze the urban dynamic effect,thermal effect and the influence of urban vegetation and man-made heat on the concentration of main pollutants such as SO_(2),NO_(2),O_(3) and PM_(2.5).Results show that the temperature in most urban areas increases by about 1℃,the relative humidity decreases by about 6%,the wind speed decreases by about 0.8 m·s^(-1),and the turbulent kinetic energy increases by about 0.03 m^(2)·s^(-2).The urban dynamic effect mainly increases the concentration of pollutants in the urban area by reducing the urban wind speed,hence the concentration of SO_(2) increases nearly by 5μg·m^(-3) and the concentrations of PM_(2.5) and O_(3) also increase nearly by 15μg·m^(-3).Urban thermal effect mainly transports urban pollutants upward through heat island circulation so as to reduce the concentration of ground pollutants.PM_(2.5) decreases about 10μg·m^(-3) in most urban areas.The urban dynamic effect is greater than the thermal effect.The overall function of the city is to increase the concentration of pollutants.Another mechanism for the increasing of pollutant concentration by urban underlying surface is to replace the underlying surface with natural vegetation and reduce the dry sedimentation rate of pollutants,but this effect is less than the dynamic effect.On the other hand,anthropogenic heat plays a role in reducing the concentration of main pollutants in cities,in which the concentration of SO_(2),NO_(2),O_(3) and PM_(2.5) decreases by about 2.5,3.0,6.0 and 10.0μg·m^(-3),respectively.Urban vegetation can significantly increase the dry deposition rate of pollutants,and increase the dry sedimentation rates of SO_(2),NO_(2),O_(3),PM_(2.5) by about 0.1,0.1,0.03 and 0.06 m·s^(-1),respectively.The increasing in the dry sedimentation rate also has a concentration reduction effect on the above pollutants of about 2.5,6.0,4.0 and 6.0μg·m^(-3).

关 键 词：城市动力效应 城市热力效应 污染扩散 城市植被 人为热 

分 类 号：X513[环境科学与工程—环境工程]