珠江三角洲地区城市群发展对局地大气污染物扩散的影响

Study on the effect of the city group development in Pearle River Delta on local air pollutant dispersion by numerical modeling

为探讨城市群发展对局地气象环境和污染物输送的影响,以珠江三角洲不同时期的下垫面为例,选取有利于和不利于污染扩散的较典型的气象条件,采用数值模拟手段,模拟并分析比较该地区城市群的形成与发展对城市气象环境、污染物分布、城市间污染物输送的影响.结果表明,重污染气象条件下出现长时间逆温现象,凌晨3 :0 0到6:0 0间逆温最强,强度约为2 1℃·hm- 1 ,逆温层厚度达3 0 0m .城市群的发展使得城市夜间的逆温强度增强,逆温持续时间增长;城市群的发展使得城市地区风速减小,重污染气象条件下广州小风区面积约增加2 8% ,佛山约增加45 2 % ,轻污染气象条件下增加较小;重污染气象条件时广州和佛山二氧化硫浓度一般大于45 μg·m- 3,城市群的发展使污染物扩散范围变小,对本地贡献率增大,对其它地区的贡献率减小;地区间氮氧化物和二氧化硫的输送基本量级为10 0 t·d- 1 到数10 1 t·d- 1 ,城市群的发展使污染物不易向外输送,在重污染气象条件时广州二氧化硫输出量由5 1 3 7t·d- 1 减小为42 81t·d- 1 .

A numerical experiment is employed to investigate the impact of the city group's change on local meteorological conditions and pollutant transport. The land-use conditions in Pearl River Delta in two decades had been taken as an example to understand how the change and development of city group affecting the local urban meteorological environment, pollutant dispersion, transporting of airborne pollutant among cities. The results showed that a strong temperature inversion appeared under the heavity polluted meteorological condition. The intensity of the inversion temperature reached the peak about 2.1℃·hm^(-1)during 3:00 to 6:00. The height of the inversed temperature layer was 300m. The inversion temperature was strengthened and lasted for a longer time due to the development of cities. The wind speed was less and the pollutant stayed longer due to the development of the city group. The low wind speed area increased by 28% in Guangzhou and 45.2% in Foshan, the increase of low wind area was less under lightly polluted meteorological conditions. The SO_2 concentration of Guangzhou and Foshan was more than 45μg·m^(-3) in heavity polluted meteorological condition, and the development of the city group made the pollutant disperse more widely. The sources contributed more pollutants to the local area, and less to others. The transported mass of SO_2 and NO_x among different areas reached a magnitude of 10~0t·d^(-1) to 10~1t·d^(-1). The development of cities made the pollutant transport more weakly, for example the transported mass of SO_2 from Guangzhou decreased from 51.37(t·d^(-1) to (42.81t·d^(-1).))