The Simulation Of PM_2.5 Pollution In Autumn Over Beijing, Tianjin And Hebei Region

With the rapid development of the economy and the impact of human activities, regional aerosol pollution shows a trend of increasing. PM2.5 is listed as one of the most important air pollutants, especially in China’s Beijing, Tianjin and Hebei region(so called Jing-Jin-Ji region). Nearly half of the PM2.5 formed in the atmosphere through oxidation and neutralization of precursor gases(SO2, NOX, NH3), which are mainly from anthropogenic emissions. High concentration of PM2.5 results in haze-fog weather, and thus directly effects on health, agriculture and visibility.In this study, a fully coupled online Weather Research and Forecasting/Chemistry(WRF/Chem) model is utilized to simulate meteorological conditions, PM2.5 and its chemical composition and compare with observational data from multiple sites. The modeling meteorological results have a considerable correlation with the observation, especially for the temperature. The simulation of PM2.5is more accurate for PM2.5 concentration slower than 200μg/m3. Moreover, the effect of the emission reduction during the APEC is evaluated.A case of regional PM2.5 pollution over Jing-Jin-Ji region during October 6-12 was simulated. PM2.5 mainly spread over the south of Hebei, southern Beijing, most part of Tianjin, and northern Shandong, due to the weak-high pressure system and a dominant wind direction of south and southwest.Vertical distribution of PM2.5 from the south to Beijing is discussed. We find there was a process of particulate matter transportation from the south to north during the severe pollution. Specifically, concentration of BC decreased from ground to the upper part of the planetary boundary layer(PBL). High concentrations of secondary aerosols such as NO3-and SO42- mainly located near the surface at night. There was also some high concentration areas existed in the upper PBL during daytime. Time series of the vertical distribution of PM2.5 over Baolian Station in urban Beijing shows an opposite trend of PM2.5 concentration with the PBL height.