Toward Understanding the Differences of PM2.5 Characteristics Among Five China Urban Cities

Abstract

Characteristics of PM2.5 are investigated and compared based on observations from 2008 to 2017 in Beijing, Shenyang, Shanghai, Chengdu, and Guangzhou, which cover five different climate regions of China. Significant seasonal variations of PM2.5 are found for all five cities, with the largest values in winter and the smallest in summer. The differences of PM2.5 among the five cities are most likely associated with the emission sources, meteorology and topography. The strong emissions with surrounded mountains in Beijing make PM2.5 high, particularly in winter. The basin topography surrounding by mountains in Chengdu makes the pollution hard to disperse and then causes high PM2.5. By contrast, the sea-land breeze helps disperse the air pollution in coastal cities such as Guangzhou and Shanghai by mixing and transport and makes PM2.5 in those cites relatively low. Moreover, the population shows high values in Beijing and Shanghai, and the vehicle amount shows high values in Beijing and Chengdu, contributing to their high PM2.5. Similar monthly variations of PM2.5 are found for the five cities, while the magnitude of variations are different. The five cities demonstrate more different diurnal variations of PM2.5. Associated with the sea-land breeze, there are very weak diurnal variations of PM2.5 in Shanghai and Guangzhou. Differently, significant diurnal variations exist for Beijing, Shengyang and Chengu, with the minimum values in the afternoon and high values at night.