Urban-rural differences in PM2.5 concentrations in the representative cities of China during 2015~2018

Observation sites in the 11 representative cities from 6 main city clusters in China were selected in this study. These observation sites were categorized into urban, suburban and rural to investigate urban-rural differences in PM2.5 concentrations. Results showed that the diurnal variation patterns of PM2.5 were relatively similar in the cities from the same city cluster, and they were also similar among the urban, suburban and rural areas in a specific city. In Jingjinji Megalopolis and Yangtze River Delta Megalopolis, the PM2.5 concentrations from the urban sites were the highest, 7.8%~9.7% higher than those from the suburban sites and 11.3%~16.9% higher than those from the rural sites. However, in Guangdong-Hong Kong-Macao Greater Bay Area and the inland city clusters (i.e., Chengyu Megalopolis, Middle Yangtze River Valley Megalopolis and Guanzhong Plain Megalopolis), the PM2.5 concentrations from the suburban sites were the highest, 2.6%~11.2% higher than those from the urban sites and 16.7%~26.5% higher than those from the rural sites. Moreover, different diurnal variation patterns of urban-rural PM2.5 concentration differences were observed in different cities. For example, the diurnal variation of urban-rural PM2.5 concentration difference was unimodal in Shanghai but bimodal in Hangzhou. The maximum of urban-rural PM2.5 concentration difference occurred during the daytime in Guangzhou but during the nighttime in Shenzhen. Further, the PM2.5 concentration distribution in the urban, suburban and rural areas of the 11representative cities were under the combined effects of PM2.5 emission, transportation and diffusion. © 2019, Editorial Board of China Environmental Science. All right reserved.