Radiative Effects of Particular Matters on Ozone Pollution in Six North China Cities

摘要

While the particulate matters (PM) concentration has been reduced across North China in recent years, the surface ozone level has been increasing in many cities in the region. There is a widely held speculation that the elevated ozone level was caused by increased solar radiation due to the reduced PM level in recent years. This study quantifies the radiation effect of PM on O_3 by analyzing data from years 2013 to 2018 in six major cities in North China. We first evaluate PM's effect on the radiation by controlling meteorological factors to radiation, which include the cloud cover, the humidity and time of the day. The PM's effect on the radiation was statistically significant in all six cities, but was the least significant among all significant factors. The PM's radiative effect on the ozone was also statistically significant, but the average ozone increase due to the decreased PM level was rather small, ranging from 0 to 0.12 μg/m~3 (0-0.056 ppb) in the spring and 0-0.36 μg/m~3 (0-0.168 ppb) in the summer per 10 μg/m~3 PM reduction. Therefore, the wide spread springsummer increase of the ozone level in North China should not be attributed to the radiation increase caused by the reduced PM.