Distinct Imact of Precipitation with Different Intensity on PM2.5 over Typical Regions of China

Abstract:

Atmospheric aerosol pollution has high impacts on human health and economic society. One of the most efficient way to remove the pollutants from the atmosphere is wet deposition. This study investigates the removal impacts of precipitation on PM_2.5 using hourly precipitation and PM_2.5 mass concentration data from 2015 to 2017 over three typical atmospheric pollution regions in China, which are Beijing-Tianjin-Hebei (BTH), the Yangtze River Delta (YRD) and the Pearl River Delta (PRD) regions. The PM_2.5 mass concentration difference before and after the hourly precipitation events has been used to denote as the impacts of precipitation. Hourly precipitation event is selected so that the time difference between two PM_2.5 observations is short enough to limit PM_2.5 change caused by other factors. This study focuses on the differences in the removal effect of precipitation on PM_2.5 under different precipitation intensities and pollution levels. The results show that both precipitation intensity and aerosol amount affect the removal effect. Negative removal effect exists for both light precipitation and low PM_2.5 mass concentration conditions. In contrast, positive removal effect occurs for both high precipitation and high PM_2.5 mass concentration conditions. Similar results are also found for relationships between precipitation and PM₁₀ mass concentration based on case studies. The removal effect increases with increasing precipitation intensity and PM_2.5 mass concentration before precipitation, and is consistent with the change trend of wind speed at 100 m height. The findings of this study can help understand the mechanism of wet scavenging on air pollution, providing supports for air pollution control in future.