The Aggravation of Summertime Nocturnal Ozone Pollution in China and Its Potential Impact on the Trend of Nitrate Aerosols

Abstract

Abstract Tropospheric ozone (O3) concentration continued to increase over past years, thereby becoming a growing environmental concern in China. Most studies have focused on the analysis of daily maximum 8‐hr O3 concentration, while there is still a dearth of investigations of nocturnal O3. Here, by analyzing the data of 1,313 sites from the China National Environmental Monitoring Center, we show a remarkable increase in the nocturnal O3 concentration during summertime of 2015–2019 in most regions of China, revealing an aggravation of nocturnal O3 pollution. Combining with a GeoDetector model and statistical analysis, we clarify that the aggravation of nocturnal O3 pollution is mainly caused by reduction in both ambient nitrogen dioxide (NO2) concentration and wet scavenging in recent years. We further reveal that the increasing O3 may have enhanced the nocturnal particulate nitrate (NO3−) formation through N2O5 heterogeneous hydrolysis, and thereby driving the variation and long‐term trend of nocturnal NO3−.

Keywords

• nocturnal O3
• nitrate formation
• interannual variations
• GeoDetector model
• factor analysis