Analysis of characteristics and meteorological causes of surface ozone pollution in Chengdu during the COVID-19 epidemic

ABSTRACT

Affected by the COVID-19 epidemic, a series of lockdown control measures adopted by various regions have reduced the emission intensity of air pollutants. Taking Chengdu as an example, this study analyzed the meteorological conditions and pollution concentration characteristics in the first half of 2020 and focused on a detailed analysis of variations in ozone (O3) concentration. The results showed that ①Compared with 2019, except for O3, all five pollutants in Chengdu showed a decreased trend, and the concentrations of NO2, CO, SO2, PM10 and PM2.5 decreased by 13.60%, 8.96%, 6.30%, 4.56%, 1.80%, respectively. On the contrary, O3 concentration increased abnormally, with the largest increase in February (35.1%) and May (36.1%). ②During the first half of 2020, the high O3 concentration level appeared earlier than in previous years (2015-2019). Meteorological conditions were more supportive to the generation of O3 also. The geopotential heights of 100 hPa and 500 hPa showed positive anomalies, the temperature and sunshine duration was higher than in previous years, and the relative humidity as well as precipitation were lower with a quiet breeze. ③The O3 formation process lasted a long time from April 25th to May 6th, mainly due to the increased emissions of O3 precursors during this period and the relatively stable weather situation, which kept the Chengdu area exposed to unfavorable weather conditions of high temperature (average temperature>30℃), low humidity (40%~60%), and quiet breeze (1.3 m•s-1) for a long time. The backward trajectories and potential sources of air pollution showed that the air quality was affected by the short-distance transportation of high-polluted air masses from the East of Chengdu and southern Sichuan. © 2021, Science Press. All right reserved.