Characteristics and Causes of Ozone Pollution in 16 Cities of Yunnan Plateau

Abstract

In order to study the characteristics and causes of ozone (O3) pollution in 16 cities of Yunnan Plateau, the methods of COD, backward trajectory and potential source contribution function (PSCF) were used to analyze the O3 concentrations from 2015 to 2020 of all state-controlled environmental monitoring stations in 16 cities of Yunnan. The results show that the O3 concentrations in Yunnan gradually increased from 2015 to 2019, and the concentration in 2020 was the lowest due to the COVID-19 pandemic. The peak O3 concentration appears in spring. The daily change trend is a typical single peak shape, the lowest value appears around 8: 00, and the highest value is between 15:00 and 16:00. High concentrations of O3 are from the cities of Zhaotong and Kunming in northeastern Yunnan, while low concentrations of O3 mainly occur in the southwest and northwest border areas. Temperature and relative humidity are two meteorological parameters that have significant effect on O3 concentration. Temperature has the best correlation with O3 in winter, and relative humidity has a better correlation with O3 in autumn and winter than in spring and summer. Finally, source analysis of O3 showed that local ozone precursor emission sources and long-distance transmission from South and Southeast Asia constituted the major contributions of O3 in Yunnan.