Comparative Analysis of Ozone Pollution Characteristics between Urban Area and Southern Mountainous Area of Urumqi, China

Abstract

The difference in ozone (O3) concentration between stations in the urban and southern mountainous areas of Urumqi was explored based on mathematical statistics and comparative analysis of pollutant concentrations. Besides, potential source contribution function (PSCF) analysis and concentration weighted trajectory (CWT) analysis were performed to identify the potential sources of PM2.5 and O3. The results showed that the daily and monthly mean O3 concentrations in the urban area of Urumqi showed a bimodal variation from October 2017 to August 2018, and the O3 concentration had obvious seasonal characteristics, with the highest in July (120.57 μg/m3) and the lowest in January (22.38 μg/m3). The overall variation of O3 concentration in the mountainous area in the southern suburb of Urumqi was not significant (56.69–84.06 μg/m3), and the O3 concentration was slightly higher in summer than in other seasons. The daily O3 concentration in the urban area showed a unimodal variation in all seasons, and the daily variation was the smallest in winter and the largest in summer. However, the daily variation in the mountainous area was not significant. The O3 concentration in the urban area showed a significant negative weekend effect in winter and a positive weekend effect in spring and summer. However, the O3 concentration only showed a significant positive weekend effect in the mountainous area in summer. The PSCF and CWT analysis results of urban O3 concentration showed that Urumqi, Shihezi, and Wusu were the main O3 source areas. In addition, some areas bordering Kazakhstan in Xinjiang, China were also important source areas.