[Distribution Characteristics of Near Surface Ozone Volume Fraction in Shanxi Province Based on Atmospheric...

Based on the continuous data of O₃， NO， NO₂， and NO and the meteorological data from March 2019 to February 2020 at six atmospheric composition observation stations in Shanxi Province， the characteristics and influence factors of O₃ volume fractions were studied using statistical analysis and backward trajectory analysis. The results showed that O₃ volume fractions were generally higher from April to September and lower from October to the following March. During the study period， O₃ pollution represented by φ（MDA8O₃）， i.e.， the maximum daily 8-h average of O₃ volume fractions， was the most serious at the Jincheng and Linfen stations in the south of Shanxi， followed by that in the Wutaishan， Shuozhou， and Datong stations in the north， with the least pollution occurring at the Taiyuan station in the middle. There were differences between the urban and alpine stations， although their seasonal O₃ volume fractions were both summer > spring > autumn > winter. O₃ volume fractions at the urban station were usually lower than those at the alpine station； O₃ at the urban station might have been influenced by photochemical reactions with precursor NO； however， this was not the main source of high O₃ at the alpine station. The peak and valley values appeared at 15：00 and 06：00， respectively， at the urban station， whereas they appeared at 20：00 and 10：00， respectively， at the alpine station， representing diametrically opposite diurnal variation patterns. Further， the daily amplitude of O₃ at the urban station was much larger than that at the alpine station. For urban stations specifically， temperature was the most important meteorological factor affecting O₃ volume fraction， compared with sunlight hours， precipitation， and total cloud cover. The NO₂ volume fraction in the daytime affected the daily amplitude of O₃； although the photochemical generation potential of O₃ at the Taiyuan station was good， the O₃ volume fractions were the lowest among urban stations due to strong NO titration. The higher O₃ corresponded to lower NO in which NO₂ was dominant， and the higher NO was largely composed of NO， under which conditions O₃ would be depleted completely. The surface wind that affected O₃ volume fractions of all stations primarily came from the southeast， south， and southwest， and specific wind speed led to the increase in O₃ volume fraction. The geographical situation of the station would cause the difference in the transport of atmospheric pollutants， whereas the horizontal transmissions of high O₃ from the North China Plain and Fenwei Plain were likely to be the common reason for the increase in O₃ volume fraction in Shanxi.