Radical budget and ozone chemistry during autumn in the atmosphere of an urban site in central China

Abstract

The ROx (=OH + HO2 + RO2) budget and O3 production at an urban site in central China (Wuhan) during autumn were simulated and analyzed for the first time using a UW Chemical Model 0‐D box model constrained by in situ observational data. The daytime average OH, HO2, and RO2 concentrations were 2.2 × 106, 1.0 × 108, and 5.2 × 107 molecules cm−3, respectively. The average daytime O3 production rate was 8.8 ppbv h−1, and alkenes were the most important VOC species for O3 formation (contributing 45%) at this site. Our sensitivity test indicated that the atmospheric environment in Wuhan during autumn belongs to the VOC‐limited regime. The daily average HONO concentration at this site during the study period reached 1.1 ppbv and played an important role in the oxidative capacity of the atmosphere. Without the source of excess HONO, the average daytime OH, HO2, RO2, and O3 production rates decreased by 36%, 26%, 27%, and 31% respectively. A correlation between the HONO to NO2 heterogeneous conversion efficiency and PM2.5 × SWR was found at this site; based on this relationship, if the PM2.5 concentration met the World Health Organization air quality standard (25 µg m−3), the O3 production rate in this city would decrease by 19% during late autumn. The burning of agricultural biomass severely affected the air quality in Wuhan during summer and autumn. Agricultural burning was found to account for 18% of the O3 formation during the study period. Our results suggest that VOC control and a ban on agricultural biomass burning should be considered as high‐priority measures for improving the air quality in this region.

A Spatial-Temporal Resolved Validation of Source Apportionment by Measurements of Ambient VOCs in Central China

“…Among the 10 VOC species with the highest concentrations, propane was the most abundant in ZY and ZK, this funding is consistent with that of previous research [21]. The measured concentrations of ethylene, and benzene measured were lower than previous study in Wuhan [19], whereas most of the abundant species were higher than those of a previous study. The propane concentration level-of different cities was significantly higher than that of other cities, especially at the ZY and ZK sites, probably due to vehicular consumption of LPG.…”

“…Extensive research on resolving VOC sources through PMF have been conducted in recent years in different regions of China, including Beijing-Tianjin-Hebei, the Yangtze River Delta, and the Pearl River Delta [5,[12][13][14][15][16][17]. However, limited studies are available on VOC resources in central China [18,19]. As the capital city of Hubei Province in central China, Wuhan has more than 10 million residents and is characterized by its unique terrain and a rapidly growing economy.…”

Explicit diagnosis of the local ozone production rate and the ozone-NOx-VOC sensitivities

“…Numerous studies have been performed to study the formation of ozone pollution and its controlling factors. However, the study of ozone formation, from the perspective of an analysis of the instantaneous production rate, is currently still sparse [5][6][7][8][9][10][11].…”

Evidence of heterogeneous HONO formation from aerosols and the regional photochemical impact of this HONO source

“…Known atmospheric sources of OH radicals include (but are not limited to) reactions between water vapor and electronically excited oxygen atoms (O 1 D), the photodissociation of some types of volatile organic compounds (Jaeglé et al 2011), and the photolysis of nitrous acid (HONO) (Liu et al 2012a). According to Lu et al (2017), HONO can contribute to over 30% of the O 3 production rate during the daytime at a site of central China in Wuhan City.…”