Direct evidence of local photochemical production driven ozone episode in Beijing: A case study.
Sci Total Environ
; 800: 148868, 2021 Dec 15.
Article
in En
| MEDLINE
| ID: mdl-34384967
ABSTRACT
We present a comprehensive field campaign conducted in Beijing, September 2016, to elucidate the photochemical smog pollution, i.e. Ozone (O3). The observed daily maximum hydroxyl radical (OH) and hydroperoxy radical (HO2) concentrations were up to 1â¯×â¯107â¯cm-3 and 6â¯×â¯108â¯cm-3, respectively, indicating the active photochemistry in autumn Beijing. Photolysis of nitrous acid (HONO) and O3 contributed 1-2 ppbv h-1 to OH primary production during daytime. OH termination were dominated by the reaction with nitric oxide (NO) and nitrogen dioxide (NO2), which were in general larger than primary production rates, indicating other primary radical sources maybe important. The measurement of radicals facilitates the direct determination of local ozone production rate P (Ox) (Oxâ¯=â¯O3â¯+â¯NO2). The integrated P(Ox) reached 75 ppbv in afternoon (for 4â¯h) when planetary boundary layer was well developed. At the same time period, the observed total oxidant concentrations Ox, increased significantly by 70 ppbv. In addition, the Ox measurement showed compact increase in 12 stations both temporally and spatially in Beijing, indicating that active photochemical production happened homogenously throughout the city. The back-trajectory analysis showed that Beijing was isolated from the other cities during the episode, which further proved that the fast ozone pollution was contributed by local photochemical production rather than regional advection.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Ozone
/
Air Pollutants
Country/Region as subject:
Asia
Language:
En
Journal:
Sci Total Environ
Year:
2021
Type:
Article