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Variations and sources of nitrous acid (HONO) during a severe pollution episode in Beijing in winter 2016.
- Source :
-
Science of the Total Environment . Jan2019, Vol. 648, p253-262. 10p. - Publication Year :
- 2019
-
Abstract
- Abstract HONO is an important precursor of OH radical and plays a key role in atmospheric chemistry, but its source and formation mechanism remain uncertain, especially during complex atmospheric pollution processes. In this study, HONO mixing ratios were measured by a custom-made instrument during a severe pollution event from 16 to 23 December 2016, at an urban area of Beijing. The measurement was divided into three periods: I (haze), II (severe haze) and III (clean), according to the levels of PM 2.5. This pollution episode was characterized by high levels of NO (75 ± 39 and 94 ± 40 ppbV during periods I and II, respectively) and HONO (up to 10.7 ppbV). During the nighttime, the average heterogeneous conversion frequency during the two haze periods were estimated to be 0.0058 and 0.0146 h−1, and it was not the important way to form HONO. Vehicle emissions contributed 52% (±16)% and 40% (±18)% to ambient HONO at nighttime during periods I and II. The contribution of homogeneous reaction of NO with OH should be reconsidered under high-NO x conditions and could be noticeable to HONO sources during this pollution event. Furthermore, HONO was positively correlated with PM 2.5 during periods I and II, suggesting a potential chemical link between HONO and haze particles. Graphical abstract Unlabelled Image Highlights • High HONO concentrations were observed in a severe pollution episode in Beijing. • The NO 2 conversion was not an important pathway to form HONO at nighttime. • Direct emissions could be critical to the observed HONO. • The homogeneous reaction could be a noticeable HONO source. • Good relation of HONO with PM 2.5 implied a chemical link between HONO and PM 2.5. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00489697
- Volume :
- 648
- Database :
- Academic Search Index
- Journal :
- Science of the Total Environment
- Publication Type :
- Academic Journal
- Accession number :
- 132347167
- Full Text :
- https://doi.org/10.1016/j.scitotenv.2018.08.133