Nitrous acid (HONO) in a polluted subtropical atmosphere: Seasonal variability, direct vehicle emissions and heterogeneous production at ground surface

Although nitrous acid (HONO) plays an important role in the chemistry of polluted atmospheres, its atmospheric abundances and sources are still not well understood. This paper reports ambient measurements of HONO taken over four select months in different seasons at a suburban site in Hong Kong. The...

Full description

Saved in:
Bibliographic Details
Published in:Atmospheric environment (1994) 2015-04, Vol.106, p.100-109
Main Authors: Xu, Zheng, Wang, Tao, Wu, Jueqi, Xue, Likun, Chan, James, Zha, Qiaozhi, Zhou, Shengzhen, Louie, Peter K.K., Luk, Connie W.Y.
Format: Article
Language:English
Subjects:
Black carbon
Heterogeneous reaction
Nitrous acid
Seasonal variation
Vehicle emission
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Although nitrous acid (HONO) plays an important role in the chemistry of polluted atmospheres, its atmospheric abundances and sources are still not well understood. This paper reports ambient measurements of HONO taken over four select months in different seasons at a suburban site in Hong Kong. The data were analyzed to elucidate the seasonal characteristics, emission ratios and rates of heterogeneous production. The monthly averaged HONO concentrations ranged from 0.35 ± 0.30 ppbv in late spring (May) to 0.93 ± 0.67 ppbv in late autumn (November). The similar variation patterns of HONO, NOx, and traffic flow from midnight to rush hours suggest that the HONO concentration was strongly influenced by vehicle emissions. The emission ratios (HONO/NOx) were derived from an analysis of 21 fresh plumes (NO/NOx > 0.80), with the range of 0.5–1.6%. The large variability in the emission ratios is attributed to the reaction of NO2 on black carbon (BC) emitted from vehicles, based on a strong correlation between the HONO/NOx and concurrently measured BC. The mean conversion rate of NO2 to HONO on ground surface during nighttime estimated on nine select days was 0.52 × 10−2h−1, which is relatively low compared with other reported values. This paper highlights a large variability in vehicle emission ratios and heterogeneous conversions of NO2 at ground surface. Photochemical models must consider this variability to better simulate the primary sources of HONO and subsequent photochemistry in the lower part of the troposphere. •Seasonal variation of HONO is reported for the first time in the PRD region.•Direct emission from vehicles is an important source of HONO during rush hours.•HONO emission ratios from vehicles positively correlate with freshly emitted BC.•A low average conversion rate of NO2 to HONO at ground (0.52% h−1) is derived.
ISSN:1352-2310
1873-2844
DOI:10.1016/j.atmosenv.2015.01.061