TY - JOUR
T1 - Contribution of Vehicle Emission and NO2Surface Conversion to Nitrous Acid (HONO) in Urban Environments
T2 - Implications from Tests in a Tunnel
AU - Li, Sheng
AU - Song, Wei
AU - Zhan, Hao
AU - Zhang, Yanli
AU - Zhang, Xinran
AU - Li, Weiran
AU - Tong, Shengrui
AU - Pei, Chenglei
AU - Wang, Yujun
AU - Chen, Yanning
AU - Huang, Zuzhao
AU - Zhang, Runqi
AU - Zhu, Ming
AU - Fang, Hua
AU - Wu, Zhenfeng
AU - Wang, Jun
AU - Luo, Shilu
AU - Fu, Xuewei
AU - Xiao, Shaoxuan
AU - Huang, Xiaoqing
AU - Zeng, Jianqiang
AU - Zhang, Huina
AU - Chen, Duohong
AU - Gligorovski, Sasho
AU - Ge, Maofa
AU - George, Chritian
AU - Wang, Xinming
N1 - Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/12/7
Y1 - 2021/12/7
N2 - Nitrous acid (HONO) is an important photochemical precursor to hydroxyl radicals particularly in an urban atmosphere, yet its primary emission and secondary production are often poorly constrained. Here, we measured HONO and nitrogen oxides (NOx) at both the inlet and the outlet in a busy urban tunnel (>30 000 vehicles per day) in south China. Multiple linear regression revealed that 73.9% of the inlet-outlet incremental HONO concentration was explained by NO2 surface conversion, while the rest was directly emitted from vehicles with an average HONO/NOx ratio of 1.31 ± 0.87%, which was higher than that from previous tunnel studies. The uptake coefficient of NO2, γ(NO2), on the tunnel surfaces was calculated to be (7.01 ± 0.02) × 10-5, much higher than that widely used in models. As tunnel surfaces are typical of urban surfaces in the wall and road materials, the dominance of HONO from surface reactions in the poorly lit urban tunnel demonstrated the importance of NO2 conversion on urban surfaces, instead of NO2 conversion on the aerosol surface, for both daytime and night-time HONO even in polluted ambient air. The higher γ(NO2) on urban surfaces and the elevated HONO/NOx ratio from this study can help explain the missing HONO sources in urban areas.
AB - Nitrous acid (HONO) is an important photochemical precursor to hydroxyl radicals particularly in an urban atmosphere, yet its primary emission and secondary production are often poorly constrained. Here, we measured HONO and nitrogen oxides (NOx) at both the inlet and the outlet in a busy urban tunnel (>30 000 vehicles per day) in south China. Multiple linear regression revealed that 73.9% of the inlet-outlet incremental HONO concentration was explained by NO2 surface conversion, while the rest was directly emitted from vehicles with an average HONO/NOx ratio of 1.31 ± 0.87%, which was higher than that from previous tunnel studies. The uptake coefficient of NO2, γ(NO2), on the tunnel surfaces was calculated to be (7.01 ± 0.02) × 10-5, much higher than that widely used in models. As tunnel surfaces are typical of urban surfaces in the wall and road materials, the dominance of HONO from surface reactions in the poorly lit urban tunnel demonstrated the importance of NO2 conversion on urban surfaces, instead of NO2 conversion on the aerosol surface, for both daytime and night-time HONO even in polluted ambient air. The higher γ(NO2) on urban surfaces and the elevated HONO/NOx ratio from this study can help explain the missing HONO sources in urban areas.
KW - heterogeneous reactions
KW - nitrogen oxides (NO)
KW - nitrous acid (HONO)
KW - on-road fleet
KW - tunnel test
KW - vehicle exhaust
UR - http://www.scopus.com/inward/record.url?scp=85119321810&partnerID=8YFLogxK
U2 - 10.1021/acs.est.1c00405
DO - 10.1021/acs.est.1c00405
M3 - Article
C2 - 34756032
AN - SCOPUS:85119321810
SN - 0013-936X
VL - 55
SP - 15616
EP - 15624
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 23
ER -