期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 55, 期 23, 页码 15616-15624出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c00405
关键词
nitrous acid (HONO); nitrogen oxides (NOx); on-road fleet; tunnel test; vehicle exhaust; heterogeneous reactions
资金
- National Natural Science Foundation of China [41530641/41961144029]
- Themebased Research Scheme of Hong Kong [T24-504/17-N]
- Chinese Academy of Sciences [QYZDJ-SSW-DQC032/XDPB1901]
- Department of Science and Technology of Guangdong Province [2017B030314057/2017BT01Z134/2019B121205006]
By measuring HONO and NOx in an urban tunnel, this study found that the conversion of NO2 on urban surfaces is important for HONO production compared to NO2 conversion on aerosol surfaces. The high uptake coefficient of NO2 on tunnel surfaces helps explain the missing HONO sources in urban areas.
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, gamma(NO2), on the tunnel surfaces was calculated to be (7.01 +/- 0.02) x 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 gamma(NO2) on urban surfaces and the elevated HONO/NOx ratio from this study can help explain the missing HONO sources in urban areas.
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