Observation and simulation of HOx radicals in an urban area in Shanghai, China

Guoxian Zhang; Renzhi Hu; Pinhua Xie; Shengrong Lou; Fengyang Wang; Yihui Wang; Min Qin; Xin Li; Xiaoyan Liu; Yue Wang; Wenqing Liu

doi:10.1016/j.scitotenv.2021.152275

Observation and simulation of HOx radicals in an urban area in Shanghai, China

Sci Total Environ. 2022 Mar 1:810:152275. doi: 10.1016/j.scitotenv.2021.152275. Epub 2021 Dec 10.

Authors

Guoxian Zhang¹, Renzhi Hu², Pinhua Xie³, Shengrong Lou⁴, Fengyang Wang⁵, Yihui Wang⁵, Min Qin⁵, Xin Li⁶, Xiaoyan Liu⁷, Yue Wang⁵, Wenqing Liu⁵

Affiliations

¹ Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, China; University of Science and Technology of China, Hefei, China.
² Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, China. Electronic address: rzhu@aiofm.ac.cn.
³ Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, China; University of Science and Technology of China, Hefei, China; College of Resources and Environment, University of Chinese Academy of Science, Beijing, China; CAS Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China. Electronic address: phxie@aiofm.ac.cn.
⁴ State Environmental Protection Key Laboratory of the Formation and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai, China.
⁵ Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, HFIPS, Chinese Academy of Sciences, Hefei, China.
⁶ State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China.
⁷ College of Pharmacy, Anhui Medical University, Hefei, China.

PMID: 34902401
DOI: 10.1016/j.scitotenv.2021.152275

Abstract

A continuous wintertime observation of ambient OH and HO₂ radicals was first carried out in Shanghai, in 2019. This effort coincided with the second China International Import Expo (CIIE), during which strict emission controls were implemented in Shanghai, resulting in an average PM_2.5 concentration of less than 35 μg/m³. The self-developed instrument based on the laser-induced fluorescence (LIF) technique reported that the average OH radical concentration at noontime (11:00-13:00) was 2.7 × 10⁶ cm^-3, while the HO₂ concentration was 0.8 × 10⁸ cm^-3. A chemical box model utilizing the Regional Atmospheric Chemical Mechanism 2 (RACM2), which is used to simulate pollutant reactions and other processes in the troposphere and which incorporates the Leuven isoprene mechanism (LIM1), reproduced the OH concentrations on most days. The HO₂ concentration was underestimated, and the observed-to-modelled ratio demonstrated poor performance by the model, especially during the elevated photochemistry period. Missing primary peroxy radical sources or unknown behaviors of RO₂ for high-NOx regimes are possible reasons for the discrepancy. The daytime ROx production was controlled by various sources. HONO photolysis accounted for more than one half (0.83 ppb/h), and the contribution from formaldehyde, OVOCs and ozone photolysis was relatively similar. Active oxidation paths accelerated the rapid ozone increase in winter. The average ozone production rate was 15.1 ppb/h, which is comparable to that of a Beijing suburb (10 ppb/h for the 'BEST-ONE') but much lower than that of Beijing's center (39 ppb/h in 'PKU' and 71 ppb/h in 'APHH') in wintertime. Cumulative local ozone based on observed peroxy radicals was five times higher than the value simulated by the current model due to the underprediction of HO₂ and RO₂ under the high-NOx regime. This analysis provides crucial information for subsequent pollution control policies in Shanghai.

Keywords: Atmospheric oxidation; FAGE-LIF; OH and HO(2) radicals; ROx budget.

MeSH terms

China
Formaldehyde
Oxidation-Reduction
Ozone* / analysis
Photolysis

Substances

Formaldehyde
Ozone