Assessment of surface ozone production in Qinghai, China with satellite-constrained VOCs and NOx emissions

Wen Li; Xiao Han; Jialin Li; Xiaoxiu Lun; Meigen Zhang

doi:10.1016/j.scitotenv.2023.166602

Assessment of surface ozone production in Qinghai, China with satellite-constrained VOCs and NO_x emissions

Sci Total Environ. 2023 Dec 20:905:166602. doi: 10.1016/j.scitotenv.2023.166602. Epub 2023 Sep 1.

Authors

Wen Li¹, Xiao Han¹, Jialin Li², Xiaoxiu Lun³, Meigen Zhang⁴

Affiliations

¹ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
³ College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
⁴ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: mgzhang@mail.iap.ac.cn.

PMID: 37659549
DOI: 10.1016/j.scitotenv.2023.166602

Abstract

The implementation of the western development strategy of China and the migration of air pollutants from eastern China might lead to a rapid increase in volatile organic compounds (VOCs) concentrations in the Qinghai-Tibet Plateau (QTP) and an amplified role of Nitrogen Oxides (NO_x) in ozone (O₃) pollution. Qinghai province, situated on the northeast of the QTP, had fewer human activities compared to eastern China, while ozone pollution worsened over the years. To better capture recent emission trends and improve the accuracy of O₃ simulation in Qinghai, this study proposed a top-down method, which combined the air quality modeling system RAMS-CMAQ, with formaldehyde (HCHO) and nitrogen dioxide (NO₂) columns derived from TROPOMI as the constraints to improve the emission estimates of VOCs and NO_x in July 2020, respectively. Through a series of sensitivity experiments, better quantified emission estimates of VOCs and NO_x were obtained to be 1.33 and 0.34 Tg/yr, 2.5 and 2.1 times larger than the bottom-up ones. The results demonstrated the effectiveness of the top-down method and satellite observations constraints in improving VOCs and NO_x emission estimates, resulting in a reduction in the differences between the observed and modeled HCHO and NO₂ columns to 0.7 and 0.2 × 10¹⁵ molec/cm², respectively. As a result, the simulated maximum daily 8-h average (MDA8) O₃ concentrations increased from 58.9 to 81.6 μg/m³, which were closer to observations (85.4 μg/m³), the normalized mean bias (NMB) and normalized mean error (NME) values of hourly O₃ concentrations changed from -24.7 % to -2.9 % and from 29.9 % to 22.3 %, respectively. This study showed the potential of top-down estimates to aide in the development of emission scenarios, which were critical for accurately simulating the O₃ pollution and pollution control policy studies.

Keywords: Nitrogen oxides; Ozone; Qinghai Province; RAMS-CMAQ; Volatile organic compounds.