Drivers of 2013-2020 ozone trends in the Sichuan Basin, China: Impacts of meteorology and precursor emission changes

Kai Wu; Yurun Wang; Yuhong Qiao; Yiming Liu; Shigong Wang; Xianyu Yang; Haolin Wang; Yaqiong Lu; Xiaoling Zhang; Yu Lei

doi:10.1016/j.envpol.2022.118914

Drivers of 2013-2020 ozone trends in the Sichuan Basin, China: Impacts of meteorology and precursor emission changes

Environ Pollut. 2022 May 1:300:118914. doi: 10.1016/j.envpol.2022.118914. Epub 2022 Feb 3.

Authors

Kai Wu¹, Yurun Wang¹, Yuhong Qiao², Yiming Liu³, Shigong Wang⁴, Xianyu Yang⁵, Haolin Wang³, Yaqiong Lu⁶, Xiaoling Zhang⁴, Yu Lei⁴

Affiliations

¹ Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China; Department of Land, Air, and Water Resources, University of California, Davis, One Shields Avenue, Davis, CA, USA.
² Sichuan Academy of Environmental Sciences, Chengdu, China.
³ School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China.
⁴ Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China.
⁵ Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu, China. Electronic address: xyang@cuit.edu.cn.
⁶ Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu, China.

PMID: 35124125
DOI: 10.1016/j.envpol.2022.118914

Abstract

The Sichuan Basin (SCB) of China is known for excessive ozone (O₃) pollution owing to high anthropogenic emissions combined with terrain-induced poor ventilation and weak wind fields against the surrounding mountains. While O₃ pollution has emerged as a prominent concern in southwestern China yet variations in O₃ levels during 2013-2020 are still unclear and the dominant factor in explaining the long-term O₃ trend throughout the SCB remains elusive due to uncertainties in emission inventory and variability associated with meteorological conditions. Here, we use extensive basin-wide ambient measurements to examine the spatial pattern and trend of O₃ and leverage OMI and TROPOMI satellites in conjunction with MEIC emission inventory to track emission changes. Sensitivity simulations are conducted by using WRF-CMAQ model to investigate the impacts of meteorological variability and emission changes on O₃ changes over 2013-2020. O₃ concentrations exhibit obvious interannual increases during 2013-2019 and a slight decrease in 2020. Both decreases in the MEIC emission inventory (-2.9% yr^-1) and OMI NO₂ column density (-3.1% yr^-1) reflects the declining trend in NO_x emissions over 2013-2020, while anthropogenic VOCs were not adequately regulated during 2013-2017, which explained the majority of deteriorated O₃ pollution from 2013 to 2017. Furthermore, attribution analysis based on CMAQ simulations indicate that the unexpected aggravated O₃ levels in 2019 is not only modulated by disproportional reductions in VOCs and NO_x emissions, but also associated with unfavorable meteorological conditions featured by profound heatwaves and frequent stagnant conditions. In 2020, the abnormal meteorological conditions in May leads to substantial increase of O₃ by 26.8 μg m^-3 as compared to May 2019, while the considerable enhancement was fully offset by low O₃ levels over the whole period which attributes to substantial emission reductions. This study reveals the long-term trend of O₃ levels and precursor emissions and highlights the effects of meteorological variability and emission changes on O₃ pollution over the SCB, with strong implications for designing effective O₃ control measures.

Keywords: Complex terrain; Emission abatements; Meteorological variability; Ozone pollution.

MeSH terms

Air Pollutants* / analysis
Air Pollution* / analysis
China
Environmental Monitoring
Meteorology
Ozone* / analysis

Substances

Air Pollutants
Ozone