Variations in Vertical Distributions of O3, Its Precursors, and Formation Sensitivity in Beijing, China, Based on Ground-Based Remote Sensing

Developing effective emission reduction strategies to mitigate ozone (O₃) pollution requires a comprehensive understanding of its dynamics and formation sensitivity. Herein, the continuous vertical profiles of O₃ and its precursors (formaldehyde and nitrogen dioxide), and O₃ formation sensitivity, as well as their temporal variations, were investigated by ground-based remote sensing observations at urban and rural sites in Beijing, China, from 2018 to 2023. The maximum monthly mean O₃ concentration within the boundary layer was observed at an altitude of 100–300 m. Concentrations of O₃ and its precursors declined from 2018 to 2021, followed by slight increases in 2022 and 2023. The combined temporal percentages of O₃ formation under the NO_x-limited and transition regimes were accessed at both sites. These percentages for the boundary layer condition have reached 69.2% at the rural site during summer 2023. The trend toward a shift from the VOC-limited to NO_x-limited regime was observed. This shift occurred at a much faster rate at the rural site than at the urban site. The findings of the study indicate that a predominantly VOC-limited regime is expected to be confined to a narrow near-surface layer within the urban areas of Beijing by 2030 if current trends continue.

This paper explores the spatiotemporal characteristics, evolutionary trends, and their urban−rural differences in the profiles of O₃ and its precursors, as well as O₃ formation sensitivity at different altitudes, based on vertical observations in Beijing.