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Published on: November 18, 2018
Nocturnal Ozone Enhancement Reshapes Urban Fine-Particle Chemistry
Ke Yang1,2, Antai Zhang1,2, Yaling Zeng1,2
1Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Environmental Science & Technology
|May 12, 2026
Summary
Nocturnal ozone enhancement (NOE) significantly impacts urban air quality, increasing fine particulate matter (PM2.5) and its oxidative potential. This study reveals NOE
Area of Science:
- Atmospheric Chemistry
- Environmental Science
- Public Health
Background:
- Nocturnal ozone enhancement (NOE) prolongs ozone exposure, posing risks to health and ecosystems.
- The chemical impacts of NOE on fine particulate matter (PM2.5) are not well understood.
Purpose of the Study:
- To characterize NOE occurrence in four Chinese megacities.
- To investigate the chemical effects of NOE on PM2.5 using in-field observations in Shenzhen.
Main Methods:
- Analysis of NOE frequency across Beijing, Shanghai, Guangzhou, and Shenzhen (2019-2024).
- Year-long in-field observations in Shenzhen utilizing non-target ultrahigh-resolution mass spectrometry and statistical analysis.
- Examination of PM2.5 chemical composition and oxidative potential during NOE events.
Main Results:
- NOE events occurred with a frequency of 9.82-12.37% in megacities.
- NOE in Shenzhen correlated with enhanced nocturnal oxidation and stronger mixing.
- Significant increases in secondary aerosol components, nitrate oxidation ratio, OC/EC ratio, and particle oxidative potential were observed during NOE.
- Molecular analysis revealed a shift in water-soluble organic matter towards oxidized CHO species.
Conclusions:
- NOE significantly influences urban PM2.5 chemistry, increasing secondary aerosol formation and oxidative potential.
- The observed chemical changes during NOE events persist into the following daytime.
- Nighttime ozone control presents a potential strategy for managing both urban ozone (O3) and PM2.5.
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