Long-term drivers of increasing diurnal NO2 difference in representative cities of the Pearl River Delta

Key Points

• The diurnal difference in nitrogen dioxide has been increasing, indicating significant air quality changes.
• A notable increase of 20% in NO2 levels during peak hours was observed compared to previous decades.
• Observational analysis across representative cities in the Pearl River Delta highlights urbanization effects on air quality.
• These findings suggest that understanding local emission sources is crucial for managing air pollution.