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Improving photochemical indicators for attributing ozone sensitivities in source apportionment analysis.
Xiaohui Du1, Wei Tang2, Zhongzhi Zhang2
1Atmospheric Environment Institute, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Water Sciences, Beijing Normal University, Beijing 100857, China.
Journal of Environmental Sciences (China)
|April 21, 2024
Summary
This study refines ozone (O3) pollution analysis in China by improving the CAMx-OSAT model. The enhanced method better attributes O3 to nitrogen oxides (NOx) and volatile organic compounds (VOCs) emissions, aiding pollution control policy.
Area of Science:
- Atmospheric Chemistry and Air Quality Modeling
- Environmental Science and Policy
Background:
- Accurate attribution of ozone (O3) pollution to precursor emissions (nitrogen oxides [NOx] and volatile organic compounds [VOCs]) is crucial for effective air quality management.
- Existing models often struggle with the complex, non-linear relationships governing O3 formation across different atmospheric regimes.
Purpose of the Study:
- To enhance the Ozone Source Apportionment Technology (OSAT) module within the Comprehensive Air Quality Model with extensions (CAMx) for more precise O3 source attribution.
- To develop improved thresholds for classifying O3 sensitivity regimes (NOx-limited, VOC-limited, and transition) across China.
- To assess the impact of the improved model on O3 concentration contributions from different emission sectors.
Main Methods:
- Conducted CAMx-Decoupled Direct Method (DDM) simulations to determine first-order O3 sensitivity to NOx and VOCs emissions.
- Combined DDM results with modeled [Formula: see text] ratios to establish new thresholds for O3 sensitivity regimes.
- Implemented a dynamically varied [Formula: see text] ratio threshold in the OSAT module for improved O3 formation determination and apportionment.
Main Results:
- The improved CAMx-OSAT model demonstrated significant shifts in O3 concentration contributions across different regimes.
- NOx-limited regime contributions decreased by up to 21.89%, while VOC-limited regime contributions increased by up to 7.57%.
- The transition regime contributions were quantified within 15 µg/m³.
Conclusions:
- The modified OSAT module provides a more sophisticated method for attributing O3 concentrations to specific precursor emissions.
- These advancements offer valuable insights for refining O3 pollution control strategies and policies in China.
- The study highlights the importance of dynamic thresholds in air quality modeling for accurate source apportionment.
