A modeling approach to dynamically estimating local photochemistry process and its contribution to surface O₃...

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Air Quality Modeling

Background:

• Urban ozone (O3) pollution stems from local photochemistry and long-range transport.
• Surface O3 is a major air pollutant in urban areas, impacting public health.
• Existing models struggle to dynamically differentiate local O3 contributions.

Purpose of the Study:

• To develop a novel modeling approach for quantifying local photochemical ozone production (Chem_O3) in urban environments.
• To assess the role of local O3 formation in overall surface O3 pollution across different city types.
• To disentangle local O3 contributions from physical transport for informed policy-making.

Main Methods:

• Utilized the ISAM model to establish the hourly response of O3 to local NOx emissions (R_O3-NO2).
• Combined R_O3-NO2 with ambient NO2 concentrations to quantify time-varying Chem_O3.
• Analyzed Chem_O3 and its proportion (Chem%) in relation to total O3 across various North BTH urban areas.

Main Results:

• Local photochemical ozone (Chem_O3) constituted 46.7%-62.6% of total O3 in major North BTH urban areas.
• Chem_O3 contribution varied by city type: mega-city > industrialized > normal > forest city.
• Daily Chem% trends differed from daily O3, showing negative correlations in most cities except mega-cities.

Conclusions:

• The developed method effectively quantifies local ozone formation and its impact on urban air quality.
• Findings highlight the significant role of local photochemistry in ozone pollution, guiding targeted reduction strategies.
• The approach aids environmental managers in developing effective policies for ozone mitigation.