Significantly mitigating PM_2.5 pollution level via reduction of NO_x emission during wintertime.

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Air Pollution Control

Background:

• Chinese megacities have reduced fine particulate matter (PM2.5), but second- and third-tier industrial cities face challenges.
• Nitrogen oxides (NOx) significantly impact PM2.5 formation, yet a direct link between NOx emissions and PM2.5 mass loading is needed.
• Policies aim to eliminate heavily polluted weather, necessitating effective strategies for PM2.5 reduction in industrial areas.

Purpose of the Study:

• To construct an evaluation system linking daily NOx emissions to PM2.5 production in a typical industrial city.
• To validate the system's ability to reproduce PM2.5 pollution events and assess the impact of NOx emissions.
• To provide guidelines for regional PM2.5 mitigation and industrial cleaner production through NOx emission indicators.

Main Methods:

• Developed an evaluation system for PM2.5 production based on daily NOx emissions.
• Incorporated parameters for NOx (NO2) evolution into nitric acid and then nitrate.
• Validated the system using 19 pollution cases, calculating root mean square errors.

Main Results:

• The evaluation system accurately reproduced PM2.5 pollution increases with a root mean square error of 19.2 ± 16.4%.
• High NOx emissions in the studied industrial city hinder achieving PM2.5 environmental capacity targets.
• The impact of NOx emissions on PM2.5 is particularly severe under conditions of high initial PM2.5, low planetary boundary layer height, and long pollution duration.

Conclusions:

• The developed NOx emission indicators are feasible for mitigating atmospheric PM2.5.
• Source-oriented NOx indicators can guide industrial cleaner production, including denitrification and low nitrogen combustion.
• The findings offer practical methodologies for regional PM2.5 mitigation strategies in industrial cities.