Cityscape struggling for air pollution with computer model

Unmasking Air Pollution: How Cities Can Use Data to Clear the Air

Elliot Brynn in Climate & Environment August 2025 • 4 min read.

"A new study reveals the hidden processes driving PM2.5 pollution, offering a roadmap for cleaner air in coastal cities."

Urban air pollution, especially fine particulate matter (PM2.5), poses a significant threat to public health. Heavy pollution events are increasingly common, making it crucial to understand how these pollutants form and accumulate.

Traditional methods of tracking pollution can be limited. Air quality models, on the other hand, offer a powerful way to study pollution events and manage air quality more effectively. By simulating atmospheric processes, these models help identify pollution sources and design targeted reduction strategies.

A recent study used the Community Multiscale Air Quality (CMAQ) modeling system to analyze PM2.5 pollution events in Qingdao, a coastal city in China. The research revealed the contributions of various atmospheric processes to PM2.5 concentrations, providing valuable insights for policymakers and environmental managers.

Decoding PM2.5: How Pollution Forms in Coastal Cities

Cityscape struggling for air pollution with computer model

The CMAQ model's performance was validated against observed surface PM2.5 concentrations, demonstrating its ability to reproduce the temporal and spatial variations of pollution events. This validation step is crucial for ensuring the model's reliability in guiding pollution control efforts.

Here's what the process analysis revealed about PM2.5 formation:

Primary Emissions Dominate: Before and after pollution events, direct emissions accounted for a staggering 72.7% to 93.2% of surface PM2.5 accumulation.
Event-Driven Shifts: During pollution events, primary emissions remained the major contributor, but their contribution decreased (51.4% to 71.8%), indicating the increasing role of other processes.
Transport Matters: Horizontal and vertical transport of pollutants played a significant role, with their contribution increasing during events.
Secondary Formation: PM processes and aqueous chemistry contributed a smaller but still significant portion (6.0% to 11.8%) during events.
Removal Pathways: Pollutants were primarily removed through horizontal transport, vertical transport, and dry deposition. Wet deposition (rain) became the dominant removal pathway when precipitation occurred.

These findings highlight the complex and dynamic nature of PM2.5 pollution in coastal cities. While direct emissions are a constant concern, atmospheric transport and secondary formation processes can significantly amplify pollution during specific events.

Turning Data into Action: A Cleaner Future for Cities

This study demonstrates the power of air quality models like CMAQ to dissect the intricate processes driving PM2.5 pollution. By understanding the specific contributions of various sources and atmospheric mechanisms, cities can develop more effective and targeted pollution control strategies.

The findings suggest that coastal cities should focus on reducing primary emissions while also addressing the factors that contribute to pollutant transport and secondary aerosol formation. Continuous monitoring and modeling are essential for adapting strategies to changing conditions and emerging pollution patterns.

Ultimately, data-driven approaches offer a pathway to cleaner air and healthier urban environments. By embracing these tools, cities can proactively manage air quality and safeguard the well-being of their citizens.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.jes.2018.09.007, Alternate LINK

Title: Process Analysis Of Pm2.5 Pollution Events In A Coastal City Of China Using Cmaq

Subject: General Environmental Science

Journal: Journal of Environmental Sciences

Publisher: Elsevier BV

Authors: Qiang Zhang, Di Xue, Xiaohuan Liu, Xiang Gong, Huiwang Gao

Published: 2019-05-01

Everything You Need To Know

What is PM2.5 and why is it important?

PM2.5, or fine particulate matter, is a type of air pollution that poses a significant threat to public health. It consists of tiny particles suspended in the air, originating from various sources like vehicle emissions, industrial processes, and combustion. The significance of PM2.5 lies in its ability to penetrate deep into the lungs and bloodstream, leading to respiratory and cardiovascular diseases. It is crucial to understand the formation and accumulation of PM2.5 to mitigate its adverse health effects and improve air quality.

What are air quality models and why are they important?

Air quality models, such as the Community Multiscale Air Quality (CMAQ) modeling system, are sophisticated tools used to study air pollution events. They simulate atmospheric processes to identify pollution sources and design effective reduction strategies. These models are essential because they help in understanding the complex interactions that lead to pollution spikes. CMAQ's performance is validated against observed PM2.5 concentrations to ensure its reliability in guiding pollution control efforts. Without the use of models like CMAQ, it would be difficult to dissect the intricate processes driving PM2.5 pollution.

What are primary emissions in the context of air pollution?

Primary emissions refer to the direct release of pollutants, such as PM2.5, into the atmosphere from sources like vehicles, factories, and other industrial processes. The study found that primary emissions accounted for a significant portion of PM2.5 accumulation, ranging from 72.7% to 93.2% before and after pollution events. However, during pollution events, the contribution of primary emissions decreased, indicating the increasing role of other processes. This highlights the importance of controlling direct emissions at their source, especially in mitigating pollution.

What happens during a PM2.5 pollution event?

During PM2.5 pollution events in coastal cities, several atmospheric processes play significant roles. Horizontal and vertical transport of pollutants contribute to the increase in PM2.5 concentrations, as pollutants are moved from one location to another. Secondary formation processes, including PM processes and aqueous chemistry, contribute a smaller but still significant portion during events. These processes amplify pollution during specific events, making the overall situation worse. Removal pathways include horizontal transport, vertical transport, and dry deposition, with wet deposition (rain) becoming the dominant removal pathway when precipitation occurs. These processes highlight the complex and dynamic nature of PM2.5 pollution.

How can the CMAQ model help improve air quality?

The study utilized the US EPA's CMAQ model with the Process Analysis tool to simulate and quantify the contribution of individual atmospheric processes to PM2.5 concentration in Qingdao during three representative PM2.5 pollution events. This modeling approach allowed researchers to dissect the complex interplay of factors that lead to pollution spikes. By understanding the specific contributions of various sources and atmospheric mechanisms, cities can develop more effective and targeted pollution control strategies. This could involve reducing primary emissions, managing transport of pollutants, and addressing the factors that contribute to secondary formation.