The focal point of this groundbreaking study revolves around massive wildfires that scorched vast areas of the Western U.S. in the summer of 2020. Between August 15 and 26, over one million acres were engulfed by fire across seven northern California counties alone, triggering unprecedented economic damage estimated at $12 billion. Simultaneously, large fires such as Utah’s East Fork blaze and Oregon’s Lionshead and Beachie Creek fires ravaged hundreds of thousands more acres. While the immediate effects of these fires—smoke, ash, and destruction—are visible and well-known, this research peels back the veil to examine the invisible chemical transformations occurring high above the infernos.

Central to these discoveries is the work of Jan Mandel, a mathematics professor emeritus at the University of Colorado Denver, whose expertise in applied and computational mathematics was key to modeling the wildfire chemical emissions and their interactions within the atmosphere. Mandel’s sophisticated approach integrates atmospheric chemistry with advanced weather prediction software, allowing the research team to simulate the processes by which wildfire-derived compounds, under sunlight, react to form ozone far from their source. This coupling of fire dynamics with atmospheric chemistry models represents a significant technical achievement in understanding wildfire pollution.

Wildfires release a complex mixture of volatile organic compounds (VOCs) and nitrogen oxides (NOx), the precursors necessary for ozone formation through photochemical reactions. However, unlike direct emission of ozone, smoke acts as a chemical incubator where these precursors undergo transformations driven by solar radiation. This distinction not only challenges traditional assumptions about wildfire emissions but also complicates efforts to predict ozone surges during wildfire events. By simulating these processes across broad spatial scales, the study fills critical gaps in capturing the interaction between fire behavior, pollutant chemistry, and meteorological conditions.

Quantifying the magnitude of this effect, the research finds that ozone levels increase by an average of 21 parts per billion (ppb) across the impacted regions during wildfire episodes. This increase is superimposed on already elevated ozone baselines prevalent in the Western United States, often pushing concentrations beyond the 70-ppb threshold established by the U.S. Environmental Protection Agency (EPA) as a health standard. Elevated ozone levels are not only detrimental to respiratory health, causing symptoms from coughing to chronic cardiovascular stress, but they also exacerbate climate warming due to ozone’s role as a short-lived but powerful greenhouse gas.

The study’s computational simulations leveraged the Weather Research and Forecasting model with Chemistry (WRF-Chem), a state-of-the-art coupled atmosphere-chemistry model, fine-tuned with wildfire fire behavior data. This integration enabled unprecedented spatiotemporal resolution in tracking how fire emissions disperse, react, and impact air quality on regional scales. Importantly, it allowed the researchers to attribute spikes in ozone concentrations specifically to wildfire smoke, distinguishing them from other anthropogenic and natural pollution sources.

The collaborative nature of this research is noteworthy as it unites expertise from several prestigious institutions. Alongside Mandel, Derek Mallia, a research assistant professor at the University of Utah with extensive experience in wildfire modeling, led the simulation efforts. Adam Kochanski, an associate professor at San Jose State University, also contributed vital insights from his long-standing work on fire-atmosphere interactions. Supporting these senior researchers, the research team included emerging scholars such as Cambria White, an undergraduate student, and postdoctoral researchers affiliated with the Wildfire Interdisciplinary Research Center, drawing from a rich blend of scientific backgrounds.

Financial and logistical support from agencies such as the Utah Division of Air Quality, NASA’s FireSense Project, and the University of Utah’s Wilkes Center for Climate Science & Policy underscored the strategic relevance of this work. Their funding facilitated high-performance computing resources essential for running such computationally intensive simulations, as well as enriching interdisciplinary dialogue necessary to translate complex atmospheric chemical phenomena into actionable environmental insights.

In addition to its scientific contributions, the study serves as a clarion call for public health authorities and policymakers. The linkage between wildfire smoke and increased ozone concentrations amplifies the urgency to mitigate wildfire risks, improve air quality monitoring, and strengthen public advisories during wildfire seasons. Regions prone to wildfire smoke must prepare for compounded health threats, particularly among vulnerable populations such as those with pre-existing lung or heart conditions.

Jan Mandel’s storied career embodies the convergence of mathematics, computational science, and practical problem-solving. With nearly two hundred published articles and a pedigree spanning numerical mathematics to aerospace applications, Mandel’s computational models have proven versatile and impactful. His work on wildfire emissions simulation builds upon this foundation, exemplifying how mathematical rigor and interdisciplinary collaboration can drive breakthroughs in understanding environmental crises.

The researchers emphasize that wildfires’ contribution to ozone pollution is often underestimated, partly because ozone is not a direct emission product of combustion. It emerges through a cascade of photochemical reactions far from the burning site, which complicates real-time detection and attribution. By integrating fire behavior with atmospheric dynamics and chemistry, this study paves the way for more accurate predictive models that can better inform both firefighting strategies and public health responses.

Finally, the research highlights the growing interplay between climate change and public health, where the rising prevalence of wildfires driven by warming temperatures further inflates ozone levels. These compounded effects risk creating a feedback loop of escalating air quality degradation and health issues, accentuating the importance of scientific research that can guide mitigation policies. Understanding and forecasting the chemical legacy of wildfires will be vital as societies confront the twin challenges of environmental change and human well-being.

Subject of Research: Not applicable

Article Title: Simulating the impacts of regional wildfire smoke on ozone using a coupled fire-atmosphere-chemistry model

News Publication Date: 25-Jul-2025

Web References:

• Atmospheric Environment Journal
• Weather Research and Forecasting Model with Chemistry (WRF-Chem)
• U.S. Environmental Protection Agency Ozone Standards
• Colorado Department of Public Health – Ozone Pollution and Your Health
• NASA FireSense Project
• University of Utah Wilkes Center

References:
Derek Mallia, Jan Mandel, Adam Kochanski, et al. “Simulating the impacts of regional wildfire smoke on ozone using a coupled fire-atmosphere-chemistry model.” Atmospheric Environment, 25 July 2025. DOI: 10.1016/j.atmosenv.2025.121404

Image Credits: Photo credit: Brian Maffly

Keywords: Air pollution, Wildfire smoke, Ozone formation, Atmospheric chemistry, Computational modeling, Environmental health, Climate change

Wildfires have become an increasingly significant ecological and environmental challenge, particularly across the Western United States, where recent decades have witnessed a disturbing trend of escalating frequency, intensity, and scale of fires. These catastrophic events do more than reshape landscapes; they fundamentally transform the composition of the atmosphere, with profound implications for air quality, human health, and regional climate dynamics. Central to these effects are the aerosols and gases emitted during wildfires—microscopic particulate matter that infiltrates the air we breathe and interacts with atmospheric processes in complex, often competing ways. A recent comprehensive study helmed by researchers at the Desert Research Institute (DRI) delves deep into these wildfire emissions, meticulously characterizing the particle size distributions and chemical signatures of aerosols to decode their multifaceted influences on health and weather patterns.

Conducted over a 19-month observational period between 2017 and 2020, the study meticulously monitored air quality in Reno, Nevada, one of the Western cities frequently engulfed in seasonal wildfire smoke. During this timeframe, smoke plumes from over 106 separate wildfire incidents drifted over the city, creating unique opportunities to compare air composition during smoky versus clear days. By leveraging an integrative approach that combined ground-level aerosol particle sizing, pollution concentration metrics, satellite imagery, and atmospheric back-trajectory modeling, the research team unveiled striking disparities in particulate matter and gaseous pollutant profiles linked explicitly to wildfire smoke presence. Notably, fine particulate matter (PM2.5)—particles smaller than 2.5 microns in diameter known to penetrate deep into the human respiratory system—showed increases of 56 to 65 percent attributable to wildfire smoke during peak summer months.

The scientific significance of delineating particle size lies in its direct correlation with particle behavior in the atmosphere and interaction with human health. Larger aerosol particles are typically filtered in the upper respiratory tract, whereas ultrafine and fine particles bypass these defenses and deposit in lung alveoli, potentially causing cardiovascular and pulmonary ailments. The DRI researchers employed advanced aerosol sizing instruments stationed atop the DRI campus, systematically capturing real-time size distribution data. This methodology enabled them to characterize wildfire-derived aerosol populations with high granularity, crucial for refining predictive air quality models and health risk assessments.

Augmenting these data, time-resolved measurements from a downtown Reno Environmental Protection Agency (EPA) monitoring station quantified concentrations of critical air pollutants such as carbon monoxide (CO), ozone (O3), nitrogen oxides (NOx), and potassium (K). Potassium, in particular, serves as a reliable tracer for biomass burning, and its atmospheric abundance during the study period helped confirm the contribution of wildfire smoke to local pollution spikes. Intriguingly, while CO concentrations surged by 18 to 26 percent during smoky days—reflecting incomplete combustion processes common to wildfires—levels of nitrogen oxides and ozone remained relatively steady, a phenomenon attributed to their predominant sources in vehicular emissions and secondary photochemical formation.

To robustly attribute the observed pollution enhancements to wildfire sources, the researchers employed satellite thermal infrared imagery and aerosol optical depth data to spatially and temporally identify active fires and smoke plumes traversing the Reno air shed. This remote sensing information was further coupled with meteorological back-trajectory analyses using NOAA’s Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, which traced air parcel paths backward in time. Such trajectory analyses verified that air masses reaching Reno during pollution events had indeed intersected regions of active burning, conclusively linking measured aerosol and gas anomalies to wildfire smoke.

Understanding the climatic effects of wildfire aerosols introduces additional complexity, as these particles exert competing radiative forcings. Aerosols containing light-scattering compounds can reflect incoming solar radiation, imparting a net cooling effect at the Earth’s surface. Conversely, light-absorbing components such as black carbon and brown carbon organic compounds absorb sunlight, warming the atmosphere and potentially exacerbating regional heat extremes. The DRI team’s size distribution data revealed that wildfire smoke contained aerosol populations capable of acting as cloud condensation nuclei at concentrations up to thirteenfold higher than background levels. This elevation in cloud nucleating particles has implications for cloud microphysics, including changes in cloud lifetime, albedo, and precipitation dynamics, thereby feeding back into local and perhaps larger-scale weather systems.

Beyond atmospheric and climate considerations, the health risks posed by wildfire smoke exposure are considerable. Elevated carbon monoxide levels during smoky periods present a known hazard by binding to hemoglobin and reducing oxygen transport in the bloodstream, increasing risks of hypoxia particularly in vulnerable populations such as children, the elderly, and individuals with cardiovascular disease. The persistence of fine particulate matter further compounds these risks due to deep pulmonary deposition and associated inflammatory responses. The study emphasizes that distinguishing between particle sizes and their chemical origins is essential not only for environmental monitoring but also for targeted public health interventions and communication strategies.

One of the standout aspects of this research lies in its methodological innovation. The team developed an approach to discriminate wildfire smoke aerosols from other urban pollution sources based on combined particle size instrumentation, chemical tracers, satellite imagery, and atmospheric transport modeling. This holistic strategy, although calibrated in Reno, Nevada, is theoretically adaptable to any geographic location subjected to periodic biomass burning influences. Such adaptability enhances the potential for broader application in air quality and climate research communities.

Looking ahead, Siying Lu, one of the lead researchers, is advancing a machine learning framework designed to automate the identification of wildfire smoke presence in air quality datasets. This cutting-edge computational tool promises to revolutionize the monitoring and real-time assessment of smoke impacts, paving the way for smartphone applications or public databases that dynamically track smoke exposure by location. The integration of artificial intelligence in environmental monitoring holds promise for enhancing both scientific understanding and public health responsiveness, particularly as wildfire incidents continue to escalate under climate change scenarios.

The implications of this research extend beyond academic circles, influencing policy, public health advisories, and community resilience strategies. As wildfire seasons lengthen and intensify, understanding precise aerosol characteristics becomes critical for refining air quality standards, developing effective air filtration technologies, and crafting health guidelines. Moreover, insights into aerosol-cloud interactions contribute knowledge vital for improving climate models, enabling better projections of wildfire feedback loops and associated weather pattern shifts.

In summary, the Desert Research Institute’s study represents a landmark effort to characterize wildfire aerosols’ physical and chemical fingerprints, clarify their diverse impacts on air quality, public health, and climate, and innovate methodologies adaptable across regions. Through a synthesis of ground-based measurements, satellite data, and atmospheric modeling, the research unearths nuanced insights with far-reaching implications. As wildfires grip the Western United States with unprecedented ferocity, such rigorous scientific inquiry becomes indispensable for safeguarding environmental and human health in a changing world.

Subject of Research: Characterization of wildfire aerosol particle size distributions and their effects on air quality, human health, and weather in the Western United States.

Article Title: Particle size distributions of wildfire aerosols in the western USA

News Publication Date: April 2025

Web References:

• Study DOI: https://doi.org/10.1039/D5EA00007F
• NASA Fire Data: https://lpdaac.usgs.gov/products/mod14v061/
• NOAA Hazard Mapping System: https://www.ospo.noaa.gov/products/land/hms.html#maps
• NOAA HYSPLIT Model: https://www.ready.noaa.gov/HYSPLIT.php
• Carbon Monoxide Health Effects: https://ww2.arb.ca.gov/resources/carbon-monoxide-and-health#:~:text=Carbon%20monoxide%20is%20harmful%20because,oxygen%20delivery%20to%20the%20brain.

References: Lu, S., Bhattarai, C., Samburova, V., Khlystov, A. (2025). Particle size distributions of wildfire aerosols in the western USA. Environmental Science: Atmospheres. DOI:10.1039/D5EA00007F

Image Credits: Lu et al., 2025/Desert Research Institute (DRI)

Keywords: Wildfires, Air Pollution, Aerosols, PM2.5, Carbon Monoxide, Atmospheric Particles, Cloud Condensation Nuclei, Air Quality Monitoring, Satellite Remote Sensing, Machine Learning, Environmental Health, Climate Impact