Air quality in America’s largest cities has steadily improved thanks to tighter regulations on key sources of particulate pollution. However, increased heat, wildfire smoke and other emerging global drivers of urban aerosol pollution are now combining to create a new set of challenges for public health officials tasked with protecting millions of people on the East Coast.

Research from Colorado State University published in npj Climate and Atmospheric Science begins to unpack and characterize these developing relationships against the backdrop of New York City. The research quantifies how existing particulate pollution from sources such as vehicle exhaust or consumer products are now combining with wildfire smoke –– transported from thousands of miles away –– to create secondary, often more toxic, pollution or contribute to the formation of ozone in hot weather.

Professor Delphine Farmer in the Department of Chemistry led the research with data collected from continuous on-the-ground readings at a site on Long Island during the summer of 2023.

“We did not set out to study air quality, wildfire and heat in that way, but smoke from fires in Canada arrived and, unfortunately, that is likely to be more and more common in the future,” Farmer said. “Cities on the West Coast have been dealing with these combined issues for a while, but the developing situation in New York is a good test case to understand how variables like the nearby natural forests and denser populations on the East Coast may contribute to these emerging drivers of air pollution in mega cities.”

Aerosol pollution consists of tiny particles of smoke or other compounds from many common sources such as cleaning solutions or cooking in restaurants. It can also occur naturally from the gases plants release every day. Hotter temperatures can cause plants to release more of those gases and speed the evaporation of some of those consumer products into particulate air pollution. Meanwhile, wildfire smoke particles absorb and react to those same gasses –– further amplifying both natural and man-made sources of pollution. Because these particles can enter the lungs, they may lead to heart disease, cancer and even dementia, making them a key focus area for health regulation.

Farmer said the situation in New York presented an opportunity to start to untangle the relationships between sources and their impacts overall. Her team found evidence that 90 percent of the aerosol pollution found over the city was indeed sensitive to at least one aspect of these global changes, such as high temperatures –– meaning effects from the pollutants were made worse during a heat wave, for example.

Some volatile chemical products such as paints and solvents are sensitive to these changes, and the team’s work shows that those sources are responsible for more than double the estimated contribution from cars to the city’s air pollution total in this category.

New York also has plenty of restaurants where the daily cooking and cleaning activities can contribute to overall pollution totals as well. However, the team found that while those emissions were also sensitive to the introduction of smoke or higher temperatures the effects were localized.

“We found that restaurants do have a big impact on their own local neighborhoods, but their associated aerosols are only a minor component of the total average load across the region,” Farmer said. “Still, any worsening of those conditions from the arrival of wildfire smoke –– for example –– could lead to environmental health inequality for those areas that health policy makers will need to consider.”

She added that context like that will help policy makers prioritize sources of pollution to target for both their overall contributions to the area’s air quality and their localized impact on public health.

Machine learning techniques aid research into urban air pollution

Emily Franklin led aerosol data collection on the ground and follow-up analysis for the project as a CSU postdoctoral fellow funded by the National Science Foundation. She has since taken a position as a research scientist at CSIRO, Australia’s national science agency.

Franklin said the team pulled measurements from many different instruments on the site and worked closely with fellow researchers from the universities of Minnesota, Columbia, Michigan and the University of California, Berkeley for the project. Together, these instruments generated thousands of individual indicators of aerosol composition, including characterization of hundreds of unique but unidentifiable compounds in the atmosphere. To take advantage of these complex measurements, she leveraged machine learning techniques.

“This was an incredibly rich and complex dataset. In a place like New York, you have compounds coming from trees in city parks, fires in Canada, construction sites miles away, and the barbecue joint up the road,” Franklin said. “Machine learning was a powerful tool allowing us to embrace this complexity and leverage it to better understand how all of these sources interact with the climate to make the air pollution experienced by the community.”

Funding for this project came from the National Oceanic and Atmospheric Administration as part of their AGES+ campaign, which is focused on improving air quality understanding through extensive, coast-to-coast observation using ground sites, research aircraft and satellite data.

The CSU team will now continue to study air quality in the region through the NSF funded GOTHAAM Campaign using a C-130 aircraft as a flying chemistry lab to measure atmospheric composition in real time across New York, New Jersey and Connecticut. That project focuses on volatile organic compounds –– a broad term for gases from car exhaust, industry, vegetation and consumer products that react in the atmosphere to form ground-level ozone, secondary organic aerosols and particulate matter.

Farmer said measurements taken from the plane will give the team a better sense of the chemistry happening in the region as they will be able to get readings over the ocean and at different altitudes. Ideally, they will be able to provide more information to the millions of residents in the broader region about their air quality and potential health risks from it.

“We worry about what we are breathing on the ground but in reality, the chemistry happening above us has a big impact on that. This research project will again help us understand key interactions better and improve our ability to predict potentially hazardous air quality conditions,” she said.

Atmospheric aerosols, microscopic particles suspended in the air, play an instrumental role in modulating climate and air quality. These tiny entities interact with solar radiation and clouds, influencing the Earth’s radiative balance and weather patterns. Professor Cheng’s investigations extend beyond mere observation; she aims to establish a predictive framework that elucidates the sources, intricate transformations, and ultimate environmental consequences of aerosols within the Earth system. In doing so, her work addresses core challenges of global change in the current Anthropocene epoch, where human activities profoundly alter the planet.

What sets Professor Cheng’s research apart is the integrative methodology that intertwines laboratory experiments, extensive field campaigns, and theoretical advancements. By pioneering novel instrumental techniques and computational models, she has been able to bridge previously disconnected domains of aerosol science. This holistic approach not only enhances the accuracy of climate predictions but also opens new research pathways that inspire the global atmospheric science community.

The Copernicus Gesellschaft e.V. highlighted in their official congratulatory letter the groundbreaking advances that Professor Cheng has achieved. They noted that her efforts transcend academia by engaging in impactful public outreach, raising awareness about aerosol-related environmental issues. Such dual commitment to scientific excellence and societal communication underscores the profound influence of her contributions.

Since 2024, Professor Cheng has been at the helm of the newly established Aerosol Chemistry Department at the Max Planck Institute for Chemistry in Mainz. Under her leadership, the department delves into the chemical composition, formation mechanisms, and atmospheric processing of aerosols. Her role there is supplemented by her appointment as a guest professor at Peking University, further solidifying her stature as an international leader in Earth system chemistry.

Beyond institutional achievements, Professor Cheng’s professional recognitions are numerous and well-deserved. She is an elected member of Academia Europaea and a Fellow of both the American Association for the Advancement of Science and the American Geophysical Union. These honors reflect her broad influence across disciplines and continents. Additionally, she serves as Editor-in-Chief of the American Geophysical Union’s flagship Journal of Geophysical Research – Atmospheres, a testament to her expertise and thought leadership.

Aerosols themselves constitute one of the most challenging elements in atmospheric research. Their sources range from natural phenomena like wildfires and ocean spray to anthropogenic emissions from industry and transportation. Moreover, aerosol particles undergo complex physicochemical transformations in the atmosphere, affecting their properties and interactions. Professor Cheng’s research rigorously unpacks these transformations, employing state-of-the-art analytical tools to observe particle dynamics with unparalleled precision.

One landmark facet of her work involves quantifying how aerosols influence cloud formation and precipitation processes. Clouds are crucial regulators of Earth’s climate, and even subtle changes in aerosol concentrations can alter cloud reflectivity and lifespan. By combining field data with innovative models, Professor Cheng has elucidated the pathways through which aerosols modulate cloud microphysics, advancing understanding that is critical for refining climate projections.

Professor Cheng’s approach also integrates insights from Earth system chemistry—a discipline that examines biogeochemical cycles and atmospheric interactions. This broad perspective equips her research with the ability to assess aerosol impacts not just on climate, but on ecosystems and human health. Her findings reveal feedback mechanisms whereby aerosols influence atmospheric chemistry, which in turn affects aerosol properties, fostering a dynamic interplay that shapes environmental outcomes.

The award ceremony celebrating Professor Cheng’s Copernicus Medal will be held during the European Geosciences Union (EGU) General Assembly on Tuesday, April 29, 2025, at the Austria Center Vienna. The event will feature a laudation by Professor Ulrich Pöschl and a medal lecture delivered by Professor Cheng herself. Open to all assembly participants, this gathering promises a vibrant forum to showcase frontier aerosol research.

This recognition from the Copernicus Gesellschaft e.V., a nonprofit society founded to promote geo- and space science collaboration, highlights the transformative nature of Professor Cheng’s work. Since its inception at the Max Planck Institute for Aeronomy, the society has honored outstanding scientists who combine ingenuity with impactful research; Professor Cheng exemplifies this ideal through her integrative and innovative endeavors.

The trajectory of aerosol science has critical implications for policy and societal resilience to climate change. Professor Cheng’s research offers vital guidance for mitigating air pollution and anticipating future environmental shifts. By deepening scientific understanding, her work enables more informed decisions as societies worldwide contend with the intertwined challenges of atmospheric health and global warming.

Professor Yafang Cheng’s outstanding career and scientific contributions vividly illustrate the power of interdisciplinary research in confronting complex environmental problems. Her visionary synthesis of experimentation, observation, and modeling not only advances atmospheric aerosol science but also catalyzes global scientific collaboration. The 2025 Copernicus Medal duly honors her exceptional role in forging new frontiers of knowledge about our planet’s delicate atmospheric balance.

Subject of Research: Atmospheric Aerosols and Their Role in Earth System Chemistry and Climate Change

Article Title: Professor Yafang Cheng Receives the 2025 Copernicus Medal for Breakthrough Advances in Aerosol Science

News Publication Date: (Not provided in the text; presumed 2025)

Web References: None provided

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Keywords

Atmospheric aerosols, Earth system chemistry, aerosol-climate interactions, aerosol-cloud interactions, Max Planck Institute for Chemistry, Copernicus Medal, Anthropocene, climate change, aerosol transformation, field measurements, laboratory experiments, aerosol modeling, international scientific collaboration