New research from Purdue University is demonstrating how organic aerosol molecules can influence each other's behavior in ways that existing atmospheric models do not fully capture.
A team led by Alexander Laskin, professor in the James Tarpo Jr. and Margaret Tarpo Department of Chemistry , recently discovered that neighboring molecules in aerosol mixtures tend to "hold on" to each other, dramatically reducing the time it takes for them to evaporate and escape from the atmosphere.
Existing atmospheric models estimate evaporation based on an individual chemical's volatility — how easily it escapes from the air — rather than how they actually exist, surrounded by hundreds of other molecules.
Using a novel mass spectrometry technique developed in Laskin's lab, the research team tracked the behavior of over 1,500 individual chemical species across 33 complex mixtures representative of real biomass-burning smoke and urban haze. Across this massive dataset, the pattern was clear: The surrounding molecular neighborhood, rather than a chemical's intrinsic properties, often dictates how easily it escapes.
To illustrate this "matrix effect," Laskin cites how scents cling to different types of materials.
"Spray perfume onto a glass plate and the scent disappears quickly. Spray the same perfume onto a thick wool sweater and the smell lingers for days because the fabric traps the fragrance molecules," Laskin said. "An aerosol mixture acts like the wool sweater, holding molecules much more strongly than if they were alone."
When neighboring molecules hold on to each other, evaporation slows and creates a volatility suppression of three to five orders of magnitude degree, which Laskin identified as "unexpectedly large."
"As a result, current models often assume smoke disappears too quickly and therefore underestimate how long it remains in the atmosphere," Laskin said.
By collaborating with the Weizmann Institute of Science to integrate explainable machine learning and the Department of Energy's Pacific Northwest National Laboratory to run WRF-Chem atmospheric models, the team proved that these findings significantly increase predicted aerosol persistence, smoke transport and cloud formation.
Ultimately, this research answers vital real-world questions: "How long does wildfire smoke stay in the air? Where will it travel? And how will it affect our health, weather and climate?"
According to Laskin, "This research lays the foundation for a new generation of machine learning models that can predict the volatility of complex environmental mixtures by accounting for interactions among thousands of molecules rather than treating each compound independently."
Looking forward, the team aims to build machine learning models that account for interactions among thousands of molecules simultaneously, providing a stronger foundation to improve air-quality forecasts, assess public health risks and guide environmental mitigation policies.
Laskin's team consisted of Qiaorong Xie, a postdoctoral researcher who executed the study, along with graduate students Abigail Smith, Sara Botero Carrizosa and Steven Sharpe who contributed to data acquisition and assisted with dataset curation.
Related publications:
Sharpe, Y. Li, S. Benjemina, F. Rivera-Adorno, T. Olayemi, J. Ese, X. Shen, M. Fraund, R. Moffet, N. N. Lata, Z. Chen, S. China, M. Marcus, J. Dykema, F. Keutsch, D. Cziczo and A. Laskin, "Chemical imaging of individual atmospheric particles present in the summer stratosphere," Environmental Science: Atmospheres 6, 47-60 (2026). DOI: 10.1039/D5EA00127G
Xie, E. Windwer, I. S. Morton, K. E. Lavin, E. R. Halpern, D. Nissenbaum, S. A. Nizkorodov, Y. Rudich and A. Laskin, "Molecular characterization of composition and volatility of ambient organic aerosol sampled by a UAV-mounted portable aethalometer," Analytical Chemistry 97, 17743-17751 (2025). DOI: 10.1021/acs.analchem.5c03027.
A. Rivera-Adorno, J. M. Tomlin, N. N. Lata, L. Azzarello, R. A. Washenfelder, A. Franchin, A. Middlebrook, S. China, S. Brown, C. J. Young, M. Fraund, R. Moffett and A. Laskin, "Chemical imaging of atmospheric biomass burning particles from North American wildfires," ACS ES&T Air 2(4), 508-521 (2025). DOI: 10.1021/acsestair.4c00242.
About Purdue Chemistry
The James Tarpo Jr. and Margaret Tarpo Department of Chemistry is internationally acclaimed for its excellence in chemical education and innovation, boasting two Nobel laureates in organic chemistry, the No. 1-ranked analytical chemistry program and a highly successful drug discovery initiative that has generated hundreds of millions of dollars in royalties. Learn more about chem.purdue.edu .
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The Department of Earth, Atmospheric, and Planetary Sciences (EAPS) combines four of Purdue's most interdisciplinary programs: geology and geophysics, environmental sciences, atmospheric sciences, and planetary sciences. EAPS conducts world-class research; educates undergraduate and graduate students; and provides our college, university, state and country with the information necessary to understand the world and universe around us. Our research is globally recognized; our students are highly valued by graduate schools and employers; and our alumni continue to make significant contributions in academia, industry, and federal and state government.
