Dr. Lee Tiszenkel and Dr. Shanhu Lee from The University of Alabama in Huntsville (UAH) have made an exciting discovery. Their findings showed strong seasonal differences in new urban particle formation in Houston, Texas. Their study was recently published in Communications Earth & Environment. In particular, it investigates the dynamics of atmospheric ultrafine particles (< 100nm) and underscores the different formation processes occurring in urban hubs in the United States and megacities in China.
The study’s authors point out that ultrafine particles can be detected at diameters as small as 3 nanometers. Their source and igneous process depends on location, tectonic setting, and availability of light, heat, and pressure. This research is tremendously exciting and relevant. This is its first, and furthest reaching, challenge to the use of data from Chinese megacities to assess air quality in U.S. cities, exposing major flaws in that practice.
Understanding Ultrafine Particles
Ultrafine particles add a special twist to this challenge for air quality monitoring. Additionally, they can penetrate deeply into the lungs, increasing their toxicity and making them especially harmful. Dr. Tiszenkel notes, “The knowledge that particles less than 100 nm penetrate deeply into the lungs has been known for a few decades now.” With advancements in detection technology over the last 10 to 15 years, researchers can now better analyze these particles’ chemical compositions and formation processes.
The science surrounding air pollution is rapidly changing. Though gradual, this process has afforded us with a much richer understanding of gas-to-particle conversion, especially in urban, polluted settings. Dr. Tiszenkel elaborates, “Similarly, the knowledge that these ultrafine particles form via gas-to-particle conversion in significantly polluted areas has been known since the 80s or 90s.”
Dr. Tiszenkel taking field research in Houston. He talks about the role of observations of the real world, putting them ahead of lab work. “My previous research was mostly in the lab, where we can very precisely control the kind of environment we want to observe,” he explains. “Results from those experiments are extremely useful for making conclusions about very specific chemical mechanisms.”
Seasonal Variations and Urban Differences
Dr. Tiszenkel and Dr. Lee’s findings reveal that urban air quality is not only a product of human activity but is influenced by natural emissions from green spaces. In U.S. cities like Houston, these factors combine to produce a very different mood than in packed Chinese megacities. “In the United States, the existence of green spaces in and surrounding urban areas means that emissions from trees and other emerging air pollutants emitted from urban human activities form particles by a different mechanism than was found in urban China,” states Dr. Tiszenkel.
The production of ultrafine particles from human activity, including traffic, cooking and industry, and especially residential heating, create a pollution cocktail for the megacities of China. Compared to their counterparts in other advanced economies, American urban contexts are a pretty unique case. The atmospheric chemistry in the U.S. is highly biased toward anthropogenic compounds, dominated by oxidation of anthropogenic precursors from both anthropogenic and natural emission sources.
Dr. Tiszenkel further explains this disparity: “Much of our understanding of particle formation comes from studies conducted in Chinese megacities, so predictions and models of air quality in the urban United States will not be accurate.” This suggests that relying on data from one region to assess another could lead to flawed conclusions regarding public health and environmental policies.
Research Implications and Future Directions
Dr. Tiszenkel and Dr. Lee’s research holds significant implications not just for Houston. This underscores the critical importance of localized studies focused on air quality and particle formation mechanisms in increasingly crowded, chemically diverse urban centers. These researchers are dedicated to continuing to develop their methodologies so that we can better understand atmospheric dynamics at a molecular scale.
“We are the first group in the U.S., to our knowledge, to simultaneously measure size-resolved aerosol concentrations from newly formed particles up to micron sizes, gas-phase precursors and particle-phase chemical composition in-situ,” states Dr. Tiszenkel. Their innovative methodology makes them uniquely suited to make definitive conclusions about new particle formation, while decreasing the number of unknown variables.
“UAH offers a complete set of advanced instruments,” said Dr. Tiszenkel. He feels they are prepared, having developed the science and practice to make significant contributions in this arena. “It was easy to pursue that in Dr. Lee’s lab at UAH where we have one of the most comprehensive instrument suites for understanding atmospheric particle formation and evolution in the country.”