Asphalt-based materials are almost everywhere in U.S. urban areas, whether they be used for road-paving or roofing applications. A recent Yale study, led by Drew Gentner, associate professor of Chemical and Environmental Engineering, found that asphalt-related materials are a significant source of air pollutants, even days after initial application.
The team of researchers placed asphalt-based materials in controlled chambers that simulated a range of temperature and sunlight conditions typically encountered by asphalt in urban areas. They then recorded and measured the chemical composition of the organic gases emitted using high resolution analytical chemistry.
The results revealed that asphalt produces larger organic compounds that lead to the formation of secondary organic aerosols (SOA), a key component of PM2.5—an air pollutant composed of fine, particulate matter that poses a great public health risk. Additionally, asphalt-related emissions showed a strong dependence on temperature, meaning that asphalt released more harmful chemicals as temperatures rose.
Contributions of traditional combustion-related sources to air pollution have decreased with successful control of sources like motor vehicles or power generation. However, that decrease leads to higher contributions from other anthropogenic sources, such as asphalt. Genter’s research suggests that emissions from asphalt may increase with rising urban temperatures, amplifying asphalt’s impact on urban air quality over time. Genter emphasized that there is still a lot more information to gather in order to make cities more environmentally-friendly. “Asphalt is just one piece of the current-day urban SOA puzzle with motor vehicles and volatile chemical products, like cleaning products or paints, also being major contributors,” Genter said.
Sources:
Khare, P., Machesky, J., Soto, R., He, M., Presto, A. A., & Gentner, D. R. (2020). Asphalt-related emissions are a major missing nontraditional source of secondary organic aerosol precursors. Science advances, 6(36), eabb9785.
McDonald, B. C., De Gouw, J. A., Gilman, J. B., Jathar, S. H., Akherati, A., Cappa, C. D., … & Cui, Y. Y. (2018). Volatile chemical products emerging as largest petrochemical source of urban organic emissions. Science, 359(6377), 760-764.