Aerosols are ubiquitous in the atmosphere. Outdoors they are involved in the climate system via cloud droplet formation. They also contribute to indoor and outdoor air pollution, impacting human health and man-made environmental change.
Aerosols are created indoors by routine tasks like cooking and cleaning. In the Western world, people may spend up to 90% of their time indoors. Therefore, it is essential to comprehend how inside aerosols are treated in addition to outdoor aerosols.
According to research from the University of Birmingham, dangerous compounds frequently found in aerosols, such as those made during cooking and cleaning, can be ‘protected’ in 3D structures made by surfactants, prolonging their time in the atmosphere.
The research was conducted in collaboration with the University of Bath and the Central Laser Facility at the Science and Technology Facilities Council.
Over the past 5–6 years, scientists have accumulated a substantial body of knowledge, starting with an investigation of how one of these surfactants, oleic acid, an everyday cooking and marine emission, forms intricate nanoscale structures and how these affect how oleic acid interacts with other airborne chemicals. Recent studies investigated increasingly complicated surfactant mixtures to determine the effects of various aerosol components found in the air.
The researchers found that by combining laboratory and computational studies, dangerous, reactive materials may be shielded within aerosol particles and beneath highly viscous (honey-like) shells, potentially extending the atmospheric residence times and, consequently, their reach from the emission source of the otherwise short-lived species.
In many experimental studies, scientists found self-organization in particles levitating in the air, thin films on solid surfaces, and floating on water. Using advanced techniques, scientists analyzed these self-organized aerosols by following the structure on the nanoscale with small-angle X-ray scattering and the chemical behavior with Raman microscopy.
Scientists also used newly developed computer models to understand how surfactants may organize themselves in the atmosphere. It was found that surfactants can organize into various 3D structures when combined with other atmospheric aerosol constituents. The compounds’ reactivity is drastically decreased by this self-organization, extending their lifetime. Hazardous compounds may be shielded and have an extended period of survival in the atmosphere if a crust of product material forms on the surface of the particles.
Professor Christian Pfrang from the University of Birmingham, who led the work, said, “Our complex multi-scale experimental studies intimately linked to tailored computational modeling indicate that these surfactant structures may offer an effective shield for harmful chemicals common in aerosols which could persist in the atmosphere for longer and travel much further.”
“For those of us who spend the vast majority of our time indoors, which is most people in the Western world, this should be cause for concern. We know that aerosols contribute to air pollution and can have a negative impact on human health. These findings indicate that we breathe in more harmful chemicals longer than we thought, especially after cooking and cleaning.”
Scientists want to determine how these surfactant arrangements impact the climate and indoor and outdoor air quality.
Journal Reference:
- Adam Milsom, Adam M. Squires, Andrew D. Ward, and Christian Pfrang*. Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies. Accounts of Chemical Research. DOI: 10.1021/acs.accounts.3c00194