New insights into the behaviour of aerosols from cooking emissions and sea spray reveal that particles may take up more water than previously thought, potentially changing how long the particles remain in the atmosphere.
Research led by the University of Birmingham found pollutants that form nanostructures could absorb substantially more water than simple models have previously suggested. Taking on water means the droplets become heavier and will eventually be removed from the atmosphere when they fall as rain.
The team, also involving researchers from the University of Bath, used facilities at Diamond Light Source, to study the water uptake of oleic acid, a molecule commonly found in emissions from cooking and in spray from the ocean's surface. They used a technique called Small-Angle X-ray Scattering (SAXS) to chart the relationship between the structure inside the particle and both its ability to absorb water and its reactivity.
Working at Diamond's I22 beamline with the I22 team and experts from the Central Laser Facility operated by the Science and Technology Facilities Council at the Rutherford Appleton Laboratory, the team also studied changes in the structures of polluting particles, caused by changes in humidity. They showed that as molecules react with ozone in the atmosphere and break down, they can also reform into different 3-D structures with varying abilities to absorb water and to react with other chemicals.
The findings, published in Atmospheric Chemistry and Physics, suggest these combined effects work to keep oleic acid particles circulating in the atmosphere for longer.
"As we develop our understanding of how these particles behave in the atmosphere, we will be able to design more sophisticated strategies for the control of air pollution," said lead researcher
Professor Christian Pfrang. "For example, protecting harmful emissions from degrading in the atmosphere could allow them to travel and disperse further through the atmosphere, thus substantially increasing the pollutant's reach."
He added: "Our results show that aerosols exist in a really dynamic state, with complex structures being formed as well as being destroyed. Each of these states allows polluting molecules to linger in the atmosphere for longer. To reduce exposure to pollutants from cooking, people should consider making more use of extractor fans and ensuring that kitchens are well ventilated to allow aerosol particles to escape rapidly."