First direct determination of the chemical diffusivity and viscosity of secondary organic aerosols
“Results: For the first time, scientists measured the chemical diffusivity and viscosity of atmospheric organic particles, thanks to a new approach from scientists at Pacific Northwest National Laboratory, University of Washington, and Imre Consulting. The team doped atmospherically important organic nanoparticles, known as secondary organic aerosols (SOAs), with tracer molecules and measured their diffusion rate as they slowly worked their way out of the particles. Knowing the diffusion rate, the scientists calculated the particle’s viscosity.
‘Over the past two years, we have shown that long-standing assumptions about the most fundamental properties of SOA particles — phase and volatility — are wrong. Here, for the first time, we quantify chemical diffusivity in SOA particles and show that SOA viscosity is larger — a million times higher than assumed,’ said lead author Dr. Alla Zelenyuk, physical chemist at Pacific Northwest National Laboratory.
Determining the viscosity of tar-like secondary organic aerosols, ubiquitous atmospheric particles, is now possible thanks to a new method developed by scientists at Pacific Northwest National Laboratory, University of Washington, and Imre Consulting.
Why It Matters: Convenient, but unsubstantiated, assumptions have haunted atmospheric scientists studying SOAs for years, making it impossible to model how the particles affect climate and human health. With the development of new approaches and precise characterization instruments, scientists have disproved the common assumption. With this current study, Zelenyuk and her colleagues have given atmospheric modelers and others data that are invaluable for accurately portraying the particles and their effects in different scenarios, such as new regulations.”
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Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy National Laboratories, managed by the Department of Energy’s Office of Science. The main campus of the laboratory is in Richland, Washington.
PNNL scientists conduct basic and applied research and development to strengthen U.S. scientific foundations for fundamental research and innovation; prevent and counter acts of terrorism through applied research in information analysis, cyber security, and the nonproliferation of weapons of mass destruction; increase the U.S. energy capacity and reduce dependence on imported oil; and reduce the effects of human activity on the environment. PNNL has been operated by Battelle Memorial Institute since 1965.
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