Nav: Home

Semi-volatile organic compounds diffuse between atmospheric particles

October 24, 2016

Researchers led by Carnegie Mellon University's Neil M. Donahue have shown that semi-volatile organic compounds can readily diffuse into the billions of tiny atmospheric particles that inhabit the air, easily moving among them. The findings, published in the early online edition of the Proceedings of the National Academy of Sciences (PNAS), provide greater understanding into how organic particles behave in the atmosphere.

The air is full of microscopic airborne particles called aerosols. Aerosols can come from natural sources, like fires or sea spray, or they can come from man-made sources, like emissions from cars and power plants. As the aerosol particles travel through the atmosphere, they encounter other particle populations and chemically evolve, resulting in a dense soup of oxidized organic matter. While many atmospheric particles start off too small to influence climate, as they grow their potential to impact climate increases. Understanding how these particles change is crucial to understanding how they affect the environment and human health.

As the particles grow and travel through the atmosphere, they pick up material called secondary organic aerosol (SOA). Much of the SOA consists of semi-volatile organic compounds (SVOCs) that can diffuse into particles--moving from one particle, entering the gas phase, and moving to another particle.

Recently, there has been controversy as to whether or not SVOCs are able to diffuse into "glassy" atmospheric particles. If SVOCs can't diffuse into these particles, they will not condense onto them, which will slow down particle growth rates.

"Our work shows that some particles are kind of crunchy when they are dry -- they are glassy -- but they turn gooey when they get wet; under most conditions, the semi-volatile compounds will diffuse into particles quite easily," said Donahue, the Lord Professor of Chemistry in the Mellon College of Science, and Professor of Chemical Engineering and Engineering and Public Policy in the College of Engineering. Donahue is also a member of Carnegie Mellon University's Center for Atmospheric Particle Studies (CAPS), which is a leader in studying the chemistry of atmospheric particles and has completed groundbreaking studies that are revealing how these atmospheric particles change over time.

In the current study, chemistry doctoral student Qing Ye used single-particle mass spectrometry to see if SVOCs diffused from one group of particles into another, adding to the particles' complexity. Ye looked at two different types of secondary organic aerosols formed by the oxidation of organic gases: alpha-pinene, a molecule given off by pine trees, and toluene, an aromatic hydrocarbon in gasoline that is also often used as a solvent or in the production of industrial materials. She combined two populations of the particles, one of which was isotopically labeled, and measured the populations over time. In the alpha-pinene particles, the isotopes from the labeled particles easily evaporated into the unlabeled particles. The toluene particles also diffused easily, but only if the relative humidity was above 30 percent.

The findings show that SVOCs can travel between atmospheric particles, but the conditions under which they can travel are dependent on the particle's original source.
Other study authors include: Ryan Sullivan and Penglin Ye, and Ellis S. Robinson Carnegie Mellon University; and Xiang Ding, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences.

This research was supported by the National Science Foundation (CHE1412309 and CBET0922643), the Wallace Research Foundation, the US EPA STAR Program, and the Faculty for the Future Fellowship from the Schlumberger Foundation.

Carnegie Mellon University

Related Engineering Articles:

Engineering a new cancer detection tool
E. coli may have potentially harmful effects but scientists in Australia have discovered this bacterium produces a toxin which binds to an unusual sugar that is part of carbohydrate structures present on cells not usually produced by healthy cells.
Engineering heart valves for the many
The Wyss Institute for Biologically Inspired Engineering and the University of Zurich announced today a cross-institutional team effort to generate a functional heart valve replacement with the capacity for repair, regeneration, and growth.
Geosciences-inspired engineering
The Mackenzie Dike Swarm and the roughly 120 other known giant dike swarms located across the planet may also provide useful information about efficient extraction of oil and natural gas in today's modern world.
Engineering success
Academically strong, low-income would-be engineers get the boost they need to complete their undergraduate degrees.
HKU Engineering Professor Ron Hui named a Fellow by the UK Royal Academy of Engineering
Professor Ron Hui, Chair Professor of Power Electronics and Philip Wong Wilson Wong Professor of Electrical Engineering at the University of Hong Kong, has been named a Fellow by the Royal Academy of Engineering, UK, one of the most prestigious national academies.
More Engineering News and Engineering Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...