The predictions are based on the assumption that the particles are like liquid spheres, whose fluidity allows PAHs to escape. But they don't escape, and one recent advance has helped to pin down why PAHs are remaining stuck in their particle lairs. Zelenyuk and her colleagues at EMSL, DOE's Environmental Molecular Sciences Laboratory at PNNL, developed an ultra-sensitive instrument that can determine the size, composition and shape of individual particles.
Called SPLAT II, the instrument can analyze millions of tiny particles one by one. The ability of this novel instrument to characterize individual particles provides unique insight into their property and evolution.
Using SPLAT II to evaluate laboratory-generated SOA particles from alpha-pinene, the molecule that gives pine trees their piney smell, Zelenyuk has already discovered that SOA particles aren't liquid at all. Her team's recent work revealed they are more like tar -- thick, viscous blobs that are too solid to be liquid and too liquid to be solid.
Armed with this data, Zelenyuk and researchers from Imre Consulting in Richland and the University of Washington in Seattle set out to determine the relation between the SOA particle and the PAHs. Again they used alpha-pinene for the SOA. For the PAH, they used pyrene, a toxic pollutant produced by burning fossil fuels or vegetation such as forests.
They created two kinds of particles. The first kind exemplified the classical SOA: first they produced the particles with alpha-pinene and then coated them with pyrene. The second kind resembled what likely happens in nature: they mixed alpha-pinene and pyrene and let the particles form with both molecules present. Then they sent the particles through SPLAT and watched what happened to them over time.
With the pyrene-coat
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory