Temperature effect on physical and chemical properties of secondary organic aerosol from m-xylene photooxidation

Abstract

The chemical and physical differences of secondary organic aerosol (SOA) formed at select isothermal temperatures (278 K, 300 K, and 313 K) are explored with respect to density, particle volatility, particle hygroscopicity, and elemental chemical composition. A transition point in SOA density, volatility, hygroscopicity and elemental composition is observed near 290-292K as SOA within an environmental chamber is heated from 278K to 313 K, indicating the presence of a thermally labile compound. No such transition points are observed for SOA produced at 313K or 300K and subsequently cooled to 278 K. The SOA formed at the lowest temperatures (278 K) is more than double the SOA formed at 313 K. SOA formed at 278K is less hydrophilic and oxygenated while more volatile and dense than SOA formed at 300K or 313 K. The properties of SOA formed at 300K and 313K when reduced to 278K did not match the properties of SOA initially formed at 278 K. This study demonstrates that it is insufficient to utilize the enthalpy of vaporization when predicting SOA temperature dependence. © 2010 Author(s).