Abstract
Abstract. We examine the hygroscopic properties of secondary organic aerosol particles generated through the reaction of α-pinene and ozone using a continuous flow reaction chamber. The water activity versus composition relationship is calculated from measurements of growth factors at relative humidities up to 99.6% and from measurements of cloud condensation nuclei activity. The observed relationships are complex, suggesting highly non-ideal behavior for aerosol water contents at relative humidities less than 98%. We present two models that may explain the observed water activity-composition relationship equally well. The first model assumes that the aerosol is a pseudo binary mixture of infinitely water soluble compounds and sparingly soluble compounds that gradually enter the solution as dilution increases. The second model is used to compute the Gibbs free energy of the aerosol-water mixture and shows that the aerosol behaves similarly to what can be expected for single compounds that contain a certain fraction of oxygenated and non-polar functional groups.
Highlights
Nucleation scavenging into water drops, followed by wet deposition, is the most important pathway for removal of fine particles from the atmosphere (Poschl, 2005), and descriptions of nucleation scavenging require accurate knowledge of the hygroscopic properties of the aerosol
A number of recent studies have characterized the hygroscopic properties, including their ability to serve as cloud condensation nuclei (CCN), of secondary organic aerosols (SOA) formed in the laboratory from known biogenic and anthropogenic precursors using a variety of oxidants and reaction conditions
In a companion manuscript (Wex et al, 2009) we present hygroscopic growth factors measured at up to 99.6% relative humidity with the Leipzig Aerosol Cloud Interaction Simulator (LACIS) (Stratmann et al, 2004) and CCN activity measured with a Droplet Measurement Technologies (DMT) continuous flow CCN instrument (Roberts and Nenes, 2005; Lance et al, 2006; Rose et al, 2008)
Summary
Nucleation scavenging into water drops, followed by wet deposition, is the most important pathway for removal of fine particles from the atmosphere (Poschl, 2005), and descriptions of nucleation scavenging require accurate knowledge. Petters et al.: Hygroscopicity of secondary organic aerosols hypothesized explanations, in part because water uptake data for 92%
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
