title: CCN spectra, hygroscopicity, and droplet activation kinetics of secondary organic aerosol resulting from the 2010 Deepwater Horizon oil spill.
abstract: Secondary organic aerosol (SOA) resulting from the oxidation of organic species emitted by the Deepwater Horizon oil spill were sampled during two survey flights conducted by a National Oceanic and Atmospheric Administration WP-3D aircraft in June 2010. A new technique for fast measurements of cloud condensation nuclei (CCN) supersaturation spectra called Scanning Flow CCN Analysis was deployed for the first time on an airborne platform. Retrieved CCN spectra show that most particles act as CCN above (0.3 ± 0.05)% supersaturation, which increased to (0.4 ± 0.1)% supersaturation for the most organic-rich aerosol sampled. The aerosol hygroscopicity parameter, κ, was inferred from both measurements of CCN activity and from humidified-particle light extinction, and varied from 0.05 to 0.10 within the emissions plumes. However, κ values were lower than expected from chemical composition measurements, indicating a degree of external mixing or size-dependent chemistry, which was reconciled assuming bimodal, size-dependent composition. The CCN droplet effective water uptake coefficient, γ(cond), was inferred from the data using a comprehensive instrument model, and no significant delay in droplet activation kinetics from the presence of organics was observed, despite a large fraction of hydrocarbon-like SOA present in the aerosol.
authors.affiliation: School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Moore
authors.forename: Tomi
authors.initials: T
authors.lastname: Raatikainen
authors.forename: Justin M
authors.initials: JM
authors.lastname: Langridge
authors.forename: Roya
authors.initials: R
authors.lastname: Bahreini
authors.forename: Charles A
authors.initials: CA
authors.lastname: Brock
authors.forename: John S
authors.initials: JS
authors.lastname: Holloway
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Lack
authors.forename: Ann M
authors.initials: AM
authors.lastname: Middlebrook
authors.forename: Anne E
authors.initials: AE
authors.lastname: Perring
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Schwarz
authors.forename: J Ryan
authors.initials: JR
authors.lastname: Spackman
authors.forename: Athanasios
authors.initials: A
authors.lastname: Nenes
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000737:chemistry*; D004784:Environmental Monitoring; D060851:Gulf of America; D007700:Kinetics; D009930:Organic Chemicals / Q000737:chemistry; D059392:Petroleum Pollution; D013057:Spectrum Analysis / Q000379:methods; D017155:Wettability
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D009930:Organic Chemicals