Characterization of Aerosol Organics by LC-MSn
EMSL Project ID
39493
Abstract
Aerosols contribute to the Earth's radiation balance directly by absorbing and scattering light and indirectly by nucleating cloud droplets which increase planetary albedo. Both effects depend on hygroscopic growth, but the contribution of organics to aerosol hygroscopicity is not well understood, limiting efforts to model those effects. The proposed study addresses several important questions through field measurements, laboratory experiments, and modeling: (1) what are the chemical and physical properties of WSOC?; (2) what is the contribution of water-soluble organic carbon (WSOC) to hygroscopic growth under sub- and super-saturated conditions?; and (3) how well can k-Kohler theory and thermodynamic equilibrium modeling account for observed hydroscopic growth and CCN activity of mixed inorganic and organic aerosols? To answer these questions, aerosol samples will be collected at the Desert Research Institute's high elevation Storm Peak Laboratory (SPL) during summer, 2010. Detailed inorganic and organic composition of aerosol samples collected at SPL will be measured with a variety of state-of-the-art analytical techniques to identify heretofore unspeciated high molecular weight WSOC. Our analysis scheme will determine molar mass, elemental composition, the numbers of key functional groups (particularly -OH and -COOH) that affect water uptake, and S- and N-containing groups using GC-MS, LC-MS, and ultra-high resolution mass spectrometry by Fourier Transform-Ion Cyclotron Resonance MS (FT-ICR MS). To further enhance identification of high molecular weight WSOC, we are requesting that portions of our samples be analyzed using two mass spectrometers at EMSL: 1) Linear Ion Trap Quadrupole (LTQ) Orbitrap MS; and 2) FT-ICR 6 T (Ion Surface Collisions) in collaboration with Drs. Alexander and Julia Laskin. Extracts of these samples and isolated WSOC will be re-aerosolized to directly measure their hygroscopic growth and CCN activity. Measured growth factors and CCN activity will be reconciled using thermodynamic and activation models of increasing sophistication including k-Kohler theory and the extended-AIM model.
Project Details
Project type
Exploratory Research
Start Date
2010-12-01
End Date
2011-12-04
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members