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Organic Composition of Aerosol Particles over the Southern Ocean by STXM-NEXAFS
LYNN RUSSELL, Georges Saliba, Kevin Sanchez, Cynthia Twohy, Greg Roberts, Savannah Lewis, Jeramy Dedrick, Christina McCluskey, Kathryn Moore, Paul DeMott, Cynthia Twohy, Scripps Institution of Oceanography
Abstract Number: 165
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
The OM fraction of the submicron marine aerosol has been linked to cloud properties. Very few measurements exist of the organic composition and contribution to cloud condensation nuclei (CCN) over the Southern Ocean. Airborne and shipboard samples of particles, cloud residuals, and ice nucleating particles were collected to measure organic composition during the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) by scanning transmission X-ray microscope (STXM) with near edge X-ray absorption fine structure (NEXAFS) for particles 0.25–1.75 µm diameter. Organic functional groups from STXM-NEXAFS microscopy indicate that the majority of particles between 0.25 and 1.75 µm diameter with detectable organic components were consistent with marine organic signatures associated with sea spray particles. Specifically, 73 out of the 96 particles analyzed by STXM-NEXAFS were consistent with sea spray organic components with and without a salt core. These particles were characterized by absorption in the alkyl, carbonyl, carboxylic carbonyl, carbonate, and potassium regions. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDS) analysis of a subset of the particles analyzed with STXM-NEXAFS confirmed the sea spray origin for the majority of the particles between 0.25 – 1.75 µm diameter sampled over the Southern Ocean. Ice nucleating particles sampled by immersion freezing <-27°C were also largely consistent with sea salt and sea spray organic functional groups, although 2 of 33 particles were consistent with long-range transport of particles from continental sources.