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October 5, 2007

Atmospheric Aerosols: A New Challenge for Measuring Organic Compounds
Dr. Lynn Russell
Scripps Institution of Oceanography
UC San Diego

Organic aerosol particles constitute one of the largest uncertainties in quantifying the effects of man-made emissions on the radiative balance of the Earth. Organic composition of aerosol particles collected during recent field projects was measured by Fourier Transform Infrared Spectroscopy (FTIR), Aerosol Mass Spectrometry (AMS), and Near-Edge X-ray Absorption Fine Structure/Scanning Transmission X-ray Microscopy (NEXAFS/STXM) to characterize organic functional group abundance and morphology of atmospheric aerosols. We present a summary of spectra, sizes, and shapes observed in 595 particles that were collected and analyzed between 2000 and 2006. These particles ranged between 0.1 and 12 microns and represent aerosols found in a large range of geographical areas, altitudes, and times. They include samples from seven different field campaigns. At least fourteen different classes of organic particles show different types of spectroscopic signatures. Different particle types are found within the same region while the same particle types are also found in different geographical domains. Particles chemically resembling black carbon from fuel combustion, humic acids from soils, pine ultisol, and secondary or processed organic acids have been identified from functional group abundance and comparison of spectra with those published in the literature.