AVS 49th International Symposium
    Advancing Toward Sustainability Topical Conference Tuesday Sessions
       Session AT-TuM

Paper AT-TuM2
Individual Particle TOF-SIMS Imaging Analysis of Aerosol Collected During the April 2001 Asian Dust Event

Tuesday, November 5, 2002, 8:40 am, Room C-210

Session: Aerosols and Climate Change, Growing Energy Demands, and Benign Semiconductor Manufacturing
Presenter: R.E. Peterson, University of Utah
Authors: R.E. Peterson, University of Utah
B.J. Tyler, University of Utah
Correspondent: Click to Email
Time of Flight Secondary Ion Mass Spectroscopy can provide information regarding the surface chemistry, including both organic and inorganic compounds, of individual atmospheric aerosol in the micrometer size range. X-ray analysis has commonly been used to analyze the composition of single particles but has several important limitations. Principally, X-ray analysis cannot be used to study organic compounds in the aerosol, it offers low sensitivity for light elements common in crustal material and it cannot distinguish isotopes. TOF-SIMS has the potential to provide superior performance in these areas. We have developed statistical image processing methods to allow extraction of individual particle spectra from TOF-SIMS images. In mid April 2001 a strong Asian dust event was tracked by satellite across the Pacific Ocean and into the continental United States. While Asian dust deposition is common in Hawaii, strong events characterized by significant visibility degradation have been much less frequently reported in the Rocky Mountain west. Samples were taken during and after the event at the University of Utah in Salt Lake City, Utah. Size segregated samples were collected on aluminum substrates using an 8 stage Graseby-Anderson cascade impactor and total aerosol samples were collected with 47 mm Fluoropore filters. Surface and depth profile analysis of the particles was performed using a Phi Trift I TOF-SIMS instrument. Statistical methods, including PCA, mixture models and neural networks, were used to extract spectra of individual particles from the TOF-SIMS images and to classify particles based on their surface chemistry and depth profiles. Differences in both the chemistry and size distribution of the particles could be seen between the aerosol collected during the Asian dust event and aerosol collected post-event at the University of Utah site.