Atmospheric Environment 36 (2002) 6041–6049 Analysis of organic and inorganic species on the surface of atmospheric aerosol using time-of-flight secondary ion mass spectrometry (TOF-SIMS) Richard E. Peterson, Bonnie J. Tyler* Department of Chemical and Fuels Engineering, University of Utah, 50 S Central Campus Dr., Room 3290, Salt Lake City, UT 84112, USA Received 28 May 2002; accepted 15 August 2002 Abstract This work explores the utility of time-of-flight static secondary-ion mass spectrometry (TOF-SIMS) for the analysis of the surface organic layer on individual atmospheric aerosol particles. The surface sensitivity and minimal fragmentation available with TOF-SIMS suggest that it can be a powerful tool for the examination of the organic and inorganic species on the surface of individual particles. Cascade impactors were used to collect aerosol from summer 2000 Montana forest fires, winter snowmobile samples in Yellowstone National Park, Hawaiian lava and sea salt, from an Asian Dust event reaching Salt Lake City, Utah in April 2001 and from Salt Lake Valley summer urban aerosol. TOF-SIMS analysis and multivariate statistical techniques combined gave chemical and morphological information about the particles. Surfaces of the aerosol from forest fires, snowmobile exhaust, and sea salt were all dominated by aliphatic hydrocarbons and their amphiphilic derivatives. Each source showed a different organic chemical signature. The extent and composition of the organics layer which typically covers the surface of atmospheric particles are expected to effect all of the surface related aerosol properties such as health effects, the ability of the particle to activate and form cloud droplets, and the aggregation of particles as well as reactions between the particle and gas phase species. r 2002 Published by Elsevier Science Ltd. Keywords: Aerosol; Particle; Surface analysis; TOF-SIMS 1. Introduction The atmospheric aerosol consists of a complex mixture of organic and inorganic compounds. It has important effects on human health, visibility, climate, and precipitation chemistry. X-ray microanalysis has frequently been used to analyze the composition of single particles (Anderson et al., 1992, 1996; Ganor et al., 1998; Pina et al., 2000; Katrinak et al., 1995; Artaxo et al., 1992; Ma et al., 2001), but it is useful only for bulk elemental analysis and cannot be used to study surface chemistry. It offers low sensitivity for light elements (C, O, N) common in particles and so is of limited use in the study of organic compounds. Aerosol laser mass spectrometry is also being used to investigate the chemistry of individual aerosol (Middlebrook et al., 1998; Noble and Prather, 1996; Silva and Prather, 1997) but does not provide information on species enriched at the surface and has limited ability to identify organic species. Dynamic secondary ion mass spectroscopy (SIMS) use for aerosol study was pioneered by N. Klaus at the University of Vienna (Klaus, 1983, 1984a, b, 1985a, b), but as used was not surface sensitive and was destructive of organic species. More recent dynamic SIMS aerosol studies have yielded depth profiles of individual particles (Goschnick et al., 1993, 1994; Bentz et al., 1995a, b). Identification of inorganic salts was achieved, but molecular compound identification has been hampered by the destructive nature of dynamic *Corresponding author. E-mail address: bonniet@eng.utah.edu (B.J. Tyler). 1352-2310/02/$ - see front matter r 2002 Published by Elsevier Science Ltd. PII:S1352-2310(02)00686-6