The chemical composition and size of individual particles derived from combustion products of several species found in Southern California were obtained using aerosol timeof-flight mass spectrometry. The major inorganic species observed in >90% of all biomass burning particles is potassium, indicated by the atomic ion, as well as clusters containing chloride, nitrate, and sulfate ions in the mass spectra. By obtaining positive and negative ion mass spectra it is possible to identify distinct chemical marker combinations in particles resulting from the burning of plant species, which in turn allows for differentiation from particles produced from other combustion sources such as vehicle emissions. Using these markers, particles derived from biomass burning were identified in ambient aerosol samples.

[1] In August 1999 an intensive field campaign was conducted in Atlanta, Georgia, focusing on the characterization of urban particulate matter. During the study an aerosol time-of-flight mass spectrometer (ATOFMS) was used to measure continuously the aerodynamic size and chemical composition of individual particles in the fine fraction (0.2-2.5 mm) of the atmospheric aerosol. The inorganic and organic components of the particles were analyzed using laser desorption ionization time-of-flight mass spectrometry, generating positive and/or negative ion mass spectra. Here an overview of the ATOFMS results is presented with respect to the major species detected, including sodium, carbon (EC, OC, EC/OC), dust (Li, Na, Al, K, Ca, Fe), sulfate, nitrate, and ammonium. As described, many of the dust particle types have similar composition to those observed in ATOFMS coal source characterization studies. The ion signals, size distributions, and temporal evolution (30-60 min resolution) of the different particle types are described. The complexity of the Atlanta aerosol is shown here on an individual particle basis, demonstrating how single particle data obtained with ATOFMS can be used to gain unique insights into the mixing state of urban aerosols. The second paper in this two part series focuses on the scaling procedures used for converting the unscaled ATOFMS data presented in this paper into atmospherically representative number concentrations [Wenzel et al., 2002].

Aerosol time-of-flight mass spectrometry (ATOFMS) allows for simultaneous determination of the aerodynamic particle size and chemical composition of individual particles in real time. Polydisperse particles originating from July 4, 1995, fireworks displays were monitored using ATOFMS over a 4-day period. Fireworks particles were identified by ion combinations in the single-particle mass spectra of potassium, aluminum, magnesium, barium, and lead and grouped into chemically specific categories. The relative number of ambient fireworks particles peaked on the morning of July 5, 1995, with representative particles being detected as late as July 19, 1995. The mass spectra of the detected particles are indicative of the original chemical composition of typical fireworks mixtures. This study demonstrates the ability of ATOFMS to serve as a real-time monitor of aerosols in the atmosphere, capable of detecting and tracking aerosol particles of a specific size and chemical composition from a particular source over time.

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