Aerosol time‐of‐flight mass spectrometry during the Atlanta Supersite Experiment: 1. Measurements

Abstract

[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].

Comparison of elemental and black carbon measurements during normal and heavy haze periods: implications for research

“…Fig. 4 Temporal variations in EC and BC Particles are considered "aged" when a high percentage of secondary species is formed (Liu et al 2003;Yang et al 2011); aged carbonaceous aerosols become more internally mixed in, e.g., a shell-core structure with other species. For example, Yang et al (2011) observed that most submicron carbonaceous aerosols were internally mixed with ammonium nitrate and secondary organic compounds during the HH episode of Shanghai winter.…”

Single particle analysis of amines in ambient aerosol in Shanghai

“…Particles containing amines were identified by the mass spectrometric marker of alkylamines at m/z þ86 [NCH 2 (C 2 H 5 ) 2 þ ] [17] with a threshold of an absolute peak area larger than 100 and a relative peak area greater than 0.05. Other aerosol time-of-flight mass spectrometry markers used were m/z þ18 [NH 4 þ ] (absolute peak area greater than 30), [49] À97 [HSO 4 À ] (absolute peak area greater than 100) [49] and À195 [H(HSO 4 ) 2 À ] (absolute peak area greater than 30), indicative of ammonium salts, sulfate compounds and particle acidity index [44] respectively. Particles were clustered into six major types using the ART-2a (adaptive resonance theory) [50] method with a vigilance factor of 0.7, a learning rate of 0.05 and 20 iterations based on the similarities of mass-to-charge ratio and peak intensity.…”

Enhanced trimethylamine-containing particles during fog events detected by single particle aerosol mass spectrometry in urban Guangzhou, China

“…The peak lists were subsequently imported into MATLAB 7.1 (The Mathworks Inc.) and analyzed using YAADA 2.1 (www.yaada.org), a MATLABbased software toolkit used for processing the single-particle mass spectral data. Peak identification described in this paper corresponds to the most probable assignments for each specific mass-to-charge ratio (m/z), and more details can be found in the published work by Liu et al (2003) and Murphy and Thomson (1997a, b).…”