Chemical components of single particles measured with Particle Analysis by Laser Mass Spectrometry (PALMS) during the Atlanta SuperSite Project: Focus on organic/sulfate, lead, soot, and mineral particles

[1] Using a Particle Analysis by Laser Mass Spectrometery (PALMS) instrument, we have measured the chemical components of 0.35-2.5 mum in aerodynamic diameter aerosols during the Atlanta SuperSite Project in August 1999. During the whole campaign period, over a half million single-particle mass spectra were obtained, and about 380, 000 spectra were selected for our data analysis. This paper describes the results for organic/sulfate, lead, soot, and mineral dust particles. The most common feature of the Atlanta single particles was the internal mixture of organic compounds and sulfate: 70-99% of the total spectra contained ions characteristic of organic species, and 90-98% contained sulfate ions. These organic/sulfate particles often contained other chemical components such as nitrate, ammonium, halogens, metals, soot/hydrocarbons, and aluminosilicates. Various metals and metal oxides were also observed in Atlanta particles, including Li, B, Na, Mg, K, Ca, Fe, Cu, Zn, V, Sn, and Pb. In particular, small amounts of lead were observed in nearly half of the mass spectra with high signal-to-noise ratio. Many soot/hydrocarbon particles in Atlanta had water-soluble species such as sulfate, nitrate, and oxidized organic components in addition to metals. Mineral particles were detected as large aluminosilicates that also often contained sulfate and nitrate. More than 50 different elements were observed in single particles in Atlanta, which might be an issue for human health effects. Many aerosol components were not strongly dependent on wind direction, indicating that these aerosols were characteristic of the metropolitan area. The mass spectra observed in Atlanta were further compared with our previous results from Idaho Hill, Colorado (relatively remote continental air). These combined results show that the internal mixture of organic components and sulfate can be a general characteristic of tropospheric aerosols in the continental region.