Composition and oxidation state of sulfur in atmospheric particulate matter

• Published in: Atmospheric chemistry and physics 2016-10, Vol.16 (21), p.13389-13398
• Main Authors: Longo, Amelia F, Vine, David J, King, Laura E, Oakes, Michelle, Weber, Rodney J, Huey, Lewis Gregory, Russell, Armistead G, Ingall, Ellery D
• Format: Article
• Language: English
• Subjects: Aerosol particles; Aerosols; Air pollution; Ammonium; Ammonium compounds; Ammonium salts; Ammonium sulfate; Analytical methods; Atmospheric aerosols; Atmospheric particulate matter; Atmospheric particulates; Atmospheric transport; Azotobacter; Bacteria; Biomass; Biomass burning; Burning; Cellulose acetate; Coal-fired power plants; Combustion; Composition; Diesel fuels; Emissions; Fire stations; Fluorescence; Fluorescence spectroscopy; Fly ash; Gasoline; Heavy metals; Industrial plant emissions; Metal sulfates; Metals; Microscopy; Outdoor air quality; Oxidation; Oxidation-reduction reactions; Parks & recreation areas; Particulate emissions; Particulate matter; Particulate matter emissions; Particulate matter sources; Soil; Speciation; Spectroscopy; Sulfates; Sulfur; Sulphates; Sulphur; Suspended particulate matter; Valence; Volcanic aerosols; Volcanic ash; Volcanic soils; X rays; X-ray fluorescence; X-ray spectroscopy
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-16-13389-2016

The chemical and physical speciation of atmospheric sulfur was investigated in ambient aerosol samples using a combination of sulfur near-edge x-ray fluorescence spectroscopy (S-NEXFS) and X-ray fluorescence (XRF) microscopy. These techniques were used to determine the composition and oxidation state of sulfur in common primary emission sources and ambient particulate matter collected from the greater Atlanta area. Ambient particulate matter samples contained two oxidation states: S0 and S+VI. Ninety-five percent of the individual aerosol particles (> 1 µm) analyzed contain S0. Linear combination fitting revealed that S+VI in ambient aerosol was dominated by ammonium sulfate as well as metal sulfates. The finding of metal sulfates provides further evidence for acidic reactions that solubilize metals, such as iron, during atmospheric transport. Emission sources, including biomass burning, coal fly ash, gasoline, diesel, volcanic ash, and aerosolized Atlanta soil, and the commercially available bacterium Bacillus subtilis, contained only S+VI. A commercially available Azotobacter vinelandii sample contained approximately equal proportions of S0 and S+VI. S0 in individual aerosol particles most likely originates from primary emission sources, such as aerosolized bacteria or incomplete combustion.