Particle size distribution and chemistry of late winter Arctic aerosols


  • Shao-Meng Li,

  • John W. Winchester


Mass size distributions of element concentrations in Arctic aerosols at Barrow, Alaska, were measured from March 16 to May 6, 1986, and their correlations were examined statistically by absolute principal component analysis. In eight particle size fractions from <0.25 to >16 μm aerodynamic diameter (μmad), from eight-stage cascade impactor sampling and proton-induced X-ray emission (PIXE) analysis, four types of aerosol components were resolved. One, resembling sea salt in composition, shows a maximum mass at 2–4 μmad and not detected at <0.25 μmad. Sulfur is enriched in fine particles 0.25–1 μmad but not in coarse; chlorine is depleted in 0.5–1 μmad particles, conforms to sea salt composition >8 μmad, but is about 50% enriched in other fine and coarse fractions, suggesting gas-particle chemical interactions during aerosol aging. The sea salt aerosols appear only in a few elevated concentration periods, with transport likely from open ocean areas. Dust components are found in all size fractions, with a maximum concentration at 1–2 μmad and a rough symmetry about the maximum when sulfur is not included, suggesting eolian dust particles. Their compositions resemble average crust materials. On these dust particles, sulfur contents show a linear relationship with surface areas, suggesting uptake of gaseous sulfur compounds. Carbonaceous fuel combustion pollutants are indicated by the presence of Si, Cl, and several trace metals and the absence of Al. They are present in all size fractions, usually rich in sulfur with the highest concentration in ultrafine particles <0.25 μmad, strongly suggesting a gas phase origin and consistent with condensation of chloride salt and SiO vapors formed during coal or other fuel combustion. Bromine-sulfur components are in every size fraction and contain most of the measured bromine, greatly in excess of sea salt Br. The greatest mass is at <0.25 μmad, suggesting a gas phase origin that may involve both nucleation and surface adsorption.