Particle size distribution and chemistry of late winter Arctic aerosols

Abstract

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 }xm aerodynamic diameter (gmad), 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 gmad and not detected at <0.25 }xmad. Sulfur is enriched in fine particles 0.25-1 gmad but not in coarse; chlorine is depleted in 0.5-1 gmad particles, conforms to sea salt composition >8 gmad, 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 I. tmad and a rough symmetry about the maximum when sulfur is not included, suggesting eolian dust paxticles. Their compositions resemble average crust materials. On these dust paxticles, 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, C1, and several trace metals and the absence of A1. They are present in all size fractions, usually rich in sulfur with the highest concentration in ultrafine paxticles <0.25 I. tmad, 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 I. tmad, suggesting a gas phase origin that may involve both nucleation and surface adsorption.

Biomass burning signatures in the atmosphere of central Greenland

“…Only a minor fraction of the mass of Fe, Ca, and K is located in the submicrometer size range for the background sample W11. This is in agreement with general observations worldwide [Milford and Davidson, 1985], studies in the low Arctic [Li and Winchester, 1990], and previous studies on the Greenland Ice Sheet [Hillarno et al, 1993]. As pointed out previously, these species are mostly from crustal origin and thus located in the coarse mode.…”

“…It is noteworthy that the peak in coarse mode sulfur is closer to the maximum in the surface area distribution of the crustal species. Similar switches in the size distributions of sulfur have been presented for the Arctic aerosol at sea level by Li and Winchester [1990]. This result is expected if sulfate is primarily formed through heterogeneous reaction of SO2 at the particle surface [Kerninen et al, 1998], as opposed to a primary origin in soil particles as calcium sulfate in the coarse fraction [Legrand, 1995].…”

Characterization and transport of aerosols over equatorial eastern Africa

“…Fine-fraction aerosols are commonly accepted to be good indicators of long-range transport [Li and Winchester, 1990;Thurston and Spengler, 1985;Junge, 1979]. In general, coarse aerosols tend to have local origins [Gatebe, 1999;Li and Winchester, 1990;Maenhaut et al, 1996]. An exception is coarse-fraction C1, which has been shown to be a clear indicator of transport from ocean areas .…”

Dimethyl sulfide in the Arctic atmosphere

“…Since previous work by Li and Winchester [1990] had shown that marine biogenic sulfur was a significant fraction of the fine-mode aerosol mass at Barrow in late April 1986, we carried out a third set of field measurements over the Arctic Ocean in April 1992. Table 3 Unfortunately, two of the gold tubes for the "final experiment" samples were damaged and produced no usable results.…”