AEROSOL SILICON AND ASSOCIATED ELEMENTS IN THE ARCTIC HIGH AND MIDTROPOSPHERE

In six aircraft flights of AGASP-II, 2-15 April 1986, from ca. 1300-81 00 m altitude, the most abundant elements measured in size separated a erosol samples were silicon, chlorine, and sulfur. Concentrations were higher than at ground level (G), particularly at highest altitudes (H T, 5600-8100 m, upper troposphere to lower stratosphere) compared to m id troposphere (MT, 1300-4700m), especially for ultrafine particles <0 .0625 mu m aerodynamic diameter. HT and MT median and G average concen trations, mu g m(-3) STP, respectively (1) Si = 3.64, 1.30, 0.092; (2) S = 1.44, 0.265, 0.087; (3) Cl=1.62, 0.36, 0.213. The weight ratio Al /Si was less than half that expected for Earth crust material (0.3), e vidence against fine silicon originating mainly by dispersion of volca nic debris or other eolian dust particles. Instead, pollution from hig h rank (mainly bituminous) coal combustion, which can form SiO vapors from quartz in the ash and fine alkaline aerosol with low Al/Si ratio, is a more likely source of apparently widespread aerosol silicon cont amination of the Arctic atmosphere. Chlorine and sulfur gases may be s cavenged by coarse alkaline dust particles and acidic chlorine and sul fur may be derived from coal combustion processes, thus also accountin g for their high concentrations.