Multi-elemental composition and sources of the high Arctic atmospheric aerosol during summer and autumn

Abstract

During the International Arctic Ocean Expedition 1991 (IAOE-91), total (i.e., < 10 μm equivalent aerodynamic diameter (EAD)) and size-fractionated aerosol samples were collected using single filters, stacked filters and cascade impactors. The samples were analyzed for the particulate mass (PM) and up to about 50 particulate species and elements by gravimetry, instrumental multi-elemental analysis techniques and ion chromatography. The results from parallel samples, taken with the different devices and analyzed by independent techniques, were intercompared. In the samples collected over open waters (ocean subset), the median total (< 10 μm EAD) concentrations of non-sea-salt S (nss-S) and Na were 124 and 490 ng/m³, respectively, but these medians were reduced to 25 and 20 ng/m³ in the samples collected in the pack ice covered high Arctic (pack ice subset). For the mineral dust elements and anthropogenic metals, however, the levels tended to be higher in the pack ice subset than in the ocean subset. Overall, very low concentrations were observed for PM and the various particulate species in the pack ice subset, but the levels were quite similar to those obtained for background samples from the Ymer-80 expedition. With the exception of elemental carbon, S and I, all species and elements measured, including the typical anthropogenic metals (e.g., Zn, As, and Sb), were predominantly associated with the coarse (> 2, μm EAD) size fraction. The highest levels of the anthropogenic metals and of the mineral dust elements were found in air which in general had not been in contact with large continental or anthropogenic source regions during the last 5 or even 10 days prior to its arrival, and in an area of the pack ice which was influenced by continental river run-off from the Siberian coast. It is tentatively suggested that the elevated concentrations of both those metals and the crustal elements were the result of local mechanical windblown generation of coarse aerosols from the river effluent materials which were present on or at the surface of the ice. By relating the observed atmospheric nss-S levels to 3-dimensional air back trajectories, and from intercomparing the nss-S time trend with the trends of various other particulate species, it was concluded that the nss-S was mainly from anthropogenic origin (transported through the free troposphere) near the end of the IAOE-91, but that the marine biogenic sulfur source must have dominated during the first month and a half of the expedition. DOI: 10.1034/j.1600-0889.1996.t01-1-00011.x