MULTIELEMENTAL COMPOSITION AND SOURCES OF THE HIGH ARCTIC ATMOSPHERICAEROSOL DURING SUMMER AND AUTUMN

During the International Arctic Ocean Expedition 1991 (IAOE-91), total (i.e., < 10 mu m equivalent aerodynamic diameter (EAD)) and size-frac tionated aerosol samples were collected using single filters, slacked filters and cascade impactors. The samples were analyzed for the parti culate mass (PM) and up to about 50 particulate species and elements b y gravimetry, instrumental multi-elemental analysis techniques and ion chromatography. The results from parallel samples, taken with the dif ferent devices and analyzed by independent techniques, were intercompa red. In the samples collected over open waters (ocean subset), the med ian total ( < 10 mu m EAD) concentrations of non-sea-salt S (nss-S) an d Na were 124 and 490 ng/m(3), respectively, but these medians were re duced to 25 and 20 ng/m(3) in the samples collected in the pack ice co vered 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 concentrat ions were observed for PM and the various particulate species in the p ack ice subset, but the levels were quite similar to those obtained fo r background samples from the Ymer-80 expedition. With the exception o f elemental carbon, S and I, all species and elements measured, includ ing the typical anthropogenic metals (e.g., Zn, As, and Sb), were pred ominantly associated with the coarse ( > 2 mu m EAD) size fraction. Th e highest levels of the anthropogenic metals and of the mineral dust e lements were found in air which in general had not been in contact wit h 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 w hich was influenced by continental river run-of from the Siberian coas t. It is tentatively suggested that the elevated concentrations of bot h those metals and the crustal elements were the result of local mecha nical windblown generation of coarse aerosols from the river effluent materials which were present on or at the surface of the ice. By relat ing the observed atmospheric nss-S levels to 3-dimensional air back tr ajectories, and from intercomparing the nss-S time trend with the tren ds 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 o f the expedition.