TRACE-ELEMENTS IN THE ATMOSPHERE OVER THE NORTH-ATLANTIC

The concentrations of trace elements in aerosol particles from the atm osphere over the North Atlantic Ocean were determined as part of a pro gram designed to characterize the chemical climatology of the region. For these studies, which were part of the Atmosphere-Ocean Chemistry E xperiment (AEROCE), 2 years of samples were collected at Tudor Hill, B ermuda (BTT), and at Ragged Point, Barbados (BAT); and 1 year of sampl es was collected at Mace Head, Ireland (MHT) and at the Izana Observat ory, Tenerife, Canary Islands (IZT). One major component of the aeroso l was atmospheric dust, and the ranking for the median mineral dust co ncentrations as represented by aluminum was BAT > IZT > BTT > MHT. The Al concentrations at BAT, IZT, and BTT ranged over 4 orders of magnit ude, i.e., from 0.001 to 10 mu g m(-3). At MHT the maximum dust concen trations were about a factor of 10 lower than at the other sites, but the lower end of the range in dust concentrations was similar at all s ites. The mineral dust concentrations generally were highest in summer , and the flux of atmospheric dust was dominated by sources in North A frica. The elements showing clear enrichments over the concentrations expected from sea salt or crustal sources were I, Sb, Se, V, and Zn. A t Izana, which is in the free troposphere (elevation similar to 2360 m ), the concentrations of Se and I were much lower than at the boundary layer sites; this difference between sites most likely results from t he marine emissions of these elements. The impact of pollution sources on trace element concentrations was evident at all sites but varied w ith season and location. The concentrations of elements originating fr om pollution sources generally were low at Barbados. Analyses of trace element ratios indicate that there are large-scale differences in the pollution emissions from North America versus those from Europe and A frica. Emissions from pyrometallurgical industries, steel and iron man ufacturing, and possibly biomass burning are more evident in the atmos pheric samples influenced by transport from Europe and Africa.