ANTHROPOGENIC VS LITHOGENIC ORIGINS OF TRACE-ELEMENTS (AS, CD, PB, RB, SB, SC, SN, ZN) IN WATER COLUMN PARTICLES - NORTHWESTERN MEDITERRANEAN-SEA

The distribution of heavy metal was analyzed in water column particles collected in autumn (October 1985) and spring (March 1986) by two series of sediment traps from a mooring located in the northeastern Mediterranean Sea continental slope. Four traps were set, at 50, 100, 300, 600 m depths on the mooring in 645 m deep water in the Lacaze-Duthier canyon. The total metal concentrations were determined by ICP-MS. Results show that Rb and Sc contents display typical shale values. As, Cd, Pb, Sb, Zn, (normalized to Sc) display high enrichment factors (up to 50) over shale compositions. Distinctive temporal variability as well as the respective contributions of local (Tet, Aude) and remote (Rhone) rivers and Sahara-derived aerosols have been identified. Fluxes of most elements observed in the upper 100 m can be attributed to atmospheric fluxes. In the deepest traps (300 and 600 m) these fluxes are, however, mostly dominated by riverine particles advected from the continental shelf. Most of the trace-element enrichments are more likely to be related to the anthropogenic input, rather than to biological cycling. Isotopic composition of lead determined by ICP-MS enabled to evaluate that the proportion of anthropogenic lead derived from European gasoline consumption ranged between 50 and 100%.