LEAD AND ALUMINUM IN ATLANTIC SURFACE WATERS (50-DEGREES-N TO 50-DEGREES-S) REFLECTING ANTHROPOGENIC AND NATURAL SOURCES IN THE EOLIAN TRANSPORT

Lead and aluminum were measured with a 40-100 km resolution in surface water on two transects across the Atlantic Ocean. one in May 1990 fro m Cape Town to the North Sea, the other in November 1990 from the Nort h Sea to the Strait of Magellan. Samples were drawn 14 m below surface at normal speed from a 2-m-long snorkel system mounted on the bottom of the ship directly into a clean-room area. In the tropics, both Pb a nd Al show maximum concentrations in the Intertropical Convergence Zon e (ITCZ) correlated with each other and with minimum salinities, indic ating wet deposition as their common source. Even in this area charact erized by large inputs of mineral aerosols, the Pb/Al ratio shows that the major source of soluble lead (>95%) is anthropogenic. At higher l atitudes, Al is low throughout (10-20 nmol/kg), whereas enhanced Pb va lues show the anthropogenic inputs off south Africa, northern Argentin a and especially western Europe. Very low Pb and especially Al concent rations in the upwelling areas associated with die Canary and Benguela currents show that the enhanced biogenic particle fluxes cause an eff icient scavenging of both lithogenic particles known to arrive here by dry deposition. and of the adhering reactive trace metals.