LEAD IN ATLANTIC SURFACE WATERS AS A TRACER FOR ATMOSPHERIC INPUT

The present report provides information about lead concentrations in Atlantic surface waters over a wide geographical range. Differential pulse anodic stripping voltammetry (DPASV) was applied for the analysis of lead in surface water of the Atlantic Ocean. Sampling on board of the research vessel Polarstern was performed from the bow boom of the ship but also with a newly installed snorkel system which allowed continuous sampletaking. In both cases special precautions were taken in order to avoid contamination by the ship. A limited number of samples could immediately be measured aboard Polarstern in a newly constructed clean room laboratory container. A part of the samples had to be irradiated before the voltammetric measurement. In 1989 lead concentrations in the North Atlantic between 22-degrees-N and 46-degrees-N continuously increased from 42.5 pmol/kg up to 147 pmol/kg. The comparison with results from a cruise in 1981 shows that the lead concentration in the eastern North Atlantic has diminished by more than 50%. A similar trend is documented for the consumption of alkyl leaded gasoline in the United States of America. Seawater samples from a cruise in 1990 exhibited a very low background concentration of 6.1 - 14 pmol/kg Pb in the middle Atlantic, while higher values were measured in the Intertropical Convergence Zone (ITCZ). In a certain area of the Atlantic Ocean lead has been identified as a tracer for terrigenous input, in another area, however, as a transient tracer for anthropogenic input. This demonstrates that atmospheric input of lead into the surface water of the Atlantic can have different origins.