Use of stable lead isotopes to characterize the sources of anthropogenic lead in North Atlantic surface waters

Stable lead isotopes are used to illustrate the impact of surface water circulation on dissolved lead distribution in North Atlantic surface waters during oligotrophic conditions. Using stable lead isotopic signatures from (1) the Sargasso Sea and (2) direct tropospheric deposition to the North Atlantic, we estimate that 10–40% of the lead accumulated in surface waters of the European Basin is transported from the western North Atlantic by the North Atlantic Current. South of 50°N, lead appears to be primarily distributed by the Subtropical North Atlantic Gyre that extends well beyond the western basins to 30°W in the North African Basin (at 30–40°N). There are different lead isotopic signatures between the subtropical gyre to the Guiana and western Guinea Basins, which suggests that the Inter Tropical Convergence Zone acts as an efficient barrier limiting chemical exchanges between the gyre and the equatorial currents.