Mechanisms of Pb supply and removal in two remote (sub-)polar ocean regions
2019
Today, four decades past peak anthropogenic lead emissions in the 1970s, dissolved lead (DPb) concentrations in the surface ocean remain elevated. To constrain contemporary sources and sinks of DPb, we studied high latitude surface waters of the North Atlantic and the Southern Ocean. We observed high concentrations of surface DPb (46 pmol kg⁻¹) near South Georgia in the Southern Ocean, sourced from glacial flour, while offshore DPb concentrations of 3–9 pmol kg⁻¹ were attributable to aeolian Pb inputs mainly from Patagonia. Dissolved Pb in the North Atlantic (4–29 pmol kg⁻¹) originated from aeolian particles from Northern Hemisphere sources. Extremely low DPb concentrations of <5 pmol kg⁻¹ found in both polar regions were the result of scavenging of DPb onto biogenic particles formed during spatially confined phytoplankton blooms, indicating that changes in phytoplankton abundance may alter the residence time and distribution of DPb in the surface ocean.
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