Lead Concentrations and Stable Lead Isotopes in the North Atlantic and Labrador Sea

Dissolved seawater samples collected on the 2014 GEOVIDE (GA01) cruise have been analyzed for lead (Pb). Near-surface Pb concentrations were similar to other recent sampling campaigns (i.e., GEOTRACES GA-03 KN199, KN204), and were substantially lower than in the 1980s and 1990s. Across the entire transect, subsurface profiles were oceanographically consistent and showed a broad subsurface maxima (1000 – 2000m). Stable Pb isotope ratios indicate this elevated Pb was from old North American and European leaded gasoline emissions in the 1970s – 1990s, whereas Pb in surface waters were consistent with more recent inputs from United States industrial Pb (e.g., Pb ores). At a station at 46˚N 20˚W, previous detailed profile data from 1989 and 1999 show that Pb concentrations have decreased at all depths from the surface (115 pmol kg^-1 in 1989; 20 pmol kg^-1 in 2014) down to 2500m. Two other stations near Greenland and Labrador with less detailed profile data from 1999 also show decreases down to at least 2000m. Seawater samples collected near the bottom had elevated Pb concentrations compared with the other deep water samples, possibly due to a flux from seafloor sediments.