Dissolved Pb and Pb isotopes in the North Atlantic from the GEOVIDE transect (GEOTRACES GA-01) and their decadal evolution
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Author(s)
Wu, Jingfeng
Planquette, Hélène
Shelley, Rachel
Boutorh, Julia
Cheize, Marie
Contreira, Leonardo
Menzel Barraqueta, Jan-Lukas
Lacan, François
Sarthou, Géraldine
Zurbrick, Cheryl M
Date Issued
August 2018
Journal
Biogeosciences
Publisher
Copernicus GmbH/European Geosciences Union
Citation
Zurbrick, Cheryl M. et al. “Dissolved Pb and Pb Isotopes in the North Atlantic from the GEOVIDE Transect (GEOTRACES GA-01) and Their Decadal Evolution.” Biogeosciences 15, 16 (August 2018): 4995–5014 © 2018 Author(s)
Version
Final published version
Abstract
During the 2014 GEOVIDE transect, seawater samples were collected for dissolved Pb and Pb isotope analysis. These samples provide a high-resolution snapshot of the source regions for the present Pb distribution in the North Atlantic Ocean. Some of these stations were previously occupied for Pb from as early as 1981, and we compare the 2014 data with these older data, some of which are reported here for the first time. Lead concentrations were highest in subsurface Mediterranean Water (MW) near the coast of Portugal, which agrees well with other recent observations by the US GEOTRACES program (Noble et al., 2015). The recently formed Labrador Sea Water (LSW) between Greenland and Nova Scotia is much lower in Pb concentration than the older LSW found in the West European Basin due to decreases in Pb emissions into the atmosphere during the past 20 years. Comparison of North Atlantic data from 1989 to 2014 shows decreasing Pb concentrations consistent with decreased anthropogenic inputs, active scavenging, and advection/convection. Although the isotopic composition of northern North Atlantic seawater appears more homogenous compared to previous decades, a clear spatiotemporal trend in isotope ratios is evident over the past 15 years and implies that small changes to atmospheric Pb emissions continue. Emissions data indicate that the relative proportions of US and European Pb sources to the ocean have been relatively uniform during the past 2 decades, while aerosol data may suggest a greater relative proportion of natural mineral Pb. Using our measurements in conjunction with emissions inventories, we support the findings of previous atmospheric analyses that a significant portion of the Pb deposited to the ocean in 2014 was natural, although it is obscured by the much greater solubility of anthropogenic aerosols over natural ones.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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Creative Commons Attribution 4.0 International License
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DOI of Published Version
https://doi.org/10.5194/bg-15-4995-2018
