Decline of the anthropogenic lead imprint to the ocean confirmed by data from the South West Atlantic Ocean

29 March 2023

Olivelli and co-authors (2023, see reference below) present total dissolvable lead (Pb) concentrations and isotope compositions for 23 surface waters collected in 2011 along a latitudinal transect offshore of the South American coast from Punta Arenas to the Equator (Leg 3 of the Dutch GEOTRACES GA02 section). They reveal that the mean Pb concentrations in the surface waters of the western South Atlantic Ocean decreased by 34 % between the 1990s and 2011. Pb isotope compositions also show a shift towards a more natural Pb isotope signal: 2011-samples show that natural Pb sources contributed 36 ± 6 % of the Pb present in western South Atlantic surface waters, while it was 24 ± 4 % in 1996.

As for the preceding work of the same team in the North Atlantic Ocean (Bridgestock and al, 2016 – read the science highlight here) these results evidence the positive effect of environmental and health policies that banned the use of leaded gasoline in South America since the 1990s.

**Figure:** Top panel: Map of sampling locations (triangles) along GEOTRACES GA02 Leg 3, and surface currents (green arrows) in South Atlantic Ocean. Bottom panel: three-isotope plot showing the Pb isotope composition of the samples analysed in this study (triangles), historical samples (circles) and potential sources of Pb from Africa and South America (coloured fields). The mixing envelope between the inferred anthropogenic and natural endmembers shows that anthropogenic Pb is still predominant, but there is relatively more natural Pb in the 2011-samples than in those from 1996.

References:

Olivelli, A., Murphy, K., Bridgestock, L., Wilson, D. J., Rijkenberg, M., Middag, R., Weiss, D. J., van de Flierdt, T., & Rehkämper, M. (2023). Decline of anthropogenic lead in South Atlantic Ocean surface waters from 1990 to 2011: New constraints from concentration and isotope data. Marine Pollution Bulletin, 189, 114798. Access the paper: 10.1016/j.marpolbul.2023.114798

Bridgestock, L., van de Flierdt, T., Rehkämper, M., Paul, M., Middag, R., Milne, A., Lohan, M.C., Baker, A.R., Chance, R.,, Khondoker, R., Strekopytov, S., Humphreys-Williams, E., Achterberg, E.P., Rijkenberg, M.J.A., Gerringa, L. J.A., de Baar, H. J. W. (2016). Return of naturally sourced Pb to Atlantic surface waters. Nature Communications, 7, 12921. Access the paper:10.1038/ncomms12921

View the short minute video: Lead, Humans and Oceans (in YouTube or YouKu) to learn how scientists have found that lead pollution in the marine environment has been reduced…

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