Testament of the efficiency of environmental policies

Human activities, such as the combustion of leaded petrol, emissions from non-ferrous metal smelting, coal combustion and waste incineration constitute major environmental lead (Pb) sources during the past century. This resulted in a considerable increase of anthropogenic Pb in the surface and deep waters of the North Atlantic, large enough to mask the natural lead signal.

Increased usage and then phasing-out of leaded-petrol since the mid-70’s yielded a decrease of this contamination. By measuring lead concentrations and isotopes (excellent tracers of the different sources of lead) along the GEOTRACES sections GA02 and GA06, Bridgestock and his co-workers (2016, see reference below) reveal for the first time that natural lead can be detected again in the surface water of the North Atlantic. Indeed, significant proportions of up to 30–50% of natural Pb, derived from mineral dust, are observed in Atlantic surface waters off the Sahara. This clearly reflects the success of the global effort to reduce anthropogenic Pb emissions.

16 Bridgestockl
Figure: Locations of the surface seawater samples analyzed in this study (left). The brown shaded box shows the area found to contain the highest amounts of naturally sourced lead (Pb) resulting from the deposition of North African mineral dust. Significant inputs of natural Pb can be identified by higher Pb isotope ratio values (206Pb/207Pb and 208Pb/207Pb; right).

Reference:

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. doi:10.1038/ncomms12921

Latest highlights

Science Highlights

Updated compilation of the global continental and marine lithogenic neodymium isotopic measurements

This new compilation and gridded datasets offer a concrete way forward to improve the application of Nd isotopes as a useful tracer of ocean circulation.

05.05.2021

Science Highlights

Neodymium concentrations and isotopes help disentangling Siberian river influences on the Arctic Ocean

Paffrath and co-autors followed the relative contributions of the main Siberian rivers to the waters of the Transpolar Drift using neodymium parameters.

Science Highlights

A new and more quantitative atlas of the deep-sea burial fluxes of major and trace elements

Among other findings, authors find that the new opal flux is roughly a factor of 2 increase over previous estimates having important implications for the global silicon cycle.

04.05.2021

Science Highlights

Manganese: a surprising co-limiting factor of phytoplankton growth in the Southern Ocean

One of the main consequences of this work is that manganese should be included in ocean-climate models, more particularly to improve the accuracy of their predictions in this area.

Rechercher