Arctic mercury export flux with marine particles higher than anticipated

In the ocean, the residence time of mercury (Hg), is largely driven by two removal mechanisms: evasion to the atmosphere and downward export flux with settling particles. The later was particularly poorly constrained in the Arctic Ocean, as was the Hg burial rate into the sediment.

Using samples collected during the German GEOTRACES TransArcII (GN04) and the U.S. Arctic GEOTRACES (GN01) cruises in August−October 2015, authors estimated the particulate mercury (Hgp) export flux in the central Arctic Ocean and the outer shelf. These new data allowed them to i) calculate Hgp normalized to suspended particulate matter and partition coefficient for the Arctic Ocean; ii) use Hgp and 234Th observations to estimate the Hgp export flux based on the 234Th/238U disequilibrium and iii) re-estimate the net Hg burial rates from Arctic sediment cores.

This comprehensive study of the Arctic particulate Hg behaviour led to the estimate of 156 Mg year−1 Hgp export from the surface ocean and 28 Mg year−1 Hg burial rate, fluxes extrapolated to the entire Arctic Ocean, including the inner shelf.

Figure: Arctic mercury mass balance (fluxes in tons per year).

Reference:

Tesán Onrubia, J. A., Petrova, M. V., Puigcorbé, V., Black, E. E., Valk, O., Dufour, A., Hamelin, B., Buesseler, K., Masqué, P., Le Moigne, F. A. C., Sonke, J. E., Rutgers van der Loeff, M. Heimbürger-Boavida, L.-E. (2020). Mercury Export Flux in the Arctic Ocean Estimated from 234 Th/ 238 U Disequilibria. ACS Earth and Space Chemistry, acsearthspacechem.0c00055. DOI: https://doi.org/10.1021/acsearthspacechem.0c00055

Latest highlights

Science Highlights

Extremely high radioactive levels in the manganese nodules

Volz and co-authors demonstrate that radioisotopes in the manganese nodules mostly exceed exempt activity levels…

22.05.2023

Science Highlights

The North Pacific Ocean, a key actor for the zinc oceanic cycle

Sieber and his colleagues lift the veil on some of the mechanisms that control the behavior of zinc in the Pacific Ocean, and more globally.

17.05.2023

Science Highlights

Disentangling what controls the cadmium distribution in the Pacific Ocean

Sieber and his colleagues established the distribution of dissolved cadmium concentrations and isotopes a section from Alaska to Tahiti.

16.05.2023

Science Highlights

Solid-solution distribution of the cosmogenic beryllium-7 in the water column

This work questions the validity and limits of the hypothesis that particulate beryllium-7 can be neglected in the oceanographic applications of this tracer.

12.05.2023

Rechercher