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

The biogeochemical ventures of dissolved iron and manganese across the Arctic Ocean

The spatial distributions and biogeochemical cycling of dissolved Fe (dFe) and dissolved manganese (dMn) across the Arctic Ocean were established during summer and fall 2015. The Canadian GEOTRACES transect extended from the Canada Basin (CB) to the Labrador Sea (LS) via the Canadian Arctic Archipelago (CAA). The surface, subsurface and deep water distributions for both […]

15.05.2020

Science Highlights

Land inputs in the Arctic transported up to the North Pole

A new study found that freshwater runoff from rivers and continental shelf sediments are bringing significant quantities of carbon and trace elements into parts of the Arctic Ocean

05.05.2020

Science Highlights

Loihi Seamount, hydrothermal Helium-3 and dissolved iron sources and their dispersion within the Pacific Ocean

As part of the GEOTRACES cruise GP15, Jenkins and co-workers (2020, see reference below) observed large water column anomalies in helium isotopes and trace metal concentrations above the Loihi Seamount (~19°N, 154°W) that extends along the GP15 track for hundreds of kilometers. Expanding their data with historical ones, they observe that the Loihi Helium-3 (3He) […]

04.05.2020

Science Highlights

Silicon isotopes reveal the different Arctic endmembers contributing to the deep water formed in the North Atlantic Ocean

Combining a multiparametric analysis, biogenic and dissolved silicon (Si) isotope data (30Si-bSiO2 and δ30Si-DSi, respectively) in the Arctic Ocean, Liguori and co-workers (2020, see reference below) could unravel the influence of water masses on the δ30Si-DSi distribution within the Arctic Ocean. Any deviation of the δ30Si-DSi signature from pure mixing was attributed to the contribution […]

20.04.2020

Rechercher