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Article Dans Une Revue ACS Earth and Space Chemistry Année : 2020

Mercury Export Flux in the Arctic Ocean Estimated from 234 Th/ 238 U Disequilibria

Jeroen Sonke

Résumé

High mercury (Hg) levels have been observed for arctic biota despite limited local sources of anthropogenic Hg in the Arctic. Scavenging of Hg exerts an important control on the residence time of Hg in surface waters. The downward Hg export flux, as well as Hg burial rates in bottom sediments, are not well constrained due to the lack of particulate Hg (pHg) observations in the Arctic Ocean. Here we estimated downward Hg export flux based on Hg concentrations in suspended particulate matter (SPM) and by using the radionuclide pair 234Th/238U, coupled to pHg/234Th ratios in particles. Using new observations made during the German GEOTRACES TransArcII (GN04) and the U.S. Arctic GEOTRACES (GN01) cruises in August - October 2015, we estimated the pHg export flux in the central Arctic Ocean and the outer shelf. We find that 81 ± 58 Mg y-1 pHg are exported from the upper 100 m, of which 16 ± 10 Mg y-1 are ultimately buried in marine sediments. An extrapolation to the entire Arctic Ocean, including the inner shelf, results in 156 Mg y-1 pHg export from the surface ocean and 28 Mg y-1 Hg burial rate. Our study shows that the pHg export flux could be higher than previously thought and this should be taken into consideration for future arctic Hg budget estimations.
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Dates et versions

hal-02935259 , version 1 (13-11-2020)

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Javier Tesán Onrubia, Mariia Petrova, Viena Puigcorbé, Erin Black, Ole Valk, et al.. Mercury Export Flux in the Arctic Ocean Estimated from 234 Th/ 238 U Disequilibria. ACS Earth and Space Chemistry, 2020, 4 (5), pp.795-801. ⟨10.1021/acsearthspacechem.0c00055⟩. ⟨hal-02935259⟩
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