Mercury Export Flux in the Arctic Ocean Estimated from 234 Th/ 238 U Disequilibria
International audience High mercury (Hg) levels have been observed for arctic biota despite limited localsources of anthropogenic Hg in the Arctic. Scavenging of Hg exerts an important control onthe residence time of Hg in surface waters. The downward Hg export flux, as well as Hgburial rates in bot...
Published in: | ACS Earth and Space Chemistry |
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Main Authors: | , , , , , , , , , , , , |
Other Authors: | , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2020
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Subjects: | |
Online Access: | https://hal.science/hal-02935259 https://hal.science/hal-02935259/document https://hal.science/hal-02935259/file/Final_version_exported_from_the_PhD.pdf https://doi.org/10.1021/acsearthspacechem.0c00055 |
Summary: | International audience High mercury (Hg) levels have been observed for arctic biota despite limited localsources of anthropogenic Hg in the Arctic. Scavenging of Hg exerts an important control onthe residence time of Hg in surface waters. The downward Hg export flux, as well as Hgburial 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 basedon Hg concentrations in suspended particulate matter (SPM) and by using the radionuclidepair 234Th/238U, coupled to pHg/234Th ratios in particles. Using new observations made duringthe 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 ArcticOcean and the outer shelf. We find that 81 ± 58 Mg y-1 pHg are exported from the upper 100m, of which 16 ± 10 Mg y-1 are ultimately buried in marine sediments. An extrapolation tothe entire Arctic Ocean, including the inner shelf, results in 156 Mg y-1 pHg export from thesurface ocean and 28 Mg y-1 Hg burial rate. Our study shows that the pHg export flux couldbe higher than previously thought and this should be taken into consideration for future arcticHg budget estimations. |
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