Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5783372 | Geochimica et Cosmochimica Acta | 2017 | 16 Pages |
Abstract
Concentrations of MeHgT ranged from <0.02 to 0.48 pmol Lâ1 with highest values associated with the oxygen-deficient zone of the open sea. The methylated mercury to total mercury proportion (MeHgT/HgT) increased from 2% to 4% in the Rhône River to up to 30% (averaging 18%) in the North Gyre waters, whereas, within the shelf waters, MeHgT/HgT proportions were the lowest (1-3%). We calculate that the open sea is the major source of MeHgT for the shelf waters, with an annual flux estimated at 0.68 ± 0.12 kmol aâ1 (i.e., equivalent to 12% of the HgT flux). This MeHgT influx is more than 80 times the direct atmospheric deposition or the in situ net production, more than 40 times the estimated “maximum potential” annual efflux from shelf sediment, and more than 7 times that of the continental sources. In the open sea, ratios of MMHg/DMHg in waters were always <1 and minimum in the oxygen deficient zones of the water column, where MeHg concentrations are maximum. This observation supports the idea that MMHg could be a degradation product of DMHg produced from inorganic divalent Hg.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Daniel Cossa, Xavier Durrieu de Madron, Jörg Schäfer, Laurent Lanceleur, Stéphane Guédron, Roselyne Buscail, Bastien Thomas, Sabine Castelle, Jean-Jacques Naudin,