Enrichment of Trace Metals (V, Cu, Co, Ni, and Mo) in Arctic Sediments-From Siberian Arctic Shelves to the Basin

With 50% of the Arctic Ocean is consisted of continental shelves, extensive shelf-basin exchange processes exist here and plays a key role in regulating the biogeochemical recycling process of trace metals in the Arctic region. In this study, short sediment cores were collected along three transects from Siberian-Chukchi shelves to adjacent slope/basin areas. An increasing trend was found for the bulk concentrations of several metals (V, Cu, Co, Ni, and Mo) from shelf to slope/basin cores with increasing water depth. Sequential extraction experiments indicated that the Fe/Mn oxide fractions increased significantly from shelf (9%-21%) to basin cores (24%-76%) for Cu, Co, Ni, and V, while the organic/sulfide phase remained significant (similar to 40%) for Mo. In addition, the observed dissolved metal concentrations in porewater indicated the remobilization of Fe, Mn, and Mo from shelf sediment, while V was always removed from water to the sediment, both on the shelf or in the slope/basin. Overall, in combination with the statistical analysis, we proposed that metals are transported from shelves to the central Arctic and are scavenged mainly by Mn oxides from the water column, which results in the enrichment of metals in slope/basin sediment. With the climate change, such transport and accumulation mechanism may be intensified over time, slowly leading the Arctic sediment to be a more and more important sink for those metals.

Automated summary

This study reveals the key role of shelf-basin exchange processes in regulating biogeochemical recycling of trace metals in the Arctic Ocean, with metal transport mainly scavenged by Mn oxides from the water column. As climate change progresses, this transport and enrichment mechanism may intensify over time.