Carbon dynamics control comtemporary mercury burial in Arctic Ocean sediments

Mercury (Hg) contamination is a familiar concern in the Arctic. However, this study shows that variations of Hg concentration in 30 sediment cores collected across the North American Arctic Margin (NAAM) and in the deep central Arctic Ocean (AO) can be entirely explained by carbon sources and cycling. An apparent enrichment in Hg toward the sediment surface results from remineralization of organic carbon in the sediments, not from increased Hg flux. Hg values in AO sediments can be predicted with a high degree of confidence, based on three carbon sources with distinct Hg contents. Terrigenous organic carbon (OCTERR) dominates Hg delivery (80-95%) in the western NAAM, whereas inorganic carbon is the predominant carrier of Hg at many eastern NAAM sites (50-70%). Marine organic carbon (OCMAR) contributes <20% of the total Hg concentrations. The sedimentary Hg:OCTERR and Hg:OCMAR endmembers are higher in the deep AO than in the NAAM, likely due to greater organic matter remineralization during transit through the system. We conclude that the interplay among sedimentary carbon sources governs the scavenging, transportation and sequestration of Hg, and that Hg variations with depth in the sediments result mainly from diagenesis, not from changes in the modern Hg flux.