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Abstract Title: The Budgets of Mercury Species at the Sediment-Water Interface at the Denmark Strait and the Influence on Mercury Transport
Presenter Name: Xiangming Shi
Company/Institution: University of Connecticut
Session: Special Session - Climate-Driven Perturbations of Arctic Mercury Cycling
Co-Authors: Xiangming Shi,Robert Mason,Amber Annett,Rhiannon Jones,Rob Middag

Abstract Information :

Methylmercury (MeHg), a neurotoxin, is found at higher relative concentrations in biota in high-latitude oceans, where the sources and the transfer of mercury species are important for understanding the biogeochemical influence. The Denmark Strait is an important region of deep water formation. The addition of mercury (Hg) species to the deep water can even have a crucial impact on the global Hg cycle. Although sediment is generally regarded as an important source of MeHg, quantification studies on benthic exchange are poorly constrained in this area. With the opportunity of the GEOTRACES expedition (64PE474, July-August 2021), the benthic fluxes of dissolved MeHg and total Hg were quantified with the 224Ra/228Th disequilibrium approach. The rate of particulate Hg redeposition was traced with the excess 234Th of the top sediment. Results indicate that the sediment on the sides of Greenland-Iceland Rise was a main source of Hg species. The strong underwater current of the Denmark Strait cataract carried these Hg southwards into the North Atlantic. While for the stations on the top of the rise, excess 224Ra and excess 234Th relative to their parents were observed in sediment columns, suggesting the precipitation of the resuspended particles. The concentrations of MeHg and total Hg in the bottom water at atop rise stations were lower than those at the rise side stations, implying that the redeposited particles scavenged considerable Hg from water column. Sediments on the rise is likely a sink for Hg transported from the Arctic.

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