Total mercury and total methylmercury during the POLARSTERN cruise ARK-XXVI/3 (TransArc) ...

• Main Authors: Heimbürger, Lars-Eric, Sonke, Jeroen E, Cossa, Daniel, Point, David, Lagane, Christelle, Laffont, Laure, Galfond, Benjamin T, Nicolaus, Marcel, Rabe, Benjamin, Rutgers van der Loeff, Michiel M
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: Event label; Date/Time of event; Latitude of event; Longitude of event; Elevation of event; DEPTH, water; Pressure, water; Methylmercury; Mercury; Bottle number; CTD/Rosette; see comment; ARK-XXVI/3; Polarstern; Global marine biogeochemical cycles of trace elements and their isotopes GEOTRACES; Arctic; Arctic Ocean; Laptev Sea; North Pole; Beaufort Sea; Canadian Archipelago; Human health; laptev; Sea ice
• Online Access: https://dx.doi.org/10.1594/pangaea.844492; https://doi.pangaea.de/10.1594/PANGAEA.844492

Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79-90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81-85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the ... : The four profiles between the Siberian shelf/Laptev Sea and the North Pole (79 - 90°N) were sampled during the TransArc ARK XXVI/3 cruise in summer 2011 on the Research Vessel Polarstern and consist of 81 unfiltered acidified (HCl double-distilled, 0.4 %, v:v) samples. Acidification rapidly converts dimethylmercury (DMHg) into monomethylmercury (MMHg), and we thus measured methylmercury (MeHg) as the sum of MMHg and DMHg. For this study, we applied one of the best known reference methods, isotope dilution (ID), to a high sensitivity coupled gas chromatography - sector field ICP-MS (GC-SF-ICP-MS) method at the GET laboratory. MeHg and inorganic Hg species were extracted after derivatization, following previously published protocols, that we further improved for ultra-trace levels. Briefly, enriched spikes of 199iHg and 201MeHg (ISC Science, Spain) were added to a 115 mL aliquot of the sea water samples, targeting optimal ratios of 8.46 for 199iHgspike/202iHgsample and 4.25 for 201MeHgspike/202MeHgsample. The ...