Total Mercury and Methylmercury Profiles in Multiyear Sea Ice in the Southwestern Beaufort Sea

Replicate cores spanning the entire thickness of the floe were taken from a single sampling site on a multi-year sea ice floe in the southwestern Beaufort Sea in August 2011 as part of the ArcticNet 2011 cruise of the CCGS Amundsen. Quantification of total mercury (THg), methylmercury (MeHg), Chlorophyll a, dissolved organic carbon (DOC) and delta 18O was performed on separate cores, and temperature and salinity profiles were recorded. THg was analyzed via CVAFS on board the Amundsen in the Portable In-situ Lab for Mercury Speciation (PILMS), while MeHg was analyzed via GC-CVAFS in the Ultra-Clean Trace Elements Lab (UCTEL) at the University of Manitoba. Chlorophyll a concentrations were analyzed onboard the Amundsen via fluorimetry, and salinity was recorded using a Hach Sension probe. DOC was analyzed by Dr. Michel Gosselin's lab at the Université du Québec à Rimouski via a high-temperature combustion Shimadzu TOC-5000A autoanalyzer. Delta 18O analysis was performed by G.G. Hatch Isotope Laboratories, University of Ottawa, Canada. Samples and standards (calibrated against several samples of Vienna - SMOW) were flushed with a gas mixture of 2 % CO2 in helium off-line, equilibrated at 21°C for 5 d, then analyzed using the Gasbench + DeltaPlus XP isotope ratio mass spectrometer (ThermoFinnigan, Germany).