Mercury in the Atmosphere, Snow and Melt Water Ponds in the North Atlantic Ocean during Arctic Summer

International audienceAtmospheric mercury speciation measurements were performed during a 10 week Arctic summer expedition in the North Atlantic Ocean onboard the German research vessel RV Polarstern between June 15 and August 29, 2004. This expedition covered large areas of the North Atlantic and Arctic Oceans between latitudes 54°N and 85°N and longitudes 16°W and16°E. Gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated with particles (Hg−P) were measured during this study. In addition, total mercury in surface snow and meltwater ponds located on sea ice floes was measured. GEM showed a homogeneous distribution over the open North Atlantic Ocean (median 1.53 ± 0.12 ng/m3), which is in contrast to the higher concentrations of GEM observed over sea ice (median 1.82 ± 0.24 ng/m3). It is hypothesized that this results from either (re-) emission of mercury contained in snow and ice surfaces that was previously deposited during atmospheric mercury depletion events (AMDE) in the spring or evasion from the ocean due to increased reduction potential at high latitudes during Arctic summer. Measured concentrations of total mercury in surface snow and meltwater ponds were low (all samples