Circumpolar transport and air-surface exchange of atmospheric mercury at Ny-Ålesund (79° N), Svalbard, spring 2002

摘要

Mercury in different environmental compartments has been measured atNy-Ålesund (78°54' N, 11°53' E) during an intensive campaign,17 April to 14 May 2002. Time-resolved speciated determination of mercuryin the atmosphere and snow was conducted at the Norwegian research stationat the Zeppelin mountain, 474 m above the sea level, and at the Italianresearch facility Dirigibile Italia, 12 m above the sea level. Total GaseousMercury (TGM) was present in the range <0.1 to 2.2 ng m−3 during thecampaign. Three mercury depletion events, identified as periods withdecreased TGM concentrations, were observed. At the lower altitude, TGMconcentrations following such events were found to exhibit both highermagnitude and larger variability in comparison to results from the Zeppelinstation. Oxidised mercury species in air and fall-out with snow as well asmercury attached to particles were also measured and their concentrationswere found to be anti-correlated with TGM in air. concentrations of total Hg in snow (Hg-tot)showed a large (~15×) increase in response to Gaseous Elemental Mercury Depletion Events (GEMDEs, range 1.5–76.5 ng L−1).Solid evidence for photo-stimulated emissions ofHg0(g) from the snow pack in conjunction to depletion events wereobtained from gradient measurements as well as from flux chambermeasurements. Steep diurnal concentration variations of Hg0(aq) insurface seawater were also found to concur with changing solar radiation.The concentration of Hg0(aq) in seawater was found to be in the range12.2–70.4 pg L−1, which corresponds to supersaturation. Hence, theseawater surface constituted a source emitting elemental mercury.The concentrations of RGM (reactive gaseous mercury), Hg-p (particulatemercury), and BrO column densities (detected by DOAS) were very low exceptfor a few individual samples during the major Hg0 depletion event. BrO vertical columndensities obtained by the remote satellite ESR-2 and trajectory analysis indicate thatthe air masses exhibiting low Hg0 concentrations originated from areas with high BrOdensities.