Fate of Elemental Mercury in the Arctic during Atmospheric Mercury Depletion Episodes and the Load of Atmospheric Mercury to the Arctic

Abstract

Atmospheric mercury depletion episodes (AMDEs) were studied at Station Nord, Northeast Greenland, 81 degrees 36' N, 16 degrees 40' W, during the Arctic Spring. Gaseous elemental mercury (GEM) and ozone were measured starting from 1998 and 1999, respectively, until August 2002. GEM was measured with a TEKRAN 2735A automatic mercury analyzer based on preconcentration of mercury on a gold trap followed by detection using fluorescence spectroscopy. Ozone was measured by UV absorption. A scatter plot of GEM and ozone concentrations confirmed that also at Station Nord GEM and ozone are linearly correlated during AMDEs. The relationship between ozone and GEM is further investigated in this paper using basic reaction kinetics (i.e., Cl, ClO, Br, and BrO have been suggested as reactants for GEM). The analyses in this paper show that GEM in the Arctic troposphere most probably reacts with Br. On the basis of the experimental results of this paper and results from the literature, a simple parametrization for AMDE was included into the Danish Eulerian Hemispheric Model (DEHM). In the model, GEM is converted linearly to reactive gaseous mercury (RGM) over sea ice with temperature below -4 degrees C with a lifetime of 3 or 10 h. The new AMDE parametrization was used together with the general parametrization of mercury chemistry [Petersen, G.; Munthe, J.; Pleijel, K.; Bloxam, R.; Vinod Kumar, A. Atmos. Environ. 1998, 32, 829-843]. The obtained model results were compared with measurements of GEM at Station Nord. There was good agreement between the start and general features periods with AMDEs, although the model could not reproduce the fast concentration changes, and the correlation between modeled and measured values decreased from 2000 to 2001 and further in 2002. The modeled RGM concentrations over the Arctic in 2000 were found to agree well with the temporal and geographical variability of the boundary column of monthly average BrO observed by the GOME satellite. Scenario calculations were performed with and without AMDEs. For the area north of the Polar Circle, the mercury deposition increases from 89 tons/year for calculations without an AMDE to 208 tons/year with the AMDE. The 208 tons/year represent an upper limit for the mercury load to the Artic.

How relevant is the deposition of mercury onto snowpacks? – Part 2: A modeling study

“…(6)), the amount of radiation available within the snowpack to drive net photoreduction increases only gradually at high latitudes during spring. This gradual increase is crucial for the realistic, non-overenergetic revolatilization of mercury pooled in the snow during polar night (Steen et al, 2009) or deposited during springtime AMDEs (Lu et al, 2001;Berg et al, 2003;Ariya et al, 2004;Christensen et al, 2004;Heidam et al, 2004;Skov et al, 2004;Ferrari et al, 2005;Travnikov, 2005;Brooks et al, 2006;Kirk et al, 2006;Constant et al, 2007;Sommar et al, 2007;Johnson et al, 2008;Steffen et al, 2008).…”

Natural and anthropogenic atmospheric mercury in the European Arctic: a fractionation study

“…Since the discovery of the Atmospheric Mercury Depletion Event (AMDE) in 1995, significant efforts have been carried out to understand this circumpolar phenomenon (Ariya et al, 2004;Skov et al, 2004). Gaseous elemental mercury (GEM) is converted to reactive gaseous mercury (RGM) during an AMDE.…”

Total Gaseous Mercury Concentration Measurements at Fort McMurray, Alberta, Canada

“…Furthermore, unseasonably low TGM concentrations are often traced back to arctic regions as illustrated in Figure 5c. These associations suggest the possible role of atmospheric mercury chemistry, particularly oxidation of GEM to form GOM [3,5,27,32]. GOM can then undergo deposition faster than GEM, thereby reducing the ambient TGM concentration in an area.…”

“…This region has minimal land disturbance or industry, so lower TGM concentration observations from air passing through this region are not surprising. Note that this back trajectory analysis cannot clearly distinguish between lower TGM concentrations originating from arctic regions as a result of arctic atmospheric mercury depletion events (AMDEs) [1,3,5,[27][28][29][30][31] as opposed to as a result of generally cleaner air (i.e., air with lower TGM concentrations). However, given that during the study period, arctic air parcels are often associated with unseasonably lower TGM concentrations, this possibility is explored further in Section 2.4 below.…”

“…GOM can then undergo deposition faster than GEM, thereby reducing the ambient TGM concentration in an area. Previous studies have provided detailed discussions on this type of mercury chemistry, most notably in terms of arctic AMDEs during spring-time polar sunrises [1,3,5,[27][28][29][30][31]. AMDEs are associated with reduced GEM concentrations, reduced ozone concentrations, and increasing solar radiation.…”