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.
SourceAvailable from: Bjørn Munro Jenssen[Show abstract] [Hide abstract]
ABSTRACT: Hepatic concentrations of mercury (Hg), selenium (Se) and cadmium (Cd) were determined in black-legged kittiwakes (Rissa tridactyla) and little auks (Alle alle) from two fjords in Svalbard (Kongsfjorden; 78°57'N, 12°12'E and Liefdefjorden; 79°37'N, 13°20'E). The inflow of Arctic and Atlantic water differs between the two fjords, potentially affecting element accumulation. Trophic positions (TP) were derived from stable nitrogen isotope ratios (δ(15)N), and stable carbon isotope ratios (δ(13)C) were assessed to evaluate the terrestrial influence on element accumulation. Mercury, Cd, TP and δ(13)C varied significantly between locations and years in both species. Trophic position and feeding habits explained Hg and Cd accumulation in kittiwakes, but not in little auks. Biomagnification of Hg and Cd were found in the food webs of both the Atlantic and the Arctic fjord, and no inter-fjord differences were detected. The δ(13)C were higher in the seabirds from Kongsfjorden than in Liefdefjorden, but this did not explain variations in element accumulation. Selenium concentrations were not influenced by Hg accumulation in kittiwakes, indicating baseline levels of Se in this species. In contrast, correlations between Hg and Se and lower Se:Hg ratios in little auks from Kongsfjorden than in Liefdefjorden indicate a more pronounced influence of Se-Hg complex formation in little auks feeding in Atlantic waters. Copyright © 2014. Published by Elsevier Ltd.Chemosphere 11/2014; DOI:10.1016/j.chemosphere.2014.10.060 · 3.50 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: A review of mercury in the Canadian Arctic with a focus on field measurements is presented in part I (see Steffen et al., this issue). Here we provide insights into the dynamics of mercury in the Canadian Arctic from new and published mercury modeling studies using Environment Canada's mercury model. The model simulations presented in this study use global anthropogenic emissions of mercury for the period 1995-2005. The most recent modeling estimate of the net gain of mercury from the atmosphere to the Arctic Ocean is 75Mgyear(-1) and the net gain to the terrestrial ecosystems north of 66.5° is 42Mgyear(-1). Model based annual export of riverine mercury from North American, Russian and all Arctic watersheds to the Arctic Ocean are in the range of 2.8-5.6, 12.7-25.4 and 15.5-31.0Mgyear(-1), respectively. Analysis of long-range transport events of Hg at Alert and Little Fox Lake monitoring sites indicates that Asia contributes the most ambient Hg to the Canadian Arctic followed by contributions from North America, Russia, and Europe. The largest anthropogenic Hg deposition to the Canadian Arctic is from East Asia followed by Europe (and Russia), North America, and South Asia. An examination of temporal trends of Hg using the model suggests that changes in meteorology and changes in anthropogenic emissions equally contribute to the decrease in surface air elemental mercury concentrations in the Canadian Arctic with an overall decline of ~12% from 1990 to 2005. A slow increase in net deposition of Hg is found in the Canadian Arctic in response to changes in meteorology. Changes in snowpack and sea-ice characteristics and increase in precipitation in the Arctic related with climate change are found to be primary causes for the meteorology-related changes in air concentrations and deposition of Hg in the region. The model estimates that under the emissions reduction scenario of worldwide implementation of the best emission control technologies by 2020, mercury deposition could potentially be reduced by 18-20% in the Canadian Arctic. Copyright © 2014. Published by Elsevier B.V.Science of The Total Environment 01/2015; 509-510. DOI:10.1016/j.scitotenv.2014.10.112 · 3.16 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: Long-range atmospheric transport and deposition are important sources of mercury (Hg) to Arctic aquatic and terrestrial ecosystems. We review here recent progress made in the study of the transport, transformation, deposition and reemission of atmospheric Hg in the Canadian Arctic, focusing on field measurements (see Dastoor et al., this issue for a review of modeling studies on the same topics). Redox processes control the speciation of atmospheric Hg, and thus impart an important influence on Hg deposition, particularly during atmospheric mercury depletion events (AMDEs). Bromine radicals were identified as the primary oxidant of atmospheric Hg during AMDEs. Since the start of monitoring at Alert (NU) in 1995, the timing of peak AMDE occurrence has shifted to earlier times in the spring (from May to April) in recent years, and while AMDE frequency and GEM concentrations are correlated with local meteorological conditions, the reasons for this timing-shift are not understood. Mercury is subject to various post-depositional processes in snowpacks and a large portion of deposited oxidized Hg can be reemitted following photoreduction; how much Hg is deposited and reemitted depends on geographical location, meteorological, vegetative and sea-ice conditions, as well as snow chemistry. Halide anions in the snow can stabilize Hg, therefore it is expected that a smaller fraction of deposited Hg will be reemitted from coastal snowpacks. Atmospheric gaseous Hg concentrations have decreased in some parts of the Arctic (e.g., Alert) from 2000 to 2009 but at a rate that was less than that at lower latitudes. Despite numerous recent advances, a number of knowledge gaps remain, including uncertainties in the identification of oxidized Hg species in the air (and how this relates to dry vs. wet deposition), physical-chemical processes in air, snow and water—especially over sea ice—and the relationship between these processes and climate change.Science of The Total Environment 12/2014; 509-510. DOI:10.1016/j.scitotenv.2014.10.109 · 3.16 Impact Factor