Mercury distribution, partitioning and speciation in coastal vs. inland High Arctic snow

Abstract

Atmospheric mercury deposition on snow at springtime has been reported in polar regions, potentially posing a threat to coastal and inland ecosystems receiving meltwaters. However, the post-depositional fate of Hg in snow is not well known, and no data are available on Hg partitioning in polar snow. During snowmelt, we conducted a survey of Hg concentrations, partitioning and speciation in surface snow and at depth, over sea ice and over land along a 100 km transect across Cornwallis Island, NU, Canada. Total Hg concentrations [THg] in surface snow were low (less than 20 pmol L À1 ) and were significantly higher in marine vs. inland environments. Particulate Hg in surface snow represented up to 90% of total Hg over sea ice and up to 59% over land. At depth, [THg] at the snow/sea ice interface (up to 300 pmol L À1 ) were two orders of magnitude higher than at the snow/lake ice interface (ca. 2.5 pmol L À1 ). Integrated snow columns, sampled over sea-ice and over land, showed that particulate Hg was mostly bound to particles ranging from 0.45 to 2.7 lm. Moreover, melting snowpacks over sea ice and over lake ice contribute to increase [THg] at the water/ice interfaces. This study indicates that, at the onset of snowmelt, most of the Hg in snow is in particulate form, particularly over sea ice. Low Hg levels in surface snow suggest that Hg deposited through early spring deposition events is partly lost to the atmosphere from the snowpack before snowmelt. The sea ice/snow interface may constitute a site for Hg accumulation, however. Further understanding of the cycling of mercury at the sea ice/ snow and sea ice/seawater interfaces is thus warranted to fully understand how mercury enters the arctic food webs.

Novel aerosol analysis approach for characterization of nanoparticulate matter in snow

“…We collected samples at several sites in Alaska, USA (2009) and Nunavut (2006) Arctic snow collection and storage have previously been described in detail elsewhere Kos and Ariya 2006a;Kos and Ariya 2006b;Kos and Ariya 2010;Mortazavi et al 2006;Poulain et al 2007). Arctic snow from the top 3 cm of the snowpack was collected into 950-mL amber glass jars (Daniels Scientific, Charleston, SC, USA), with PTFE-lined lids, pre-cleaned as previously described .…”

The fate of mercury in Arctic terrestrial and aquatic ecosystems, a review

“…The inorganic Hg II species present in snow melt are dominated by uncharged or negatively charged complexes with OH À , Cl À and Br À , with an unquantified but possibly significant fraction of the Hg II likely bound to organic matter. [15] A small increase in the MeHg concentration in the snowpack has been shown to occur just before snowmelt, [16,17] but it is not known how much of this MeHg is produced in the snowpack compared with what is delivered by falling snow. The effect of this net deposited Hg from snow melt on THg and MeHg concentrations in receiving waters (rivers, lakes, oceans) is the subject of ongoing research.…”

“…For example, DOM may provide stabilising ligands to maintain Hg in dissolved form, [97] and C-DOM absorbs UV radiation and thus provides an important control on photo-reduction and other photo-initiated processes in surface water. [15,56] In saline waters, organic compounds produced by algae are able to promote oxidation of Hg 0 even under dark conditions. [15] Coastal environments are colonised by Hg-resistant bacteria potentially able to reduce Hg.…”

“…[15,56] In saline waters, organic compounds produced by algae are able to promote oxidation of Hg 0 even under dark conditions. [15] Coastal environments are colonised by Hg-resistant bacteria potentially able to reduce Hg. Simple box modelling suggests that this bacterial reduction could be significant in ocean waters, although bacterial Hg reduction rates need to be directly quantified.…”

“…Simple box modelling suggests that this bacterial reduction could be significant in ocean waters, although bacterial Hg reduction rates need to be directly quantified. [15] In other oceans, it has recently been demonstrated that MeHg can be produced during the remineralisation of algal detritus in the water column. [44,86,98,99] The vertical transport of MeHg associated with particulate flux from surface waters was found to be relatively unimportant compared with the in situ production of MeHg that occurred in association with nutrient maxima at subsurface water depths.…”