Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution

Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean

Recent climate-related terrestrial biodiversity research in Canada's Arctic national parks: review, summary, and management implications

It is now well documented that Arctic climates and ecosystems are changing at some of the fastest rates on planet Earth. These changes are significant for all Arctic biodiversity, and they are a great challenge for cooperative management boards of Canada's Arctic national parks, those legislated to maintain or improve the ecological integrity of all national parks. Owing to the inherent complexity of natural ecosystems, it is not at all clear how, nor how rapidly, these ongoing changes will affect park biodiversity and impact the traditional land-based lifestyles of Indigenous park cooperative management partners. In this context, this paper reviews and integrates recent research carried out in Canadian Arctic national parks: (1) geophysical - a reduction in glacial area and volume, active layer thickening, warming soil temperatures, and terrain instability; (2) vegetation - widespread but ecosystem-specific increases in NDVI 'greenness', plant biomass, shrub and herb coverage, and growing season lengths; and (3) wildlife-complex changes in small mammals and ungulate populations, very negative effects on some polar bear populations, and relatively stable mammalian predator and raptor populations at this time. This work provides a partial snapshot of ongoing and evolving ecological effects of climate change in Arctic national parks, and provides a strong foundation for prioritising future research and monitoring efforts. These evolving changes also undermine the historical paradigm of place-based conservation and necessitate a new approach for managing protected areas that involves acceptance of ongoing transformational change and adoption of a risk-based, forward looking paradigm in a changing world. It is proposed that Arctic national parks are ideal locations to focus Arctic science, especially as a component of a strategic, coordinated, and pan-Arctic approach to Arctic research that makes the most effective use of limited resources in the vast areas of Canadaâ¿¿s north