Mercury in the Arctic tundra snowpack: temporal and spatial concentration patterns and trace gas exchanges

摘要

In the Arctic, the snowpack forms the major interface between atmospheric andterrestrial cycling of mercury (Hg), a global pollutant. We investigated Hgdynamics in an interior Arctic tundra snowpack in northern Alaska during twowinter seasons. Using a snow towersystem to monitor Hg trace gas exchange, we observed consistent concentrationdeclines of gaseous elemental Hg (Hg0gas) from the atmosphere tothe snowpack to soils. The snowpack itself was unlikely a direct sink foratmospheric Hg0gas. In addition, there was no evidence ofphotochemical reduction of HgII to Hg0gas in the tundrasnowpack, with the exception of short periods during late winter in theuppermost snow layer. The patterns in this interior Arctic snowpack thusdiffer substantially from observations in Arctic coastal and temperatesnowpacks. We consistently measured low concentrations of both total anddissolved Hg in snowpack throughout the two seasons. Chemical tracers showedthat Hg was mainly associated with local mineral dust and regional marine seaspray inputs. Mass balance calculations show that the snowpack represents asmall reservoir of Hg, resulting in low inputs during snowmelt. Takentogether, the results from this study suggest that interior Arctic snowpacksare negligible sources of Hg to the Arctic.