A pulse of mercury and major ions in snowmelt runoff from a small Arctic Alaska watershed

Atmospheric mercury (Hg) is deposited to Polar Regions during springtime atmospheric mercury depletion events (AMDEs) that require halogens and snow or ice surfaces. The fate of this Hg during and following snowmelt is largely unknown. We measured Hg, major ions, and stable water isotopes from the snowpack through the entire spring melt runoff period for two years. Our small (2.5 ha) watershed is near Barrow (now Utqiaġvik), Alaska. We measured discharge, made 10 000 snow depths, and collected over 100 samples of snow and meltwater for chemical analysis in 2008 and 2009 from the watershed snowpack and ephemeral stream channel. Results show an “ionic pulse” of mercury and major ions in runoff during both snowmelt seasons, but major ion and Hg runoff concentrations were roughly 50% higher in 2008 than in 2009. Though total discharge as a percent of total watershed snowpack water equivalent prior to the melt was similar in both years (36% in 2008 melt runoff and 34% in 2009), it is possible that record low p...