The fate of mercury species in a sub‐arctic snowpack during snowmelt

An extensive mercury study was conducted in April 2002 prior to and during the annual melting of a snowpack in a sub‐arctic site along the Hudson Bay (Canada). Gas‐phase measurements show that the snowmelt coincides with an elemental mercury (Hg°) pulse in the snowpack air far above ambient levels. Additional measurements of inorganic mercury (Hg2+) and methylmercury (MeHg+) in snow pits, in surface snow and in a meltwater sample clearly reveal that most of Hg is removed from the snow during the first days of snowmelt. We estimate that gas‐phase exchanges contribute poorly to remove Hg from the snowpack; consequently during a snowmelt day more than 90% of Hg present in the snow surface is likely released with the meltwater. In arctic areas, where Hg accumulates at an accelerated rate in the snow surfaces [ Lu et al., 2001 ] during mercury depletion events (MDE), the discharge of this toxic and bio‐accumulating pollutant in water systems could be a threat to ecosystems and local indigenous populations.