Chemistry of Atmospheric Deposition, the Snowpack, and Snowmelt in the Turkey Lakes Watershed

Abstract

Bulk and wet-only deposition and the snowpack were monitored at the Turkey Lakes Watershed in northern Ontario over the winter and spring of 1986. Based on a comparison with snowpack and cumulative snowmelt, the bulk sampler overcollected major ions by factors ranging from 6 to 22%. Nitrate appeared to be preferentially collected by the bulk sampler relative to SO42− during snow events. Dry deposition was estimated to be 12 and 5% of total deposition forSO42− and NO3−, respectively. Ion budgets for cumulative bulk deposition and snowmelt supported the hypothesis that ion losses from the snowpack are insignificant during a winter having no melt episodes. Snowmelt was characterized by chemical fractionation of major ions; SO42− and H+ in initial meltwaters were 10 times more concentrated than the premelt snowpack. Preferential elution of ions in the snowmelt followed the sequence: SO42− > NO3− > H+ > Cl−. Snowmelt chemistry was used to predict changes in lake chemistry: H+, NO3−, and NH4+ levels should increase in lake waters; Ca2+ decreases through dilution by snowmelt; SO42− concentrations remain fairly constant.