GM Snow Study at the University of Michigan Biological Station, Pellston, MI (1982-1987)

Wet and dry deposition were monitored at the University of Michigan Biological Station, which is located near the northern tip of Michigan's lower peninsula, for three winters. Dry deposition was measured by both conventional bucket method and by measuring increases in concentration in snow samples. Average results of the two methods were in reasonable agreement. The cumulative wet and dry deposition quantities are in good agreement with snowpack accumulations until the first thaw period. Dry deposition to snow accounts for less than 15% of the total H+, SO4-2, NO-3, NH4+, and approximately 25% of the Ca2+, Mg2+, Na+, J+, and Cl-, during an average precipitation year. Snowpack measurements were also made under deciduous and red pine canopies. Decreases in H+ and NO-3 were observed under the red pine canopy. Snowmelt and runoff were studied during the 1986-87, 1983-84, and the 1982-83 winters at the University of Michigan Biological Station. For the 1982-83 and 1983-84 winters the first 50% of snowpack acidity was released in melt and rain water equal to 25% of the original snowpack water content. Interaction between the meltwater and the litter layer produced large changes in the concentrations of most species. Runoff to two streams had high SO4-2 and very low NO-3 concentrations. It is concluded that most of the NO-3 is either biologically utilized or retained in the ecosystem, even during the early snowmelt period at this site.