Processes and Causes of Lake Acidification during Spring Snowmelt in the West-Central Adirondack Mountains, New York

Abstract

The surface and outlets of two headwater lakes acidified during the 1978, 1979, and 1980 spring snowmelt periods. The decrease in pH was accompanied by an increase in nitrate whereas the other strong acid anion, SO₄²⁻, remained relatively constant. Chemical mass-balance calculations, using data from the Integrated Lake–Watershed Acidification Study, indicate that the peak in acidification observed in the Adirondack Mountains in the spring is caused by (1) a dilution of base cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺) and associated alkalinity by snowmelt, (2) an increase in NO₃⁻ concentration in the acidified portion of the lakes, and (3) the constant elevated concentration of SO₄²⁻. At Woods Lake, the NO₃⁻ that accumulated in the snowpack plus that deposited from the atmosphere during snowmelt was sufficient to account for the increased NO₃⁻ in and transported from the lake. At Panther Lake, an additional source of NO₃⁻ was needed and was believed to be contributed by nitrification in the upper soil horizons. If atmospheric deposition of sulfur is reduced, low-alkalinity systems like Woods and moderate-alkalinity systems like Panther will be less likely to develop strong acidity during spring acidification.