Water quality of selected lakes in Mount Rainier National Park, Washington with respect to lake acidification

Turney, G; Dion, N; Sumioka, S

Thirteen lakes in Mount Rainier National Park were evaluated for general chemical characteristics, sensitivity to acidification by acidic precipitation, and degree of existing acidification. They were found to be pristine for the most part. The lakes studied were Alien, one of the Chenuis group, Crescent, Crystal, Eleanor, Fan, one of the Golden group, Marsh, Mowich, Mystic, Shriner, and two unnamed lakes. The lakes were sampled in August 1983. Specific-conductance values were generally 21 uS/cm (microsiemens per centimeter at 25 C) or less, and dissolved-solids concentrations were generally 20 milligrams per liter (mg/L) or less. The major cations were calcium and sodium, and the major anion was bicarbonate (or alkalinity). Alkalinity concentrations ranged from 2.1 to 9.0 mg/L in 12 of the lakes. Alien Lake was the exception, having an alkalinity concentration of 27 mg/L. The pH values for all of the lakes ranged from 5.8 to 6.5. In most of the lakes vertical profiles of temperature, dissolved oxygen, pH, and specific conductance were relatively uniform. In the deeper lakes, temperature decreased with depth and dissolved-oxygen concentrations increased to about 20 feet, remained constant to 80 feet, then decreased with increasing depth. Exceptions to general water quality patterns were observed in three lakes. Alien Lake had a specific conductance value of 58 uS/cm and an alkalinity concentration of 27 mg/L. The lake of the Golden group was anaerobic at the bottom and had relatively high concentrations of dissolved organic carbon and dissolved metals. It also had a lower light transmission than the other lakes studied. One of the unnamed lakes had relatively high concentrations of phytoplankton and dissolved organic carbon and relatively low levels of light transmission. Comparisons of lake data to acid-sensitivity thresholds for specific conductance and alkalinity indicated that all of the lakes except Alien would be sensitive to acidic precipitation. The small sizes of the lakes, and their locations in basins of high precipitation and weathering-resistant rock types, enhance their sensitivity. None of the lakes in this study appeared to be presently acidified. pH values were above the levels generally accepted as indicative of acidification (pH = 5.5), and nitrate, sulfate and metals concentrations were low. Plots based on pH and calcium (which represented "original" alkalinity) suggested that most of the lakes are not being acidified.

Water quality of selected lakes in Mount Rainier National Park, Washington with respect to lake acidification

Series