Chemical and physical characteristics of lakes in the northeastern United States

Abstract

A survey of the chemical status of 252 lakes, representing an estimated 2424 lakes, was conducted in the Southern Blue Ridge province and in Florida during Fall 1984. This survey was part of the Eastern Lake Survey designed to quantify the number of acidic lakes and lakes with low acid neutralizing capacity (ANC) with surface area greater than 4 ha. Of the 102 lakes sampled in the Southern Blue Ridge, none were acidic (ANC {le} 0) and only 1.4% of the population of 258 lakes were estimated to have low (ANC {<=}50 {mu}equiv/L). In contrast, an estimated 22% of the lakes in the Florida subregion were acidic, and 35.3% were estimated to have low ANC. Almost 90% of the lakes in the Southern Blue Ridge were reservoirs. These lakes generally had moderate ANC values (median = 250 {mu}equiv/L) and had low concentrations of aluminum, dissolved organic carbon (DOC), and sulfate compared to those of Florida, the upper Midwest, and the Northeast. The lakes in the Southern Blue Ridge showed a high degree of chemical homogeneity relative to those of other regions in the East. In contrast, the chemistry of lakes in Florida exhibited a high degree of heterogeneity, indicating themore » presence of several distinct subpopulations. Florida had the highest proportion of acidic lakes in the East, some of which had moderately high concentrations of aluminum, DOC, and sulfate. Some of the Florida lakes are naturally acidic from organic acids. However, the many clear water, acidic lakes exhibit chemical characteristics that are not inconsistent with a hypothesis of acidification from deposition. The geographic separation of the Southern Blue Ridge from Florida and the strong contrasts in physical and chemical characteristics of the respective subregions require that they be treated as distinct regions.« less