Relationships Between High-Elevation Lake Water Chemistry and Soil Chemistry

Abstract

Past atmospheric deposition of sulfuric and nitric acids (“acid rain”) has acidified high elevation lakes across Maine and New England, affecting the ecology of the lakes and their surroundings. Since the passage of the Clean Air Act Amendments in 1990, acid deposition has declined and many of the affected lakes have begun to recover. However, this recovery trajectory does not look the same at all lakes. Across western Maine, nine high-elevation lakes have been part of long-term water chemistry monitoring since 1986 and show variation in their pH trends over time, with five of the lakes increasing in pH, three declining in pH, and one showing no trend. To investigate why acidification recovery trends vary by lake, we explored relationships between water chemistry pH and ANC trends as response variables, and lake and watershed morphology and current watershed soil pH and dominant ions as predictors. We found no significant relationship between lake recovery and morphology, watershed morphology, or watershed soil pH. However, there was a relationship between soil pH and the lake sulfate trends. Further studies focusing on underlying surficial geology and longitudinal data collection on watershed soil chemistry will be useful to further reveal influences on lake recovery from acid deposition