Flow path‐composition relationships for groundwater entering an acidic lake

The relationship of groundwater flow paths to the acid/base status and composition of groundwater was examined by directly monitoring groundwater inputs to an acidic Adirondack, New York, lake (Dart's Lake). Groundwater inputs near the shoreline of the lake were acidic throughout the year (pH <5 and alkalinity <0 μeq L⁻¹) and reflected the influence of shallow soil horizons. Groundwater transported within the deep surficial deposits and through sediments farther from shore was characterized by higher alkalinity and higher pH values and was enriched in nitrate (>40 μeq L⁻¹). Elevated concentrations of basic cations and alkalinity as well as lower concentrations of organic anions and sulfate were characteristic of deep groundwater entering the lake at the study site. Spatial variability of groundwater chemistry was found to be substantial over a relatively short distance (<6 m) from the lake shoreline and indicates that inputs to the lake of components dissolved in groundwater are highly flow path dependent.