Causes of acidification of four streams on Laurel Hill in southwestern Pennsylvania

A study of the chemistry of atmospheric deposition, soil leachate and stream water and fish populations was conducted during 1980-1981, emphasizing dormant season periods with runoff from snowmelt and rain. Although bedrock geology altered the natural buffering capacity of these streams, only acid precipitation could be linked to sharp drops in pH and increases in total aluminum concentrations observed during stormflows in the poorly-buffered streams. Three poorly-buffered streams exhibited drops to pH 4.4-4.5 and increases in total aluminum concentrations up to 1.5 mg/l during observed peak flows. Mineral soil leachate from the three major soil series on the basins exhibited a low pH of 4.3 and average total aluminum concentrations of 3.6 mg/l, indicating stream response during storms was closely linked to chemistry of soil leachate. Poorly-buffered streams did not support reproducing populations of trout or other fishes. In contrast, one well-buffered stream (equivalent 20 mg/l CaCO/sub 3/) only exhibited drops to pH 5.5 during peak flow and supported reproducing trout and sculpin populations. The loss of fish populations in poorly-buffered streams was attributed to acidification of forest soils by precipitation. 19 references, 14 figures, 12 tables.