A history of acid mine contamination, recovery, and eutrophication in Sandy Lake, Pennsylvania

Abstract

Sandy Lake, PA, was subject to acid mine contamination in the 1860s, which led to complete extirpation of fish. The mine effluent was soon diverted, but the watershed experienced continued deforestation, agricultural development, and population growth to the beginning of the twentieth century. Paleolimnological analyses of metals and diatoms clearly show the onset of acid mine drainage with rapid increases in concentrations of iron, manganese and sulfur, and decreases in diatom-inferred pH in the sedimentary profile, and a very rapid recovery following remediation. Diatom-inferred phosphorus suggests a period of oligotrophication following diversion of the acid mine drainage and reduction in lake catchment area. However, analyses of nutrients and algal pigments suggest continued eutrophication to the present in spite of increasing forest cover and a stable population over the last century. Pigments indicate a tenfold increase in phytoplankton, with cyanobacteria becoming a more significant portion of the biomass. Accumulation of sedimentary phosphorus has increased by a factor of 4 and sedimentary organic carbon by a factor of 5 since the mid-1800s.