Environmental Conditions of Green Valley Lake

Abstract

Green Valley Lake, western Indiana, has experienced periodic inputs of acid mine drainage (AMD) from the abandoned Green Valley Coal Mine. The lake serves as a state fishing area, and AMD inputs may affect the aquatic ecosystem and human health. The purpose of this research is to determine to what extent the sediments in Green Valley Lake are acting as sinks for metals and if they may impact water quality. Water and bottom sediment samples were taken throughout the lake to evaluate spatial variability of contamination and to determine how the metal concentrations compared to Post Archean Average Shale (PAAS) background values and sediment quality guidelines (SQGs) values. Three cores were taken from the Northwest portion of the lake, where AMD enters via surface flow to evaluate temporal changes in contamination. Results indicate that water quality at Green Valley is acceptable, pH is slightly acidic (pH=6.4) near the locations of AMD input and increases to the east (pH=8.30). The northwest portion of Green Valley Lake is an eutrophic lake, based on its nutrient levels and Secchi disk measurements. Organic matter content, based on LOI, is higher in the older portion of the lake (7-33 wt %) due to the influence of vegetation surrounding the lake. Bottom sediment at Green Valley Lake are acting as a sink for metals and nutrients. Ni and Cd concentrations are above the sediment quality guidelines severe effect level, while Zn and Pb were above the probable effect level. Metals over the severe and probably effect levels should continue to be monitored in the sediments at Green Valley Lake to ensure that organisms are not being impacted.