Water Resources Research Act Program

Details for Project ID 2015TN111B

Evaluating Environmental and Biological Impacts of Acid Runoff from Pyrite-Bearing Rock Formations

Institute: Tennessee
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $10,000 Total Non-Federal Funds: $20,094

Principal Investigators: William Sutton, DeEtra Young

Project Summary: Acid rock drainage (ARD) from iron-sulfide bearing geologic formations in road cuts and road construction can have negative impacts on receiving streams due to low pH, occurrence and transport of metals from the site, and the potential impact of these hazards on biota. The iron-sulfide minerals that cause acid-mine drainage (pyrite, marcasite, pyrrhotite) are commonly found in south-eastern United States shale formations. When these iron-sulfide minerals are exposed to oxidative weathering processes by natural or human-induced conditions, such as landslides or construction projects, bacteria induced ARD may develop. The resulting pH of ARD typically ranges from 2 to 4 and can even range as low as -0.5. Many metals found in the surrounding rocks become soluble under acidic conditions. Consequently, ARD typically releases coinciding metals, as well as, acidity to aquatic ecosystems. During the warm, dry season, the ARD escarpments continue to seep acidic waters, rich in minerals that reflect the geochemistry of the rock. The reduction in rain and increase in air temperature leads to evaporation and concentration of acidic seepage waters, resulting in the temporary storage of highly soluble efflorescent sulfate salts. This is referred to as temporary storage because moderate to heavy storms typically dissolve and transport these secondary sulfate minerals (SSM) downstream. This rapid dissolution of SSM into the runoff waters leads to a first flush rich in sulfates, calcium and coinciding metals from the surrounding bedrock. This low pH, mineral-rich first flush could have a significant impact on the biota in small receiving streams. Our study proposes to evaluate the potential environmental and biological consequences of ARD at each of two total sites in the Chattanooga and Fentress shale formations in Middle Tennessee. Overall, the primary objectives of the investigation are to identify chemical and hydrologic conditions that affect the release of acid and minerals from ARD sites into headwater streams and evaluate biological impacts of ARD on stream-dwelling fauna, primarily streamside salamanders. Activities we will undertake include coordinating with the U.S. Geological Survey Lower Mississippi Gulf Coast Water Science Center (USGS) to evaluate environmental biological impacts of acid runoff from pyrite-bearing rock formations. TSU will take the lead on evaluating the biological impacts of ARD runoff on stream ecosystems by using streamside salamanders as indicators of biological condition. TSU will also establish water-quality monitoring stations downstream of two USGS ARD sites. Collectively, our study will couple the geochemistry of first-flush aquatic inputs and the downstream impacts of ARD inputs on stream biological integrity. The results of this study will provide information on the impacts of ARD and potential remediation strategies that can be used by local, state, and federal agencies to diminish negative environmental impacts. In addition, as amphibian populations are in decline globally, our study will fill in distributional gaps in Middle Tennessee amphibians and aid in the identification of vulnerable and declining populations of stream-dwelling salamanders.