Impacts of coal pile leachate on a forested wetland in South Carolina

Abstract

This study was conducted to: (1) determine the probable cause of several areas of stressed and dead vegetation adjacent to a 15-yr-old reject coal pile in western South Carolina and (2) identify the factors limiting successful revegetation of the site. Data from an earlier study suggested that solution pH, total dissolved solids (TDS) and electrical conductivity (EC), and/or elevated trace element concentrations may have contributed to the stress and dieback. Soil water in the two vegetation kill zones is saline (TDS>10 000 mg L−1 and EC>4 dS m−1), highly acidic (soil pH 200 mg L−1 and Mn conc.>10 mg L−1). Soil water in areas of sparse vegetation is brackish (TDS>1000 mg L−1 and EC>2 dS m−1) and acidic (soil pH 40.5 mg Al L−1). Tissue samples were collected from volunteer loblolly pine (Pinns taeda L.) seedlings growing in the study area and analyzed for essential and non-essential elements. Seedling tissues did not contain abnormal concentrations of nutrients or trace elements. The strong relationship between the zones of vegetation stress and dieback and solution pH and soluble salt concentrations, and the lack of excessive metal accumulations by tree seedlings which have become established in the less toxic portions of the study area, suggest that low solution pH and high soluble salts are more important factors limiting plant establishment on this site than solution metal concentrations. The results of this study demonstrate the importance of site hydrology in determining the impacts of coal waste disposal on adjacent ecosystems.