Preliminary Assessment of Radiological Effects of Ash Disposal on Groundwater

摘要

Limited sampling in and around sluiced-ash impoundments at four coal-fueled power plants was performed to investigate potential contamination of groundwater by naturally occurring radioactive materials (NORM) in coal ash. Samples included groundwater samples from monitoring wells located both upgradient and downgradient of the ash disposal areas as well as ash leachate samples obtained from wellpoints completed in ash deposits. Filtered samples were analyzed for gross alpha, gross beta, total radium, radon-222, and uranium. Statistical analysis provided evidence that ash leachate samples contained significantly higher gross beta activities than background groundwater samples. Ash-related beta emitting isotopes were further shown to have affected groundwater downgradient of the ash disposal facilities. Statistical results were inconclusive regarding whether ash leachate samples contained significantly higher gross alpha activities than background groundwater samples. However, downgradient groundwater samples were affected by ash-related alpha activity. While exceedences of EPA's drinking water maximum contaminant levels (MCL) for gross alpha and gross beta were noted in a small number of ash leachate samples, no such exceedences were found in downgradient groundwater samples. Total radium activities of the ash leachates were found to be statistically indistinguishable from those of both background and downgradient groundwater samples. Furthermore, there were no radium MCL exceedences in either the ash leachate samples or in downgradient groundwater samples. Interestingly, radon-222 levels in background groundwater samples were significantly higher than those of both ash leachate and downgradient groundwater samples indicating the presence of natural radon sources other than coal ash in background samples.