LANDFILLING COAL COMBUSTION RESIDUALS: GEOCHEMICAL MOBILITY AND FATE

As the United States continues to utilize coal as one of its primary sources of energy production, the waste produced by the nearly six hundred coal-fired power plants must be addressed. Presently, the by-products of burning coal, coal combustion residuals (CCRs), are beneficially re-used or held in surface impoundments or landfills indefinitely. Previous studies have examined CCRs held in wet and dry storage, as well as the fresh ash before storage, and demonstrated that the behavior of constituents in fresh ash is distinct from weathered ash. Despite this, few studies have examined the geochemical stratigraphy and behavior of coal combustion residuals in an ash holding pond. This study utilized two cores (10.7 m and 9.1 m depths) from a closed ash disposal pond to investigate the leaching potential of contaminants and mobility of resources (i.e. rare earth elements) with depth in the CCR pond. Ash samples taken from discrete intervals from both cores (9 and 18) were mixed with deionized water for approximately 24 hours, then centrifuged and filtered. We analyzed the leachate samples for trace element concentration using inductively coupled plasma mass spectrometry and the concentrations of cations and anions using ion chromatography to determine. The leachate from core #9 increased in cation concentration (Ca, Na, Mg, K, and Li) with depth indicating greater cation adsorption to the surface of the CCRs and greater mobility in water. Core #18 had greater variation in leached cation concentration with depth. The cores provide the unique opportunity to study CCR weathering and geochemical behavior with depth, as well as the identification of changes in morphology between fresh and landfill-stored coal ash.