Trace Metal Leaching and Bioavailability of Coal-Generated Fly Ash
Coal-generated fly ash, leaching, hazardous
International Science Congress Association
International Research Journal of Environment Sciences
Coal-generated fly ash (FA) is being used for various applications, although there is evidence that indicates leaching or vegetative uptake of trace metals can potentially reach hazardous concentrations. In this study, FA was obtained from a coalburning power plant in Pennsylvania and was tested for its leaching potential of selected trace metals (Al, As, Ba, Ca, Cr, Co, Cu, Fe, Pb, Mg, Mn, Ni, Se, Sr, V, and Zn). SEM observations show the FA has an abundance of large, porous, irregularshaped grains that would absorb water, which would adversely affect the quality of a cement application. A comparison with another FA with typical glass spheres demonstrates the differences in FA structure and physical characteristics. An analysis of FA total metal content indicated a number of trace metals are over the cleanup standard limits for residential land over an aquifer. The FA leaching potential was determined by the Toxicity Characteristic Leaching Procedure (TCLP) and the Synthetic Precipitate Leaching Procedure (SPLP) tests. The results show that Se was over the TCLP limit, while As and V were over the U.S. drinking water Maximum Contaminate Level (MLC) for the SPLP test. However, these leachate tests have been criticized for not appropriately simulating the complex deposition and use conditions. Further research is required to develop applicable leaching test protocols for the various applications of FA.