ELEMENTAL CHARACTERIZATION OF COAL ASH AND ITS LEACHATES USING SEQUENTIAL EXTRACTION TECHNIQUES

Over 50 million tons of coal ash are produced annually in North Americ a. Technological improvements in air pollution control have decreased stack emissions-but have also increased contaminant concentrations in the ash of coal-fired boiler applications. The leaching of heavy metal s and other elements during regulatory tests may cause coal ash to be classified as hazardous waste; complicating land disposal. The hazardo us nature of coal ash remains unclear because current toxicity tests f ail to effectively characterize the elemental distribution and chemica l solubility of trace metals in the landfill environment. Leaching cha racteristics of ash samples can be investigated with various laborator y extraction procedures in association with multi-elemental analytical techniques (e.g., neutron activation analysis and inductively coupled plasma - atomic emission spectroscopy). Such methods provide more tho rough analyses of coal ash leaching dynamics than the regulatory asses sments can demonstrate. Regulatory elements including Ag, As, Ba, Cd, Cr, Hg, Pb, and Se were shown to remain in largely insoluble forms whi le elements such as B and S leached at higher levels. Experimental res ults may assist operators of coal-fired boiler industries in selecting coal types and disposal options to curtail the leaching of potentiall y toxic inorganic contaminants.