MOBILITY OF LEAD IN MINE TAILINGS DUE TO LANDFILL LEACHATE

An old lead mine tailings pile in Southeast Missouri is being used as a sanitary landfill. The tailings were found to consist of 60-70% dolo mite, 20-30% mascovite/illite and trace amounts of quartz, galena, and calcite. The pH was 8.1 and the lead concentrations were 810-3200 mg/ kg. Several samples at the site were found hazardous using the EPA tox icity characteristic leaching procedure (TCLP). Since little was known about the mobility of the lead under these conditions, laboratory sca le column experiments were conducted to determine if the lead in the t ailings might be mobilized with a landfill leachate. Total lead was de termined and lead availability was determined using sequential extract ion. The lead associated with Fractions 1 (MgCl2), 2 (NH4OAc), and 3 ( Na4P2O7) of the sequential extraction leached rapidly and immediately produced a leachate after 1 hr of 440 mg/L before decreasing to 40 mg/ L after 12 hr. Fraction 4 (EDTA) and Fraction 5 (HNO3), were unaffecte d by the leachate.