Evaluation of remedial alternatives of lead from shooting range soil

A contaminated soil from a shooting range leached sufficient lead to pose environmental risks to surface and groundwater due to the lead's mobility. The goal of this research was to evaluate remediation alternatives by improving our understanding of lead mobility. A soil was sampled from a former shooting range, and characterized for its physical and chemical properties, The soil is nonplastic, with about 30% of the particles by weight smaller than 0.075 mm, Other characteristics of the soil include pH of 5, organic carbon of 2.5% by weight, and 400 ppm of total lead. Sequential chemical extraction of the metals revealed that over 40% of the total lead is held at exchangeable sites or in the organic fraction of the studied soil, Toxicity characterization leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and pH-dependent leaching test batch experiments were conducted to examine lead mobility. Both TCLP and SPLP tests showed that the soil leached more lead than allowed under Connecticut standards for mobility. In the pH-dependent leaching test maximum leachable Pb was observed at a pH of 3, the minimum at a pH of 6, and increasing release of lead was observed at values of pH greater than 7, Three remediation techniques were investigated in an effort to reduce the mobility of lead, The first technique involved stabilization of Pb with apatite; the second was heating of the soil at 400 degrees C, and the third was solidification of the soil with Portland cement. Reduction of lead mobility to acceptable levels was achieved only by heat treatment.