Treating lead-contaminated soil by stabilization and solidification

Soil in and near transportation facilities often is contaminated with lead because lead once was used as a base for gasoline and paint. Dealing with contaminated soil is difficult because the toxic material must be treated to protect the public from direct exposure. Stabilization and solidification is a promising technique for protecting the public from toxic materials in soils by decreasing the possibility of human exposure and decreasing the mobility of the contaminant. The results of a laboratory investigation of the feasibility of stabilization and solidification of contaminated soil using cement in combination with various additives are presented. Mobility of lead and other contaminants was measured by dynamic diffusion and compared with the standard test results of the toxic characteristic leaching procedure. Several additives were tried. Apatite and sodium silicate were found to be the most effective in reducing the mobility of the lead. The compacted dry density of the solidified soil had a great effect on the leaching characteristics. The leaching of lead from deteriorated solidified soil was simulated by crushing a sample containing apatite and conducting a dynamic diffusion test on the crushed sample. The diffusion coefficient was used to compare the effect of additives and other treatments.