Contamination of a calcareous soil by battery industry wastes. I. Characterization

A study of soil contamination due to the disposal of waste from a battery i ndustry was conducted. The soil particle size, organic matter content, and buffering capacity were characterized. The heavy metal content of the soil was characterized with soil depth, soil particle size, and with respect to the fraction of the soil by which it was retained. Lead was found to be the dominant contaminant with all other metals present at considerably lower c oncentrations. Most of the lead was retained in the fraction of the soil th at had a particle size less than 2 mm. This fraction represented 40.8% of t he soil and contained 24 600 mg Pb/kg of soil. A particle size analysis ind icated that 45.3% of soil particles were found to be greater than 4.75 mm. The pH of the contaminated soil in water was found to be 7.6 and was simila r to the background soil. The similarity in pH was attributed to the high c alcium content of the native soil. The lead content in the native soil that was collected 100 m away from the contaminated site was found to be 1967 m g/kg in the soil with particle sizes less than 2 mm (contaminated soil). Th e difference in pH between KCl solution (pH 7.0) and in water was found to be -0.6 indicating that the pH value was above the point of zero salt effec t. An evaluation of the buffering capacity revealed that 297 mL of 0.5 M HN O3 per kg of soil was required to substantially modify the soil pH. The hea vy metals in the soil were sequentially extracted to quantify the water sol uble, exchangeable, carbonate, oxides, organic matter, and residual fractio ns. The Pb concentrations were mainly found in the carbonate and oxide frac tions of the soil.