Abstract

The Central Electro-Chemical Research Institute in India has a department that specializes in the design of both lead and nickel-chromium batteries. However, the laboratories activities have brought soils contamination of this department. This work involves assessing the presence of heavy metals such as lead, nickel and chromium in contaminated soils in the Center through the single and sequential extraction methods. Three samples were taken notably: the witness sample S1, which made it possible to determine the optimum parameters extraction (pH and concentrations of the extractant solutions) and then S2 and S3 which constitute the contaminated soils. Among the three extractants used for simple extraction (EDTA, CaCl₂.2H₂O and CH₃COONH₄), the results show that EDTA extracts fairly high contents of Pb (77.63 ± 0.41 mg/kg), of Ni (67.37 ± 0.36 mg/kg) and Cr (60.22 ± 0.32 mg/kg). These contents constitute the bioavailable fraction of the three heavy metals and represent 69 to 84% of their total contents. The total contents contaminated soils are determined at 111.38 ± 0.59 mg/kg for lead, 79.95 ± 0.42 mg/kg for nickel and 74.47 ± 0.39 mg/kg for chromium. Compared with AFNOR standard NF U 44-041, the lead and nickel contents are higher. Moreover, the sequential extraction shows a large margin of the mobile and mobilizable fraction of all the metals studied in the contaminated soil samples. These results allow saying that there are risks of environmental pollution in the contaminated soils of the Central Electro-Chemical Research Institute.

Key words: Heavy metals, single extraction, sequential extraction, speciation, pollution.