Assessment of toxic metals dispersed from improperly disposed tailing, Jebel Ressas mine, NE Tunisia

Mining activity is one of the most important sources of heavy metals in the environment. In NE Tunisia, the former Jebel Ressas mine represents a great hazard due to huge amounts of waste deposited in waste dumps and tailings often with high concentration of heavy metal pollution. The aim of this study was to determine total heavy metal contents in the mining wastes and in the soil samples collected in the vicinity of the former Jebel Ressas mine and to evaluate the mobility of heavy metals in the surrounding agricultural soils. The pH, CEC, organic matter content and total carbonate content in all the samples (soil and tailings) were also measured using the standard methods. The mine tailings are characterized by high levels of Cd (18-89 mg kg(-1)), Pb (433-5845 mg kg(-1)) and Zn (1682-40970 mg kg(-1)). The adjacent soils were also highly contaminated with metals. These toxic metal concentrations exceed those environmental standards proposed by the Off J Eur Communities L181: 6-12 (1986) for agricultural soils (3, 300, and 300 mg kg(-1) for Cd, Pb and Zn, respectively). Selective extractions used to estimate the risks of toxic element mobilization show that a very low proportion of heavy metals is water soluble and exchangeable.