In this regard acid mine drainage,

In this regard acid mine drainage, tailings embank- ments, mining rock dumps and metallurgical waste piles are all sources of heavy metal pollution and as such pose a serious threat to the environment. A variety of tech- niques can be used for decontaminating and remediating contaminated soils, Dess`ı et al. (1999, 2000a), that rely on in situ or ex situ processes (soil-washing, physical separation, phytoremediation, leaching, etc.) or pro- cesses for immobilizing the contaminants so as to min- imize their release into the environment (Paspaliaris, 1999).The choice of technique will hinge on a number of factors related to the anticipated future use of the areas targeted for remediation, whether for industrial activi- ties or for public use, and on technical as well as eco- nomic and legislative considerations.In particular, in those cases where decontamination proves to be economically unsustainable, because of the actual nature of the material or because of the large volumes to be handled, immobilization techniques based on the addition of suitable substances are generally ac- ceptable if accompanied by suitable environmental im- pact study.