Widespread soil contamination of heavy metals such as Cd, Cu, Hg, Pb, Ni, Zn, As, and Cr from mining, industrial, agricultural, and geological sources poses serious environmental risk around the world. Many of the elements are listed on top of the priority pollutants list because of their high toxicity to human health as well as the ecosystem at trace levels (Adriano, 2001). Their transport in the vadose zone and aquifers can lead to further pollution of surface and groundwater (Selim and Amacher, 1997).