1. Introduction
Heavy metal contamination of soil is widespread in many parts of the world. Lead derivatives, which are toxic even at low concentrations, cause brain disorders in children and peripheral nerve and kidney malfunction in adults (Ginneken et al., 2007, Padmavathiamma and Li, 2010 and Huang et al., 2012). Lead-contaminated agricultural soil is a prevalent concern because it affects consumer health through the food supply (Boussen et al., 2013).