Environmental contamination by hazardous environmental pollutants is a widespread and increasingly serious problem confronting society, scientists, and regulators worldwide (Debenest et al. 2010; Hajeb et al. 2011; Nanthi and Bolan 2012; Shahid et al. 2013a). Among these pollutants, the heavy metals, are a loosely-defined group of elements that are similar in that they all exhibit metallic properties, and have atomic masses >20 (excluding the alkali metals) and specific gravities >5 (Rascio and Navari-Izzo 2011). This group mainly includes transition metals, some metalloids, and the lanthanides and actinides. Heavy metals can be toxic to plants, animals and humans, even at very low concentrations. Heavy metals are natural components of the earth’s crust and are present in different concentrations at different sites (Shahid et al. 2012a).