Uptake of Some Toxic Elements by Wild Plants in Siwaqa Area/Central Jordan

Heavy metals and trace elements such as: arsenic (As), cadmium (Cd), selenium (Se), and strontium (Sr) are naturally occurring in rocks and soil environment resulted from pedogenetic processes of weathering (Pierzynski et al., 2000). These elements are important in contaminating surface and ground waters and decreasing crop production as a result of bioaccumulation and biomagnification in the food chain. Knowledge of basic chemistry, environmental and associated health effects of these heavy metals is important to understand their speciation, bioavailability, and remedial options. Heavy metals are absorbed in the soil, by initial fast reactions (minutes, hours), followed by slow adsorption reactions (days, years) by plants, redistributed into different chemical forms with varying bioavailability, mobility, and toxicity (Shiowatana et al., 2001). Heavy metals distribution in soils take place as a result of mineral precipitation and dissolution, ion exchange, adsorption, aqueous complexation, biological immobilization and mobilization, and plant uptake (Levy et al., 1992). Potentially toxic elements in soils and plants may come from the bedrock itself and anthropogenic sources like solid or liquid waste deposits (Wilson & Pyatt, 2007). Plants are important components of ecosystems as they transfer elements from abiotic into biotic environments. All plants have the ability to accumulate essential elements from the soil and need different concentrations from these elements for growth and development. This ability also allows plants to accumulate other non-essential elements which have not known biological function (Djingova & Kuleff, 2000). Several studies have been carried out to evaluate and describe The accumulation of toxic trace elements and its impacts on the plant diversity were investigated by many authors and in different regions (Chen et al., 2005; Tomé et al., 2002). The soils and plants contain all naturally occuring radioactive elements with half-lives comparable to the age