Assessment of Bioavailability of Some Heavy Metals to Wheat and Faba Bean in Sahl El-Tina, Egypt

Abstract

Accumulation of heavy metals viz., Mn, Zn, Cu, Ni, Pb, Co, Cd and Cr in soils and commonly grown crop plants (wheat and faba bean) was studied in the fields in Sahl El-Tina, located in the Northwestern Sinai Peninsula, Egypt. Irrigation water at different sites was slight to moderately saline with no sodium hazard. About 50% of irrigation water samples revealed salt combinations consisting of NaCl, MgCl2, MgSO4, CaSO4 and Ca(HCO3)2, thereby indicating marine salt pollution. The results also revealed that heavy metals in irrigation and drainage water were within the recommended levels. The total contents of Ni, Pb, Co and Cd in subsoil samples were higher than the levels in topsoil samples, suggesting strong evidence of indigenous supply. However, total contents of Mn, Zn, Cu and Cr in topsoil samples were higher than the levels in subsoil samples, implying anthropogenic source of contamination. The highest single-element pollution index value in soil was found for Cd, which ranged from 0.289 to 3.763, indicating low to high contamination levels. Except for Zn and Pb which showed low contamination level, other elements showed low to moderate contamination levels in soil. The combined pollution index ranged from 0.238 to 1.688, indicating low to moderate multi-element contamination levels in soil. Except for Zn and Cd, the levels of heavy metals in wheat and faba bean were greater than the permissible limits. The highest transfer coefficients of metals from soil to plant were found for Zn and Cd in wheat. On the other hand, the highest coefficients in faba bean were found for Pb, Cd, Zn and Cu. Faba bean showed the ability to accumulate heavy metals in higher amounts than wheat. It was evident that there is a multi-element pollution source for the growing crops in Sahl El-Tina that could be due to the anthropogenic activities in respect of some elements but inherently for others.