Changes in Soil Zn and Mn Forms of Some Contaminated Egyptian Soils Treated with Organic Materials.

An incubation experiment using three contaminated soils from Helwan, El-Gabal El-Asfar (Cairo governorate) and Arab El-Madabeg (Assiut governorate) was conducted for 16 weeks to evaluate effects of four organic materials including ethylene diamine tetra acetic acid (EDTA) as a synthetic organic material as well as poultry litter extract (PLE), vinase (V) and humic acid (HA) solutions as natural organic materials on zinc (Zn) and manganese (Mn) forms of thesecontaminated soils. The studied chemical metal forms were soluble plus exchangeable (S+EXCH), carbonate bound (C-bound), Mn oxide bound (MnO-bound), organic bound (O-bound,), Poorly crystalline Fe oxide bound (PCFeO-bound) and crystalline Fe oxide bound (CFeO-bound) and residual forms.
The results showed that the transformation of soil Zn among its chemical forms was great in all studied soils treated with EDTA. Vinase was in the second order, with respect of the change efficiency, followed by PLE and HA. Increase in the soluble and exchangeable Zn induced by EDTA weretransformed mainly from PCFeO-bound and residual formsinHelwan soil, from C-bound, O-bound, PCFeO-bound and CFeO- bound forms in El-Gabal El-Asfar soil, and from C-bound,MnO-bound, PCFeO-bound and residual in El-Madabeg soil. The distribution order of Mn forms in all studied soils according to Mn abundance changed with using various organic materials. As it isindicated with Zn, EDTA was the most effective organic material in increasing the soluble plus exchangeable Mn in all tested soils. The increases in the soluble and exchangeable form of Mn induced by EDTA were on the expense of decreasing mainly the Mn-oxide (33.8%), and poorly crystalline Fe oxide (31.4%) forms, and partially the crystalline Fe oxide (7.0%), organically bound (20.41%) and residual (9.7%) forms in Helwan soil.