Soils can naturally reduce mobility and bioavailability of heavy metals as they are retained in soil by sorption, precipitation and complexion reactions. Theses natural process can be accelerated by addition of some soil amendments which converting the soluble forms to more geochemical stable solid phases. Hence, the current study represents a trail towards ameliorating soils polluted with heavy metals resulted from some anthropogenic activity. To achieve this target, in situ an incubation experiment was executed on two soil samples taken from El-Gabal El-Asfar farm (Qalubia Governorate) and El-Saff (Giza Governorate), subjected to heavy metals pollution due irrigation with sewage effluent and industrial wastes, respectively. The studied two soils were mixed thoroughly in pots of 200 g soil capacity with some soils amendments i.e. poultry manure, organic compost and bentonite at a rate of 2%, then the pots were daily wetted with distilled water to reach a constant moisture content (field capacity) and incubated under room temperature at different periods of 0, 25, 50 and 75 days.
Soil samples were taken to identify the effective role of the applied soil amendments throughout at the different incubation periods, however, these values of EDTA-extractable Ni, Co and Cd were determined the most important obtained results could be summarized in the following:
1. EDTA-extricable amounts of Ni, Co showed a progressively decrease in both amended soils with poultry manure, with a more effective role by increasing time of incubation period. The removed amount of the studied metals for both investigated soils followed the decreasing order: Ni> Co > Cd. Also,, the removal capacity of poultry manure seemed a highest figure with Ni, lowest with Co and intermediate with Cd.
2. Applications of organic compost led to minimize the value of EDTA-extractable Ni, Co and Cd in both soils under study. The adsorbed amount of these metals in El-Gabal El-Asfar soils exceeded obviously the corresponding ones in El-Saff soil. This trend was emphasized by the removal capacity of the compost for Ni, Co and Cd, which was recorded higher values in El-Gabel El-Asfar soil than El-Saff one.
3. Values of EDTA-extricable Ni, Co and Cd from both the bentonite amended soils also showed progressively decreased with increasing the incubation period. The absolute adsorption amounts of Ni were the highest, whereas those pf Co and Cd were the lowest and intermediate, respectively, in the bentonite amended soils. In general, the removal capacity of bentonite for Ni was higher than Co and Cd over the studied incubation periods. It is noticed that the removal capacity of bentonite for Co was almost similar over all the incubation periods. |
