Monday, 10 April 2017 13:17

Impact of some soil amendments on controlling heavy metals toxicity in some contaminated soils.

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Impact of some soil amendments on controlling heavy metals toxicity in some contaminated soils.
Abo-El-Enein*, S. A.; S. A. Radwan**; I. A. Ashour*** and Eman. A. Mohammed**
*Physical chemistry department, Faculty of science, Ain Shams Univ., Cairo, Egypt.
** Soil chemistry and Physics department, Desert Research Center, Cairo, Egypt.
***Soil Conservation department, Desert Research Center, Cairo, Egypt.
ABSTRACT
A pot experiment was conducted under laboratory conditions at Desert Research Center, Cairo, Egypt. The aim of this experiment is to study the role of three soil amendments; i.e. rock phosphate, nano-hydroxy apatite and poultry litter manure on reducing the hazard effects of some heavy metals in contaminated soils and wheat plants grown in it. The investigated soils were alluvial silt clay and alluvial clay soils from El Salam canal and Bahr El-Baker drain areas, respectively as well as calcareous sandy clay loam from Ras Sudr. Sequential extraction was used to fractionate heavy metals, i.e., Cd, Pb and Zn to evaluate their mobility and bioavailability in such soils.
Results indicated that cadmium was predominantly associated with the crystalline Fe oxides fraction, while lead and zinc were predominantly associated with the residual fraction. By applying the modified degree of contamination index, it can be noticed that El Salam soil suffering from a high degree of contamination and Bahar El Bakar soil suffering from a very high degree of contamination, while Ras Sudr soil sample has a moderate degree of contamination.
Results also indicated that the application of rock phosphate, nano-hydroxy apatite and poultry manure reduced Cd, Pb and Zn mobility in all the investigated soils through metals transformation from non-residual to residual forms.
Mobility factor of heavy metals reduced due to the applied soil amendments and the efficiency of amendments on reducing such factor was in the following order: nano- hydroxy apatite < rock phosphate < poultry manure.
Egyptian Journal of Environmental Research EJER, Vol. 6, January 2017
79
The present data showed that the addition of all the applied materials reduced the concentration of Cd, Pb and Zn in wheat roots and shoots.
It can be concluded that the toxicity of heavy metals does not depend only on its concentration in soil, but also depends on different forms in which metals are present. The applied soil amendments, especially nano hydroxy apatite have high effects on decreasing chemically available heavy metals in soil as well as decreasing their concentrations in wheat plant. Most of these materials are available in large amounts, So the application of such materials can be used as effective strategy to remediate soils polluted with heavy metals.

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