EFFICIENCY IN PHYTOEXTRACTION OF HEAVY METALS FROM SOIL NEAR METAL DUMPSITES BY SOME SELECTED PLANTS IN ZARIA NIGERIA

Abstract

 This research work is to investigate the efficiency ofphytoextraction of heavy metals from soils near scrap-metal dumpsites by Vetiverazizanioide, Ipomoea asarifolia,Helianthusannus, Ricinuscommunis L. and Cymbopogoncitratusat Dakace, Gaskiya and Hanwa in Zaria, Nigeria. Soil and grown plant samples were collected from each dumpsite. The samples were digested using aqua regia and the concentrations of Cd, Co, Cu, Ni, Pb and Zn were determined by atomic absorption spetrophotometric (AAS) method. The pollution index of the soil and the bioaccumulation factor of the heavy metals in the plants were calculated. The results obtained indicated that the concentrations of the heavy metals at the dumpsites were higher than those at the control site and the limits recommended by WHO. The bioaccumulation factors for all the metals were greater than 1.The percentage removal of the heavy metals by the five plant species were as follows: : Dakace site: Cd- 52.5%, Co – 0.6%, Cu – 44.3%, Ni – 88.4%, Pb – 13% and Zn – 28%; Gaskiya site: Cd – 45.7%, Co – 15.7%, Cu – 24.5%, Ni – 69.7%, Pb – 21.2% and Zn – 17.1%; Hanwa site: Cd – 36.7%, Co – 1.2%, Cu – 28.4%, Ni – 20.5%, Pb – 17.4% and Zn – 17.2%. The five studied plant speciess are very efficient in removing heavy metals from soil, thus can be used in the remediation process.