PHYTOEXTRACTION OF SOME HEAVY METALS FROM SELECTED METAL DUMPSITES IN ZARIA, NIGERIA
PHYTOEXTRACTION OF SOME HEAVY METALS FROM SELECTED METAL DUMPSITES IN ZARIA, NIGERIA
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Date
2015-07
Authors
YASHIM, ZAKKA ISRAILA
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Abstract
A field trial to investigate the phyto-extraction of Cd, Co, Cu, Ni, Pb and Zn by Vetivera zizanioide (Jema), Ipomoea asarifolia (duman kada) Helianthus annus (sunflower), Ricinus communis L. (Castor oil plant) and Cymbopogon citratus (Lemon grass) planted on contaminated soils at Dakace, Gaskiya and Hanwa in Zaria, Nigeria was carried out between July to September, 2013. The effect of application of ethylenediamine-tetraacetic acid (EDTA) on the phyto-extraction of the studied metals by the test plants was also investigated. The harvested plants and the soils collected from the experimental and control sites were analyzed using atomic absorption spectrometry to determine the concentrations of these elements in different parts of each plant species and the soil treated and untreated with EDTA. The physicochemical parameters of the soil such as pH, moisture content, particle size, cation exchange capacity (CEC), organic matter (OM), chloride, phosphates, nitrates and sulphates were determined. The soils was subjected to sequential extraction to ascertain the bioavailability of the metals in the soils. Statistical analysis on the data obtained was carried out using One- way ANOVA. The results indicated that the soils at the experimental and control sites were sandy loam in texture, slightly acidic for the experimental soils and slightly alkaline for the control soil. The %OM and CEC for the experimental soils were higher than the soils of the Nigerian savanna. The concentrations of the studied metals in the soils from experimental sites were higher than the corresponding values from the control site, and higher than the recommended limits given by the Joint Food and Agricultural Organization and the World Health Organization (FAO/WHO). The Nemero Pollution Index showed that soils at the experimental sites were slightly to moderately polluted with Cd, Co, Ni and Zn and very heavily polluted with Pb. The
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percentage bioavailability of metals at the experimental sites were: At Dakace Cd - 22.7%, Co - 29.7%, Cu – 80.7%, Ni – 53.2%, Pb – 24.3%, Zn – 64.3%; at Gaskiya, Cd – 22.4%, Co – 30.3%, Cu – 56.7%, Ni – 43.0%, Pb – 22.3%, Zn – 47.6% and at Hanwa, Cd – 21.4%, Co – 34.8%, Cu – 41.2%, Ni -42.5%, Pb – 18.7%, Zn – 63.4%. The Bioaccumulation factor (BF) and Transfer factor (TF) for the metals varied from plant to plant. The percentage removal of the studied metals from the EDTA treated soils and non EDTA treated soils were: At Dakace site, without EDTA application (natural) were: Cd- 52.5%, Co – 0.6%, Cu – 44.3%, Ni – 88.4%, Pb – 13% and Zn – 28%; with EDTA application: Cd – 70.3%, Co – 1.2%, Cu – 70.5%, Ni – 89.9%, Pb – 38.3% and Zn – 36%; At Gaskiya site without EDTA application (natural): Cd – 45.7%, Co – 15.7%, Cu – 24.5%, Ni – 69.7%, Pb – 21.2% and Zn – 17.1%; with EDTA application: Cd -62%, Co – 19.2%, Cu – 60.4%, Ni – 90.5%, Pb – 27.9% and Zn – 29.1%. At Hanwa site without EDTA application (natural): Cd – 36.7%, Co – 1.2%, Cu – 28.4%, Ni – 20.5%, Pb – 17.4% and Zn – 17.2%; with EDTA application: Cd – 59.7%, Co – 2.3%, Cu – 32.1%, Ni – 35.6%, Pb – 42.1% and Zn – 19.9%. The bioaccumulation and transfer factors for the studied metals by the test plant species are indications that these plant species have the potentials for phyto-remediation under field conditions even on soils that were untreated with EDTA. The phyto-extraction potentials of the test plant species were in the order of Cymbopogon citratus (Lemon grass) > Vetivera zizanioide (Jema) > Helianthus annus (sunflower) > Ricinus communis L. (Castor oil plant) > Ipomoea asarifolia (duman kada).
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN ANALYTICAL CHEMISTRY DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
PHYTOEXTRACTION,, HEAVY METALS,, SELECTED METAL,, DUMPSITES,, ZARIA,, NIGERIA