ORIGINAL RESEARCH
An Assessment of the Bioavailability
of Metals in Soils on Oil Palm Plantations
in Nigeria
Bola O. Olafisoye1, Oluwafemi O. Oguntibeju2, Otolorin A. Osibote3
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1Faculty of Applied Sciences, Department of Chemistry, Cape Peninsula University of Technology,
P.O.Box 652,Cape Town, South Africa 8000
2Faculty of Health and Wellness Sciences, Department of Biomedical Sciences,
Cape Peninsula University of Technology, P.O.Box 1906, Bellville, South Africa 7535
3Faculty of Applied Sciences, Department of Mathematics and Physics,
Cape Peninsula University of Technology,
P.O. Box 652, Cape Town, South Africa 8000
Submission date: 2014-11-03
Final revision date: 2015-12-01
Acceptance date: 2015-12-02
Publication date: 2016-05-25
Pol. J. Environ. Stud. 2016;25(3):1125-1140
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ABSTRACT
We investigated the speciation, bioavailability, and mobility of metals in soils from selected states on
oil palm plantations in southwest Nigeria. Soils were analysed for total metal content and speciation on all
sampling locations. Metal concentrations were compared against pH, electrical conductivity (EC) and soil
organic matter (SOM), which were high at all the sampling locations. The speciation results deduced that
the concentrations of the different fractions vary widely at each sampling location. Cd is mostly abundant
in the exchangeable phase in all the samples analysed in the various locations. Ni in the Iresa-apa plantation
(29.9%) and Co in the Acharu plantation (29.9%) also showed appreciable concentrations in the Fe/Mn
oxide fractions. The concentrations of Pb and Cu were highest in the organic fraction. Metals in the organic
phase are more released into soil solution when compared to the residual phase fractions. Chromium and
Zinc were mostly associated with the residual phase when the values of the residual phase were compared
with other geochemical fractions. The plantations under study, which recorded the highest concentrations of
Cr and Zn in the residual fractions, were 87.9% (Okitipupa), 86.3% (Ikire), 82.7% (Apoje), 90.3% (Onishere),
89.7% (Benin City), and 85.6% (Nsukka).The results of the sequential extraction show that mostly Cr and
Zn were strongly bound to the residual/inert phase in all the soils under investigation. The potential mobility
of the metals with high fractions in the residual phase is as follows: Cr (74.8%), Zn (74.0%), Pb (73%),
Fe (69.5%), Ni (67.0%), Cu (63.8%), Mn (30.5%), Co (30.7%), and Cd (25.9%). These values were high
when compared to the values of other metals in the other mobile and potentially mobile fractions.