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Heavy Metals Concentration in Rhizosphere and Tissues of Smooth Pigweed ( A. hybridus ) and Bush Okra ( C. olitorius ) cultivated on an Abandoned Dumpsite
AHMED, SA; OGUNKUNLE, CO; OYEDEJI, S & FATOBA, PO
Abstract
The study assessed the concentrations of Pb, Cr, and Cd in rhizosphere and tissues of A. hybridus and
C. olitorius grown on a dumpsite converted to farmland by plant and 0-15 cm depth soil samples which were air-dried,
digested and analysed using Atomic Absorption Spectrophotometry. Some physiochemical parameters that affect
transport of soil nutrients into plant tissues were analysed using standard methods. The pH of the rhizosphere soil of C.
olitorius was 6.71 and the soil of A. hybridus was slightly alkaline in nature with pH 7.75. The rhizosphere of A. hybridus
had the highest concentration of Pb (123.20±90.04 mg/kg) and Cd (0.63±0.63 mg/kg) while Cr was highest in the
rhizosphere of C. olitorius (36.57±8.61 mg/kg). The result showed total and bioavailable metal concentrations in the soils
were in the order of Pb > Cr > Cd. The order of metal uptake varied with vegetable crop. Metal concentration in tissues
of A. hybridus followed the order of Pb > Cr > Cd while C. olitorius was Cr > Pb > Cd. Concentrations of Cd, Pb and Cr
exceeded the maximum permissible limit in soil and within allowable limit in the tissue. C. olitorius had transfer factor
(TF) < 1 for Cd, Pb and Cr. A. hybridus had similar transfer factor except for Cr with TF > 1. The study concluded that
the dumpsite converted to farmland is highly contaminated with Pb, Cr, and Cd and highly accumulated by the vegetables.
Keywords
Heavy metals; dumpsite; Transfer factor; vegetables.
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