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.
Highlights
Industrial development, increased population and unplanned urbanization have partially or completely turned our environment to dumpsites (Alimba et al, 2006)
The present study investigates Pb, Cr and Cd concentrations in rhizosphere and tissues of Amaranthus hybridus and Corchorus olitorius grown on abandoned dumpsite converted to cropland in Ilorin metropolis
There were significant differences in the concentrations of heavy metals in the rhizosphere of A. hybridus and C. olitorius cultivated on dumpsite converted to farmland
Summary
Industrial development, increased population and unplanned urbanization have partially or completely turned our environment to dumpsites (Alimba et al, 2006). Despite the high rate of turnover from dumpsite farming, high concentrations of heavy metals associated with myriads of waste deposits expose crops to contamination leaving farmers to choose between yield and quality. Due to the poor quality of savannah soils, farmers in Ilorin have resorted to the growing their vegetable crops on dumpsite for its fertile nature and high yield. The present study investigates Pb, Cr and Cd concentrations in rhizosphere and tissues of Amaranthus hybridus and Corchorus olitorius grown on abandoned dumpsite converted to cropland in Ilorin metropolis. The objectives of this study is to determine the levels of Pb, Cd and Cr in A. hybridus and C. olitorius samples grown on abandoned dumpsite; and assess mobility of the metals from the rhizosphere to the vegetables
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