Heavy Metals Accumulation in Leaves and Tubers of Cassava ( Manihot Esculenta   Crantz) Grown in Crude Oil Contaminated Soil at Ikot Ada Udo, Nigeria

Pot experiment was set up to assess the levels of heavy metals accumulation in leaves and tubers of cassava (Manihot esculenta Crantz) grown in crude oil contaminated soil in the Niger Delta Region of Nigeria. Three cassava cultivars were used for the study viz: NR-8082, TMS-30572 and a Local variety (LV). The crops were planted in pots and nurtured to maturity. They were then assessed for the concentrations of the following heavy metals: Pb, Cd, Cr, Ni, Zn and Fe in both the leaves and tubers using standard laboratory procedures. Data analysis was carried out using the Analysis of Variance (ANOVA) and significantly different means were separated using the Duncan Multiple Range Test (DMRT). The analysis revealed that TMS accumulated the highest quantities of these metals, followed by NR and lastly, the local variety (V), this being a function of biomass production. Transfer Factors also proved the order of accumulation of this heavy metal as: TMS > NR > LV. Generally, the order of prevalence of heavy metal in both the leaves and the tubers was: Fe > Zn > Ni > Pb > Cd > Cr. This study revealed that crude oil pollution is increasingly raising the levels of heavy metals in the soils of Niger Delta and these metals are being taken up by plants including cassava, which is the most important staple food crop of the area. Consequently, crops farmers are advised against cultivating at crude oil contaminated sites for the risk of accumulation of heavy metals in plant tissues.