UPTAKE AND ACCUMULATION OF SOME HEAVY METALS BY THE LEGUME, (Arachis hypogea)

Abstract

Food chain contamination is one of the important pathways which contributes 90% of heavy metals in comparison of other sources like inhalation and dermal contact. The increased uptake of heavy metals by plants may sometimes produce toxic effects in plants and subsequently to its consumers along the chain. In this study, the accumulation of the metals; Cd, Cr, Co, Cu, Zn, Ni, and Pb in the roots, stem, leaves and seeds of Arachis hypogea were determined. Fresh sample of roots, stem, leaves and seeds of groundnut were obtained from six different farms located in three different sites in Biriyel, Bayo Local Government Area, dried, ground and sieved. The sieved sample was analyzed using atomic absorption spectroscopy following digestion with aqua regia (3ml HNO3 + 9ml HCl i.e. ratio 1:3). The results showed that, the levels; 0.311±0.03, 0.018±0.07, 0.021±0.11, 0.023±0.08, and 0.021±0.22 µg/g Cd were observed in the soil, roots, stem, leaves and the seed respectively. Chromium and Cobalt were not detected in the stem, leaves and the seed of the crop. Copper had the concentrations of, 0.451±0.21, 0.097±0.09, 0.075±0.15, 0.090±0.03 and 0.126±0.07 µg/g Cu in the soil, roots, stem, leaves and the seed respectively. High levels of 0.390±0.36, 0.359±0.25, 0.032±0.10 and 0.304±0.11µg/g Zn were observed in the root, stem, leaves and the seed of the crop in the order; seed >leaves >stem >root. High level of Ni was observed in the seed (0.085±0.03µg/g Ni) followed by the leaves 0.054±0.09 µg/g, and the root had 0.041±0.31µg/g whereas the stem has the lowest concentration of 0.008±0.12 µg/g. The levels; 1.375±0.35, 1.408±0.19, 1.463±1.02 and 1.429±0.51 µg/g were observed for Pb in the root, stem, leaves and the seed of the crop respectively. Concentrations of the elements observed in this study were all within the maximum permissible limits of consumption set by FAO/WHO which signify the safety of consuming the crop. All results were found significantly not different at P = 0.05