Evaluation of Heavy Metal Contents in the Leaves, Stem and Rhizospher Soil of Selected Medicinal Plants Growing in Selected Polluted Sites in Makurdi-Nigeria

Abstract

The study assessed the concentration of Lead (Pb), Iron (Fe), Copper (Cu), Manganese (Mn) and Cadmium (Cd) in selected medicinal plants, Azadirachta indica and Phyllanthus niruri; the rhizosphere soil in mechanic and dump sites on which the plants were growingAnalysis of selected heavy metals was done using Atomic Absorption Spectrophotometer (AAS) machine. Statistical analysis was done using analysis of variance (ANOVA) at a probability level of 0.05.  From the results, it was shown that, Pb, Cd, Fe, Cu and Mn were generally higher in the rhizosphere soil and leaves than in the stems of the medicinal plants (A.indica and P.niruri). P.niruri accumulated more of the heavy metals than A.indica. There were significant differences in heavy, metals concentrations among the leaves, stems of the medicinal plants and rhizosphere soil at P≤0.05. Heavy metals concentrations in sampled plants in the polluted sites were higher than those of the control sites and were statistically significant (P≤0.05). Comparing with WHO standard, the heavy metals investigated where within the acceptable set limits. However, their presence in the investigated plants calls for concern as accumulation over time may increase the level of these metals above set limits. Based on the findings, the study recommended that medicinal plants for therapeutic use should be obtained away from polluted environments and that sorting and recycling of wastes should be intensified to reduce the quantity of these toxic metals in the dumpsites which can subsequently be leached into the soil where they could be taken up by plants.