Heavy Metals Concentration in Mango (Mangifera indica L.) Grown around Some Gold Mining Areas of Zamfara State, Nigeria

Aims: This study was aimed at determining the concentration of heavy metals (Pb, Cd, Fe and Au) in mango plant parts (roots, stem barks, leaves and fruits) from two gold mining areas (Maraba and Duke) and the control (Kadauri) in Zamfara State, Nigeria for establishment of a baseline data for these metals and determining the suitability of the mango fruit for consumption.

Study Design: Analytical study design was applied in a stratified manner for the research.

Place and Duration of Study: The study was carried out in the environmental technology laboratory, National Research Institute for Chemical Technology (NARICT), Zaria, Nigeria between March and August 2019.

Methodology: A cumulative total of 96 samples of plant parts (roots, stem barks, leaves and fruits) were collected and analysed for Lead, Cadmium, Iron and Gold using Atomic Absorption Spectrophotometer (AAS) after digestion with a mixture of 20 ml HNO3 and 8 ml HClO4.

Results: The results obtained for the mean metal concentrations were; most abundant, Pb (62.07 ± 54.09 mg/kg) in mango roots from Duke and the least abundant, Cd (0.52 ± 0.44 mg/kg) in fruits from Kadauri. All the metals had very high (> 0.5) translocation factors indicating fast movement from the roots to the shoots while the mean values of these metals in the fruits were found to be above the WHO and FAO maximum permissible limits which shows high level of contamination as a result of gold mining activities. Metals generally occurred in the order: Pb>Fe> Au > Cd and they differed across sampling stations with the mining areas having significantly (P<0.05) higher values than the control.

Conclusion: Heavy metals concentration in mango plant was found to be generally higher than the permissible limits hence the fruits are considered unsuitable for human consumption.