Evaluation of Heavy Metals Uptake by the Plants and Contamination of Ground Water in the Vicinity of E-Waste Processing Sites in Lagos, Nigeria

Metal uptake by plants and the contamination of ground water samples collected from the vicinity of sites of uncontrolled open-burning, dismantling/disposal, stockpiling and dismantling/stockpiling of e-waste, were investigated, seasonally over a period of two years. Samples of two common plants (including Lepistemon owariense, Alchornea cordifolia ) were collected along with the root soil, as well as water samples, from the sites and analysed by standard procedures entailing acid digestion of the samples followed by determination of the metals- Zn, Cd, Cr, Cu, Pb and Ni with atomic absorption spectrometer. The results showed that the mean metal contents (mg/kg) in the plants, 9.00- 35.2 Cu; 0.83-175 Pb for dry season and 10.1-101 Cu; 17.6- 300 Pb for wet season, were generally above the WHO limits. The uptake of metals from the soil by plants, expressed in terms of the transfer factor differed from one plant to the other and among plant parts, with Alchornea cordifolia, showing greater mean uptake of Zn, Pb and Cu than Lepistemon owariense from the Ojota site in the dry season. Metal concentrations in the water samples were generally within the WHO limits. Residents should be dissuaded from using these plants for medicinal and/or domestic purposes, because of concerns for human health.