Uptake and translocation of heavy metals by medicinal plants growing around a waste dump site in Pretoria, South Africa

The study investigated the uptake and translocation pattern of trace metals from two different plant species from a waste dump site in Pretoria, South Africa. Datura stramonium is used as an anti-asthmatic treatment and Amaranthus spinosus may either be used as a medicinal herb or consumed as a vegetable. The trace metal contents from different parts of these plants (leaf, stem and root) were determined by the use of ICP-OES. The concentrations of trace metals from the leaves and stems of both plants were in the order Fe > Mn > Zn > Cu > Cr > Ni > Pb. However, from the roots of D. stramonium the concentration were in the order Zn > Mn > Fe > Cr > Ni > Cu > Pb, while from the root of A. spinosus the trend of accumulation was in the order of Fe > Zn > Cr > Ni > Mn > Cu > Pb. From both plants, the concentrations of determined trace metals were in the order roots > leaves > stems. The overall concentration of heavy metals from leaves and stems appeared to be within the limit laid down for safe human consumption (17.35–78.65 μg/g Fe, 16.84–52.94 μg/g Zn, 5.65–7.31 μg/g Cu, 0.51–1.98 μg/g Pb, 4.36–5.69 μg/g Ni and 18. 20–33.56 μg/g Mn).

Research Highlights
► The work described the uptake of trace metals by medicinal plants from a waste dump site.
► The level of trace metals does not necessarily transform to the rate of plant uptake.
► Atmospheric pollution might increase the presence of trace metals as pollutants in plants through the leaf stomata.
► Plants collected from waste dump site may not be harmful; however periodic examination needs to be carried out.
► There is a need to test all plants since some plants can act as phytoremediator.