Heavy metal distribution in Laportea peduncularis and growth soil from the eastern parts of KwaZulu-Natal, South Africa

Abstract

Laportea peduncularis is a medicinal plant consumed by the native communities in South Africa. Due to its oral consumption, its potential for harming the human health and the distribution of metals in the leaves of L. peduncularis as a function of soil characteristics were evaluated. Broadly, the concentrations of metals in the soil were in decreasing order of Fe > Ca > Mg > Mn > Zn > Cr > Cu > Ni > As > Co > Cd > Pb. Low-molecular-weight organic acid, calcium chloride, and ethylenediaminetetraacetic acid extraction methods were employed to assess for exchangeable forms of metals in the soil. Geoaccumulation indices and enrichment factors showed no contamination or enrichment for most of the heavy metals studied except for Cd, which showed moderate contamination and significant enrichment at Mona, KwaZulu-Natal. Principal component and cluster analyses revealed that As, Cd, Fe, and Ni in the soil came from the same source, whilst Cu, Pb, and Zn in the soil were from a common origin. Correlation analysis showed significantly positive correlation between heavy metals As, Cd, Fe, and Ni in the soil, as well as between Cu, Pb, and Zn, confirming the metals' common origin. Concentrations of metals in plants and soil were influenced by site, but the availability and uptake of the metals solely depended on the plant's inherent controls.