Metals in environmental media: A study of trace and platinum group metals in Thohoyandou, South Africa

A detailed study has been conducted to determine the contamination of Thohoyandou roadside soils, vegetation, sewage and river waters by Zn, Cu, Cr, Pb, Cd, Fe, Pt and Pd. The study further investigated the correlation between these trace metals in roadside soils and vegetation in order to infer the potential impacts of roadside trace metals contamination of vegetation. Collected surface soil and vegetation samples were analysed with atomic absorption spectrophotometer for Zn, Cu, Cr, Pb and Cd while water samples were analysed by inductively coupled plasma atomic emission spectrometry (ICP-OES) for Zn, Cu, Fe, Pt and Pd. A linear correlation was observed between soil and vegetation metal concentration, which suggests the same source of metals in the samples except for Cu. The findings also revealed a general reduction in soil and vegetation metal concentrations some distance away from road traffic. For both experimental soil and vegetation samples, the mean concentrations were found to follow the decreasing orders: Pb > Zn > Cr > Cu >Cd and Pb>Zn >Cd >Cr>Cu respectively. For water samples, trace metals were highest in raw sewage and lowest in river waters. The sewage system leaking directly into the rivers was found to be the major source of pollution by trace metals. The mean concentrations of the trace metals in the water bodies were found to follow the following decreasing order: Fe >Zn >Pt >Cu >Pd. Keywords: trace metal contamination, roadside soil, vegetation, water, Thohoyandou, South Africa Water SA Vol. 31(4) 2005: 581-588