Spatiotemporal Assessment of Heavy Metal (Loid) Pollution in Water and Surface Sediment of the Mohlapitsi River, South Africa

Abstract

Freshwater ecosystems are being polluted in many ways with heavy metal (loid)s, mostly due to human activities that affect aquatic biota and threaten human health. Water and surface sediment samples were collected from different sites of the Mohlapitsi River, South Africa, during the high flow and low flow seasons. The samples were analyzed for As, Cr, Cu, Fe, Mn, Ni, Pb, and Zn levels using inductively coupled plasma optical emission spectrometry (ICP-OES). In the water, only Fe, Mn, and Zn were detected, but the concentrations were below the standard guideline values except for Mn. However, in the sediment, all the metal (loid)s were detected in considerable concentrations. The mean concentrations of the metal (loid)s were higher during high flow than low flow, except for Fe. The enrichment factor (EF) of the heavy metal (loid)s ranged from low enrichment to moderate enrichment. Geo-accumulation index (I geo ) Shows moderate contamination levels with Cr and Mn. The main sources of contamination are attributed to discharges from agricultural fields and grazing areas in the catchment. The results provide baseline information on metal (loid) contamination in the Mohlapitsi River for management purposes.