Metal contamination of soils collected from four different sites along the lower Diep River, Cape Town, South Africa

05 May 2020

In this study, river bank and adjacent soil samples from four different sites, Milnerton Lagoon (Site 1), Lower Estuary (Site 2), Milnerton Bowling Club (Site 3) and Woodbridge Island (Site 4) from the lower Diep River, Cape Town, South Africa were evaluated for ten metals; cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), zinc (Zn), aluminium (Al), chromium (Cr) and cobalt (Co). The highly sensitive inductively coupled plasma - mass spectrophotometry (ICP-MS) method was used to analyze the metals. Results showed that most sites were contaminated with metals evaluated. Among the metals, Al and Fe were consistently higher in all the soil samples (from both river bank and the adjacent soil) followed by Zn, Mn, Pb, Cu, Cd, Co, Cr and Ni. The concentrations of Al in river banks ranged between 1214.1 - 3176 mgkg-1. In adjacent soils, the Al concentration ranged from 434.8 - 2445.4 mgkg-1. The Fe concentrations from the adjacent soil samples ranged from 402.2 - 2459.8 mgkg-1 and the river bank values ranged from 1136.4 - 4897.2 mgkg-1 respectively. Generally, Zn ranged from 2.4 - 211.5 mgkg-1; Mn: 5.5 - 48.05 mgkg-1; Pb: 0.97 - 71.7 mgkg-1; Cu: 0.3 - 45.9 mgkg-1; Cd: 0.0 - 9.3 mgkg-1; Co: 0.2 - 2.7 mgkg-1; Cr: 0.3 - 2.1 mgkg-1; and Ni 0.02 - 2.6 mgkg-1. Overall, Ni had the lowest concentrations in the ecosystem.