GEOCHEMICAL ASSESSMENT OF SEDIMENT IN CAPE TOWN HARBOUR, SOUTH AFRICA

Geochemical assessment of marine sediments collected from Cape Town harbour was carried out using inductively coupled plasma-mass spectrometry, Fourier-Transform-infrared and X-ray diffractrometry techniques. The clay mineral phase consists of biotites, kaolinites and halites. The ranges of concentrations (mg/kg) of trace metals were: Cd (1.69 +/- 0.075 - 0.080 +/- 0.002), Si (0.37 +/- 0.11 - 0.023 +/- 0.012), Fe (30.01 +/- 2.04 - 2.23 +/- 0.12), Cu (1462 +/- 39 - 1.51 +/- 0.11), Al (19.92 +/- 2.24 - 1.25 +/- 0.13), Sn (63.98 +/- 4.97 -1.15 +/- 0.38), Pb (252 +/- 29 - 8.73 +/- 1.06), Hg (1.002 +/- 0.168 - 0.049 +/- 0.005) and Zn (1.26 +/- 0.07 -0.022 +/- 0.004) mg kg(-1). The enrichment factors of Sn, Pb, Zn, Fe, Cd, Al and Hg revealed anthropogenic inputs of these metals into the marine environment. The enrichment factor of Cu was less than 1 and this suggests that its presence was largely due to natural changes. The results are indications of the contributions of trace metals contained in the runoffs from the domestic and urban drains, as well as the inflow storm water. Ship repair activities appeared to constitute a major factor responsible for the higher metal contamination in the dockyard areas. The geomineral analyses revealed the presence of quartz, pyrite, and calcite and carrolite minerals as the main constituents of the marine sediments.