Distribution and seasonal variations of selected heavy metals in seawater from Cape Town harbour of Western Cape Province, Republic of South Africa

Abstract

This study was carried out to determine the distributions and effects of seasonal variations in concentrations of some selected heavy metals namely; Cr, Mn, Co and Ni in sea water collected from twelve locations from Cape Town harbour, Western Cape Province, Republic of South Africa. The water samples were analysed for the heavy metals by inductively coupled plasma- mass spectrometry (ICP-MS) with an Agilent 7700 ICP-MS. A significant correlation was measured for Mn and Ni during winter. For Cr and Co high concentrations were recorded in summer than in winter. Metal concentrations in the harbour ranged from (8.050 ± 0.590 μg/L ) to (44.580 ± 40.300 μg/L) for Cr, from (5.710 ± 1.870 μg/L) to (1054.420 ± 2556.320 μg/L) for Mn, from (0.330 ±0.090 microgram/L) to (30.700 ± 33.160 microgram/L) for Co and from (4.220 ± 4.210 μg/L) to (19.630 ± 12.180 μg/L) for Ni respectively. These results are indicative of the contribution of heavy metal pollution from the inflow of rain water, storm water drains, streams which carry runoff from industrial, urban and residential sources. High values of trace metals could be traced to anthropogenic and natural sources. Apparently, Ship repair activities are also suspected to be responsible for elevated concentrations in the upper reaches of the harbour.