Metal concentrations in intertidal water and surface sediment along the west coast of the Cape Peninsula, Cape Town, South Africa

Abstract

The concentrations of metals in intertidal water and surface sediment were measured at Scarborough, Hout Bay, Green Point, Milnerton and Bloubergstrand in Cape Town, South Africa, between Autumn 2010 and Autumn 2011. In terms of Pollution Load Index (PLI) of metals in the sediment, the sites were ranked in the following order: Bloubergstrand > Hout Bay > Green Point > Milnerton > Scarborough. Seasonally, metal loads were highest in Autumn 2011 and lowest in Autumn 2010. The higher metal concentrations reported in sediment suggested that both localised anthropogenic and natural weathering were the sources of metals recorded. Surprisingly, metal concentrations were similar to those reported in 1985 for the same sites, suggesting that the intertidal environment in Cape Town has not been increasingly contaminated with metals. The findings provide a baseline of metal concentrations that can be used for further research in the region.

Keywords: metals, intertidal water, sediment, contamination factor, pollution load index, Cape Town