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.

Levels of Elements in Typical Mussels from the Southern Coast of Africa (Namibia, South Africa, Mozambique): Safety Aspect

“…As filter-feeding organisms, they have accumulated a high amount of available elements from the water and suspended sediments. For example, the concentrations of Cu, Zn, As, Mo, and Cd were significantly higher in mussels than in sediments in the False Bay area [2].…”

“…The maritime transportation and different type of contamination (treated sewage effluent, agricultural, commercial and urban development) in areas of the Western Cape sector of sampling (St. [6][7][8][9][10][11] are the major contributors to the considerable stress of ecosystems [2]. Among the Cape Town area (including the False Bay) the st. 7 (Hout Bay), st. 8 (Simon's town), st. 10 (Gordon Bay) are considered as the more polluted sites due to fishing or recreational harbors (marinas) that may be affected by metal inputs associated with anthropogenic activities (e.g., discharge of untreated municipal wastewaters and polluting spills from marine traffic) [1].…”

“…However, the total hazard indices demonstrated the high (HI > 1) levels at st. 1, 12-17 that correspond to possible risk during high consumption of mussels. The major contributors to HI were such elements as Co (1)(2)(3)(4)(5)(6)(12)(13)(14)(15)(16)(17), Zn (st. 1), Se (st. 1, 2, 16) and I (st. 3,12,13,16,17), which are included in the anthropogenic group according to factor analysis (described in Section 3.2). 0 corresponded to values less than 0.01.…”

“…In several works, the trace elements in soft tissues of mussels from different regions of South Africa were determined with a focus on a limited set of samples with a variety of obtained levels [1,2,[6][7][8].…”

“…The typical species of mussels (Mytilus galloprovincialis) was used in Mussel Watch Programmes by the Department of Environmental Affairs to assess the metal concentrations at key sites along the South African coast [2] However, the existence of unstudied zones and the lack of data about levels of the high number of elements and their risks for human health because of the mussel consumption increases the necessity of new studies. The complex work based on the assessment of micro and macroelements in mussels from polluted and protected water areas along a wide region of the African coast could fill the unstudied gaps in locations, the number of elements, and levels of risks caused by the use of these mussels for food.…”