Determination of concentration of heavy metals in the sea port of Zanzibar: by energy dispersive x-ray fluorescence spectrometry

Seafood is a major source of food for large number of people residing in the coastal areas of Zanzibar. It has been reported that seafood is a connecting link for the transfer of toxic heavy metals in human beings. The present study was conducted to assess the metal concentration upon samples of sediment, fish and shellfish along the Sea Port of Zanzibar. Fish samples (namely changu, sardine, baracout and tuna fish) and shellfish (i.e. oysters, mussels, clams and crabs) were the ideal species for the assessment study on effects of heavy metal contamination in aquatic organisms. They were collected at the Sea Port and the concentrations of the assessed metals were determined using Energy Dispersive X-ray Fluorescence (EDXRF) Spectrometry. Concentrations of Cd, Cr, Ni, Mn and Zn were found to be higher in clams whilst Fe, Pb and Cu were found to be higher in crabs. Concentrations of Cd and As were found to be higher in mussels whereas Hg was only detected in changu specie. Comparing the data from this study in relation to data from other regions for the sediment sampled from the Sea Port of Zanzibar showed a moderate level of pollution. For the concentration of Fe, Cr and as in different species of fishes and Cr, Cu, Zn, As and Cd in different shellfish species collected was quite higher than the values reported in literature. As and Cr were higher in fish than the recommended value WHO/FAO (2004) The concentrations of heavy metals in most different species of shellfish were found to be higher than the recommended maximum level allowed in food by WHO/FAO (2004) and EC (2006). Thus, the concentrations of these metals in shellfish exceeded the acceptable levels for a food source for human consumption.