Abstract
The concentrations of Fe, Mn, Zn, Cu, Pb and Cd in bottom sediment and surface water in the Egyptian coastal waters along the Mediterranean Sea, and thence the soft tissues of the bivalve (Donax trunculus) were determined. The mean concentrations (mu g g(-1)) of heavy metals in bottom sediment were as follows: Fe: 1748.2-2030, Mn: 191.4-254.3, Zn: 28-42.2, Cu: 4-9.4, Pb: 18.4-24.8, Cd: 1.4-2.3, and in surface water: Fe: 744-896, Mn: 162-198, Zn: 242.6-300, Cu: 12.6-19.3, Pb: 31.3-56, Cd: 0.8-3.1, while in soft tissues of the bivalve D. trunculus, the mean concentrations (mu g g(-1) dry weight) were as follows: Fe: 47.2-66.4, Mn: 4.8-8.4, Zn: 22-36.4, Cu: 3.2-4.8, Pb: 5.6-9.2, Cd: 1.6-2.4. The present study has revealed that the concentrations of Cd and Pb in the soft tissues of the edible bivalve D. trunculus were above the maximum acceptable concentrations for human consumption proposed by FAO/WHO, EU. Moreover, estimation of concentration factor (C-f) for the studied metals in the soft tissues of the edible bivalve D. trunculus recorded high accumulation rates of Cd and Cu. The present study confirmed that, the examined bivalve species was associated with enhanced metal content in its soft tissues and was not safe within the limits for human consumption. Water and bottom sediments showed apparent seasonal variations of metals accumulation with maximum concentrations during summer and winter, respectively. Mean metal concentrations were found to be higher in some of the selected five sites than others, but, these differences in heavy metal concentrations were not statistically significant (P>0.05), suggesting that common and main anthropogenic sources contributing to the heavy metal pollution at this Egyptian coastal area on the Mediterranean sea. The results obtained in this study were compared with those reported in earlier studies and concluded that, the area of the present study was in general not considered a metal polluted area according to the OME and EPA classification criteria. However, concentrations of Cd and especially, Pb did give some cause for concern, and warrants a continued monitoring programme for inorganic and chemical organic compounds in sediments, water, and biota along the Egyptian Mediterranean coasts.