| Popis: |
This study investigated the levels of lead (Pb), cadmium (Cd), Copper (Cu), Chromium (Cr) and Zinc (Zn) in two common edible fish species, Sole, Solea solea and Croaker, Pseudotolithus typus from Makoko and Koko in Lagos and Delta states respectively. Heavy metal contents were determined by air-acetylene flame Atomic Absorption Spectrophotometer after wet digestion of dried and milled samples with 1:1 HN03: H2O2. Results obtained (~kg/g, dry weight) for Sole in Lagos and Delta states were: Pb (0.330 and 0.149), Cd (0.097 and 0.063), Cu (0.869 and 0.434), Cr (1.184 and 0.826), Zn (7.612 and 7.890); and Croaker: Pb (0.163 and 0.045), Cd (0.115 and 0.029), Cu (0.990 and 0.694), Cr (1.008 and 1.038) and Zn (6.756 and 6.168) for the wet season (April-October); and Pb (0.534 and 0.527), Cd (0.373 and 0.410), Cu (0.437 and 0.556), Cr (0.834 and 0.983), Zn (6.764 and 9.343) for sole and Pb (0.210 and 0.213), Cd (0.264 and 0.307), Cu (0.442 and 0.483), Cr (0.577 and 0.597) and Zn (4.783 and 5.924) for croaker in the wet season (July-October). Significant (P~B 0.05) variations were observed in metal content between fish in terms of species, location and season. Generally, sole had higher metal concentrations than croaker; and metal contents were higher in samples from Lagos compared to Delta, probably due to the contribution of more effluents from industrial, commercial and municipal wastes in Lagos state. Cd and Cr levels in the test species were found to exceed international standards. It is recommended that a programme of continuous monitoring and control of the physical and chemical characteristics of components and food products of Nigeria's coastal zone be incorporated as a management tool for this important ecological zone. |
