POTENTIAL TOXIC METALS CONCENTRATIONS IN DIFFERENT AQUATIC LIVES HARVESTED FROM TWO DIFFERENT LAGOONS IN LAGOS NIGERIA

Rasaq A Olowu, Abayomi A.Jimoh , Ayofe M. Hammed, Albert O. Amosu

Department of Chemistry,
Faculty of Science,
Lagos State University,
P.O. Box 0001, LASU Post Office, Lagos, Nigeria
raadeolowu@gmail.com

The level of some Potential toxic metals PTM (Zn, Fe, Mn, Cu, Pb and Cd) in Synodontis membrane (Catfish), Tilapia zilli (Tilapia), Callinectes amnicola (Crab) and Macrobrachium macrobachion (Prawn), from Lagos Island and Epe lagoon were investigated using Atomic Absorption Spectrophotometer (AAS), model Buick Scientific 210 GVP, the analysis on all the samples were done in triplicates. The analysis of PTM in Synodontis membrane and Tilapia zillii was conducted on head, gills and trunk, and the results indicated the accumulation of metals differently in various parts of the fishes. Lead (Pb) and Cadmium (Cd) were not detected (ND) from all the samples, this may be due to the existence of few or no industrial activities around the location.

The orders of accumulation in Catfish were Head>Gill>Trunk and the pattern of distribution is Zn>Fe>Mn>Cu in all the organs. In Tilapia, the accumulation follows the order; Gills (Fe>Zn>Mn>Cu)>Head (Zn>Fe>Mn>Cu)>Trunk (Fe>Zn>Mn>Cu). The mean values of the Crab obtained fell in the ranges: Fe (19.7±1.7- 24.7±7.7); Zn (8.0±2.5-11.6±1.3); Cu (9.0±3.3-10.3±1.9); Mn (5.0±2.9-7.3±3.7). While that of the Prawn falls in the ranges: Fe (6.3±1.9-4.0±1.6); Zn (6.3±2.9-8.0±2.5); Cu (2.0±1.0-2.7.±0.9); and Mn (1.7±0.5-3.0±0.8) for Lagos Island and Epe Lagoon respectively. The high concentrations of iron and zinc in the fish parts could be associated with its natural abundance in Nigerian soils. The general trend of accumulations in all the organisms were Chrysichthys nigrodigitatus> Tilapia zillii> Callinectes, mnicola> Macrobrachium macrobrachion.

The analysis of the Crab and Prawn shows that concentrations of Zn and Fe in the samples are lower than the permissible limits set by WHO and FEPA while Mn and Cu concentrations in the fish samples were above the standard set limits hence consumption of the fish from the analysed lagoon may be dangerous to health, therefore it is pertinent to regularly monitor the activities of both lagoons.