Assessment of metal contamination in an urban drainage system (using water and tilapia, Oreochromis spp.) in view of human health effect. A case study of some selected communities in Cape Coast township in Ghana

Abstract

This research work aimed at studying the metal content of water and tilapia fish sample, Oreochromis spp., from a wastewater-fed pond around the University of Cape Coast community using instrumental neutron activation analysis. The metals studied were Al, As, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, V and Zn. In the water samples the order of elemental concentrations at sampling point 1, in μg/g, was K (75.96 ± 0.92), Na (18.52 ± 0.35), Al (6.00 ± 0.89), Mn (3.28 ± 0.44), As (3.08 ± 0.40), Mg (1.56 ± 0.17), Ca (0.70 ± 0.08), Cu (0.54 ± 0.08) and V (0.04 ± 0.01). Co, Cr, Fe and Zn were below detection limits of INAA. The order of elemental concentrations in the water at point 2 was as follows: Na (4.99 ± 0.14), K (4.82 ± 0.89), Mn (4.40 ± 0.53), Mg (2.92 ± 0.37), Al (1.98 ± 0.21), As (0.69 ± 0.10), Ca (0.24 ± 0.07) and V (0.23 ± 0.06) with Co, Cr, Cu, Fe and Zn falling below the detection limit of INAA. The concentrations recorded for Al, As, Cu and Mn in the water samples were all above WHO permissible limits. The mean levels of heavy metals in the soft tissue of tilapia was of the order: K > Mg > Fe > Ca > Na > Al > Mn > Zn > V > Cu > Cr > Co. Arsenic was below detection limit. The transfer factor values calculated for the metals Al, Ca, K, Mg, Mn, Na and V were all greater than one indicating movement of metals from the water column to the tilapia species. The hazard index (HI) calculated for Al, Fe, Mn and V suggested possible occurrence of adverse health effects (HI > 1) where as the HI value obtained for Cr, Cu and Zn (i.e., HI < 1) suggested unlikely adverse effects occurring.