Assessment of Trace Metal Contamination of Selected Fish Species From Choba and Aluu Axis of New-Calabar River, Rivers State, Nigeria

ABSTRACT

This study investigated the trace metal contamination of two fish speciesClariasgariepinusandOreochromisniloticus obtained from the Choba axis (Downstream) and Aluu axis (Upstream) of New Calabar River in Rivers State. The fishes were dried, ashed and analysed for trace metals such as Zn, Pb, Cd and Cu using the atomic absorption spectrophotometer of model Unican Solar 969.The results obtained showed that Pb values ranged from 0.097 to 0.655 mg/kg with the highest obtained inOreochromisniloticusat Choba axis. There was no significant difference in the Pb values among the fishes. Cu ranged 17.7-58.2mg/kg, highest value obtained inClariasgariepinusat Aluu axis. Zinc(Zn) values ranged from 28.5 to 52.1mg/kg. At Aluu, Cd was not detected in the two fish species, values obtain at Choba were 0.17mg/kg for Clariasgariepinus and 1.39mg/kg forOreochromisniloticus. Zn and Cu levelsin the two fish species at the upstream end exceeded the FAO permissible limits. Also Pb and Cd values in Oreochromisniloticus, at the downstream end exceeded FAO permissible limit. The mean trace metal concentration of the water samples ranged from Zn: 1.145±0.01-2.58± 0.1mg/L, Cu: 0.55±0.02-1.2±0.0 mg/L, Pb: 0.018± 0.01mg/l and Cd: 0.034mg/l. Pb and Cd were not detected at Choba axis. The risk assessment for daily intake of consumers of fish from the river indicated that the non- carcinogenic risk tends to become significant with exposure duration of30years of consumption, mainly for Cd, Zn and Cu exposure since the indices exceeded the acceptable limits of non-cancer hazard quotient.

Keywords: Trace metal, fish species, risk assessment, bioconcentration