Human activities on environmental resources have negatively affected floras and faunas in maintaining fair balance. In this research study, selected heavy metals (Al, As, Cd, Cr, Cu, Fe, Hg, Pb, Ni, Zn) concentration in three fish species (Clarias gariepinus, Heterotis niloticus and Anguilla labiate), surface water and sediment samples in Ogbaru axis of River Niger, Anambra State, Nigeria. We evaluated the samples using atomic absorption spectrophotometer (AAS). The result of heavy metals (Cu, Fe, Zn, Ni, Pb, Cd, Al, Cd) analysis in fish samples showed that Cr was detected in Clarias garipinus and Anguilla labiate with a concentration of 0.001mg/kg in both species but was not detected in Heterotis niloticus. Hg and Al were not detected in Anguilla labiate but both metals were detected in the other fish species with a mean concentration of 0.311mg/kg and 0.019mg/kg respectively for Clarias garipinus and 0.001mg/kg and 0.005mg/kg respectively for Heterotis niloticus. In decreasing order, the heavy metal concentration in Clarias garipinus in increasing order of Cu >Fe > Ni > Hg > Pb > Zn > As > Cd > Al > Cr, while Heterotis niloticus followed the order Cu > Zn > Fe > Ni > Pb > Cd > Al > As > Hg > Cr, and Anguilla labiate followed the pattern of Cu > Fe > Zn > Ni > Pb > Cd > Cr > As > Hg > Al. For surface water, As (0.005mg/l), Cd (0.032 mg/l), Cr (0.099 mg/l), Cu (0.186 mg/l), Fe (2.308 mg/l), Hg (1.501 mg/l) and Pb (0.724 mg/l) showed high concentration for the raining season compared to dry season, as Al (0.246 mg/l), Ni (0.773 mg/l) and Zn (2.903 mg/l) were dominant during dry season, while sediment samples of Cr (0.112 mg/kg), Cu (0.029 mg/kg), Ni (0.945 mg/kg) and Pb (0.039 mg/kg) concentration in raining season were higher than dry season and vice versa for other As, Cd, Fe, Hg, Zn. Correlation matrices showed positive value showing that heavy metals were from a similar source with migration route and vice versa for negative correlation. Health and exposure risk assessment was conducted for carcinogenic and non-carcinogenic exposure in adults and children, where the cumulative cancer risk was within USEPA regulatory standard (1.0E-6 – 1.0E-04) and cumulative hazard index were above 1 for adults (2.02) and children (4.93), implying that children are at risk of having adverse health issues compared to adults. Therefore, there is a need for regulatory advocacy and special care to mitigate anthropogenic release and safeguard the environment.
Occurrence and probabilistic risk assessment of PAHs in water and sediment samples of the Diep River, South Africa
