ABSTRACT
The Niger Delta region is facing issues such as depletion of biodiversity, flooding, oil spillage, gas flaring, noise pollution, sewage and wastewater pollution, land degradation and deforestation. This study investigated the impact of anthropogenic activities on the surface water, sediment, and freshwater fishes (Heterotis niloticus, Papyrocranus afer, and Citharinus citharus) from the Okpare-Olomu River in Delta State, Nigeria from December 2019 to June 2021. Surface water, sediment and fish samples were analysed using various recommended standards.
The surface water physico-chemical parameters showed a highly significant difference (p<0.01) for Temp., TDS, Hardness, Cl, K, Na and Pb and a significant difference (p<0.05) for EC, BOD5, COD, Alkalinity, Ca, and Nitrogen while the sediments physico-chemical parameters showed a highly significant difference (p<0.01) for Org. Carbon, Na, Mg, Fe, Cu and Fe and a significant difference (p<0.05) for Ca, THC, Cr and Zn across the study stations. The Fe>Zn>Mn>Cr>Cu>Cd>Pb order of dominance reported in the sediments showed a slight deviation from the Fe>Zn>Cr>Pb>Cu>Cd>Mn sequence reported in the water. The mean concentration of thirteen (13) PAHs compounds were recorded in surface water in the order; station 3 (1640.80 μg/L) > station 4 (1531.10 μg/L) > station 2 (1105.13 μg/L) > station 1 (830.46 μg/L) while sixteen (16) PAHs compounds were recorded in sediments in the mean concentrations order; station 2 (15377.61 μg/kg) > station 1 (11136.62 μg/kg) > station 4 (9894.82 μg/kg) > station 3 (4442.27 μg/kg). The trend in PAHs in fishes was Phenanthrene>Fluoranthene>Naphthalene>Fluorene>Others while Acenaphthylene recorded the least value. The mean concentrations for the Twenty-eight (28) TPH compounds detected in surface water in the order: Station 4 (4362.33μg/L) > Station 2 (2164.20μg/L) > Station 1 (2048.27μg/L) > Station 3 (1655.74μg/L) while Thirty (30) TPH compounds detected in sediments in the order; station 3 (10820.77 μg/kg) > station 2 (26301.87 μg/kg) >station 4 (9510.18 μg/kg) > station 1 (9007.48 μg/kg) respectively. Estimated daily intake (EDI) of heavy metals from studied fish species were above the maximum tolerable limit with high occurrence of PAHs and TPH.
The Water Quality Index (WQI) showed that Okpare-Olomu River was degraded and unsuitable for domestic use. The investigated indices indicated anthropogenic sources of pollution and signify potential ecological risk. This study emphasizes the need to implement functional measures to curb the activities leading to the contamination of Okpare-Olomu River and ensure clean-up of the oil spills within the Niger Delta.
