ABSTRACT

Environmental pollution/contamination has led to world-wide issues of source identification and abatement practices of pollutants. In this study, water and sediment samples collected from Taylor Creek, Kolo Creek and Orashi River (all in Ahoada West Local Government Area of Rivers State) were examined for physicochemical characteristics, heavy metals and polycyclic aromatic hydrocarbons. Water physicochemical parameters indicated that all the parameters were within acceptable range for drinking water except biochemical oxygen demand (BOD), turbidity and dissolved oxygen (DO) in some instances. The result of heavy metals in water from all the sampled rivers indicated that Nickel (Ni) was the most concentrated metal, which was followed by that of iron (Fe). All the examined metals were within acceptable limits in the water except Ni and Fe (in some case). Contamination factor (Cf) analysis of the heavy metals indicated the rivers were generally contaminated with the examined metal except Ni that fall within the region of pollution. Pollution index (PI) determination gave values which indicated that the rivers were not polluted with the heavy metals. Contamination degree (Cd) assessment of the water samples indicated that the rivers showed values between low contamination to moderate contamination with heavy metals. Modified contamination degree (mCd) analysis showed that the rivers were within the range of non-contamination to very low contamination degree. The concentrations of polycyclic aromatic hydrocarbons in the rivers were in the order; Kolo Creek > Orashi River > Taylor Creek. There was the predominance of higher molecular weight (HMW) PAHs over lower molecular weight (LMW) PAHs in Kolo Creek and Orashi River, while in Taylor Creek, no particular group predominated. The concentrations of the heavy metals in sediment in all the rivers were in the order: Fe > Zn > Cu > Pb > Mn > Ni > Cr > Cd > Hg. The general order of metals concentrations in the rivers was Kolo Creek > Orashi River > Taylor Creek. Contamination factor analysis of sediment samples showed that the sediments were not contaminated with heavy metals. Pollution index examination indicated sediments free from heavy metals pollution. Contamination degree and modified contamination degree assessment indicated sediments with zero contamination with heavy metals. Geo-accumulation Index assessment showed sediments practically uncontaminated with heavy metals.  The values obtained in ecological risk assessments in the sediments showed that the environment is free from heavy metals associated risk. However, the values obtained for enrichment factor analysis, showed some form of anthropogenic enrichment of heavy metals, especially Zn and Cu. All the PAHs compounds were detected in the sediments of the rivers except naphthalene in Taylor Creek. The HMW PAHs were predominant over the LMW PAHs in all the sediments of the rivers. Source and diagnostic ratio assessment of PAHs gave both pyrogenic and petrogenic sources of PAHs thus implicating different input sources. The results obtained for all the parameters examined in both water and sediment showed that the aquatic environment generally may have health implications on human users and therefore adequate measures be taken to curb or abate the input sources.