Effect of petroleum products depot on Nwaenebo-Emene river sediments, Enugu, Nigeria: contamination by PAHs and associated exposure risks to both humans and aquatic biota

Abstract

ABSTRACT In this study, the concentration and distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediments of Nwaenebo River in Enugu, Nigeria, that received petroleum depot effluents for over twenty years were determined and the associated extent of pollution, ecological and human health risks of exposure estimated. The concentration of the PAHs was measured using gas chromatography. Extent of sediment PAHs pollution was determined using Nemerow pollution index whereas ecological risks were determined mainly by means of hazard quotient (HQ) based on Canadian interim freshwater sediment quality guidelines (ISQGs), probable effect concentration (PEC) and effect range medium (ERM) values. The non-carcinogenic and carcinogenic risks were determined using hazard index (HI) and incremental life cancer risks (ILCR) respectively. Results showed ƩPAH concentration range of 0.5–154.5 mg/kg in the sediments with 5-member ring PAHs most abundant in the downstream section of the river. The Nemerow pollution index showed that the sediments of the downstream section of the river were seriously polluted with the PAHs unlike the upstream section where there was no significant sediment PAHs pollution indicating that the petroleum depot was responsible for the pollution of the sediments with PAHs. The ISQG, PEC and ERM based HQ indicate insignificant risks to biota at upstream section but significant risks at the locations downstream where there are expectations of observable frequent adverse effects to the biota. There are no significant non-carcinogenic risks to human health but there are significant carcinogenic risks with risks at the downstream section of the river sediments in the range 9.4*10^-5 to 2*10^-4. Remediation efforts should be initiated to restore the sediments quality.