Petrochemical Pollutants and their Toxicological Fate in Sediment-Water Systems: A Combined Analytical and Ecotoxicological Study of Oguta Lake and Njaba River, Imo State, Nigeria

Abstract

Background: Petrochemicals are a severe environmental pollutant, especially in the tropical areas, where industrial and anthropogenic activities intersect in the freshwater ecosystems. Using evidence of ecological hazards and regulatory loopholes, this paper discusses the exposure, distribution, and toxicological fate of petroleum-contaminated pollutants in Lake and River Njaba and Okuta, Imo State, Nigeria.
Methods: The gas chromatography-mass spectrometry (GC-MS) and atomic absorption spectrophotometry (AAS) combined method was used to identify the multidimensional analysis change, and the biomarker analysis method based on bioassays was used in the study. Eight geo-referenced samples were sampled and assessed according to the total petroleum hydrocarbons (TPHs), 16 priority polycyclic aromatic hydrocarbons (PAHs) and six heavy metals. The biological toxicity in terms of acute bioassays, oxidative stress biosignals, and histopathological analysis were determined using clarias gariepinus, Daphnia magna and Chlorella vulgaris.
Findings: The findings were high pollutant concentration beyond the World Health Organisation (WHO), United States Environmental Protection Agency (USEPA) and National Oceanic and Atmospheric Administration (NOAA) standards. The Njaba River had cadmium (0.019 mg/L), lead (0.162 mg/L) and ΣPAHs (3.21 mg/kg) that were exceeded seven times the maximum. The bioassays indicated that there were acute effects (LC50 < 10 mg/L) and inhibition of oxidative stress. The results of sediment indices showed the presence of a high level of contamination (PLI > 1.5; Igeo = 46 moderate, 69 severe).
Conclusion: The study characterizes the first artificial study of the risk of petroleum-based pollutants in Nigeria, which reveals synergistic toxicities and severe pollutants of the sediment.