Proximal Input of Polynuclear Aromatic Hydrocarbons (PAHs) in Groundwater Sources of Okrika Mainland, Nigeria

Abstract

The Port Harcourt Refinery Company situated at Okrika Mainland discharges its effluent into the Creeks surrounding this coastal land. The current study examined the presence of polynuclear aromatic hydrocarbons in groundwater sources of the coastal settlement. Ten replicate samples were collected from 10 boreholes in the settlement using sterilized amber glass bottles and fixed with concentrated H₂SO₄. They were later analyzed using Gas chromatography (GC). The Pearson product moment correlation coefficient (r) was used to determine the interactions of the PAHs detected while the One-way ANOVA was used to determine spatial variance equality in means of the PAHs components at P < 0.05. Further structure detection was made with means plots, utilizing pH as a predictor variable. High concentrations of PAHs which exceeded the WHO maximum permissible limit for the PAHs in drinking water (0.002 mg/L) were recorded from the borehole samples. Acenaphthene had the highest concentration of 0.88317 (0.202494 ± 0.0652) mg/L, while acenaphthylene had the least maximum concentration of 0.18837 (0.04978 ± 0.0123). However, naphthalene recorded concentrations of between 0.00058 and 0.52510 (0.0874576 ± 0.03472) mg/L, fluorene 0.00018 and 0.20438 (0.0527435 ± 0.01564) mg/L, phenanthrene 0.00041 and 0.26732 (0.0603780 ± 0.018634) mg/L, and anthracene between 0.00029 and 0.25084 (0.0692785 ± 0.0176569) mg/L. There was significant variance inequality in means of the PAHs measured across the sampling locations at P < 0.05 [F_(971.1318) > F_{crit(3.85563)}]. A further structure detection revealed that the inequalities were contributed by all the PAH components, especially between BH 3 and BH 1, BH 4 and BH 2 and 5, as well as between BH 6 and BH 10. Very strong associations were observed between the PAH components at P < 0.01. BH 8 recorded the highest contamination level of the various PAHs due basically to its proximity to the refinery’s effluent discharge point (Ekerekana Creek) and channel. Hence the source of these pollutants could best be fingerprinted to the nearby Port Harcourt Refinery Company’s effluent discharges. These PAHs are not only ingested by drinking contaminated waters, but are further consumed when this water is used to prepare foods. This creates a great cause for public health concerns especially as several PAHs are known carcinogens. It is therefore, recommended that technologically advanced techniques of water treatment be developed in order to take care of the presence of PAHs in drinking water sources of the coastal dwellers.