Determination of the Contamination of Groundwater Sources in Okrika Mainland with Polynuclear Aromatic Hydrocarbons (PAHs)

Abstract

In this study, we examined the presence and concentrations of six polynuclear aromatic hydrocarbons (PAHs) in groundwater sources of Okrika mainland impacted by effluent discharges from a petroleum refinery into her surrounding Creeks. Sterile amber coloured bottles were used to collect 10 replicate borehole water samples from the mainland and fixed with concentrated H2SO4. Samples were transferred to the laboratory in iced coolers and analyzed using Gas chromatography coupled with Flame Ionization Detector (GC-FID). The interactions of the PAH components detected was determined using the Pearson product moment correlation coefficient (r) while spatial variance equality in means of concentrations was explored with the One-way ANOVA. Structure detection of observed inequalities was made with means plots. Concentrations of the PAHs were high and exceeded the WHO maximum permissible limit of 0.002mg/l in drinking water. Benzo(b)fluoranthene, with the highest mean concentration varied between 0.00037-0.51266 (0.08117±0.03330159)mg/l, fluoranthene varied between 0.00060-0.32890 (0.0473946±0.01769877)mg/l, while benzo(k)fluoranthene with the least mean concentration varied between 0.00017-0.08478 (0.0237385±0.00610045)mg/l. However, pyrene concentration ranged between 0.00015 and 0.24757 (0.0508440±0.01859716)mg/l, benzo(a)anthracene between 0.00020-0.21972 (0.0512660±0.01688275)mg/l, and chrysene between 0.00013 and 0.16571 (0.0488975±0.01090264)mg/l. Strong associations were observed between all the PAH components measured at P<0.01. Significant heterogeneity in mean variance of the PAHs [F(211.9502)>Fcrit(3.921478)] was recorded across the sampling locations at P<0.05. Structure detection of mean difference revealed that the inequalities were most contributed in BH1, BH 2, BH 5 and BH 10, while equality in mean concentrations were observed between BH 1 and BH 4, and BH 5 and BH 6. BH 8 recorded the highest contamination level of the various PAHs due basically to its proximity to the refinery’s effluent channel. The most probable source of these PAHs is therefore the nearby Port Harcourt Refinery Company’s effluent discharges into the surrounding creeks of the mainland. This contamination is of public health concern as several PAHs are known carcinogens. It is recommended that advanced technological engineering be applied to contain the presence of these pollutants in drinking water sources of residents of the area.