ABSTRACT
This study was conducted to evaluate the impact of gas flaring on the quality of rainwater and groundwater samples from Ogulagha community, Delta State and the human health risk associated with consumption.
Water samples (rainwater and groundwater) were collected from three points – 600 metres, 800 metres and 1,000 metres from the flare point, and from the University of Benin which served as the control point. The samples were analyzed for physicochemical parameters using standard methods. Variations in physicochemical parameters were evaluated, and water quality was assessed using water quality index (WQI). Human health risk was assessed using human intake models to evaluate the risk of exposure to heavy metals through drinking of contaminated water.
Results showed that water pH (6.40 – 7.00), temperature (26.30 – 28.70 oC), TDS (7 – 24 mg/L), EC (12.00 – 40.80 µS/cm), turbidity (0.01 – 0.26 NTU), DO (4.90 – 5.90 mg/L), bicarbonate (0.32 – 0.54 mg/L), chlorine (1.13 – 3.86 mg/L), sulphate ( 0.00 – 0.03 mg/L), THC (0.00 – 0.08 mg/L), PAHs (0.00 – 0.01 mg/L), Pb (0.00 – 0.001 mg/L) and Cd (0.00 – 0.0001 mg/L) for rainwater from Ogulagha community did not exceed their respective WHO permissible limits. For groundwater samples from Ogulagha Community, water pH (6.80 – 7.50), temperature (26.30 – 28.40 oC), TDS (147 – 241 mg/L), EC (249 – 40.80 µS/cm), turbidity (0.41 – 1.26 NTU), DO (3.90 – 4.90 mg/L), bicarbonate (0.42 – 0.66 mg/L), chlorine (23.51 – 39.04 mg/L), SO32- (0.09 – 0.31 mg/L), NO32- (0.00 – 0.12 mg/L) and Fe (0.00 – 0.01 mg/L) did not exceed their respective WHO permissible limits. For the study control: rainwater pH (5.10 – 5.80), temperature (26.40 – 29.30 oC), TDS (4 – 7 mg/L), EC (6.60 – 8.90 µS/cm), turbidity (0.08 – 1.10 NTU), DO (4.80 – 5.90 mg/L), bicarbonate (0.07 – 0.30 mg/L) and Cl- (0.56 – 1.06 mg/L); Groundwater pH (5.50 – 5.90), temperature (26.00 – 29.30 oC), TDS (10 – 21 mg/L), EC (16.40 – 36 µS/cm), turbidity (0.38 – 0.72 NTU), DO (4.30 – 5.20 mg/L), bicarbonate (0.14 – 0.35 mg/L), Cl- (1.61 – 3.24 mg/L) and Fe (0.00 – 0.01 mg/L) did not exceed their respective WHO permissible limits. Water Quality Index (WQI) revealed excellent water quality for rainwater and groundwater samples from Ogulagha Community, an indication that the water is suitable for human consumption and use for other domestic purposes. Human health risk assessment showed hazard index values for rainwater and groundwater from Ogulagha Community were less than 1 (HI < 1) indicating no potential non-carcinogenic human health risk. The integrated carcinogenic risk (ICR) for rainwater from Ogulagha community was 1.97× 10-7 indicating extremely low risk to human health. Although the examined physicochemical parameters in rainwater and groundwater from Ogulagha community were within their respective permissible limits, the significantly higher (p > 0.05) mean values for water pH, TDS, EC, bicarbonate, chlorine, THC, sulphate, nitrate, PAHs, Pb and Cd for rainwater and groundwater from Ogulagha community compared to rainwater and groundwater values from University of Benin implies that the water sources in Ogulagha Community have been impacted by gas flaring activity hence the need for environmental regulation and the continuous quality monitoring of water sources to protect public health.
