Hydrochemical assessment of groundwater quality using water quality index, irrigation indices, and corrosivity models in a hydrocarbon-impacted coastal aquifer

Abstract

Abstract Coastal regions heavily involved in hydrocarbon extraction often depend on underlying aquifer reserves to meet domestic, agricultural, and industrial demands. These groundwater systems, however, face risks from saline intrusion and anthropogenic activities. This research aims to comprehensively assess groundwater hydrochemistry within a key hydrocarbon-affected coastal aquifer in Eastern Obolo, southern Nigeria, evaluating its suitability for domestic, agricultural, and industrial use. Groundwater samples from the region were analyzed for concentrations of major ions, heavy metals, and physicochemical parameters. The Water Quality Index (WQI) was used to assess the potability of groundwater sources. Sodium Percentage (%Na), Kelly’ s Ratio (KR), Sodium Adsorption Ratio (SAR), and Magnesium Adsorption Ratio (MAR) were employed to evaluate the suitability of groundwater for agriculture and irrigation. The Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI) were used to determine groundwater suitability for industrial purposes. Results showed that groundwater had a WQI range of 27. 66 to 45. 79, indicating its suitability for domestic use. Although the water was generally classified as freshwater, oily surface films were observed on water sources, a possible result of geogenic processes. The results also revealed mixed suitability for agriculture based on %Na (1. 27 to 2. 02), KR (0. 23 to 0. 40), SAR (0. 40 to 0. 57), and MAR (95. 82 to 99. 99.88). LSI values (− 0. 42 to – 1. 53) and RSI (7. 73 to 9. 12) suggested a high corrosion potential, which poses risks to industrial infrastructure. Pearson correlation coefficients indicated significant interrelationships among the physicochemical parameters. This study provides novel insights into groundwater quality in a major coastal aquifer impacted by hydrocarbon activities and saline intrusion. It contributes to the limited global literature on integrated groundwater quality assessment in coastal sedimentary basins, especially in hydrocarbon-producing regions. The results highlight the importance of continuous groundwater monitoring to safeguard water resources for various uses.

Keywords

• Corrosion indices
• Hydrogeochemical assessment
• Langelier saturation index
• Physicochemical analysis
• Saline intrusion
• Water quality index