Geochemical and PAHs evaluation of Water resources within the lignite series of Obomkpa and environs, Southern Nigeria

The study evaluated the drinking water quality from surface water overlying lignite seams and groundwater in Obomkpa, and environs. Nineteen groundwater (19) samples were collected and tested following the APHA standard to assess physicochemical properties, including Cl, HCO3, SO4, Fe, Mn, Pb, Zn, Cr, Ca, Mg, and Na (mg/l). Additionally, six surface water samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) alongside the physicochemical parameters. Water portability indices were employed to determine the portability of the water. This includes the Contamination Factor (CF), Pollution Index of Groundwater (PIG), Nemerow Pollution Index (NPI), Geoaccumulation Index (Igeo), and Entropy Water Quality Index (EWQI) for groundwater; while CF, Igeo, and EWQI. Results of the Hydrogeochemical evaluation using the Chadha plot indicated a predominant Ca-Mg-HCO3 water type, the evaluated PIG reveals approximately 31.5% of groundwater samples fell within the low pollution categories. EWQI revealed that 20% of total samples fell within the good water quality categories, while 12% of samples were slightly polluted according to the evaluated NPI. The evaluated CF and Igeo revealed that the groundwater quality ranged from slightly polluted to significantly contaminated due to Fe. PAH content was minimal, ranging from 0 to 1x10 ^− 5 mg/l, which falls within the WHO,2015 acceptable limit for water consumption. An in-depth evaluation of the health hazards stemming from the cancer-causing properties of PAH-polluted water using B(A)Pteq and ECR, confirms that the water meets the standards for consumption. Inferences from the Principal component analysis suggested the dissolution of ferruginous sandstone as the major influencer of the groundwater quality, highlighting the need for ongoing monitoring.