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Geoelectrical and hydrogeochemical assessment of groundwater sources of Nkpor metropolis Southeastern Nigeria

Udegbunam Innocent Ejike*, Okoyeh E I, Anaekwe Michael U, Okpara Augustine O

Electrical resistivity and hydrogeochemical investigations have been carried out to determine the groundwater potentials and aquifer parameters in Nkpor Southeastern Nigeria. Vertical Electrical Sounding Survey (VES) and hydrogeochemical studies were employed in this research. Twelve Vertical Electrical Sounding (VES) curves were obtained across the area using the Schlumberger configuration. The result of the VES survey shows that the subsurface layers ranged from 3 to 6. The depth to water ranges from 25 m to 114 m. Aquifer thicknesses range between 20 m to 60 m. The hydraulic conductivity (K) ranged from 0.25 m/day to 3.027 m/day while the transmissivity (T) ranged from 8.2 m2/day to 166.49 m2/day. The hydrochemical analysis of groundwater samples collected from twenty sample points within the study area reveals that all ionic components are within the acceptable limits, with the exception of heavy metals like Fe and Cd. The pH values reveal that they are acidic waters. The study revealed that the mean value of Fe (0.832000 ± 1.0626228 ppm) and Cd (0.043750 ± 0.0181713 ppm) exceeded the permissible limit for NSDWQ water quality standard. Water Quality Index (WQI) revealed that 80% of the samples are of good quality for drinking purpose. The Heavy Metal Pollution Index (HPI) and degree of contamination (Cd) also revealed that most of the samples are of low level of pollution whereas Heavy Metal Evaluation Index (HEI) revealed that only 5% of the samples are of low level of pollution. The Sodium Adsorption Ratio (SAR) model revealed that 40% (8 samples) of the samples were excellent for irrigation, 45% (9 samples) are of good quality, 10% (2 samples) were fair while 5% (1 sample) is of poor quality for irrigation. However, Kelly’s Ratio (KR) model shows that 100% of the samples are unsuitable for irrigation purposes while the Magnesium Adsorption Ratio (MAR) revealed that 30% (6 samples) of the samples are acceptable and 70% (14 samples) not acceptable. Moreover, the Sodium Percentage (Na%) model revealed that only 5% (1 sample) of the samples is good for irrigation, 55% (11 samples) are permissible while 40% (8 samples) are doubtful. The Permeability Index (PI) revealed that 70% of the samples are of excellent quality while 30% are of good quality for irrigation purposes. In all the hydrochemical facies classification applied, they confirmed that the groundwater in the study area is dominantly sodium chloride waters. This research is expected to help water resource planners taking adaptive measures for groundwater quality monitoring in the study area.

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