Integrated Physicochemical, Hydrochemical, Trace-element and Microbiological Assessment of Groundwater across Contrasting Geological Settings
Madu Onyeka Emmanuel
African Union Commission, Addis Ababa, Ethiopia.
Modestus Ohaegbulem
Department of Geology, Gregory University, Uturu, Abia State, Nigeria.
Okpoji Awajiiroijana Uriah *
Department of Pure and Industrial Chemistry, University of Port Harcourt, Choba, Rivers State, Nigeria.
Okoro Mary Ugomma
Department of Chemistry, Federal University of Technology, Owerri, Imo State, Nigeria.
Okata-Nwachukwu Maria Okwudili
Department of Science Laboratory Technology (Microbiology Unit), Akanu Ibiam Federal Polytechnic, Unwana, Afikpo, Ebonyi State, Nigeria.
Joseph Jerry
Department of Chemistry, Kaduna State College of Education, Gidan Waya, Kafanchan, Kaduna State, Nigeria.
Inyang Godwin Edet
Department of Geology, Federal University of Technology, Owerri, Imo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Groundwater is an important source of domestic water supply, but its quality may vary according to geological setting, mineral–water interactions and microbiological contamination. This study evaluated the physicochemical, hydrochemical, trace-element and microbiological characteristics of groundwater across Basement Complex, Younger Granite, shale/sedimentary and weathered-regolith geological settings. Groundwater samples were analysed for pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, total hardness, alkalinity, major ions, selected trace and potentially toxic elements, heterotrophic bacteria, total coliforms, faecal coliforms, Escherichia coli and enterococci. Hydrochemical facies were determined from the major-ion composition, while differences among geological settings were evaluated using one-way analysis of variance, and relationships between chemical and microbiological variables were assessed using Pearson's correlation analysis. The groundwater was slightly acidic to near neutral, with pH values ranging from 6.21 ± 0.14 to 6.78 ± 0.16. Basement Complex groundwater exhibited the highest EC (486 ± 42 µS/cm), TDS (312 ± 28 mg/L), total hardness (146 ± 12 mg/L), calcium (48.6 ± 4.2 mg/L), magnesium (18.4 ± 2.1 mg/L) and bicarbonate (118 ± 10 mg/L). The shale/sedimentary setting recorded the highest concentrations of several trace elements, including Pb (0.014 ± 0.003 mg/L), Cd (0.0026 ± 0.0005 mg/L), Cr (0.018 ± 0.004 mg/L) and Ni (0.021 ± 0.004 mg/L). Ca–Mg–HCO₃ was the predominant hydrochemical facies. Microbiological contamination varied spatially, with weathered-regolith groundwater recording the highest total coliforms (31 ± 7 CFU/100 mL), faecal coliforms (15 ± 4 CFU/100 mL), E. coli (11 ± 3 CFU/100 mL) and enterococci (9 ± 3 CFU/100 mL). Significant differences occurred among geological settings for the assessed physicochemical, chemical and microbiological parameters (p < 0.05). Turbidity and nitrate showed positive associations with the principal microbiological indicators. The findings demonstrate that geological setting influences groundwater mineralisation and trace-element distribution, while microbiological quality may respond to additional factors associated with groundwater vulnerability and contamination pathways. Integrated chemical and microbiological monitoring is therefore important for evaluating groundwater quality and its suitability for domestic use.
Keywords: Groundwater quality, hydrochemistry, trace elements, potentially toxic elements, hydrochemical facies, mineralisation, microbiological contamination, faecal indicators