Combining multiple numerical and chemometric models for assessing the microbial and pollution level of groundwater resources in a shallow alluvial aquifer, Southeastern Nigeria

Abstract

Water contamination assessment could serve as an effective tool for pollution control and prevention. However, using only standard groundwater pollution assessment techniques is not enough to provide a holistic contamination assessment. In this study, standard hydrogeochemical and microbial techniques, multiple numerical indices (heavy metal evaluation index [HEI], heavy metal pollution index [HPI], water quality index [WQI], pollution index of groundwater [PIG]), and chemometric models (principal component analysis and correlation analysis) were integrated to assess the aquifer intrinsic vulnerability and pollution sources of groundwater within the Adani suburban, southeastern Nigeria. Twenty groundwater samples from drinking wells were collected and subjected to physicochemical and microbiological analysis. The results revealed that the water is moderately acidic (pH 4.8–6.9), fresh (TDS < 1000), and soft (Hardness 5–25 mg/L). All analyzed physicochemical constituents occurred within the WHO acceptable standards except for NO₃, PO_4, and NH_4, due to influx and leaching from poor sanitary conditions, agricultural activities, and solid waste materials. The concentration of heavy metals was in the order of Mn > Zn > Ni > Fe > Cu > Pb > As > Cd, with Ni, Mn, Cu, and As, recording values above the required standards. Microbial analysis revealed the presence of pathogens such as Staphylococcus aureus, Escherichia coli, and Salmonella/Shigella in the water; attributable to poor sanitary conditions. WQI and PIG revealed that 80–85% of the water samples are unfit for drinking. The groundwater flow map shows that the direction of flow of groundwater is majorly from the eastern to western regions of the study area, suggesting that contaminants will be moved mostly from the eastern to western regions. Public waste disposal sites and agricultural activities are therefore recommended to be limited to the western regions. Frequent monitoring and evaluation of the water resources in the region is recommended for the sustainability of public health and water resource management.