Imprints of sea surge and municipal activities on non-potability of groundwater in shallow coastal sandy aquifer system of Lagos State, Southwestern Nigeria

Coastal areas are usually characterized by a high human population with attendant groundwater pollution through increased salinization from varied sources. This study was done to assess the pollution status, suitability of groundwater and associated hydrogeochemical processes of the shallow sandy aquifer near the coastal section of Lagos State, Southwestern Nigeria. A total of fifty-nine hand-dug wells were randomly selected, from which water samples were collected and subjected to physicochemical and statistical analyses. Water quality indices (Pollution Index of Groundwater (PIG) and Irrigation quality indices) and Chloro-Alkaline Indices (CAI 1&2) were calculated while plots of Gibbs and Piper diagrams as well as factor analysis were also carried out. The order of abundance of dissolved ions were Na > Ca > Mg > K for cations and HCO3>Cl > SO4>NO3 for anions. Presently, there appears to be no pollution threat to the groundwater, and the bulk of the samples are found fit for agricultural use. Rock weathering, ion exchange, occasional sea surge and municipal contamination activities constitute the geochemical processes affecting the groundwater quality in the study area. It could be postulated that consistent activities of sea water surge and municipal contamination might impair the groundwater quality of the sandy aquifers in the nearest future. Potential threats and resultant effects on the quality of groundwater in Ibeju-Lekki and Ajah areas. [Display omitted] •The groundwater in the study areas is good and placed in pollution free status from a numerical technique, Pollution Index of Groundwater (PIG) assessment.•This result was disproved by the ionic ratios evaluations, showing the traces of occasional sea water surge and municipal contamination.•These kinds of traces might result to the non-potability of the groundwater resource in the study areas.