Geo-chemical investigation of groundwater salinity status in selected coastal areas of south western Nigeria

Groundwater remained main source of drinking water in Nigeria. Hydro-geochemical study was carried out to assess the influence of seawater on the chemical composition of groundwater in Badagry, Ikorordu, Epe, and Ondo Water side south western Nigeria. One hundred and ninety two (192) groundwater samples were collected from forty-eight (48) sampling points along the coastlines for four seasons (2015 through 2017). Analyses were carried out using standard procedures. Salinity-related parameters of the groundwater samples showed a range of 5.09–7.29 (pH), 1056–2249 µS/cm (electrical conductivity), 513.30–1439.30 mg/L (total dissolved solid), 43.15–2147 mg/L (alkalinity), 51.5–995. 5 mg/L (Cl − ), 2.75–11.75 mg/L (SO 4 2− ), 8.78–32.11 mg/L (Na + ), 24.42–45.44 mg/L (K + ) 0.56–2.75 mg/L (Ca 2+ ), 0.09–5.55 mg/L (Mg 2+ ), and 7.2–39.15 mg/L (Hardness), respectively. Groundwater ionic characters were in order of HCO 3 − > Cl − > SO 4 2− for anions and K + > Na + > Ca + > Mg 2+ for cations. Though concentration of bicarbonate was high as expected of inland water, salinity-related parameters were above the acceptable limits. Results revealed that the groundwater samples in the areas have saline water signatory probably as a result of prevailing climate influence (sea-level rise and flooding) which predisposes the users to diverse infections and other cardiovascular diseases associated with intake of saltwater. Water quality index also showed that groundwater in the areas are contaminated and unfit for human consumption. Achieving water sustainability in the area would demand appropriate water safety plan and proper water treatment.