Hydrogeochemical characterization of surface water around canal and lagoon in parts of Lagos, Southwestern Nigeria

Abstract

southeastern suburbs of Lagos was carried out. The physicochemical parameters of the water including TDS, EC, pH, Salinity Ca, Mg, Na, K, HCO3, CO3, Cl, SO4, NO3, and heavy metals were determined for characterization of the water. The water samples were processed and analyzed using atomic absorption spectrophotometry and inductively coupled plasma mass spectrometry respectively. The results show that canal waters are slightly acidic-neutral with a pH range of (6.48 7.14), while the lagoon waters are alkaline with a pH range of (7.83-8.25). The lagoon waters are brackish-marine with salinity range between (11-32) % while the canal waters are fresh with salinity values generally less (<1) %. The lagoon waters have constant TDS value of (2000 ppm) and EC value of (3999 ms/cm), whereas the canal water has low TDS value ranging from (77-460 ppm ) and EC range of (151-917 ms/cm). Based on the Geoaccumulation indices, both waters from the canal and lagoon are considered to be unpolluted with respect to Zn, Cu, As, Ni, Co, Cr, Cd, Pb, and Fe. Hg is the only pollutant in both canal and lagoon water. While the lagoon water is moderately contaminated with respect to Hg, the canal water is very highly polluted. The canal water is Ca-Mg-HC03 water type, while the lagoon water is Ca-Mg-Na-SO4- Cl water type. Possible contamination sources are industrial and anthropogenic. These need to be monitored and controlled effectively.