Characterization of Groundwater Hydro-Chemistry and Quality Assessment in Eti –Osa, Lagos- Nigeria

Abstract

Water samples collected from forty-four hand dug wells using random sampling technique were measured for pH, electrical conductivity, total dissolved solids. Total hardness, calcium, chloride, bicarbonate and carbonates were analyzed using titrimetry method. Magnesium, potassium and sodium by Atomic Absorption Spectrophotometer while sulfate was analyzed usi ng spectrophotometer. Thestudy is aimed at characterization of groundwater hydrochemistry and quality assessment in Eti–Osa, Lagos-Nigeria using multivariate statistical techniques, piper diagram, surfer software and water quality indices. Factor 1 explains 71.19% of the total variance, with loading on TDS, Cl, Na, TH, SO⁴, Mg, EC, K and Ca while Factor II accounts for 13.731% of the total variance with moderate loading on HCO₃,CO₃ and pH. The residual sodium carbonate shows that 18.2%, 13.6% and 15.9% of the samples are suitable, marginal and unsuitable water respectively for irrigation purpose. Magnesium ratio shows that 75% of the samples are suitable while the remaining 25% are unsuitable for irrigation purpose. Computed water quality index shows that, 31.8% has excellent water quality, 50%, 15.9% and 2.3% indicate good, poor and water unfit for drinking respectively. The hydrochemical facies of the study area is characterized by Ca-HCO₃ and Ca-Cl types. It was concluded that water quality of the study area is unsuitable for irrigation whereas, it is suitable for domestic and drinking purposes. Appropriate treatment methods to make it more potable for human consumption, routine monitoring and periodic water quality testing coupled with appropriate treatment for agricultural activity should also be employed in the study area.

Key words: Assessment, characterization, Groundwater quality, Hydrochemical facies, Lagos-Nigeria