Assessment and characterisation of groundwater quality in Akure metropolis, southwestern Nigeria

Abstract

The geology of an area plays a significant role in the chemistry of groundwater. The quality of groundwater can also be adversely affected by anthropogenic activities if not properly monitored. The composition of groundwater in Akure was assessed and characterised in order to determine the chemical behavior of the groundwater system within the city. A total of thirty-six representative groundwater samples were randomly collected within Akure metropolis. The chemical composition of the water samples was analysed and determined using AAS, flame photometry and titration methods. The analysis of the results showed that the chemical concentrations of EC ranged from 35.5 to 1670.0µS/cm; TDS (in mg/l) ranged from 5.0 to 1700.0; Na+(1.0–122.0); K+(1.2–156.7); Ca2+(1.2–17.3); Mg2+(3.9–6.4); Fe3+(0.03–1.03); HCO3− (0.0–622.5); NO3−(0.01–0.25); Cl−(1.99–216.4); SO42−(22.6–`873.9); Mn2+(0.05–0.30); Zn2+(0.06–0.78); Cu2+(0.02–0.32); Pb2+(0.01–0.18); Ni2+(0.0–0.02); Cr3+(0.02–0.32); and Se2+(0.06–0.37). Statistical evaluation of the data showed that the water samples collected within the centre of the ancient city as well as the samples obtained from downstream of the major river draining the city have elevated EC and TDS higher than the WHO and NIS recommended limits. Further evaluation of the results by piper diagram, Gibb’s plot and Chadha classifications showed that the chemistry of the groundwater system in Akure metropolis is largely dominated by rock water interactions. The primary character of the water falls within the alkali metals exceeding alkaline earth metals and strong acidic anions exceeding weak anions. The indicates that the groundwater system in the study area has salinity challenges for both domestic uses and irrigation purposes.