HYDROGEOCHEMICAL SIGNATURES AND QUALITY ASSESSMENT OF GROUNDWATER IN OKPOKO AND ENVIRONS, SOUTHEASTERN NIGERIA

This study is aimed at assessing the hydro-geochemical signatures of groundwater in Okpoko and Environs in Anambra State, Southeastern Nigeria. Fifteen groundwater samples were collected and analyzed for physico-chemical, heavy metals and hydrocarbon content. Heavy metals in groundwater were analyzed using Atomic Absorption Spectrometer. The groundwater analyses revealed that average pH (6.05), Fe (0.68 mg/L) and Ni (0.028 mg/L) values exceeded WHO and NSDWQ guidelines. Total Petroleum Hydrocarbons (TPH) in groundwater were relatively very low and recorded only in BH1 (0.04 mg/L) and BH2 (0.002 mg/L) and below detectable limit for all other sampled boreholes. Piper diagram revealed two hydro-chemical facies: Mg-HCO3 and Ca-HCO3 rich water, while Stiff diagrams confirmed four distinct water types (Ca2+, Mg2+, HCO3; Ca2+, HCO3; Ca2+, Na++K+, Cl-, HCO3; Ca2+, Cl- Class). Gibb’s diagrams revealed that chemical weathering of rock and precipitation are the major influences on the groundwater quality. The various ionic ratios: Mg/Ca (0.56), HCO3/Cl (3.31), (Na + K)/Cl (1.45), Na/K (1.61), Ca/Na (7.0), SO4/Cl (0.67) and CEV (-0.45) suggests the groundwater sources are of inland origin. Groundwater flow direction shows that the area is drained by the Niger River on the western part of the study area.