Hydrochemical and Health Risk Assessment of Groundwater of Ladigbolu and Ojongbodu in Oyo Town, Southwestern Nigeria

Abstract

Groundwater is the predominant source of drinking water in Oyo Town. Consequently, this work was designed to evaluate the concentration of some potentially toxic elements in the groundwater in order to determine its health risk and potability for human consumption.  A total of 20 samples, 10 samples per area, were collected from boreholes at Ladigbolu and Ojongbodu areas of Oyo town during the dry season. Total Dissolved Solid (TDS), Conductivity, and pH of the samples were measured at the point of collection. Pb, Cd, Cr, Ni, Fe, Zn, Cu, Co, and Mn concentrations were determined using Fast Sequential Atomic Absorption Spectrophotometer. The Ca²⁺, Mg²⁺, K⁺, and Na⁺ concentrations were measured using flame photometry while Spectrophotometer was employed to measure the concentrations of NO₃, SO₄^2-, Cl, CO₃^2-and HCO₃. The concentration of major cations and anions in ppm at Ladigbolu were in the order of Ca²⁺> Na⁺> Mg²⁺>K⁺ and HCO₃^- > SO₄^2- >NO₃> Cl> CO₃, while at Ojongbodu the order was Ca²⁺> Mg²⁺ >Na⁺ >K⁺ and HCO₃^- >SO₄^2->NO₃> Cl> CO₃². The concentration of potentially toxic elements at Ladigbolu and Ojongbodu were in the order Fe > Mn > Cu > Cr > Pb > Zn > Ni > Co > Cd and Fe > Mn> Cu > Pb > Zn > Cr > Cu> Co > Cd respectively. The hydrogeochemical facies of the groundwater is dominantly CaHCO₃. Chronic Daily Iingestion (CDI) across all age groups was relatively low for the two communities. The hazardous quotient (HQ) was less than one (HQ <1) for Pb, Cu, Cr, Mn, Co, and Cd but greater than one (HQ >1) for Fe, Zn, and Ni which indicated potential health risk across all age groups in the two communities.