A Study of Fluoride Occurrence and some Heavy Metals in Groundwater from Shallow Aquifers near Ogbomosho, Southwest Nigeria

Abstract

The present study evaluates the presence of fluoride and some heavy metals in groundwater from shallow aquifers around Ogbomosho, Southwest Nigeria. The fluoride concentration ranged from 1.35 mg/l to 2.75 mg/l with a mean value of 1.58 mg/l as against the recommended value of 1.50 mg/l by World Health Organization and Nigerian Standard for Drinking Water Quality. Continuous use of water from this area may result to colouration of the teeth (dental fluorosis) and deformation of the bone and skeleton (skeletal fluorosis) especially in children below the age of five. The high fluoride content in groundwater from shallow aquifers in the area as well as the heavy metals may be attributed to water-rock interaction during the process of percolation with fluoride-bearing rocks under arid, low precipitation, and high evapotranspiration conditions leading to intensive chemical weathering and bedrock dissolution of the granite aquifers in the area. The heavy metal enrichment is in the increasing order of: Ni > Mn > Cr > Cd > Fe > Cu > Zn. These findings suggest that the enrichment of the groundwater system in the area is geogenic and is a function of the local geology. It is recommended that people living in the coarse grained porphyritic biotite granite dominated area should discontinue the use of groundwater from hand dug wells for domestic and drinking purposes in order to avoid the occurrence of fluorosis in future. Regular monitoring of the groundwater in the area is advocated. Furthermore, environmental friendly techniques such as phyto-remediation and bio-remediation should be employed to absorb the fluoride and heavy metal in the groundwater system.