Occurrence of Fluoride and some Heavy Metals in Groundwater from Shallow Aquifers Near Ogbomosho, North-central Nigeria

Abstract

Groundwater is one of the most important natural resources that when contaminated by either natural or anthropogenic means is difficult and expensive to clean-up. Fluorosis is a disease affecting the bone and teeth of humans due to excessive intake of fluoride either through water or food. Heavy metal pollution is a burning environmental issue due their toxic, persistent and bio-accumulative nature. The present study evaluates the presence of fluoride and some heavy metals in groundwater from shallow aquifers around Ogbomosho, north-central Nigeria and the result of investigation confirmed their enrichment. The fluoride concentration ranged between 1.35mg/l to 2.75mg/l with a mean value of 2.18mg/l as against the recommended value of 1.50mg/l. This is an indication that continuous use of water from this area may result to colouration of the teeth and deformation of the bone among the people especially children since they are the most vulnerable. High fluoride content in groundwater can be attributed to the continuous water-rock interaction during the process of percolation with fluoride-bearing country rocks under arid, low precipitation, and high evapotranspiration conditions. The study has established that the fluoride-rich groundwater as well as heavy metal contamination in the area may have emanated from geochemical processes of dissolution and weathering of the granite aquifers in the area. The heavy metal enrichment is in the order of: Ni > Mn > Cr > Cd > Fe > Cu > Zn. These findings suggest that the enrichment of the groundwater system is geogenic and related to the local geology of the area. It is recommended that people living in the coarse grained porphyritic biotite granite dominated area should discontinue the use of groundwater for domestic and drinking purposes in order not to experience fluorosis in future. Environmentally friendly techniques such as phyto-remediation and bio-remediation should be employed to monitor and control fluoride and heavy metal content in the groundwater system.

Keywords: Groundwater Quality, Fluorosis, Heavy metals contamination, Shallow Aquifers Ogbomosho and North-central Nigeria