Fluoride Contamination of Shallow Groundwater in Parts of Zango Local Government Area of Katsina State, Northwest Nigeria

Abstract

Serious health problems are experienced in many parts of the world due to high concentration of fluoride in drinking water which causes dental and skeletal fluorosis to humans. Zango Local Government Area of Katsina State, Nigeria is one such area where high concentration of fluoride occurs in groundwater. Though there are no major studies with reference to fluoride in the area in the past, the present study was carried out to provide baseline information on groundwater quality in Zango Local Government Area of Katsina State, Nigeria with emphasis on fluoride concentration. A total of 87 groundwater samples each were collected from hand-dug wells and boreholes in the area for both dry and wet seasons, between February 2011 to March 2012 and analyzed for fluoride concentration and other quality parameters at the National Research Institute for Chemical Technology Laboratory Zaria, Nigeria. The fluoride concentration in groundwater of the area ranged between 0.10 to 3.16 mg/l with a mean value of 0.94 mg/l for dry season and between 0.10-1.47 mg/l and an average value of 0.52 mg/l for the rainy season. The low concentration of fluoride in the rainy season is due to the dilution effect of rain-water. The study revealed that about 75% of the groundwater samples in the area that are suitable for human consumption fall within the sedimentary rocks of the Gundumi and Chad Formations as well as the Basement Complex rocks while 25% of the samples with high fluoride concentration above the permissible limit of 1.5 mg/l are from the Younger Granites Suites. Fluorite, a hydrothermal mineral in granite and due to its fast dissolution kinetics, is probably the source of fluoride in the groundwater in the area. The fluoride concentration map developed for the study was in agreement within the interpretation as the area dominated with sedimentary formations show low concentration of fluorite while the region occupy by younger granites show high fluoride concentration. This implies that fluoride-rich groundwater in the area emanates from the granite aquifers and the problem of fluorosis in the area is purely by natural processes. Communities living in the granite/rhyolite dominated region where cases of fluorosis have been observed should discontinue the use of groundwater from the area for domestic and drinking purposes. The Katsina State Government should provide an alternative source of drinking water for the people in the region.