Comparative Geological study and physico-chemical parameters of Groundwater in Hong and Zango Settlements in Northern Nigeria

Abstract

This present study examined the impact of geology on the quality of groundwater in Hong and Zango communities in northern Nigeria with a view of establishing the source and extent of pollution of the groundwater systems in these areas. The geological mapping of Hong and Zango communities revealed that the area is partly underlain by granitic rock as well as other rock types. Petrographic study of the granitic rock domiciled in Hong and Zango areas showed quartz, feldspar, mica and some accessory minerals while the laboratory analysis using XRD indicated the presence of nacaphite (Na2CaPO4F) in the granite sample. Interestingly, the nacaphite, which is a fluoride bearing mineral was conspicuously absent in the other rock samples analyzed. The concentration of other parameters investigated was below the maximum permissible limits except electrical conductivity and total dissolved solid. Groundwater samples from Zango area had higher concentration compared to Hong area. This may be attributed to the age of the rocks, Zango are underlain by the older granites while Hong is domiciled by the younger granites. The older granites had more resident time for rock-water interaction than younger granites. An integration of the results of laboratory analysis from Hong and Zango areas against the respective geology further revealed that water samples collected from areas underlain by granitic rock showed higher concentration of fluoride (> 2.0 mg/L) compared to those underlain by other rock types. The paper has established the source of fluoride in groundwater as a possible cause of fluorosis in the study areas. Gibbs plot also confirmed that rock-water interaction and precipitation are the geochemical processes responsible for groundwater evolution and composition in these areas. Conclusively, the use of water in the granite dominated zone for domestic purposes especially drinking in Hong and Zango communities should be discontinued and alternative source of water provided for inhabitants until remediation processes targeted at extracting the fluoride from the groundwater systems in these settlements are executed.