Fluoride enrichment in groundwater of semi-arid urban area: Khan Younis City, southern Gaza Strip (Palestine)

200 Groundwater samples analyzed; and WATQ4F model applied for SI calculations. Francolite, F bearing mineral, it reach the aquifer by phosphate minerals mining. Francolite dissociated producing fluorite. Fluorite and calcite controlling fluoride enrichment in the aquifer. Fluorite SI increase with F increase. The aim of this study is to determine fluoride enhancement in the groundwater of semi-arid urban area of Khan Younis City, southern Gaza Strip. Physicochemical data for a total of 200 groundwater samples were analyzed. The fluoride concentrations were varied from 0.3 to 6.45mg/L with average value of 2.87mg/L. Correlations between fluorides with other measured ions were relatively observed, negative correlation with calcium and the positive correlation with pH, bicarbonate and sodium increase the dissolution/solubility of fluoride bearing minerals, leading to fluoride leaching into the groundwater. Fluoride enrichment in the groundwater of the area is due to water hydrochemistry, mineral-water interaction (mainly calcite and fluorite), fluorite resulted from fluorapatite dissolution. The saturation indexes evaluation indicated that 42% of the samples are over saturated with respect to calcite and 35.5% under saturated with respect to fluorite, while 40.5% approached equilibrium with respect to both calcite and fluorite. At fluoride concentrations of less than 2.2mg/L fluorite saturation indexes show under-saturation condition for fluorite and at higher fluoride concentrations show near saturation condition.