Geochemical modeling, source apportionment, health risk exposure and control of higher fluoride in groundwater of sub-district Dargai, Pakistan

The present study examined the hydrogeochemical profile of higher fluoride (F-) in groundwater of mixed industrial and mining areas of Dargai, northern Pakistan. Groundwater samples (n = 75) were collected from three hydrogeochemical environments. The mean concentrations of pH, EC, TDS, Depth and Temperature were (7.6, 1081 mu S/cm, 590 mg/L, 75 m, 28.03 degrees C), for chemical ions viz. NO3, PO4, SO4, Cl, HCO3, Na, K, Ca and Mg were (18.5, 2.7, 161, 107, 330, 150, 9.76, 33, 52) mg/L respectively. Whereas, the mean concentration of F- was 2.0 mg/L. Therefore, 51% groundwater samples exceeded the WHO guideline of F- 1.5 mg/L. Additionally, we measured the mean F- concentration in rocks, coal and wastewater, which were (670, 98) mg/Kg and 2.3 mg/L respectively. The principal component analysis multilinear regression (PCA-MLR) extracted five significant factors which shows natural, mixed and anthropogenic pollution. Thus, fluorite is the primary source of F- contamination in groundwater. While apatite, biotite and muscovite minerals are the secondary sources which occurs in association with quartzite, granite rocks. Under alkaline conditions, F- contamination is supported by higher Na+, HCO3- and lower Ca++ concentrations. The accuracy and reproducibility of the measurement of fluoride was assessed by adopting a standard method of water. The percentage recovery of F- was 97% and reproducibility was within +/- 5% error limit. Lastly, a health risk community fluorosis index (CFI) was calculated through Dean's formula which shows unsuitability of groundwater sources conceiving community fluorosis in the entire study area. (C) 2019 Elsevier Ltd. All rights reserved.