- Groundwater of Dargai region, Pakistan was analyzed for fluoride concentrations.
- 51% of groundwater samples exceeded the WHO guideline value of 1.5 mg/L of F–.
- F– occurrence in water is linked to ion exchange, weathering and mining actions.
- PCA-MLR results of groundwater shows 64% contamination was due to geogenic source.
- CaHCO3 (49%), NaHCO3 and NaCl (51%) are the major water type of the study area.
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 uS/cm, 590 mg/L, 75 m, 28.03 °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.
*Original abstract online at https://www.sciencedirect.com/science/article/pii/S0045653519326499?via%3Dihub