Hydrogeochemical characteristics, stable isotopes, positive matrix factorization, source apportionment, and health risk of high fluoride groundwater in semiarid region.
Chronic exposure to high fluoride (F-) levels in groundwater causes community fluorosis and non-carcinogenic health concerns in local people. This study described occurrence, dental fluorosis, and origin of high F-groundwater using δ2H and δ18O isotopes at semiarid Gilgit, Pakistan. Therefore, groundwater (n = 85) was collected and analyzed for F- concentrations using ion-chromatography. The lowest F- concentration was 0.4 mg/L and the highest 6.8 mg/L. F- enrichment is linked with higher pH, NaHCO3, NaCl, δ18O, Na+, HCO3-, and depleted Ca+2 aquifers. The depleted δ2H and δ18O values indicated precipitation and higher values represented the evaporation effect. Thermodynamic considerations of fluorite minerals showed undersaturation, revealing that other F-bearing minerals viz. biotite and muscovite were essential in F- enrichment in groundwater. Positive matrix factorization (PMF) and principal component analysis multilinear regression (PCAMLR) models were used to determine four-factor solutions for groundwater contamination. The PMF model results were accurate and reliable compared with those of the PCAMLR model, which compiled the overlapping results. Therefore, 28.3% exceeded the WHO permissible limit of 1.5 mg/L F-. Photomicrographs of granite rocks showed enriched F-bearing minerals that trigger F- in groundwater. The community fluorosis index values were recorded at > 0.6, revealing community fluorosis and unsuitability of groundwater for drinking.
Rashid A
，Ayub M
，Gao X
，Khattak SA
，Ali L
，Li C
，Ahmad A
，Khan S
，Rinklebe J
，Ahmad P
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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 μS/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.
Rashid A
，Farooqi A
，Gao X
，Zahir S
，Noor S
，Khattak JA
... -
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Fluoride prevalence in groundwater around a fluorite mining area in the flood plain of the River Swat, Pakistan.
This study investigated the fluoride (F-) concentrations and physicochemical parameters of the groundwater in a fluorite mining area of the flood plain region of the River Swat, with particular emphasis on the fate and distribution of F- and the hydrogeochemistry. To better understand the groundwater hydrochemical profile and F- enrichment, groundwater samples (n=53) were collected from shallow (24-40m), mid-depth (48-65m) and deep (85-120m) aquifers, and then analysed using an ion-selective electrode. The lowest F- concentration (0.7mg/L) was recorded in the deep-aquifer groundwater, while the highest (6.4mg/L) was recorded in shallow groundwater. Most groundwater samples (62.2%) exceeded the guideline (1.5mg/L) set by the World Health Organization (WHO); while for individual sources, 73% of shallow-groundwater samples (F- concentration up to 6.4mg/L), 42% of mid-depth-groundwater samples, and 17% of deep-groundwater samples had F- concentrations that exceeded this permissible limit. Assessment of the overall quality of the groundwater revealed influences of the weathering of granite and gneisses rocks, along with silicate minerals and ion exchange processes. Hydrogeochemical analysis of the groundwater showed that Na+ is the dominant cation and HCO3- the major anion. The anionic and cationic concentrations across the entire study area increased in the following order: HCO3>SO4>Cl>NO3>F>PO4 and Na>Ca>Mg>K, respectively. Relatively higher F- toxicity levels were associated with the NaHCO3 water type, and the chemical facies were found to change from the CaHCO3 to (NaHCO3) type in calcium-poor aquifers. Thermodynamic considerations of saturation indices indicated that fluorite minerals play a vital role in the prevalence of fluorosis, while under-saturation revealed that - besides fluorite minerals - other F- minerals that are also present in the region further increase the F- concentrations in the groundwater. Finally, a health risk assessment via Dean's classification method identified that the groundwater with relatively higher F- concentrations is unfit for drinking purposes.
Rashid A
，Guan DX
，Farooqi A
，Khan S
，Zahir S
，Jehan S
，Khattak SA
，Khan MS
，Khan R
... -
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Two distinct mechanisms of fluoride enrichment and associated health risk in springs' water near an inactive volcano, southeast Iran.
Groundwater fluoride contamination is a major issue of water pollution in the world with health hazards such as dental and skeletal fluorosis. This research focused on exposure to the high concentration of fluoride in the springs water in the Bazman volcanic area, southeast Iran. The combination of chemical/isotopic analysis, geochemical modeling, health risk assessment and multivariate statistical methods were applied to investigate the contamination and sources of fluoride in the samples. Groundwater samples were collected from cold and thermal springs. Major ions, fluoride, trace elements and stable isotopes δ18O and δD were measured in the samples using standard methods, ICP-MS and OA-ICOS, respectively. Fluoride content in springs varied from 0.5 to 3.75 mg/L with an average value of 1.66 mg/L. The highest fluoride concentrations were observed in the eastern cold springs while thermal springs showed the minimum fluoride contents. The majority of samples showed F contents higher than the calculated optimal concentration of fluoride (0.75 mg/L). Reaction of fluorite mineral with HCO3 and replacement of F in clay minerals and metal oxy-hydroxides with OH- in water were likely cause fluoride enrichment in the eastern springs. Whereas, in the western springs and thermal springs, origin of fluoride was related to weathering of muscovite, cryolite, apatite and fluoroapatite minerals. The δ18O and δ2H of the water samples displayed the impact on evaporation on fluoride enrichment in all spring water samples. The average value of contamination index (Cd) in the water samples was 1.94 categorizing medium risk level while springs S7, S8, S9 and S4 were above the threshold value of Cd index. The fluoride hazard quotient (HQ) showed that 25%, 44%, 56% and 0% of springs' water resources had high risk level for age group of adults, teenager, children and infants, respectively. Therefore, health risk of fluoride in drinking water resources were in the following order: children > teenager > adults > infants.
Naderi M
，Jahanshahi R
，Dehbandi R
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