Fluoride Contamination In Groundwater Research Articles

Fluoride Contamination in Groundwater of Community Tube Wells, Source Distribution, Associated Health Risk Exposure, and Suitability Analysis for Drinking from Arid Zone

Fluoride (F−) pollution in potable groundwater (GW) is a serious environmental concern in Pakistan with substantial human health hazard reports. The research on F− pollution in GW resources in Sindh Province is still incomplete. To explore the realistic conditions, the present research aimed to investigate the GW quality of community tube wells concerning F− contamination in Tharparkar, Sindh, Pakistan. A total of 53 samples were collected and examined for F−, along with other physicochemical parameters. The F− values observed varied from 0.2–4.2 mg/L, with a mean value of 1.63 mg/L. Among the 53 samples, 46% had F− levels that were higher than the World Health Organization’s (WHO) recommended limit (1.5 mg/L). The water type of the studied region was Ca-HCO3 type, which can be attributed to fresh recharged water. The interaction of rock–water contact controls the hydrochemistry of GW. The GW resources of the research zone were highly saturated with fluorite minerals. Human health risk calculation outcomes exposed that 21 samples showed high HQ values for children and 7 samples showed high values for adults in the research zone. Children are at high risk in the study area from drinking F−-contaminated GW. WQI results showed that 31 samples were not suitable for drinking.

Occurrence of and Factors Affecting Groundwater Fluoride in the Western Coastal Area of Hainan Island, South China

Hainan, a well-known center of tropical agricultural production in south China, has received little attention regarding groundwater fluoride contamination. This study investigates the occurrence of fluoride in the western coastal area of Hainan Island and discusses factors affecting groundwater fluoride contamination in various aquifers and areas with different land-use types using hydrochemistry and multivariate statistical analysis. A total of 100 groundwater samples were collected from the western coastal area of Hainan Island. The results show that the groundwater fluoride concentration is as high as 4.18 mg/L and that F−-high (>1 mg/L) groundwater accounts for 9% of total groundwater. The proportion of F−-high fissure water is about two times that of F−-high pore water. Among the different land-use types, the proportion of F−-high groundwater from highest to lowest is as follows: bare land > cultivated land > woodland > construction land > grassland. The main factor affecting fluoride in pore water is the leaching of fluorine/aluminum-containing minerals such as phlogopite and calcite in the vadose zone, which is characterized by the co-enrichment of fluoride and aluminum in pore water. The leading cause of fluoride in fissure water is the leaching of fluorine-containing fertilizers, and continuous irrigation promotes the cation exchange of sodium, strontium, and calcium, which is characterized by the co-enrichment of fluoride with sodium and strontium in fissure water. Consequently, it is advised to minimize the excessive use of fluoride fertilizers and increase groundwater quality monitoring in order to decrease the emergence of F−-high groundwater in the western coastal area of Hainan Island.

Relative extents, mechanisms, and kinetics of fluoride removal from synthetic groundwater by prevalent sorbents

Fluoride (F) contamination in groundwater affects millions of people across the world. Although several sorbents have been identified for low-cost F removal, the choice of the optimal sorbent is dictated by the specific chemistry of contaminated groundwater. In this contribution, eight prevalent sorbents—activated alumina (AA), calcite, hydroxyapatite-coated calcite (HCC), natural chitosan, chalk, Mg–Al–CO3 layered double hydroxide (LDH), calcined Mg–Al–CO3 LDH (cLDH), and hydrous ferric oxide (HFO)—were categorized on their relative F removal mechanisms, extents, and kinetics from a typical synthetic groundwater, representative of contaminated aquifers of North India. Initially, batch experiments containing sorbents at 4 g·L−1 were conducted at a high F concentration (2.9 mM). The dominant F removal processes were identified by aqueous- and solid-phase characterization of reaction by-products. While chalk and calcite removed F by secondary precipitation of fluorite, HCC removed F by fluorapatite precipitation, and other sorbents removed F by sorption. Depending on the immobilization mechanism identified, the F uptake kinetics on each sorbent was modeled with either pseudo-second order or generalized rate equations. Among sorptive F uptake, cLDH exhibited the highest (10−2.15 mg·g−1·h−1) and HFO showed the lowest (10−4.15 mg·g−1·h−1) rates. Fluoride removal by precipitation was the fastest with chalk at 10−1.3 (h−1) (0.16). Subsequent experiments with AA and HCC at lower initial F concentration (0.42 mM) suggested increased uptake by ∼30x and ∼7x, respectively, relative to uptake in 2.9 mM initial F systems. For AA, apart from the widely-accepted mechanism of adsorption, an unidentified F-containing surface precipitate was formed. HCC was identified as the most promising sorbent with no sludge generation.

Bone-char from various food-waste: Synthesis, characterization, and removal of fluoride in groundwater

Fluoride (F), an essential trace element, plays a significant role in the skeletal systems of teeth and bone. However, drinking water with a high level of fluoride (more than 1.5 ppm) would cause fluorosis, seriously damaging the teeth and bone structures. In central Vietnam, there is a village called no smile village, where local people highly drink fluoride-contaminated groundwater. Finding an efficient fluoride removal solution with an acceptable cost is required. In this work, highly porous carbonaceous bone-char (Bc) materials were synthesized by calcination of various sources of bones (fish, chicken, pig, and cow) at 600 °C for removing fluoride in drinking water. We investigated the effects of the precursors on synthesized materials’ characteristics and their efficiency of fluoride removal. As a result, the Bc materials exhibit interesting characteristics via high specific surface area (up to 211.8 m2/g, and the abundance of micro-mesoporous, and hydroxyapatite structures formed during the calcination process. In addition, Bc materials illustrated an outstanding fluoride adsorption performance with a removal efficiency of more than 98 %. Moreover, the pseudo-first and pseudo-second-order kinetic models were applied to determine the fluoride adsorption behaviors of the prepared Bc. The studied results promoted a potential and sustainability pathway for utilizing low-cost food waste synthesizing green adsorbent to remove fluoride in drinking water without using toxicity chemical approaches.

Fluoride Contamination of Groundwater in a Coastal Region- A Growing Environmental Pollution Threat

<p>The research work's main objective is to correctly examine and find out the proper hydro-geochemistry of groundwater during the dry and wet seasons and hence evaluate it’s quality in India, Tamil Nadu state's Thirukkazhukundram Block. Data from two seasons-the "Pre-monsoon" in August 2016 and the "Post- monsoon" in February 2017-have just been used to do subjective assessments of the chemical composition of the underground water. The results of a thorough geochemical investigation of the subsurface zone are given. Gibbs emphasizes that the majority of samples in both seasons are dominated by evaporation and weathering mechanism sector. The majority of the sample's mixed water type is interpreted hydro-chemically in accordance with Piper's classification. According to the Wilcox diagram, the majority of PRM and POM samples fall into the group of "very good to good and good to permissible." The USSL diagram shows that just 23% of the samples for the C1-S1 type were collected during POM. 23% samples align under C2-S1 during PRM and 57% fall under C2-S1 during POM for. It was noted that 67% and 20% of the samples accounted under C3-S1type respectively, for POM and PRM. The C4-S1type is in PRM only, as of 13% of the samples. The irrigation quality of the groundwater samples showed that they were basically suitable for the very same purpose. Fluoride contamination in groundwater has nowadays become a slowly creeping issue in the study area. Steps need to be taken promptly to avert the resulting human health hazard on account of this pollution, in due course of time. Using ArcGIS 10.0, the groundwater quality chart was produced. Using inverse distance weighting, the regional distribution of groundwater quality measurements was interpolated. The findings of this study highlight the significance of creating techniques for managing aquifer systems.</p>

Socio-spatial Infrastructures

This paper explores the social and spatial implications of drinking water infrastructures in rural southern Bihar. Hardiya, a multi-caste and multi-religion village, has a complex social arrangement. This village consists of original households, households resettled due to dam construction, and households resettled due to excessive fluoride contamination in groundwater. Excessive fluoride produces incidences of fluorosis among households, and historically, households have low access to clean drinking water. In response to the drinking water and public health crisis, multiple state, non-state, and transnational institutions intervened in Hardiya to provide safe technologies and infrastructures for clean drinking water. These twenty years of interventions have brought different technologies, institutions, and actors together to supply drinking water. However, these schemes are functioning inadequately on the ground, and access to clean water remains a big question amidst the development of drinking water infrastructures in Hardiya. This paper explores the dialectical relationship between drinking water infrastructures and social spaces, how both shape each other, through which assemblages, and what it renders. It explores the uneven outcomes of this technological intervention across different socio-spatial groups in Hardiya...

Health Risk Assessment of Nitrate and Fluoride in the Groundwater of Central Saudi Arabia

High nitrate and fluoride contamination in groundwater cause a variety of disorders, including methemoglobinemia, teratogenesis, and dental and skeletal fluorosis. The present work assesses the non-carcinogenic health risks posed by nitrate and fluoride in infants, children, and adults using the daily water intake (CDI), hazard quotient (HQ), and non-carcinogenic hazard index (HI). Groundwater samples were collected from 36 wells and boreholes in three central Saudi Arabian study areas for nitrate and fluoride analysis using ionic chromatography and fluoride selective electrode, respectively. Nitrate concentrations varied from 0.70 to 47.00 mg/L. None of the 36 studied boreholes had nitrate levels that exceeded WHO guidelines (50.00 mg/L). Fluoride ranged from 0.63 to 2.00 mg/L, and 30.55% of the fluoride samples (11 out of 36) exceeded the WHO recommendations for acceptable drinking water (1.5 mg/L). The average hazard index (HI) values for adults, children, and infants were 0.99, 2.59, and 2.77, respectively. Water samples surpassed the safety level of 1 for adults, children, and infants at 44.44, 97.22, and 100%, respectively. Accordingly, water samples from Jubailah and a few from Wadi Nisah may expose infants, children, and adults to non-cancer health concerns. Infants and children are more vulnerable to non-carcinogenic health risks than adults, possibly due to their lower body weight. Immediate attention and remedial measures must be implemented to protect residents from the adverse effects of F- in the study area.

Exploration of urease-mediated biomineralization for defluoridation by Proteus columbae MLN9 with an emphasis on its genomic characterization

Fluoride (F-) contamination of groundwater is a silent killer of human health that has now become a global problem. In the present study, we sought to isolate fluoride-resistant, urease producing bacteria from F- contaminated groundwater to evaluate their potential F- biomineralization. Strain MLN9, isolated from the fluoride-contaminated village of Madhabpur in Birbhum, could resist up to 5600 mg L−1 F- concentration. Taxonomic classification of strain MLN9 based on whole genome sequence identified it as Proteus columbae MLN9. Strain MLN9 showed 88.9% of maximum F- removal efficiency at pH 8.0, 1.0 g L−1 CaCl2, and 10.0 g L−1 urea concentration. Scanning electron micrographs showed dense and porous biological crystal precipitates surrounding the surface of the bacterial cells, and the adherence of F- to the cell surface was confirmed by the energy dispersion spectrum. Moreover, the X-ray diffraction pattern showed that the F- precipitates on the cell surface were biological crystals of Ca5(PO4)3F and CaF2. Genomic analysis of strain MLN9 revealed the presence of crcB gene homologs possibly encoding F- transporters and urease regulatory proteins such as UreA, UreB, UreC, UreD, and UreG suggesting a role in defluoridation. Our findings provide new insights into the urease based MICP technology using a noble bacterium Proteus columbae MLN9 for fluoride removal.

Building high-capacity mesoporous adsorbents for fluoride removal through increased surface oxygen anions using organogel-assisted synthesis

In this work, mesoporous calcium-based adsorbents are prepared with the assistance of an organogel, 1,3:24-Bis (3,4-dimethylobenzylideno) sorbitol (DMDBS), which can self-assemble into nanoscale fibrillar networks and act as soft template to create mesopores. Particularly, it is found that the specific surface area of adsorbent is increased about 25 times by adding an extremely low concentration of DMDBS template (0.4 wt%) during the adsorbent production, which is much more efficient than common template materials. Additionally, the physical property and adsorption capability of calcium-based adsorbents can be tuned by control over calcination temperatures and DMDBS loadings. Under optimal preparation conditions (700 °C and 0.4 wt% DMDBS), the synthesized mesoporous adsorbent can achieve a Langmuir adsorption capacity of 48.8 mmol g−1 at pH of 7 and a removal efficiency of 70% in a mimicking natural water with the existence of NaCl. Thermodynamic analysis of equilibriums indicates that the adsorption reaction of fluoride with synthesized adsorbents from water is endothermic and spontaneous in nature. Most significantly, the results demonstrate that adsorbents with surface mesopores possess enriched ionized surface hydroxyl groups, CaO-, which act as the dominant species for fluoride attraction via electrostatic force at a neutral environment. This finding can be supported by the zeta potential analysis and surface speciation calculation. Moreover, the fluoride adsorption capacities of DMDBS-synthesized adsorbents are stable over neutral pH range of 6–8, revealing a promising potential for practical applications in fluoride-contaminated groundwater.

Influence of interflow carbonate-clay association for groundwater fluoride contamination in eastern Deccan, central India.

In central India, fluoride contamination in deeper basaltic aquifer is geogenic. This study demonstrates the source of fluorine enrichment in aquifer matrix and its release mechanism into groundwater. Magmatic-hydrothermal residual melt, i.e., albitic-calcic-amphibole-apatite-rich intrusive rock is the main source of fluorine enrichment. The association of this rock with interflow carbonate-clay assemblage played a significant role for fluoride contamination. Fluorine-enriched residual melt interacted with interflow carbonate-clay association, and this interaction metasomatized the carbonates and enhanced fluorine concentration in sediments. Bulk fluorine concentration of 988ppm is measured in the soil developed over the association of intrusive rock and carbonate-clay assemblage. X-ray diffraction and electron-probe micro analysis confirmed the presence of fluorine-bearing and/or containing minerals, i.e., fluorite, fluorapatite, and palygorskite. The presence of bicarbonate and Na+ (from albitic feldspar) in alkaline water enhanced desorption of fluoride from clays, and dissociation from fluorapatite and fluorite from carbonate-clay assemblage, which released fluoride from aquifer matrix to groundwater. Clay horizon acts as an impervious cap on the deeper aquifer and increases the residence time of groundwater. In such favorable physico-chemical condition, fluoride released from aquifer matrix to groundwater and gradually increasing the degree of fluoride contamination.

Ameliorative effects of nano Moringa on fluoride-induced testicular damage via down regulation of the StAR gene and altered steroid hormones

Fluoride is a common environmental contaminant that has harmful effects on human health when it is present in high concentrations. Fluoride enters the bloodstream after being absorbed by the gastrointestinal system when fluoride-contaminated groundwater is consumed by people. The aim of the present study was to determine whether polyphenol-rich nano Moringa oleifera (NMO) could protect rat testicles from sodium fluoride (NaF) damage by evaluating sperm quality, sex hormones, testicular oxidative status, histopathology, and StAR gene expression. Twenty-eight adult Wistar rats were divided equally and randomly into four groups: group one received distilled water; group two received NMO at a dosage of 250mg/kg/body weight; group three received NaF at a dosage of 10mg/kg/body weight; and group four received NaF and NMO. The rats were orally administrated daily for a duration of eight weeks. The study's findings demonstrated that, in comparison to rats exposed to NaF alone, co-administration of NMO and NaF enhanced sperm motility and viability, decreased sperm morphological changes, restored the balance between oxidant and antioxidant status, improved testosterone and dehydroepiandrosterone, improved testicular histology, raised the Johnson score, and upregulated the StAR gene in testicular tissue. These findings show that NMO is promise as a prophylactic medication against sodium fluoride-induced testicular damage because administration of NMO had no adverse effects and enhanced reproductive health.

A novel hybrid random forest linear model approach for forecasting groundwater fluoride contamination.

Groundwater quality in the Datong basin is threatened by high fluoride contamination. Laboratory analysis is a standard method for estimating groundwater quality parameters, which is expensive and time-consuming. Therefore, this paper proposes a hybrid random forest linear model (HRFLM) as a novel approach for estimating groundwater fluoride contamination. Light gradient boosting (LightGBM), random forest (RF), and extreme gradient boosting (Xgboost) were also employed in comparison with HRFLM for predicting fluoride contamination in groundwater. 202 groundwater samples were collected to draw up the performance capability of several models in forecasting subsurface water fluoride contamination. The performance of the models was assessed utilizing the receiver operating characteristic (ROC) area under the curve (AUC) and the confusion matrix (CM). The CM results reveal that with nine predictor variables, the hybrid HRFLM achieved an accuracy of 95%, outperforming the Xgboost, LightGBM, and RF models, which attained 88%, 88%, and 85%, respectively. Likewise, the AUC results of the hybrid HRFLM show high performance with an AUC of 0.98 compared to Xgboost, LightGBM, and RF, which achieved an AUC of 0.95, 0.90, and 0.88, respectively. The study demonstrates that the HRFLM can be applied as an advanced approach for groundwater fluoride contamination prediction in the Datong basin and could be adopted in various areas facing a similar challenge.

Fluoride Contamination, Toxicity and its Potential Therapeutic Agents

Fluoride is the thirteenth most abundant element in the earth’s crust. It is highly electronegative and distributed ubiquitously in nature. During weathering of rocks and soil, fluoride can leach out and dissolve in the groundwater. Both plants and animals are exposed to several compounds of fluoride through contaminated soil and water. Fluoride contamination in groundwater is a major global concern as groundwater is frequently used for drinking in various parts of the world, especially in developing countries. Fluoride compounds have been reported to impose acute and chronic health hazards. Millions of global populations are suffering from dental and skeletal fluorosis due to high fluoride intake through drinking water. In green vegetation, fluoride accumulation causes necrosis in the tip and marginal portions of leaves. Diverse detrimental effects of fluoride on health have insisted researchers globally to identify compounds having protective potential against fluoride toxicity. Several plant extracts, vitamins, polyphenols, melatonin, hypophyseal proteins, and lycopene have been demonstrated to enhance the antioxidant status and subvert fluoride-induced health hazards in model organisms. However, more studies are required to forward conclusive opinions in terms of the real-life efficacy of these antioxidants against fluoride toxicity.

Bio remedial Process: A Review on Removal of Fluoride from the Waste Water

Ground water has always been an important and most dependable source of water since prehistoric ages, but with rapid industrialization to meet the needs of growing population has stressed the ground water reservoir. Stress to ground water reservoir is just one problem; industrial waste has also introduced lots of new chemical substances in water bodies. Fluorides are one such pollutant that undermines living life forms especially human beings .There are primarily two sources of fluoride contamination in ground water. Geogenic sources and anthropogenic sources. Talking about the status of fluoride contamination it can be seen in more than 25 countries worldwide. In India itself 19 states and at least 132 districts have witnessed the problem of water contamination, Fluoride contamination is also impacting the health of people adversely. Diseases like skeletal fluorosis, non –skeletal fluorosis, and dental fluorosis are the most common health problem from fluoride contamination .Due to fluoride contamination diseases in plants like Chlorosis, Necrosis is impacting plant body. Thus, to remove fluorine contamination from water we can use bioremediation process. Bioremediation strategies can be classified mainly in two categories in – situ techniques and ex –situ techniques. Its mode of action primarily includes use of microbes in processing the fluoride contamination. This shows that bioremediation has lots of advantages like it’s a natural process, cost effective etc. But it too have some disadvantages like they are highly specific and it takes longer time etc. Considering all the merits and demerits of bioremediation, it is the most effective technological tool that holds great value for the future as scientists learn more about its capabilities and the curiosity to find more appropriate methods are still going on. This review article deals with ground water pollution due to fluoride concentration. We have thoroughly reviewed on its impact on health of plants and animals and the bioremediation processes to cure the water contamination

A review on source, impacts and mitigation measures of groundwater fluoride contamination: a major health issue

Fluoride (F¯) in groundwater is one such ion that makes the groundwater unsuitable for drinking purposes and responsible for serious human health problems such as dental, skeletal, and non-skeletal fluorosis in more than 25 countries worldwide. Recent studies estimated that cases of fluorosis are prevalent in 67 million people in 19 out of the 32 states of India due to intake of fluoride-enriched groundwater ranging from 0.01 to 37.0 mg/l affecting 8 and 18 million people among them by skeletal and dental fluorosis, respectively. The distribution of fluoride in groundwater varies due to geogenic or anthropogenic sources or combined factors. The various geological and artificial factors that govern the F¯ prevalence in aquifers have been discussed. Different types of adverse health hazards of fluoride on humans and plants have also been enlightened. Since fluoride occurrence above 1.0 mg/l (BIS) or 1.5 mg/l (WHO) in groundwater can produce endemic health issues, there is an essential requirement to monitor groundwater fluoride levels frequently. Higher concentration in water needs treatment to bring them under the guideline value. Some available fluoride removal techniques from groundwater have been deliberated in study. Groundwater fluoride contamination is generally natural and unpreventable. However, most people unintentionally consume the untreated groundwater in developing countries leading to a widespread problem worldwide. A prominent solution is to educate and aware people about this issue. Frequent monitoring and defluoridation of the contaminated groundwa ter must be needed before consumption for a healthy world. The present review work is a step toward this fluoride hazard awareness with compact information about its various sources, status, removal technologies, and their relation with the environment.

Characterization of high fluoride resistant Pseudomonas aeruginosa species isolated from water samples

Groundwater fluoride contamination is one of the most serious toxicological environmental issues in India and around the world. Water samples were taken from Natham taluk and screened for fluoride resistant bacteria. Initially, twenty-four fluoride resistant colonies were selected from 50 mM NaF supplemented LB agar plates. On blood agar plates, all isolates showed β-haemolysis, confirming their status as pathogens. Virulence factors (algD, plcH, toxA, gyrB, rhlC, lasB) and biofilm-forming genes (ppyR, pelA, pslA) were identified in these isolates by PCR analysis. The fluoride ion transporter ‘crcB’ was successfully amplified from these isolates by gene-specific PCR. Genus Pseudomonas and P. aeruginosa species-specific PCR analysis identified that all strains as belonging to the P. aeruginosa species. Besides, three high fluoride resistance strains were selected based on high fluoride resistance and confirmed as P. aeruginosa species by 16S rRNA sequencing and NCBI blast analysis.

Pilot-Scale Field Demonstration of Environmental Nanotechnology for Groundwater Defluoridation

Fluoride contamination in groundwater is a global issue. Nanoscale oxides of Zr(IV), Al(III), and Ti(IV) can form the inner-sphere complex with fluoride through ligand exchange, offering a new chance for efficient groundwater purification. However, pilot-scale field demonstration of nanotechnology in groundwater defluoridation is very rare. Herein, we conducted a 150-day field defluoridation study using the nanocomposite HZO@D201, which was prepared by encapsulating nano-hydrated zirconium oxide (HZO) inside the strongly basic anion exchanger D201. The HZO@D201 beads were packed in five-stage series columns (40 L for each column), and the groundwater was pumped through the columns sequentially. The effective treatment amount for the single column ([F–] < 1.0 mg/L) exceeded ∼3000 bed volume (BV). The exhausted HZO@D201 was fully refreshed through ex situ treatment with NaOH–NaCl solution for repeated use without significant loss in defluoridation reactivity. Owing to the specific interaction with HZO, the fluoride concentration could be steadily reduced below 1.0 mg/L throughout the 150-day field demonstration, while the common anions coexisting in groundwater (K+, Na+, Ca2+, Mg2+, SO42–, Cl–, etc.) remained almost unchanged. The operational cost for deep defluoridation was estimated as 0.574 RMB per ton of groundwater, much less than that of the widely studied reverse osmosis. TEM, XPS, and Fourier transform infrared (FTIR) analysis indicated that negligible change occurred in the structure and chemical composition of HZO@D201 after the long-term field assay. This study may inspire more attempts at the pilot scale and engineering demonstration of nano-enabled water treatment techniques.

Effect of groundwater residence time on geogenic fluoride release into groundwater in the Mt. Meru slope area, Tanzania, the Great Rift Valley, East Africa

People living in the Great Rift Valley in East Africa suffer from fluorosis resulting from their consumption of groundwater. This paper shows that geogenic fluoride contamination in a natural water system has changed in the last two decades in the Mt. Meru slope area of northern Tanzania based on water quality, dating of the residence time, and stable isotopes of groundwater. The results demonstrate that 1) the average recharge altitude of groundwater with a high geogenic fluoride concentration is estimated to range from 1900 m to 3000 m on the southern slope of Mt. Meru, and the fluoride concentration tends to increase with an increase in the recharge altitude, 2) the fluoride concentration increases with increasing groundwater residence time for groundwater with a residence time of 20 years or longer, suggesting that water-rock interaction processes (weathering, dissolution, and ion exchange), which depend on the contact time between the volcanic aquifer and groundwater, have predominated for approximately 20 years or longer, and 3) the mixing of aerobic young water and old groundwater has been active for approximately 20 years, and the fluoride concentration is increasing in some shallower well waters. The mixing of fluoride-contaminated groundwater with aerobic water infiltrating the aquifer through pumping groundwater in the last two decades may increase the spread of groundwater contaminated with fluoride due to increased water demand caused by rapid population growth, and urbanization, industrial growth, and the expansion of irrigated agriculture.

Fluoride Contamination of Groundwater from Semi-Arid Regions of Western India

A study on fluoride risk assessment was carried out in the semi-arid region of North Gujarat, India. The intricate link between groundwater fluoride and human health, lack of awareness, limited access to fluoride treatment facilities, and poor socio-economic conditions of the ~5.0 million rural population in the studied region make them vulnerable to fluoride. This study aimed to evaluate non-carcinogenic health risk, its severity, and the total population at risk in these regions due to chronic fluoride exposure. Fluoride in our samples (n=132) exhibits large spatial variability, and it ranges from ~0.13-8.64 mg.L-1 (average: 1.64 ± 1.50 mg.L-1) and 43% of them are more than the WHO limit of 1.5 mg.L-1. Hazard Quotient (HQ) was used to assess health risks through the ingestion exposure route. The comparison of the range (0.1-8.55 versus 0.06-4.11), average (1.63 ± 1.49 versus 0.78 ± 0.72), and median (1.26 versus 0.60) of HQ between children and adults highlights that the former are at more risk compared to latter. Our conservative estimates suggest that ~0.45 million children and ~1.06 million adult population, ~55% and ~20% of the respective population classes, of the region, are potentially at risk. The empirical Bayesian Kriging model was used to produce risk-assessments maps. These can help policymakers in prioritizing the application of mitigation funding and resources, and in increasing testing efforts in high-risk areas. We believe this study should guide policymakers to adopt strategies in ensuring the public health safety of the rural population, children in particular, of the studied region.

Thermal activation of palygorskite for enhanced fluoride removal under alkaline conditions

Fluoride contamination of groundwater is a global environmental problem. Based on adsorption treatment strategies, magnesium-based materials have shown potential for defluoridation of this water source. In this research, we calcined raw palygorskite (RPAL), a natural magnesium-rich clay, at different temperatures (100–1000 °C), to examine the defluoridation performance. The evolution of the morphology, physical-chemical properties, and crystal structure was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and 27Al and 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy. Palygorskite calcined at 200 °C (CP200) had F− uptake of ∼1.6 mg F−/g within a neutral-to-basic pH region of F-contaminated groundwater (e.g., pH 7–9), which is 5–6 times larger than that for RPAL. Additionally, CP200 and CP400 exhibited comparatively greater adsorption performance for fluoride removal compared with activated alumina (AA) under alkaline conditions (e.g., 1.5–3 times at pH ≥ 9). The dependence of fluoride uptake by the calcined samples appeared to be related to major changes in the crystal structure of palygorskite, particularly the dehydration of zeolite waters and partially coordinated water within pores. The exposed > MgOH2 groups at tunnel edges may play an important role in fluoride removal, especially at elevated pH. The higher stability under alkaline conditions and the lower sensitivity to pH compared with AA demonstrated the potential of calcined palygorskite as an effective magnesium-based clay for the remediation of fluoride contamination of groundwater.