Fluoride Concentration In Groundwater Research Articles

Groundwater chemical evolution characteristics and human health risk assessment in Shicheng County, Jiangxi Province.

Groundwater plays a pivotal role in the water resources of Shicheng County; however, the issue of excessive fluoride content in groundwater and its associated health risks often goes unnoticed. Groundwater assumes a crucial role in the hydrological dynamics of Shicheng County; nevertheless, the matter concerning elevated levels of fluoride within groundwater and its accompanying health hazards frequently evades attention. The hydrogeochemical analysis, obscure comprehensive water quality assessment based on cloud model, and probabilistic human health risk assessment using Monte Carlo simulation were conducted on 34 collected water samples. The findings indicate that the predominant groundwater hydrochemical types are SO4·Cl-Na and HCO3-Na. The processes of rock weathering and cation exchange play crucial roles in influencing water chemistry. Groundwater samples generally exhibit elevated concentrations of F-, surpassing the drinking water standard, primarily attributed to mineral dissolution. The concentrations of F- in more than 52.94% and 23.53% of the groundwater samples exceeded the acceptable non-carcinogenic risk limits for children and adults, respectively. Considering the inherent uncertainty in model parameters, it is anticipated that both children and adults will have a probability exceeding 49.36% and 30.50%, respectively, of being exposed to elevated levels of F ions in groundwater. The utilization of stochastic simulations, in contrast to deterministic methods, enables a more precise depiction of health risks. The outcomes derived from this investigation possess the potential to assist policymakers in formulating strategies aimed at ensuring the provision of secure domestic water supplies.

Machine learning prediction of health risk and spatial dependence of geogenic contaminated groundwater from the Hetao Basin, China

Geogenic contaminated groundwater (GCG), characterized by elevated arsenic, fluoride, and iodine levels, present a significant challenge to public health and government management. Conventional survey-based approaches of collecting groundwater samples, conducting physicochemical tests, and performing spatial interpolation to obtain regional groundwater chemical component maps are inefficient and costly. More importantly, it does not take into account the actual hydrogeological conditions or the characteristics of pollutant transport and enrichment. To address this issue, we utilized Support Vector Machine (SVM), Random Forest (RF), Adaptive Boosting (AdaBoost), and Extreme Gradient Boosting (XGBoost) to analyze the likelihood of occurrence of arsenic, fluoride, and iodine as well as their spatial distribution in shallow groundwater from the Hetao Basin. Our study incorporated 20 indicators related to meteorology, soil physicochemical properties, and groundwater conditions, along with 1505 labeled samples consisting of groundwater arsenic, fluoride, and iodine concentrations and their corresponding coordinates. Subsequently, the study automatically analyzed the meteorological, soil physicochemical properties and groundwater conditions by constructing a machine learning model using the available data. In order to optimise and select the best prediction model, this paper presents a quantitative evaluation of the prediction performance of various machine learning models. The accuracy (AC), area under curve (AUC) and mean squared error (MSE) were calculated to predict the spatial distribution of CGC. Subsequently, the optimized model for predicting the spatial distribution of GCG was selected. The results showed that the XGBoost algorithm provided optimal predictions for groundwater with arsenic concentrations above 10 μg/L and fluoride concentrations exceeding 1.5 mg/L, whereas the RF model provided the best predictions for groundwater with arsenic concentrations surpassing 50 μg/L and iodine concentrations exceeding 100 μg/L. Subsequently, groundwater health risk zones were delineated based on an optimal prediction model, and demographic analysis was conducted in both the direct and potential groundwater risk zones. Model predictions indicated that hundreds of thousands of people in the Hetao Basin were facing a public health crisis caused by high concentrations of arsenic, fluoride and iodine in groundwater. These findings underscore the significant health challenge in the study area. Considering the agricultural development and increasing groundwater use in the area, our findings can guide local governments in managing the extent of groundwater development, establishing control zones, and enhancing protection measures for populations at risk from groundwater contamination.

Fluoride concentration in groundwater of the Jalisco Highlands, Mexico

La principal fuente de abastecimiento de agua potable en la mayoría de las regiones administrativas del estado de Jalisco (México) son los acuíferos subterráneos, que en muchos casos son de origen hidrotermal, los cuales se caracterizan por la presencia de compuestos químicos potencialmente nocivos para la salud humana y animal. El área de estudio de este trabajo se ubica en el noreste del estado de Jalisco, comprendiendo 10 municipios en dos regiones administrativas. El presente estudio tiene como objetivo determinar la tendencia de la concentración de flúor en pozos profundos que abastecen de agua potable a los municipios del área de estudio, a partir de dos evaluaciones realizadas durante los años 2021 y 2022. En los resultados se puede observar una tendencia creciente en la concentración de flúor de la mayoría de los pozos analizados en los periodos estudiados, las mayores concentraciones se reportan en las localidades de: Tepatitlán, Arandas, Mexticacán y San Miguel el Alto, así como en los municipios de Valle de Guadalupe y Cañadas de Obregón, representando el uso de estas fuentes como agua potable un mayor riesgo para la salud de la población local, ratificándose así mismo, una tendencia creciente en la concentración de fluoruros en las aguas subterráneas extraídas del área de estudio, una posible causa es la continua disminución en el nivel dinámico de extracción que presentan la mayoría de los pozos evaluados. Es necesario implementar programas y estrategias para garantizar la sostenibilidad de este recurso vital en esta y otras regiones del país.

Effect of Groundwater Fluoride Concentration on Human Health: A Systematic Review

Effect of Groundwater Fluoride Concentration on Human Health: A Systematic Review

Investigation of fluoride concentrations, water quality, and non-carcinogenic health risks of borehole water in bongo district, northern Ghana

Access to potable water is a significant concern due to the increasing global threat posed by fluoride contamination in groundwater sources. This study investigated the concentrations of fluoride (F−), the suitability of groundwater for human consumption, the physicochemical characteristics affecting the water quality, and non-carcinogenic adverse health risks to both children and adults in the Bongo district in Northern Ghana. The findings revealed that the groundwater had a mean pH, salinity, TDS, conductivity, and turbidity below the WHO guideline values with a mean fluoride concentration of 1.76 mg/L above the guideline limit of 1.5 mg/L. The study also found that there was no strong relationship between fluoride and the measured water parameters, which may be attributed to poor control of distribution, transport mechanisms, and sources. The WQI scores ranged from 42.62% to 70.72%, indicating that all borehole water samples were of good and excellent quality. The average chronic daily intake showed that children are often more exposed to the harmful impact of fluoride than adults. The average HQ > 1 indicates the probability of dental and skeletal fluorosis after continuous exposure over time in adults and children. The study recommends taking immediate action to mitigate high groundwater fluoride concentrations, implementing appropriate water management strategies, and raising public awareness of the health risks. These measures can guide future groundwater management practices and help policymakers address contamination and protect local communities.

Effect of Excessive Fluoride in Ground Water on Human Health and Fluorosis

The issue of fluoride in the geo-environment is one of the most important geo-environmental issues in the coming days. The excessive ingestion of fluoride causes the disease, is called fluorosis. The excessive ingestion of fluoride can result in the development of fluorosis, which is a disease that causes bone loss. The present study focuses on fluoride content in groundwater and its health effects.

Seawater intrusion-triggered high fluoride groundwater development on the eastern coast of China.

High-fluoride groundwater is commonly found in coastal areas worldwide, while its formation mechanism remains elusive. Herein, a comprehensive study was performed to identify the major controlling factor of high-fluoride groundwater occurrence along the eastern coast of China. Hydrogeochemical methods were employed to examine the distribution patterns of seawater intrusion and fluoride concentration and the impact of seawater intrusion on the fluoride concentration. The results indicate that seawater intrusion significantly influences the groundwater evolution process in the study areas. The groundwater in Laizhou Bay was affected by brine, and the groundwater in Tianjin and Jiangsu was affected by seawater with a mixing ratio lower than 40% and 20%, respectively. And the fluoride concentration in groundwater from Tianjin, Laizhou Bay, and Jiangsu generally exceeded 1mg/L, with the average of 2.3mg/L, 24.9mg/L, and 34.6mg/L, respectively. Both the degree of seawater intrusion and the fluoride concentration exhibit a consistent pattern: Laizhou Bay > Tianjin > Jiangsu. Cl- concentration in groundwater varies positively with the F- concentration (y = 0.66x - 1.31). Moreover, the spatial distribution of areas with high-fluoride groundwater mirrors that of seawater intrusion. The high-fluoride groundwater varies spatially and is related to the degree, stage, and type of seawater intrusion. In other words, when seawater intrusion intensifies more or groundwater in the freshwater renewal phase with higher Na+/Ca2+ or the presence of paleo-seawater intrusion with higher fluoride concentration of brine, the concentration of fluoride in groundwater is higher. As seawater intrusion intensifies, the high-fluoride groundwater in the study areas generally poses a higher health risk to human. These findings enhance our comprehension of the mechanisms underpinning high-fluoride groundwater in coastal regions and the environmental ramifications of seawater intrusion.

Pengukuran Anion Anorganik Secara Simultan dalam Sampel Air Tanah dan Air Ledeng Menggunakan Kromatografi Ion

Ion chromatography is an advanced and highly sensitive form of ion exchange chromatography that can effectively detect ion species, whether organic or inorganic ions. This research study utilized ion chromatography with a suppressed conductivity detection system to separate and measure the concentration of fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate ions in groundwater and tap water samples. The eluent solution used in this separation contained 6.0 mmol/L Na2CO3 and 0.25 mmol/L NaHCO3, which was crucial in ensuring the accuracy and selectivity of the detections. The samples were collected in 3 sub-districts in Ternate City, and the study's findings shed light on the water quality in the area.

Groundwater Vulnerability Assessment in Pavagada taluk, Tumakuru district, Karnataka, India, using a GIS-based DRASTIC model

Throughout the world, one of the most accessible resources is groundwater. Groundwater quality is rapidly declining due to anthropogenic and geogenic sources, resulting from over-reliance. Previous research indicates that the concentration of pollutants such as Fluoride, Arsenic, Iron, and Total Dissolved Solids has rapidly increased. This affects crop yield and human health as well as the socioeconomic development of the region. For this reason, identifying areas where groundwater is vulnerable is crucial to reducing pollution in groundwater and maintaining its quality. In this study, groundwater-vulnerable zones in Pavagada Taluk are evaluated using the GIS-based DRASTIC model. The seven DRASTIC parameters are combined with data on land use and land cover to help explain how anthropogenic sources and possible human intervention affect groundwater quality. It is observed that the groundwater samples we collected had high concentrations of Iron, Sulphate, Fluoride, and Nitrate, as per BIS 10500 (2012). The study area's northeastern, southeastern, northern, southern, and southwestern regions are classified as high to moderate risk zones on the final DRASTIC map. The high Fluoride content in groundwater is caused by bore wells situated on rocks such as Granite, Granodiorite, Hornblende-Biotite Gneiss, and Biotite. In order to validate the model, the results of the physicochemical analysis were compared to the final drastic map. This comparison shows that the model is 80.39% valid for the region.

Evaluating hydrogeochemical controls and noncarcinogenic health risk assessment of fluoride concentration in groundwater of Palacode and Pennagaram taluk, Dharmapuri district, Tamil Nadu, India.

This study focuses on assessing hydrochemical characteristics and non-carcinogenic health risks associated with fluoride contamination in groundwater within the Palacode and Pennagaram taluks of Dharmapuri district. The presence of fluoride in drinking water is a significant concern due to its potential health impacts on both adults and children. We collected a total of 158 groundwater samples during both the summer (SUM) and monsoon (MON) seasons in 2021 to evaluate the suitability of water for drinking purposes in this region. During the SUM season, groundwater exhibits alkaline characteristics with a pH range of 6.70 to 8.73 and a mean value of 7.43, while the MON season falls within the neutral pH range with values ranging from 6.60 to 7.60 and a mean of 7.00. Hydrogeochemical analysis reveals that fluoride concentrations during the SUM season range from 0.13 to 2.7 mg/L, with a mean of 0.82 mg/L, whereas the MON season exhibits concentrations ranging from 0.08 to 1.6 mg/L, with a mean of 0.5 mg/L. Spatial distribution analysis indicates a gradual increase in fluoride concentrations from the northeast to the central and southern parts of the study area during both seasons. Residents in these areas have been exposed to high fluoride levels for an extended period, leading to health issues related to fluorosis. Our hydrogeochemical analysis attributes fluoride dominance to the Cl--SO42- water type in both seasons. Furthermore, the relationship between fluoride and pH, HCO3-, Ca2+, and Na+ suggests the influence of geological factors in fluoride dissolution under alkaline conditions, while a reverse cation exchange process and increasing calcium concentration inhibit fluoride concentration. Saturation indices indicate that the unsaturated state of gypsum dissolution contributes to elevated fluoride levels in groundwater. Additionally, Gibbs plots highlight rock-water interactions as a significant factor influencing groundwater chemistry in the study area. Based on our hazard quotient (HQ) investigation, children are at a higher risk during both seasons compared to adults, with the central and northern regions showing alarming HQ values. These findings underscore the urgent need for enhanced groundwater quality monitoring and a comprehensive assessment of health risks, providing valuable insights for groundwater safety management in vulnerable areas of this region.

Spatial Variability Characteristics and Influencing Factors of Soil Fluoride in the Western Nansihu Lake Basin

The western plain of the Nansihu Lake Basin (NLB) is an important agricultural economic zone in Shandong Province, where there is a high content of fluoride in soils. Studying the content and influencing factors of fluoride in soils is of great significance for the maintenance of regional eco-logical security and human health. This study takes the farmland soils in the west of NLB as the research focus and uses a method based on GIS and geostatistics to quantitatively analyze the spatial variation characteristics of soil total fluoride and water-soluble fluoride contents to draw a map showing their spatial distribution. The effects on the spatial distribution of soil total fluoride and water-soluble fluoride were analyzed from the aspects of geomorphological type, soil parent material (stratigraphic lithology), crop type, and groundwater fluoride concentration, among others, and the correlation between groundwater and soil fluoride contents was also analyzed. Our study results in the following findings: (1) The average content of total fluoride in topsoil in the study area is 652.8 mg/kg, the national background value is exceeded in 99.5% of the sampling sites, and the background value of Shandong Province is exceeded in 98.7% of the sampling sites. The average water-soluble fluoride is 15.2 mg/kg and exceeds 5.0 mg/kg in 94.3% of the sampling sites. Topsoils have high values of total fluoride and water-soluble fluoride. (2) The total fluoride and water-soluble fluoride in topsoils exhibit moderate spatial variability, indicating that their spatial distribution is the result of structural factors such as soil parent materials and man-made random factors such as fluorinated fertilizers. (3) In the 2 m vertical profile of shallow soils, total fluoride and water-soluble fluoride increase with the increase in soil viscosity, and the water-soluble fluoride has the characteristics of surface aggregation due to the influence of soil adsorption. Because fluoride ions as ligands are easily adsorbed and form fluoride complexes with other ions such as aluminum ions, the water-soluble fluoride shows the characteristics of surface aggregation and fractionation. (4) The analysis of influencing factors reveals that the lithology of Quaternary strata, geomorpho-logical types, and planting crop types have significant effects on the distribution of the total fluoride and water-soluble fluoride in the topsoils, and the distribution of the groundwater soluble fluoride in the topsoils is not related to that in groundwater. Our study provides data and technical support for improving both the soil environmental quality and water quality of the eastern route of the South-to-North Water Transfer Project, thus helping to promote the sustainable development of the social economy and ecological environment in the NLB.

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.

Hydrogeochemical and multivariate statistical approaches to investigate the characteristics of groundwater quality in fluoride-enriched hard rock region in Tirupathur district of Tamil Nadu, India.

Fluoride pollution is a major issue worldwide, posing health risks such as dental and skeletal fluorosis. This study was conducted in fluoride enrichment hard rock regions of Vaniyambadi and Ambur talks in Tirupathur district, Tamil Nadu. Four hundred eighty groundwater samples were collected from May 2021 to April 2022 and grouped as summer, southwest monsoon (SWM), northeast monsoon (NEM), and winter. Maximum concentration of fluoride was found to be 4mg/L in the summer season in Vellakuttai region of Vaniyambadi taluk. The study aims to investigate the hydrogeochemical process and mechanism influencing groundwater chemistry and it also provides the confirmation of exploratory data analysis in groundwater quality using structural equation modeling. The Piper and Gibbs diagrams illustrate the rock-water interaction and anthropogenic sources that contribute to the NaHCO3 and NaCl-type waters, respectively. Multivariate statistical analysis such as hierarchical cluster analysis (HCA), principal component analysis (PCA), multiple linear regression (MLR), and structural equation modeling (SEM) has been carried out to determine the groundwater quality. HCA manifests the nature and sources of groundwater, whereas PCA divides all the physicochemical parameters into two PC loadings, accounting for 97.46%, 99.46%, 99.18%, and 98.93% of cumulative % of variance during the summer, SWM, NEM, and winter seasons, respectively. PC1 has a higher loading factor to Cl, Ca, and Mg, whereas PC2 has a higher loading factor to Na, HCO3, SO4, and NO3. The results of the MLR model provide higher accuracy in detecting the contamination factors associated with the environment and natural rocks. SEM revealed the goodness-of-fit indices 0.993, 0.999, 1.000, and 0.999 in summer, SWM, NEM, and winter, respectively. Hence, this study provides insight view of variation of fluoride concentration in groundwater in different seasons and also mentions the factors that influence fluoride concentration in Vaniyambadi and Ambur taluk.

An Appraisal of Hydrogeological Conditions and Fluoride Problem in Makrana Block of Nagaur District in Rajasthan, India

Abstrct: Groundwater is one of the important sources of potable water supply in rural India. The study area of Makrana block is located in the south-eastern part of Nagaur district of Rajasthan covering about 1140 sq. km. area. The marble from the Makrana town gets the GHSR (Global Heritage Stone Resources) status recently from the IUGS. The study area experiences arid to semi-arid type of climate. Older alluvium, Quaternary Alluvium and Schist are important aquifers occur in Makrana block. Groundwater occurs under unconfined to semi-confined conditions. Groundwater quality and depth of water varies widely in Makrana block. High concentration of fluoride and nitrate are major quality problem associated with groundwater and having adverse effects on human health. High concentration of fluoride in a particular belt is so remarkable that the term BANKA PATTI (a strip of land where deformed people reside) has been in used covering parts of Parbatsar, Makrana and Degana blocks of Nagaur district wherein some villages the fluoride concentration in groundwater is over 4 ppm. The concentration of Fluoride mainly comes from Schists, Gneiss and Limestone of Proterozoic age. Higher concentration of fluoride affects metabolic activities of an individual which may cause skeletal and dental fluorosis. The disease fluorosis is non curable but preventable

Relationships between dental fluorosis and fluoride concentrations in bottled water and groundwater in low-income children in Mexico.

The aim of the current study was to investigate associations between dental fluorosis in children living in low socioeconomic areas in Mexico, and fluoride concentrations in tap water, fluoride concentrations and in bottled water, and body mass index (BMI). A cross-sectional study involving 585 schoolchildren aged 8-12 years was conducted in communities in a southern state of Mexico with >0.7 parts per million (ppm) fluoride in the groundwater. The Thylstrup and Fejerskov index (TFI) was used to evaluate dental fluorosis, and the World Health Organization growth standards were used to calculate age-adjusted and sex-adjusted BMI Z-scores. A BMI Z-score ≤ -1 SD was used as the cut-off point for thinness, and multiple logistic regression models for dental fluorosis (TFI ≥ 4) were constructed. The mean fluoride concentration in tap water was 1.39 ppm (SD 0.66), and the mean fluoride concentration in bottled water was 0.32 ppm (SD 0.23). Eighty-four children (14.39%) had a BMI Z-score ≤ -1 SD. More than half (56.1%) of the children presented with dental fluorosis in TFI categories ≥ 4. Children living in areas with higher fluoride concentrations in the tap water [odds ratio (OR) 1.57, p = 0.002] and bottled water (OR 3.03, p < .001) were more likely to have dental fluorosis in the severe categories (TFI ≥ 4). BMI Z-score was associated with the probability of dental fluorosis (TFI ≥ 4; OR 2.11, p < 0.001), and the effect size was 29.3%. A low BMI Z-score was associated with a higher prevalence of dental fluorosis in the severe category. Awareness of the fluoride concentrations in bottled water may help prevent dental fluorosis, particularly in children exposed to several high fluoride content sources. Children with a low BMI may be more vulnerable to dental fluorosis.

The Protective Effect of Breastfeeding on Dental Fluorosis Among Children in Rural Fluoride-Endemic Areas.

Background: Living in fluoride-endemic areas and the inevitable use of groundwater for consumption have imposed children at high risk of dental fluorosis. To mitigate exposure to excessive fluoride at age of developing dentition, breastfeeding might serve as a natural public health intervention against dental fluorosis in that socially disadvantaged context. Objective: This study aimed to evaluate the preventive effect of breastfeeding against dental fluorosis in children living in fluoride-endemic areas in Nakhon Pathom Province, Thailand. Evaluation of the association through several epidemiological models depicted by a directed acyclic graph (DAG) was undertaken. Methods: A case-control study of 127 cases of dental fluorosis and 85 controls was conducted. Independent factor of breastfeeding, along with other past exposure variables, were traced backwardly since infancy by caregiver history taking. Fluoride concentrations in groundwater utilized for household supply matching to residence and number of years by age of each child were collected from 2008 to 2015. Multivariable Poisson regression with robust standard errors was sequentially executed to estimate prevalence ratio (PR) according to models in DAG. Results: Breastfeeding was significantly higher (95.3%) among controls compared to cases (84.2%), p = 0.014. Contrastingly, prevalence of using toothpaste larger than pea-sized and having fluoride ≥1.5 ppm in household water supply was higher among cases. Univariable and subsequent five multivariable regression models according to DAG consistently unveiled significant protective effect of breastfeeding on dental fluorosis with PR ranging from 0.66 to 0.75. Conclusions: Breastfeeding for at least 6 months had preventive effect against dental fluorosis among children living in fluoride-endemic areas.

Comparing Deterministic and Stochastic Methods in Geospatial Analysis of Groundwater Fluoride Concentration

Dental and skeletal fluorosis caused by consuming high-fluoride groundwater has been reported over several decades globally. Prediction maps to estimate the fluoride contaminated area rely on interpolation methods. This study presents a comparison of the accuracy of nine spatial interpolation methods in predicting the fluoride in groundwater. Leave-one-out cross-validation (LOOCV), hold-out validation and validation with an independent dataset were used to assess the precision of the interpolation methods. This is the first study on fluoride with a large dataset (N = 13,585) applied at the regional level in India. Our findings showed that the inverse distance weighted (IDW) algorithm outperformed other methods in terms of less discrepancy between measured and predicted fluoride. IDW and local polynomial interpolation (LPI) were the only methods to predict contaminated areas (fluoride &gt; 1.5 mg/L). However, the area estimated by the typical assessment of the percentage of unsuitable samples was much higher (6.1%) compared to that estimated by IDW (0.2%) and LPI (0.2%). LOOCV provided viable results than the other two validation methods. Interpolation methods are accompanied with uncertainty which are regulated by the sample size, sample density, sample distribution, minimum and maximum measured concentrations, smoothing and border effects. Drawing a comparison among variegated interpolation methods capturing a wide range of prediction uncertainty is suggested rather than relying on one method exclusively. The high-fluoride areas identified in this study can be used by the Government in planning remediation actions.

Spatial evolution analysis of groundwater chemistry, quality, and fluoride health risk in southern Hebei Plain, China.

The present study investigated ion and fluoride concentrations in groundwater and their associated health risks to local populations in the southern Hebei Plain during 2018-2020. A total of 336 groundwater samples were collected from monitoring wells at 112 different locations. Statistical analysis, Gibbs diagram, principal ion ratio, and saturation index were carried out to clarify the chemical characteristics and control mechanism of groundwater. The results indicated that the groundwater types in the study area were mainly HCO3-Ca, Cl-Na, and SO4-Ca. The concentrations of cations and anions were Na+ > Ca2+ > Mg2+ > K+ and HCO3- > SO42- > Cl- > NO3- > F-, respectively. Based on the water chemical parameters, the pollution index of groundwater (PIG) was used to comprehensively evaluate the water quality. The results showed that during the study period, 60.41% of groundwater samples were suitable for drinking purposes, and 39.59% needed purification treatment to meet the requirements of drinking water standards. The groundwater quality in the western pre-hill plain areas was good, while the water quality in the northeastern and southeastern areas was poor and contaminated to varying degrees. Groundwater quality was mainly affected by the combined effect of total dissolved solids (TDS), Na+, Mg2+, Cl-, SO42- and HCO3- concentrations. Fluoride concentrations in the groundwater samples ranged from 0.07 to 8.51mg/L, with 44% of the samples containing fluoride below the recommended limit of 0.5mg/L, which would put the population at risk of dental caries. Also, 8% of the samples exceeded the permissible limit for fluoride in drinking water (1.5mg/L), which would expose the local population to the risk of fluorosis. The human health risk evaluation of fluoride showed significant differences in non-carcinogenic effects between two different groups of children and adults. HIin values ranged from 0.08 to 10.19 for children and 0.03 to 4.65 for adults, with hazard indices greater than 1 at 29.16% and 10.11%, respectively. This indicates that children have a greater exposure risk than adults, and the entropy of higher risk is mainly distributed in the northeast of the study area. Based on the above analysis of the spatial evolution of groundwater chemistry, water quality, and fluoride health risks in the southern Hebei Plain region, corresponding protection and management measures were proposed, which also provided reference significance for the effective use of drinking water and health risk prevention in the region.

Bone char modification by iron to improve its capacity for adsorbing fluoride from an aqueous solution

High fluoride concentrations in groundwater have attracted great concern worldwide because many people are afflicted by fluorosis due to water consumption. In this work, the fluoride adsorption from water onto bone char (BC) modified with iron sulfate (BCM) was studied as an option for eliminating fluoride from drinking water. The experimental data for the adsorption equilibrium of fluoride on BCMs were procured in a batch adsorber. The synthesis conditions of BCMs were optimized for improving the adsorption capacity of BCMs, and the optimal BCM was designated as BCM2. The BCMs were characterized by different analytical techniques, the BCMs surface exhibited an irregular morphology and the chemical nature was basic, and the BCMs were mesoporous materials. The Langmuir isotherm satisfactorily interpreted the experimental data of the fluoride adsorption isotherms on BCMs. The basic sites of BC and BCMs were quantified and identified in this work. The main adsorption mechanism of fluoride on the BCMs was the electrostatic attraction between the fluoride and the basic sites of BCMs, and the adsorption capacities of BC and BCMs towards fluoride increased almost linearly with the concentration of basic sites so that the enhancement of the adsorption capacity of BCMs was attributed to the increase of basic sites during the modification. Furthermore, the BCM2 adsorption capacity was lessened by incrementing the pH from 5 to 9, and this behavior was ascribed to the reduction of the electrostatic attraction interactions between the BCM2 surface basic sites and fluoride in the solution. The adsorption process was endothermic because the adsorption capacities of BC and BCM2 toward fluoride were raised by incrementing the solution temperature from 15 to 35 °C. The BCM2 presented a high capacity for adsorbing fluoride of 14.4 mg g−1 at 25 °C and a pH of 5.

Excess of Naturally Occurring Fluoride in Groundwater Discharge in Macaronesia: Brava Island, Cape Verde

A high concentration of fluoride in groundwater poses a risk to human health. One of the best-known problems related to excess fluoride in drinking water is dental fluorosis. The characteristic composition of volcanic rocks in oceanic islands tends to present high concentrations of fluoride in groundwater discharge in springs. This study investigates fluoride content in two springs (Encontro and Ferreiros) on the island of Brava (Cape Verde), with the objective of monitoring the operational control production and distribution of drinking water. Using a spectrophotometric method, the level of fluoride found in the water discharged from the Encontro spring was found to be in the range of 4.8 to 6.5 mg/L, whereas at the Ferreiros spring, it was 5.8 to 6.2 mg/L. These results are far above the threshold limit established in the decree No. 5 of 2017 of the Cape Verdean legislation, whose legal threshold value for fluoride is 1.5 mg/L, the same value established by the World Health Organization (WHO). Due to geological conditions and consequences for the health of the population, the water is not adequate for consumption without proper treatment.