Arsenic and fluoride co-enrichment of groundwater in the loess areas and associated human health risks:A case study of Dali County in the Guanzhong Basin

This study aims to reveal the occurrence and origin of typical groundwater with high arsenic and fluoride concentrations in the loess area of the Guanzhong Basin—a Neogene faulted basin.Key findings are as follows:(1)Groundwater samples with high arsenic and fluoride concentrations collected from the loess area and the terraces of the Weihe River accounted for 26%and 30%,respectively,of the total samples,with primary hydrochemical type identified as HCO_(3)-Na.The karst and sand areas exhibit relatively high groundwater quality,serving as preferred sources for water supply.It is recommended that local governments fully harness groundwater in these areas;(2)groundwater with high arsenic and fluoride concentrations in the loess area and the alluvial plain of rivers in Dali County is primarily distributed within the Guanzhong Basin,which represents the drainage zone of groundwater;(3)arsenic and fluoride in groundwater originate principally from natural and anthropogenic sources;(4)the human health risk assessments reveal that long-term intake of groundwater with high arsenic and fluoride concentrations pose cancer or non-cancer risks,which are more serious to kids compared to adults.This study provides a theoretical basis for the prevention and treatment of groundwater with high arsenic and fluoride concentrations in loess areas.

Fluoride contamination in groundwater resources of Alleppey,southern India

Alleppey is one of the thickly populated coastal towns of the Kerala state in southern India.Groundwater is the main source of drinking water for the 240,991 people living in this region.The groundwater is being extracted from a multi-layer aquifer system of unconsolidated to semi-consolidated sedimentary formations,which range in age from Recent to Tertiary.The public water distribution system uses dug and tube wells.Though there were reports on fluoride contamination,this study reports for the first time excess fluoride and excess salinity in the drinking water of the region.The quality parameters,like Electrical Conductivity（EC） ranges from 266 to 3900 μs/cm,the fluoride content ranges from 0.68 to2.88 mg/L,and the chloride ranges between the 5.7 to 1253 mg/L.The main water types are Na-HC03,NaCO3 and Na-Cl.The aqueous concentrations of F- and CO32- show positive correlation whereas F- and Ca2＋ show negative correlation.The source of fluoride in the groundwater could be from dissolution of fluorapatite,which is a common mineral in the Tertiary sediments of the area.Long residence time,sediment-groundwater interaction and facies changes（Ca-HCO3 to Na-HCO3） during groundwater flow regime are the major factors responsible for the high fluoride content in the groundwater of the area.High strontium content and high EC in some of the wells indicate saline water intrusion that could be due to the excess pumping from the deeper aquifers of the area.The water quality index computation has revealed that 62%of groundwater belongs to poor quality and is not suitable for domestic purposes as per BIS and WHO standards.Since the groundwater is the only source of drinking water in the area,proper treatment strategies and regulating the groundwater extraction are required as the quality deterioration poses serious threat to human health.

Current situation and human health risk assessment of fluoride enrichment in groundwater in the Loess Plateau:A case study of Dali County,Shaanxi Province,China

This study aims to investigate the mechanisms and health risks of fluoride enrichment in groundwater in the Loess Plateau,China.By taking Dali County,Shaanxi Province,China as an example,this study obtains the following results through field investigation and the analyses of water,soil,and crop samples.(1)The groundwater can be divided into two major types,namely the Quaternary pore-fissure water and Karst water.The Karst area and sandy area have high-quality groundwater and serve as the target areas for optional water supply.The groundwater in the study area is slightly alkaline and highly saline.Meanwhile,high-fluoride groundwater is mainly distributed in the loess and river alluvial plains in the depression area of the Guanzhong Basin and the discharge areas of the groundwater,with the highest fluoride concentration exceeding seven times the national standard.(2)Fluoride in groundwater mainly originates from a natural source and human activities.The natural source refers to the fluoride-bearing minerals in rocks and soil,and the fluoride from this source is mainly controlled by natural factors such as climate,geologic setting,pH,specific hydrochemical environment,ion exchange,and mineral saturation.Human activities in modern life can be further divided into industrial and agricultural sources primarily.(3)The health risks of fluoride contamination are very high in the Loess Plateau,especially for children compared to adults.Meanwhile,the risks of fluoride exposure through food intake are higher than those through drinking water intake.The authors suggest selecting target areas to improve water supply and ensure the safety of drinking water in the study area.Besides,it is necessary to plant crops with low fluoride content or cash crops and to conduct groundwater treatment to reduce the fluoride concentration in drinking water.These results will provide a theoretical basis for safe water supply in the faulted basin areas in the Loess Plateau.

Spectrophotometric Determination of Fluoride in Groundwater Using Resorcin Blue Complexes

New simple and sensitive spectrophotometric determination of fluoride in drinking groundwater has been developed using aluminium-resorcin blue complex. The method is based on the reaction of fluoride with the coloured complex to produce colourless aluminium fluoride complex and releasing of the free ligand. The relationship of the reaction of flu-oride with the complex is sixth-order polynomial function. The reaction reaches equilibrium at fluoride concentration of 0.054 mM. The equilibrium constant (Keq) was calculated as 1.12 × 1014. Beer-Lambert law is obeyed in the range 0.0 - 0.024 mM of fluoride (0.0 - 1.0 mg·L-1). The molar absorptivity at 502 nm is 6.45 × 103 L·mol-1·cm-1. Fluoride concentration higher than 1.0 mg·L-1 can be measured after proper dilution. The sensitivity, detection limit, quantitation limit, and the percentage recovery of 0.75 mg·L-1 fluoride for the method were found to be 0.357 μg·ml-1., 0.07 mg·L-1, 0.2 mg·L-1, and 101.1 respectively.

Fluoride Contamination of Groundwater and Health Hazard in Central India

The basic bed rocks of central India are contaminated with fluorite minerals. The overuse of groundwater for irrigation causes increased mineralization of F- in the groundwater. This contaminated groundwater is widely used for drinking and other household purposes. The excess F- is excreted through urine of animals. In this work, the exposure of contaminated groundwater in domestic animals of Dongargarh city, Chhattisgarh, India is studied. The symptoms of fluorosis diseases in the domestic animals i.e. cattle and buffalo are surveyed. The quality and sources of the contaminants of the groundwater are discussed.

Fluoride ions in groundwater of the Turkana County, Kenya, East Africa

Groundwater samples were evaluated throughout Turkana County(Kenya,East Africa)while looking for drinking water sources.Some samples showed high concentrations of fluoride with values in the range of 0.15–5.87 mg/L.Almost 50%of the samples exceeded the WHO and Kenyan potable water standard guideline value of 1.5 mg/L for drinking water quality.The hydrogeochemical studies revealed that the dominant cation in water is Na^(+)and the dominant anion is HCO_(3)^(-)resulting in Na-HCO_(3) type of groundwater,followed by Ca/Mg-HCO_(3) or Na-SO_(4) and Na-Cl in a few cases.Speciation modelling revealed that the groundwater is undersaturated with respect to gypsum and anhydrite,mostly undersaturated with respect to fluorite(6 samples are at equilibrium),and supersaturated or at equilibrium with respect to calcite(CaCO_(3)).Precipitation of calcite favours the dissolution of F-rich minerals in the alkaline medium.Simultaneously,groundwater is enriched with sodium and bicarbonate,probably as a result of chemical weathering of Na-feldspar.Investigated groundwater can be presumably used for drinking purposes from 17 wells,but a detailed investigation of other trace element concentrations is necessary.

Monitoring of Fluoride Concentration in Groundwater of Tosham Block, Bhiwani District, NW, India: Correlation with Physico-Chemical Parameters

Hydrogeochemical investigations were carried out in the eight villages of Tosham Block;district Bhiwani, Haryana to recognize the mechanism and sources of enrichment of fluoride in the groundwater. The results specify that concentrations of fluoride attain up to 1.9 mg/l in groundwater samples. In the soils, the overall fluorine contents vary between 1.1 and 2.7 mg/kg, which could have sufficient potential to released fluorine into the groundwater. In groundwater, the fluoride enrichment is primarily controlled by solubility of fluorite, intensity of evapotranspiration, residence time and the processes of weathering prevailing in Tosham area. Moreover, various other water quality parameters such as pH, electrical conductivity, total hardness, and total alkalinity as well as calcium, magnesium, carbonate, bicarbonate and chloride concentrations were also calculated. A logical calculation of correlation coefficients between different physico-chemical parameters was done. The 67% of groundwater samples do not comply with WHO standards of fluoride for drinking purposes. The excessive fluoride concentration in the groundwater of villages under study causes dental fluorosis among people especially the children. Except few of villages, without any prior treatment, the overall quality of water was found unacceptable for drinking purposes.

Fluoride contamination in groundwater:A global review of the status,processes,challenges,and remedial measures

Groundwater pollution by fluoride is one of the prime concerns of the world population due to its toxicity,which results in adverse health impacts.In this paper,we review the current scenario of the fluoride contamination of groundwater in various countries across the globe and its impact on human health.During the last decade,several newly affected regions have been reported all over the world,with more than 100 countries affected by fluoride contamination in groundwater(concentration exceeding the acceptable limit of 1.5 mg/L defined by the World Health Organization).Fluoride poisoning is mainly due to the unsupervised ingestion of products for dental and oral hygiene and over-fluoridated drinking water.It is estimated that more than 200 million people from different countries are affected by fluoriderelated groundwater issues and health problems.The highest among these are from the countries in Africa(38),Asia(28),and Europe(24),followed by countries like South America(5),North America(3),and Australia(2).The source of fluoride in drinking water is primarily geogenic,together with forage,grasses and grains,tea,and anthropogenic sources.These countries affected were correlated with climatic zones and geological factors to gain insights into geospatial relations.Our analyses show that most of the fluoride pollution-prone zones are located in high-grade metamorphic terranes with granitoid or alkaline intrusions,geothermal hot springs,and volcanic regions with arid or semi-arid climatic conditions.This study also finds that children across the globe are more vulnerable than adults to fluoride contamination.The review finds that,although there are efficient fluoride removal techniques,including filters with next-generation nanomaterials,to date,there has not been a single technique developed that can claim to be a practically robust solution for fluoride removal from drinking water.Therefore,we suggest developing next-generation filters that can retain essential minerals in water and remove only harmful ones and selecting purification technologies according to need,climate,geology,and geographic location.The findings from our review would help policymakers take effective and sustainable measures for safe water supply in the affected areas.Within the framework of the Sustainable Development Goals(SDGs),particularly SDG 3(Good Health and Well-being)and SDG 6(Clean Water and Sanitation),this study emphasizes the critical role of fluoride as a key indicator.It underscores the imperative of addressing elevated fluoride levels in drinking water,particularly in African and Asian countries,to achieve the overarching objective of universal and equitable access to safe,affordable,and uncontaminated drinking water for global society by the targeted year of 2030.

Application of geospatial modelling technique in delineation of fluoride contamination zones within Dwarka Basin, Birbhum, India

Dwarka River Basin is one of the fluoride affected river basin in Birbhum, West Bengal. In the present research work, various controlling factors for fluoride contamination in groundwater i.e., geology, aquifer type, groundwater table, soil, rainfall, geomorphology, drainage density, land use land cover, lineament and fault density, slope and elevation were considered to delineate the potential fluoride contamination zones within Dwarka River Basin in Birbhum. Assigning weights and ranks to various inputs factor class and their sub-class respectively was carried out on the basis of knowledge driven method. Weighted overlay analysis was carried out to generate the final potential fluoride contamination zones which are classified into two broad classes i.e., 'high' and 'low', and it is observed that major portion of the study area falls under low fluoride contamination category encompassing 88.61% of the total area which accounts for 759.48 km^2 and high fluoride contaminated region accounts for 11.40% of the total study area encompassing an area of about 97.67 km^2. Majority of high fluoride areas fall along the flood plain of Dwarka River Basin. Finally, for validation 197 reported points within Dwarka having fluoride in underground water are overlaid and an overall accuracy of 92.15% is observed. An accuracy of 83.21% and84.24% is obtained for success and prediction rate curve respectively.

Batch and Column Experiments on Fluoride Removal from Waters Using Modified Zeolite

High fluoride groundwater occurs widely in China, presenting a quite serious environmental problem. Zeolite from Xinyang, China was tested as the fluoride removing adsorbent. Batch and column experiments on fluoride removal using modified zeolites treated with hydrochloric acid, sodium hydroxide, sodium chloride and ferric chloride, respectively show that 0.1 mol/L HCl modified zeolite can be used as an adsorbent for fluoride, with an adsorption capacity of 173.16 mg/kg.

Distribution and assessment of hydrogeochemical processes of F-rich groundwater using PCA model:a case study in the Yuncheng Basin,China

Hydrogeochemistry and factor analysis were conducted together to assess the distribution and the major geochemical processes in fluoride-contaminated shallow groundwater in the Yuncheng Basin.Spatially,fluoride concentration was low(<1.5 mg/L)in the southern piedmont plain,medium(<4 mg/L)in the central basin,and high(up to 14.1 mg/L)in Kaolao lowland areas in shallow aquifers.A three-factor principal component analysis model explained over 75.1%of the total variance.Sediment weathering leaching and evapotranspiration were recognized as the first primary hydrochemical processes response for the groundwater chemistry and explained the largest portion(42.1%)of the total variance.Factor two reflects the negative influence of human activities,with a positive loading of NO3^-and HCO3^-,and negative loading of well depth.Fluoride-bearing mineral dissolution and alkaline condition was ranked as the third factors responding for groundwater chemistry and explained 11.2%of the total variance.

Formation and harmfulness of high fluoride-bearing ground-water

According to the distribution of high fluoride\|bearing groundwater in Liaoning Province, China, the cause of formation and hydrogeochemical characteristics as well as its relationship with human health and illness rate were discussed. Strategies to prevent and control fluoride pollution have also been outlined.

Distribution,enrichment mechanism and risk assessment for fluoride in groundwater:a case study of Mihe-Weihe River Basin,China

Due to the unclear distribution characteristics and causes of fluoride in groundwater of Mihe-Weihe River Basin(China),there is a higher risk for the future development and utilization of groundwater.Therefore,based on the systematic sampling and analysis,the distribution features and enrichment mechanism for fluoride in groundwater were studied by the graphic method,hydrogeochemical modeling,the proportionality factor between conventional ions and factor analysis.The results show that the fluorine content in groundwater is generally on the high side,with a large area of medium-fluorine water(0.5–1.0 mg/L),and high-fluorine water is chiefly in the interfluvial lowlands and alluvial-marine plain,which mainly contains HCO_(3)·Cl-Na-and HCO_(3)^(-)Na-type water.The vertical zonation characteristics of the fluorine content decrease with increasing depth to the water table.The high flouride groundwater during the wet season is chiefly controlled by the weathering and dissolution of fluorine-containing minerals,as well as the influence of rock weathering,evaporation and concentration.The weak alkaline environment that is rich in sodium and poor in calcium during the dry season is the main reason for the enrichment of fluorine.Finally,an integrated assessment model is established using rough set theory and an improved matter element extension model,and the level of groundwater pollution caused by fluoride in the Mihe-Weihe River Basin during the wet and dry seasons in the Shandong Peninsula is defined to show the necessity for local management measures to reduce the potential risks caused by groundwater quality.

Behavior of Arsenic and Fluoride Concentration in Guadiana Valley Aquifer of Durango, Mexico

Fluorine (F) and arsenic (As) are inorganic elements present in the subsurface depending on the geology of the region. These compounds are found in high concentrations in the underground strata of Guadiana Valley of Durango affecting water quality for human consumption (NOM-127-SSA-1994). In the present research the main objective was to assess the behavior in time and space of fluoride (F-) and arsenic concentration, from 1996 to date, in the groundwater of the city of Durango and some wells of the rural area as a reference. The highest concentration of arsenic was found in a rural well, Colonia Hidalgo (0.149 mg/L or ppm), 6 times the maximum permissible limit (MPL);within the city well 54 located in the western sector had the highest value (0.076 ppm), 3 times the MPL, 67% of the wells in the city and 60% of the Guadiana Valley had levels that exceeded the MPL (0.025 ppm), the concentration in the city ranged from 0.009 to 0.149 ppm and from 0.08 to 0.15 ppm for the rural zone. With respect to F-, the highest value was also found in the Colonia Hidalgo well (17.8 mg/L), 12 times the MPL;within the city the highest value was recorded in well 16 in the eastern sector with 7.6 ppm (5 times the MPL) 97% of the wells in the city and 100% of the wells in the Guadiana Valley rural area had concentrations greater than MPL (1.5 ppm), the concentration in the city ranged from 1.1 to 7.6 ppm, while in the Guadiana Valley from 1.7 to 17.8 ppm. Statistical analysis showed no significant difference for fluoride concentration over time (1996-2013);whereas the concentration of arsenic decreased, probably due to the degree of precision required for such small concentrations in groundwater and different analysts ran the samples.

Concentration of Fluoride and Arsenic in Bottled Drinking Water in Durango City, Mexico

Arsenic and fluoride are elements known to cause human health problems and it has been documented that both elements are found in high concentrations in the Guadiana Valley aquifer, in the state of Durango, Mexico. Since underground water is the source for potable water bottling companies commercialized in Durango City;such high concentrations reduced the quality of bottled water for human consumption according to NOM-041-SSA1-1993. Legislation establishes a maximum permissible limit (MPL) of 0.7 mg/L for fluoride and 0.025 mg/L for arsenic. In this research the main objective was to evaluate the quality of bottled water expended in Durango City with respect to the well from which water is extracted. Findings showed that the highest fluoride concentration was 5.86 mg/L (8.4 times MPL), with 100% of sampled brands exceeding the MPL (range: 1.09 to 5.86 mg/L). On the other hand, for arsenic, the highest concentration was 0.076 mg/L (threefold), with 38% exceeding the MPL (range: 0.001 to 0.076 ppm). Statistical analysis showed significant differences only for fluoride, according to Fisher LSD (Least Significant Difference) test, with an F value of 14.5 at a p value of 0.0005. According to the comparison between the quantified concentrations in bottled water and groundwater, it was found that groundwater was subjected to treatment;however, although a significant decrease in fluoride and arsenic concentration was observed, the removal processes used were not efficient to meet set standards.

Geochemical Evaluation of Groundwater in the Mandvi Taluka of Surat, India

The quality of water is a vital concern for mankind since it is directly linked to human health. The present work is carried out with an objective to assess and map the spatial variability in the groundwater quality parameters in Mandvi Taluka, Surat district Gujarat, India. A total fifty-seven representative ground-water samples from different bore wells and hand pumps from Mandvi Taluka has been collected and analyzed for major cation and anions with fluoride concentration for the pre-monsoon and post-monsoon seasons. Ground water in the region is found alkaline, with presence of bicarbonates in nature and very hard. Weathering and leaching of F- bearing minerals under the alkaline conditions favors the high F-?concentration. Presence of low total hardness, low calcium hardness, high chlorides, high bicarbonates and some anthropogenic factors such as intensive and long-term irrigation, heavy use of fertilizers are the supplementary factors to further enhance the F- concentrations in the groundwater. Moreover, GIS spatial distribution maps give better visual image to understand the spatial distribution pattern to overlook better conclusion.

Contamination of Water, Dust, Soil, Rock and Urine with Fluoride in Central India

At least 15% of 0.1 million people residing in 117 villages of Tamnar block (Chhattisgarh, central India) are suffering from fluorosis diseases. In this work, the contamination of F- in the environment (i.e. water, soil, rock and urine) of the Tamnar block is described. The concentration variations of F-, Cl-, NO3-, SO42-, Na+, K+, Mg2+, Ca2+, Al, Mn, Fe and Zn in the groundwater are reported. The F- content in the water was ranged from 1.7 - 17 mg/L with mean value of 9.0 ± 3.7 mg/L. Fluoride was enriched up to 3-, 54-, 69- and 244-folds in the urine, soil, dust and rock, respectively. The cluster and factor analysis models were used to apportion sources of F- and other elements in the water.