Distribution of fluoride in groundwater of Maku area, northwest of Iran

High fluoride groundwater occurs in Maku area, in the north of West Azarbaijan province, northwest of Iran. Groundwater is the main source of drinking water for the area residents. Groundwater samples were collected from 72 selected points including 40 basaltic and 32 nonbasaltic springs and wells, in two stages, during June and August 2006. The areas with high fluoride concentrations have been identified, and the possible causes for its variation have been investigated. Regional hydrogeochemical investigation indicates that water-rock interaction is probably the main reason for the high concentration of ions in groundwater. The concentration of F⁻ in groundwater is positively correlated with that of HCO₃ ⁻ and Na⁺, indicating that groundwater with high HCO₃ ⁻ and Na⁺ concentrations help to dissolve some fluoride-rich minerals. All of the water samples, collected from the basaltic areas do not meet the water quality standards for fluoride concentration and some other parameters. Hence, it is not suitable for consumption without any prior treatment. Inhabitants of the area that obtain their drinking water supplies from basaltic springs and wells are suffering from dental fluorosis. The population of the study area is at a high risk due to excessive fluoride intake especially when they are unaware of the amount of fluoride being ingested due to lack of awareness.     

Geochemistry, genesis, and health implications of fluoriferous groundwaters in the upper regions of Ghana

 The most appropriate and widely used source of drinking water for the populations of the upper regions of Ghana is groundwater. In general, groundwater quality is acceptable except for some parts of the Bolgatanga and Bongo Districts, where there are occurrences of elevated levels of natural groundwater fluoride. Concentrations of groundwater fluoride in excess of the World Health Organization (WHO) maximum guideline value (1.5 mg/l) in the Bongo area have been known since 1978. However, the effect of fluoride on people ingesting the water did not receive public and medical attention until October 1993, when health personnel were asked to investigate the cause of stained teeth in school children. The investigation established that 62% of the total population of school children in the Bongo area had dental fluorosis. Against this background, a study was initiated to understand the geochemistry, genesis, and distribution of fluoride in relation to the geology of the area. Groundwater fluoride in the upper regions ranges from 0.11 to 4.60 ppm, with the highest concentrations associated with the fluorine-enriched Bongo coarse-grained hornblende granite and syenite suite. The source of groundwater fluoride within the Bongo granitoids is dissolution of the mineral fluorite and dissolution of and anion exchange with micaceous minerals and their clay products. Applying the WHO recommended guideline values for fluoride in drinking water reveals that 49% of wells in the area deliver water below the optimum level of 0.5 mg/l F^–; these populations are thus prone to dental caries. Twenty-eight percent of the wells fall within the optimum interval for good dental health (0.5–1.5 mg/l F^–). Twenty-three percent of the wells have concentrations above the recommended maximum guideline limit of 1.5 mg/l F^–; this population is susceptible to dental and possibly skeletal fluorosis. Climatic conditions of the area suggest that the individual water consumption is in the order of 3 to 4 l which is higher than the WHO estimate of 2 l/adult/day. In addition, dietary intake for the upper region population is probably higher than WHO baseline values (0.2–0.5 mg/day). This implies that a much higher population is susceptible to developing dental and skeletal fluorosis than originally suspected. Geochemical symbol plot maps help geochemists understand factors controlling the distribution and uptake of fluoride in the upper regions, but they are of minimal value to health officials responsible for planning epidemiological studies and dental health education programs in the region. By casting fluoride data into contoured 'geochemical health-risk maps' using intake interval guidelines more closely aligned to regional climatic and dietary conditions, health officals can better judge the impacts (regional and population based) of fluoride on segments of the population, such as various sex and age groups. Received: 11 March 1997 · Accepted: 17 June 1997     

Fluoride in Quaternary groundwater aquifer,Nile Valley,Luxor, Egypt

The occurrence of fluoride in ground water is the focus of the public and has attracted the attention of many scientists all over the world due to its importance in public health. Deficiency or increase of fluoride uptake is considered a public health problem due to the narrow permissible limit which should not exceed 1.5 mg/l according to the World Health Organization (WHO). The range of fluoride tolerance and toxicity is narrow. Deviation from the optimal levels therefore results in dental health effects such as caries and fluorosis. Many studies have found fluorosis to be invariably associated with high concentrations of fluoride in drinking water. Fluorosis is a considerable health problem in many areas of the world including Brazil, China, East Africa, Ghana, India, Kenya, Korea, Malawi, Mexico, Pakistan, South Africa, southeastern Korea, Spain, Sri Lanka, Sudan, Taiwan, Tanzania, and Turkey. Fluoride in groundwater of Quaternary aquifer of the Nile Valley, Egypt, does not gain the attention of the authors in the Nile Valley which makes the public health status of fluoride is not certain. The present work aims at investigating the fluoride concentration of Quaternary groundwater aquifer at Luxor as a representative area of the Nile Valley to be a base line for subsequent studies and criteria for public health. Ground water samples were collected from Quaternary groundwater aquifer at Luxor area, Egypt and analyzed for the purpose of investigating fluoride content. The results showed that fluoride concentration in the study area ranges between 0.113 and 0.452 with an average of 0.242 mg/l. Sources of fluoride in the study area can result from the natural dissolution from fluoride-rich minerals, fertilizers and from groundwater recharge. It is worth mentioning that low fluoride content in the study area is considered a public health threat specially limited growth, fertility, and dental caries. Corrective measures should be taken to avoid the public health impacts of fluoride deficiency at Luxor area as well as similar areas in the Nile Valley. A public health program should be initiated to account for the deficiency of fluoride in groundwater and deal with the other supplementary fluoride sources in food or fluoridation of drinking water supplies.     

山东黄河冲积平原区地氟病与地球化学环境相关性研究

山东黄河冲积平原区是山东省地氟病的重病区,危害严重。选择其中的郓城、嘉祥、博兴3县进行土壤氟含量、饮水氟含量、儿童尿氟、儿童氟斑牙检出率、氟斑牙指数、成人尿氟、成人氟骨症检出率等指标进行调查,结果表明区内土壤、饮水氟含量和群体的尿氟含量普遍较高,高氟的危害和地方性氟中毒病情十分严重。在分析氟元素在土壤、饮水中的分布及变化规律的基础上,开展地方性氟中毒病与生态地球化学环境相关性研究,认为地方性氟中毒病与土壤中氟含量、饮水氟含量呈正相关关系。     

Delineation of potential fluoride contamination zones in Birbhum,West Bengal,India, using remote sensing and GIS techniques

Birbhum district in West Bengal, India, is one of the most severely affected districts by fluoride-contaminated groundwater. Fluoride content as high as 20.4 mg/L has been reported. Several cases of fluoride-related disorder such as dental fluorosis and skeletal fluorosis have been reported to be endemic in the district. Proper management of groundwater is very crucial. This contribution has been carried out for delineating potential fluoride-contaminated zones (PFCZ) in Birbhum district with the implementation of weighted overlay analysis in GIS environment. Twelve different potentially influential environmental parameters are integrated and evaluated. The final output map was categorised into two subclasses, i.e. ‘low’ and ‘high’, where the low region represents fluoride concentration of 1.5 mg/L and below and the high region represents fluoride concentration above 1.5 mg/L. The outcome reveals that approximately 24.35% of the study area falls under PFCZ, whereas about 75.65% of the study area falls under the safe zone with respect to potential fluoride contamination. On validation of the PFCZ, the reported fluoride contamination data in groundwater shows an overall 87.50% accuracy in prediction via superimposition method and 89.06 and 85.85% success and prediction rates, respectively, when validated with success and prediction rates.     

Occurrence and distribution of fluoride in the groundwater of the Tamiraparani River basin,South India: a geostatistical modeling approach

Fluoride in drinking water has both beneficial and detrimental effects on public health, and a narrow range between .6 and 1.5 mg/L is optimal for consumption. However, natural groundwater sources exceed these guidelines affecting the entire population. This study aims to assess the distribution and controlling factors of fluoride concentration in the Tamiraparani River basin, South India. A total of 124 groundwater samples were analyzed for their fluoride content and other hydrogeochemical parameters. The fluoride concentration in the study area varied from .01 to 1.67 mg/L, and the highest concentrations were measured in the northern and central parts of the study area, which is underlain by charnockites and hornblende biotite gneiss. The sampling indicated (as per the Bureau of Indian Standards) that 53.9% of the area has fluoride concentrations below levels that are protective of teeth from dental caries (<.6 mg/L). .1% of the area is considered to be at risk of dental fluorosis, and the remaining 46% of the area is considered to have fluoride levels at desirable to permissible limit in groundwater. The groundwater in the study area belongs to Ca–Mg–Cl–SO₄ and Ca–Mg–HCO₃ types. A positive correlation between fluoride and TDS, Na⁺, K⁺ and HCO₃ ^? indicates its geogenic origin, and positive loading between pH and fluoride shows that alkaline environment enhances the dissolution of fluoride-bearing minerals into the groundwater. An empirical Bayesian kriging model was applied to interpolate the fluoride concentration in the study area. This geostatistical model is found to be better than other kriging methods, and it yielded an average standard error of .332 and root-mean-square standardized value of .986.     

Temporal variations of fluoride concentration in Isparta public water system and health impact assessment (SW-Turkey)

Water–rock interaction is one of the prime factors affecting the fluoride contents of surface and groundwater. If fluoride concentration of drinking water has been neglected, excess fluoride can cause serious dental and medical problems on human health, which is well known at Golcuk-Isparta region. In the research area, Egirdir lake, Golcuk lake and surrounding springs have been utilized as drinking water sources. Golcuk lake water and surrounding groundwaters have high fluoride content (1.4–4.6 mg/l), which is above the WHO standards. Fluoride is predominantly supplied by dissolution of fluoride within the fluormicas of volcanics during the circulation of water. Fluoride concentrations of waters have shown variations for dry and rainy seasons depending on the degree of interaction between groundwater and volcanic rocks. It tends to decrease in rainy seasons and increase in dry seasons for all years. In this study, temporal variations and spatial distribution of fluoride concentration in public water system of Isparta were investigated to get benefit using GIS techniques from1990 to 2003 years. Extremely fluoride concentrations were measured in the public water system in 1990 at almost every district of the city. In 2003, fluoride content of the public water system decreased in some district of city due to drinking water has started obtaining from Egirdir lake in 1995. The fluoride contents of Isparta drinking water ought to be modified with suitable mixture of lake waters and groundwater point of view to health impact.     

Quality assessment of groundwater at south Al Madinah Al Munawarah area, Saudi Arabia

Groundwater is the main source of irrigation within south Al Madinah Al Munawarah region. It is also an important source of drinking water in many areas including Madinah city. The wells installed in the aquifer of the study area (south Madinah city) are not currently regulated by the local authorities although they are a key component of water supply. The aquifers in the study area range from unconfined to semi-confined and confined. The main aim of this study is to assess the groundwater in the region for drinking and agricultural uses. For this purpose, hydrochemical analyses of major, minor and trace constituents and nutrients were performed on 29 groundwater samples from the aquifer located about 20 km south of Madinah. The recharge rate of the aquifer of the study area was estimated to be 6.58 % of the annual precipitation using the chloride mass-balance method. Chloride was positively correlated with major ions, which suggests that agricultural activities have some effect on groundwater chemistry through leaching of readily soluble salts from the soil zone. Groundwater of the study area is characterized by dominance of Na over Ca. Chloride was found to be the most dominant anion and replaced by HCO₃, thus reflecting geochemical evolution in the study area. The groundwater of the study area is not safe for drinking but can be safely used for salt-tolerant crops.     

Fluoride pollution in soils and waters of Koohbanan region, southeastern Iran

Dental fluorosis occurs because of fluoride over-absorption during tooth calcification and maturation. We studied fluoride concentration in water and soil samples of the Koohbanan region in Kerman province of southeastern Iran and the effects of calcium chloride and gypsum treatments in decreasing the amount of fluoride in water samples of this region. The results indicate that the high amount of fluoride in the water samples of Koohbanan region is not in agreement with the recommended amount of fluoride concentration for drinking water by World Health Organization (that is 1–1/5 mg/l). Applying calcium chloride and gypsum treatments decreased the amount of fluoride in the water samples showing that utilizing calcium chloride (6 mg/l) or gypsum (12 mg/l) can lower the fluoride concentration in the water samples of Koohbanan, and thus solve the observed dental fluorosis problem.     

Fluoride occurrence in publicly supplied drinking water in Estonia

A study was undertaken to examine the content and spatial distribution of fluoride in drinking water. Water samples (735) from public water systems covering all Estonian territory were analysed using SPADNS method. In order to specify the natural source of fluoride, the chemistry data from five aquifer systems utilised for water supply were included into the study. Fluoride concentrations in tap water, to a great extent, ranged from 0.01 to 6.95 mg/l. Drinking water in southern Estonia, where terrigenous Middle-Devonian aquifer system is exploited, has a fluoride concentration lower than recommended level (0.5 mg/l), thus promoting susceptibility to dental caries. The western part of the country is supplied by water with excess fluoride content (1.5–6.9 mg/l). Groundwater abstracted for drinking purposes originates from Ordovician and Silurian carbonate rocks. The content of fluoride in Silurian–Ordovician aquifer system is associated with the groundwater abstraction depth and the main controlling factors of dissolved fluoride are the pH value and the chemical type of water.     

Factors controlling fluoride contents of groundwater in north-central and northwestern Sri Lanka

Chemical characterization has been made of groundwater bodies at 294 locations in four village districts in north-central and northwestern Sri Lanka, with special focus on fluorine contamination. High fluoride contents in groundwater are becoming a major problem in the dry zone of Sri Lanka, and dental fluorosis and renal failures are widespread. Field measurements of temperature, pH, and electrical conductivity were made during sampling. Chemical analyses of the water samples were later made using atomic absorption spectroscopy, spectrophotometry, and titration. Fluoride concentrations in the study area vary from 0.01 to 4.34 mg/l, and depend on pH and the concentrations of Na, Ca, and HCO₃ ⁻. Basement rocks including hornblende biotite gneiss, biotite gneiss, and granitic gneiss seem to have contributed to the anomalous concentrations of fluoride in the groundwater. Longer residence time in aquifers within fractured crystalline bedrocks may enhance fluoride levels in the groundwater in these areas. In addition, elevated fluoride concentrations in shallow groundwater in intensive agricultural areas appear to be related to the leaching of fluoride from soils due to successive irrigation.     

Evaluation of groundwater resources for drinking and agricultural purposes, Abar Al Mashi area, south Al Madinah Al Munawarah City, Saudi Arabia

A hydrogeochemical study was conducted on the groundwater of south Al Madinah Al Munawarah City, Saudi Arabia, to assess the quality of groundwater for drinking and irrigation uses. Groundwater samples have been collected and analyzed for major and some trace constituents from the study area. The nitrate concentration in most groundwater samples of the study area exceeded the safe limits for drinking purposes, whereas the concentrations of phosphate, boron, and trace constituents were below the maximum permissible limit for drinking purposes; Cr in two samples showed high content over the recommended limits of drinking purposes. Uncontrolled abstraction of groundwater in Abar Al Mashi area caused many environmental problems including water resource depletion and contamination. Correlations between chloride and major ions were positive and may be attributed to impact of agricultural activities on groundwater chemistry. Groundwater of the study area was classified into six water types. The chemical water types of groundwater in the study area contain CaHCO₃ in the eastern and southeastern parts and NaCl in western and northwestern parts, reflecting different land use characteristics and pollution sources. Piper diagram showed that almost all the samples fall in one zone, indicating similar chemical signature. Groundwater can be used safely for drinking with special treatments to eliminate the effect of increased concentrations of total dissolved solids, nitrate, and chromium. The groundwater of the study area can be used safely for irrigation on clay soil; however, specific crops should be selected according to their salt tolerance.     

Temporary fluoride concentration changes in groundwater in the context of impact assessment in the Vaniyar sub-basin,South India

India’s surface water and groundwater distribution is temporally variable due to the monsoon. Agriculture is one of the dominant economic sectors in India. Groundwater quality is regularly assessed to determine usability for drinking and irrigation. In this study, World Health Organization and Bureau of Indian Standards guidelines were used to determine suitability of groundwater near artificial recharge structures (ARS) with a focus on the structures´ impact on groundwater quality. Groundwater resources were evaluated for irrigation suitability using electrical conductivity (EC), sodium adsorption ratio, the US Salinity Laboratory diagram, sodium concentration, Wilcox’s diagram, Kelly’s index, and Doneen’s permeability index. EC and major ions were tested in recharge areas at different distances from the ARS. The construction of ARS at optimal distances along major streams has improved groundwater quantity and quality in the sub-basin. Before construction of ARS, fluoride concentrations were higher; after construction, fluoride was reduced in most locations. Water stored in the check dam and groundwater in the wells closer to the structure were suitable for both drinking and irrigation purposes. Impact of ARS on nearby groundwater quality was observed at Pallipatti, Mulayanur, Venkadasamuthram, Pudupatti, Poyyappatti, Harur1, and Sekkampatti. More distant sites included Pappiredipatti, Nambiyappati, Menasi, Harur, Todampatti, and Adikarapatti. Data demonstrated improved groundwater quality in the area of the ARS. Through recharge, the non-potable fluoride in the region is reduced to the permissible limit for human consumption.     

A GIS-based DRASTIC model for assessing shallow groundwater vulnerability in the Zhangye Basin,northwestern China

Groundwater vulnerability is a cornerstone in evaluating the risk of groundwater contamination and developing management options to preserve the quality of groundwater. Based on the professional model (DRASTIC model) and geographical information system (GIS) techniques, this paper carries out the shallow groundwater vulnerability assessment in the Zhangye Basin. The DRASTIC model uses seven environmental parameters (depth to water, net recharge, aquifer media, soil media, topography, impact of vadose zone, and hydraulic conductivity) to characterize the hydrogeological setting and evaluate aquifer vulnerability. According to the results of the shallow groundwater vulnerability assessment, the Zhangye Basin can be divided into three zones: low groundwater vulnerability risk zone (risk index <120); middle groundwater vulnerability risk zone (risk indexes 120–140) and high risk zone (risk index >140). Under the natural conditions, the middle and high groundwater vulnerability risk zones of the Zhangye Basin are mainly located in the groundwater recharge zones and the important cities. The high, middle and low groundwater vulnerability risk zones of the Zhangye Basin cover around 17, 21 and 62% of study area, respectively.     

Environmental characteristics of regional groundwater in relation to fluoride poisoning in North China

More and more data indicated that high- or low-fluoride-bearing drinking water led to endemic diseases in which fluoride poisoning was caused by high levels of fluoride (fluoride ion content >1.0 mg/I) in drinking water. Fluoride poisoning in North China is characterized by pathological changes of bones and teeth. Much attention has been devoted to the study of fluoride-bearing groundwater in North China because regionally groundwater has been the main source of water supply, and fluoride poisoning has developed to the extent that it affects human health seriously. Results from the studies in North China summarized in this article indicate that regional high-fluoride-bearing groundwater has a regular distribution corresponding with the development of endemic fluoride poisoning and has something to do with paleogeographic and paleoclimatic conditions, geology, and hydrogeology, especially with types of hydrogeochemistry, pH value of groundwater, degree of mineralization, and so forth. High-fluoride-bearing groundwater in relation to fluorosis occurs mainly in North China, and many effective measures have been taken to reduce the fluoride content in drinking water and to cure the disease after analyzing the distribution and environmental characteristics of high-fluoride-bearing groundwater.     

Fluoride and heavy metal accumulation by vegetation in the fluoride affected area of Talupula,Anantapur district,Andhra Pradesh

A detailed survey showed that groundwater fluoride was 6.1ppm in the Talupula area of the Anantapur district in southern India which is higher than is normally observed in groundwater elsewhere in India but not so extreme as that reported in Andhra Pradesh (up to 21 mg L^-1). Groundwater is used for irrigating agricultural crops as well as for drinking which may expose its population to higher concentrations of fluoride through their diet. A preliminary study examined the concentrations of fluoride in five agricultural crops in the Talupula area and the soil beneath agricultural crops. The stem and leaves of Heliathusannuas, Arachishypogaea, Morusalba, Lychopersiconesculantum, and Phaseolus vulgaris were examined for fluoride and heavy metal accumulation. Heavy metal (Zn, Cu and Pb) accumulation in the stem and leaves were examined to determine if there was any correlation between their uptake and that of fluoride. In the soil beneath the crops, fluoride concentrations ranged from 6.53±0.44 to 8.23±1.22 ppm and a significant accumulation of fluoride was observed in the stems (13.2±2.0 to 23.9±3.6 ppm; p < 0.001) and leaves (16.4±1.9 to 61.5±4.5 ppm) of the agricultural plants. A significant accumulation of fluoride was observed from the stem to the leaves for all plants (p < 0.03) except Helianthus annuas. Copper also displayed significant accumulation from the soil to the stems in some of the plants tested but there was no significant accumulation of zinc or lead. A significant translocation from the stem and accumulation in the leaves was not observed for Cu or Pb but there was significantly higher zinc in the leaves of Arachishypogaea and Morusalba when compared to their stems. This study demonstrated that agricultural plants grown under field conditions and irrigated with groundwater high in fluoride will accumulate fluoride, but that fluoride is unlikely to have a significant effect on Cu, Zn or Pb accumulation in the stems and leaves of agricultural plants of the area. While drinking water is still the major cause of fluorosis in southern India, consumption of foods with high fluoride concentrations may also increase the risk of fluorosis.     

Hydrochemical status of groundwater in district Ajmer (NW India) with reference to fluoride distribution

High fluoride in groundwater has been reported from many parts of India. However, a systematic study is required to understand the behaviour of fluoride in natural water in terms of local hydrogeological setting, climatic conditions and agricultural practices. Present study is an attempt to assess hydrogeochemistry of groundwater in Ajmer district in Rajasthan to understand the fluoride abundance in groundwater and to deduce the chemical parameters responsible for the dissolution activity of fluoride. Ajmer district falls in the semi-arid tract of central Rajasthan and is geologically occupied by Precambrian rocks (granites, pegmatites, gneisses, schists etc) where groundwater occurs under unconfined condition. A total of 153 well-water samples, representing an area of 8481 km² (further subdivided into eight blocks), were collected and chemically analyzed. The results of chemical analyses (pre-monsoon 2004) show fluoride abundance in the range of 0.12 to 16.9 mg/l with 66% of the samples in excess of permissible limit of 1.5 mg/l. Presence of fluoride bearing minerals in the host rock, the chemical properties like decomposition, dissociation and dissolution and their interaction with water is considered to be the main cause for fluoride in groundwater. Chemical weathering under arid to semi-arid conditions with relatively high alkalinity favours high concentration of fluoride in groundwater. Dental and skeletal fluorosis are prevalent in the study area which can be related to the usage of high fluoride groundwater for drinking. The suggested remedial measures to reduce fluoride pollution in groundwater include dilution by blending, artificial recharge, efficient irrigation practices and well construction.     

Assessment of Groundwater Vulnerability in Upper Betwa River Watershed using GIS based DRASTIC Model

Groundwater, the most vital water resource being used for irrigation, domestic and industrial purposes is nowadays under severe threat of contamination. Groundwater contamination risk assessment is an effective tool for groundwater management. In the study, a DRASTIC model which is based on the seven hydrogeological parameters viz: depth of water, net-recharge, aquifer media, soil media, topography, impact of vadose zone and hydraulic conductivity was used to evaluate the groundwater pollution potentiality of upper Betwa watershed. ArcGIS was used to create the ground water vulnerability map by overlaying the seven layers. Based on groundwater vulnerability map, the watershed has been divided in three vulnerable zones viz; low vulnerability zone with 42.83 km² of area, moderate with 369.21 km² area and high having 270.96 km² of area. Furthermore, the DRASTIC model has been validated by nitrate concentration over the area. Results of validation have shown that in low vulnerable zone, no nitrate contamination has been recorded. While in the moderate zone nitrate has been found in the range of 1.6-10ppm. However, in high vulnerable zone 11-40ppm of nitrate concentration in groundwater has been recorded, which proves that the DRASTIC model is applicable for the prediction of groundwater vulnerability in the watershed and in similar areas too.     

Investigation of fluoride contamination and its mobility in groundwater of Simlapal block of Bankura district,West Bengal,India

The occurrence of dental/skeletal fluorosis among the people in the study area provided the motivation to assess the distribution, severity and impact of fluoride contamination in groundwater of Bankura district at Simlapal block, West Bengal, India. To meet the desired objective, groundwater samples were collected from different locations of Laxmisagar, Machatora and Kusumkanali regions of Simlapal block at different depths of tube wells in both pre- and post-monsoon seasons. Geochemical results reveal that the groundwaters are mostly moderate- to hard-water type. Of total groundwater samples, 37% are situated mainly in relatively higher elevated region containing fluoride above 1.5 mg/L, indicating that host aquifers are severely affected by fluoride contamination. Machatora region is highly affected by fluoride contamination with maximum elevated concentration of 12.2 mg/L. Several symptoms of fluorosis among the different age-groups of people in Laxmisagar and Machatora areas are indicating consumption of fluoridated water for prolonged period. The groundwater samples were mainly Na–Ca–HCO₃ type and rock dominance indicating the dissolution of minerals taking place. Ion exchange between OH^? ion and F^? ion present in fluoride-bearing mineral is the most dominant mechanism of fluoride leaching. High concentration of Na⁺ and HCO₃ ^? increases the alkalinity of the water, providing a favorable condition for fluoride to leach into groundwater from its host rocks and minerals.     

含氟地下水饮用处理技术

目前,高氟地下水和地方性氟中毒是世界范围内的一个难题,为解决这一问题,世界各国科研人员进行了大量的试验研究,总结出了不少成功的处理方法.综述前人对含氟地下水的各种处理技术,包括吸附法、沉淀法、电凝聚法、电渗析、Donna渗析等,并对这些技术进行了总结和比较,以指导生产实践.