Assessment of groundwater quality with special emphasis on fluoride contamination in crystalline bed rock aquifers of Mettur region, Tamilnadu, India

Groundwater samples were collected from Mettur taluk of Salem district, Tamilnadu, India for two different seasons (pre-monsoon and post-monsoon) and analyzed for fluoride ion along with other chemical parameters. The major litho units of the study area are Charnockites, peninsular gneiss, and calc gneiss of meta-sedimentary group. The fluoride concentration ranges from 0.1 to 2.8?mg/L and 0.4 to 4.0?mg/L during pre-monsoon (PRM) and post-monsoon (POM) seasons, respectively. Results showed that collected water samples were contaminated by the presence of fluoride ion. During PRM and POM, 21% and 56% of samples recorded higher fluoride when compared with Indian Drinking Water Standard (1?mg/L) and (9% and 35%) of samples recorded higher fluoride when compared with World Health Organization tolerance limit (1.5?mg/L). The ratio of Na/Ca indicates high sodium content in groundwater enhances the dissolution of fluoride at higher pH. Hydrogeochemical facies indicates water-rock interaction as main source for high fluoride in groundwater. A positive correlation between pH, Mg, and F indicates high alkaline nature of water promotes fluoride leaching from source rocks into ground water. Factor analysis indicates hydro-geochemical processes like weathering, ion exchange, and anthropogenic contributes to groundwater chemistry. The saturation index indicates dissolution and precipitation contributes fluoride dissolution along with mixing.     

Appraisal of highly fluoride zones in groundwater of Kurmapalli watershed,Nalgonda district,Andhra Pradesh (India)

Fluoride (F) contamination study had been carried out to see its allocation in Kurmapalli watershed, Nalgonda district, Andhra Pradesh, India. The study area is located about 60 km SE of Hyderabad city. The groundwater is the main source of water for their living. The groundwater in villages and its surrounding are affected by fluoride contamination and consequently the majority of the people living in these villages has health hazards and is facing fluorosis. The purpose of this study is to identify the wells with high F, raise awareness in people, study the water chemistry, and also find out the source of F in groundwater. A total of 32 groundwater samples were collected from different wells in both shallow aquifers and deeper fractures zones during October 2004. The chemical analysis of groundwater has been done. Fluoride values vary from 0.7 to 19.0 mg/l. It is noted that the maximum value (19.0 mg/l) is one of the highest values found in groundwater in India and 78% of the total samples show F concentrations that exceeds the permissible limit value (1.5 mg/l). The highest value of F is found at Madanapur bore well which is located at central part of the watershed. The F value of this bore well was monitored from October 2004 to October 2006. During this period the F concentration varies from 17.8 to 21.0 mg/l with mean 19.3 mg/l. There is no correlation of F with chemical parameters except calcium. The Ca has shown inverse proportional with F. Water–rock interaction studies were also carried out to understand the behavior of F in groundwater at prominent F affected areas. Rock samples were collected and analyzed, and found their enrichment of F. The anthropogenic possibility of F is almost negligible. The rocks of this area are enriched in F from 460 to 1,706 mg/kg. It is indicated that the rock–water interaction is the main source of F in groundwater. The highest values of F are found in middle part of the region and are related to the occurrence of fluoride rich rocks and their chemical kinetic behavior with groundwater.     

Hydrogeochemical processes controlling fluoride enrichment within alluvial and hard rock aquifers in a part of a semi-arid region of Northern India

Rock–water interaction along with mineral dissolution/ precipitation plays a profound role in the control of fluoride ion concentration within the alluvial groundwater in a part of semi-arid northern India. In the premonsoon season, the alluvial region experiences evaporative processes leading to increase in Na⁺ ions which through reverse ion exchange processes are adsorbed onto suitable sites within the aquifer matrix in exchange for Ca²⁺ ion in solution. Increase in Ca²⁺ ions in solution inhibits fluorite mineral dissolution, thereby controlling premonsoon fluoride ion concentration within alluvial groundwaters (1.40?±?0.5 mg/l). In the postmonsoon season, however, higher average fluoride ion concentration within the alluvial aquifer samples (2.33?±?0.80 mg/l) is observed mainly due to increase in silicate weathering of fluoride-bearing rocks and direct ion exchange processes enabling Ca²⁺ ion uptake from solution accompanied with the release of fluoride ions. Combined effect of these processes results in average fluoride ion concentration falling above the WHO drinking water permissible limit (1.5 mg/l). Alternatively, the hard rock aquifer samples within the study area have an average fluoride ion concentration falling below the permissible limit in both the seasons.     

Geochemistry of fluoride rich groundwater in Kolar and Tumkur Districts of Karnataka

Groundwater is a significant water resource in India for domestic, irrigation, and industrial needs. By far the most serious natural groundwater-quality problem in India, in terms of public health, derives from high fluoride, arsenic, and iron concentrations. Hydrogeochemical investigation of fluoride contaminated groundwater samples from Kolar and Tumkur Districts in Karnataka are undertaken to understand the quality and potability of groundwater from the study area, the level of fluoride contamination, the origin and geochemical mechanisms driving the fluoride enrichment. Majority of the groundwater samples did not meet the potable water criteria as they contained excess (>1.5 mg/L) fluoride, dissolved salts (>500 mg/L) and total hardness (75–924 mg/L). Hydrogeochemical facies of the groundwater samples suggest that rock weathering and evaporation–crystallization control the groundwater composition in the study area with 50–67% of samples belonging to the Ca–HCO₃ type and the remaining falling into the mixed Ca–Na–HCO₃ or Ca–Mg–Cl type. The saturation index values indicated that the groundwater in the study area is oversaturated with respect to calcite and under-saturated with respect to fluorite. The deficiency of calcium ion concentration in the groundwater from calcite precipitation favors fluorite dissolution leading to excess fluoride concentration.     

Geochemical Modelling of Fluoride Concentration in Hard Rock Terrain of Madhya Pradesh, India

The aim of the present study is to locate and decipher the groundwater quality,types,and hydrogeochemical reactions,which are responsible for elevated concentration of fluoride in the Chhindwara district in Madhya Pradesh,India.Groundwater samples,quality data and other ancillary information were collected for 26 villages in the Chhindwara District,M.P.India during May 2006.The saturation index was computed for the selected samples in the region,which suggest that generally most of the minerals are saturated with respect to water.The concentration of fluoride in the region varies from 0.6 to 4.74 mg/l,which is much higher as per the national and international water quality standards.The study also reveals that the fluoride bearing rock formations are the main source of the higher concentration of fluoride in groundwater along with the conjuncture of land use change.Moreover,the area is a hard rock terrain and consists of fractured granites and amygdaloidal and highly jointed compact basalt acting as good aquifer,which is probably enriching the high content of fluoride in groundwater.High concentration of fluoride is found in deeper level of groundwater and it is possible due to rock-water interaction,which requires further detailed investigation.The highly alkaline conditions indicate fluorite dissolution,which works as a major process for higher concentration of fluoride in the study area.The results of this study will ultimately help in the identification of risk areas and taking measures to mitigate negative impacts related to fluoride pollution and toxicity.     

Groundwater quality in the lower Varuna River basin,Varanasi district,Uttar Pradesh

The lower Varuna River basin in Varanasi district situated in the central Ganga plain is a highly productive agricultural area, and is also one of the fast growing urban areas in India. The agricultural and urbanization activities have a lot of impact on the groundwater quality of the study area. The river basin is underlain by Quaternary alluvial sediments consisting of clay, silt, sand and gravel of various grades. The hydrogeochemical study was undertaken by randomly collecting 75 groundwater samples from dug wells and hand pumps covering the entire basin in order to understand the sources of dissolved ions, and to assess the chemical quality of the groundwater through analysis of major ions. Based on the total dissolved solids, two groundwater samples are considered unsuitable for drinking purpose, but all samples are useful for irrigation. Graphical treatment of major ion chemistry by Piper diagram helps in identifying hydro-geochemical facies of groundwaters and the dominant hydrochemical facies is Ca-Mg-HCO₃ with appreciable percentage of the water having mixed facies. As per Wilcox’s diagram and US Salinity laboratory classification, most of the groundwater samples are suitable for irrigation except two samples (No’s 30 and 68) which are unsuitable due to the presence of high salinity and medium sodium hazard. Irrigation waters classified based on residual sodium carbonate, have revealed that all groundwaters are in general safe for irrigation except one sample (No. 27), which needs treatment before use. Permeability index indicates that the groundwater samples are suitable for irrigation purpose. Although the general quality of groundwater of the lower Varuna River basin is suitable for irrigation purpose, fifty seven percent of the samples are found having nitrate content more than permissible limit (>45 mg/l) which is not good for human consumption. Application of N-Fertilizers on agricultural land as crop nutrients along the Varuna River course may be responsible for nitrate pollution in the groundwater due to leaching by applied irrigation water. The other potential sources of high nitrate concentration in extreme northern, southern and southwestern parts of study area are poor sewerage and drainage facilities, leakage of human excreta from very old septic tanks, and sanitary landfills. The high fluoride contamination (>1.5 mg/l) in some of the samples may be due to the dissolution of micaceous content in the alluvium. Nitrate and fluoride contamination of groundwater is a serious problem for its domestic use. Hence an immediate protective measure must be put into action in the study area.     

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.     

Fluoride incidence in groundwater in an area of Peninsular India

Groundwater samples were collected from Anantapur District, Andhra Pradesh, India. The district is mainly underlain by Peninsular Gneisses of Archaean age. The samples were analysed for fluoride (F^–) along with other chemical parameters. The results suggest that the main sources of F^– in groundwater in the district are the country rocks, in which fluorine is strongly absorbed in soils consisting of clay minerals. A strong positive correlation between F^– and lithogenic sodium reflects weathering activity. This is responsible for the leaching of F^–, which is also caused by the semi-arid climate and intensive irrigation in the area. An alkaline environment of circulating water in the investigated area mainly facilitates leaching of F^– from the soils, contributing to high F^–-containing groundwater. A longer residence time of water in the aquifer zone, caused by a high rate of evapotranspiration and a weathered zone of low hydraulic conductivity, which promotes the dissolution of fluorine-bearing minerals, is another factor that further increases the F^– content in groundwater. Suggestions are made to improve groundwater quality and, thus, the health status of the population.     

Geochemical processes regulating groundwater chemistry with special reference to nitrate and fluoride enrichment in Chhatarpur area, Madhya Pradesh, India

The present study focuses on the hydrogeochemical composition of groundwater in Chhatarpur area with special focus on nitrate and fluoride contamination, considering the fact that groundwater is the only major source of drinking water here. Carbonate and silicate mineral weathering followed by ground water–surface water interactions, ion exchange and anthropogenic activities are mainly responsible for high concentrations of cations and anions in the groundwater in the region. The average concentration of nitrate and fluoride found in 27 samples is 1.08 and 61.4 mg/L, respectively. Nitrate enrichment mainly occurs in areas occupied with intense fertilizer practice in agricultural fields. Since the area is not dominated by industrialization, the possibility of anthropogenic input of fluoride is almost negligible, thus the enrichment of fluoride in groundwater is only possible due to rock–water interaction. The highly alkaline conditions, which favor the fluorite dissolution, are the main process responsible for high concentration of fluoride.     

Morphological Dynamics of the Rivers of Brahmaputra

The Singrauli region is known for fluoride contamination and its effect on human population. In this work the possible sources of fluoride contamination in Rihand reservoir water is constrained. They include slurry water, fly ash and coal samples of various thermal power plants, coal seams and granites of the region. Petrographic study depicted the presence of fluoride bearing minerals - flour apatite in pink granite. Preliminary scanning electron microscope studies revealed presence of fluorine peak in coal samples. The chemical analysis confirmed the presence of fluoride in fly ash (12.6 mg/kg), drain water (5.34 mg/l), soil (6.1 mg/kg), coal (3.1 mg/kg). They confirmed the source of fluoride from coal of thermal power plant which utilized coal from Singrauli coal seam (1.6 mg/kg). Further the Rihand reservoir water is also enriched by fluoride contaminant (upto 4.7 mg/l). This contaminates groundwater of the area as well. The contaminated water used for drinking and agriculture affects health of inhabitants in the area. It is concluded that the main source of fluoride contamination in the study area is due to coal burnt in thermal power plant and pink granite formation of the area, both anthropogenic and geogenic sources are implied.     

Fluoride occurrence and mobilization in geo-environment of semi-arid Granite watershed in southern peninsular India

Plausible forms of fluoride (F) responsible for the persistence of fluoride toxicity in ground water of a granitic terrain of semi-arid region, which is the main source of drinking water, have been studied. The study area in Anantapur District of Andhra Pradesh, India, is one of the chronic regions with excess fluoride in groundwater and the region is under transformation into aridity due to poor rainfall and over-exploitation of groundwater. Geochemical analysis of soil, groundwater, and rock samples of the study area revealed the presence of other toxic elements also in addition to fluoride which need to be addressed in drinking water sector in near future. Soil fluoride leaching experiments demonstrated the probable mode of mobilization of F into the groundwater through natural recharge process during monsoon. Analysis of saturation indices indicates that the fluorite solubility alone is not attributable to the high fluoride content in groundwater. The groundwater flow controls fluoride mobilization in the study area as it is evidenced through fluoride concentration and electrical conductivity increase from catchment to downstream region. Creation of lesser fluoride groundwater sources through rainwater harvesting and artificial recharge of groundwater in catchment areas is suggested as a long-term sustainable safe drinking water strategy.     

Factors influencing the high fluoride concentration in groundwater of Vellore District,South India

Most of the arid and semi-arid zones of the Indian subcontinent experience serious health problems due to high concentration of fluoride in drinking water. The Vellore District of Tamil Nadu suffers from high concentration of fluoride in water. However, most of the past studies in this region focused on tannery-related pollution and not on fluoride contamination. The present study attempts to identify the factors influencing the origin and spatial distribution of fluoride in the district. From the observed hydrochemical results of 68 well samples in the context of water level, well depth and hydrochemical parameters, F^? concentration showed increasing trend in the presence of Na⁺ and HCO₃ ^?. This is due to the alkaline nature of groundwater that favors the dissolution of F^?-rich minerals. The occurrence of high fluoride in Na–HCO₃ type of water confirmed this hypothesis. However, Ca²⁺ showed an insignificant correlation with F^?. The high Na/Ca ratio (>1) in 73 % of the samples and the result of Na/Na+Cl plot suggest the occurrence of cation exchange in the study area. The major source of F^? was identified as products of the weathering and the dissolution of fluorites, amphiboles and micas present in the geological formations in the study area. The positive relationship between NO₃ ^? and F^? in few wells located in agricultural fields suggest possible source of F^? from the application of fertilizers. More than 25 % of the samples had higher values of fluoride than the permissible limit of drinking water according to Indian standards. Spatial distribution of fluoride showed a higher concentration in the southwest part of the study area, namely, Thirupathur and Vaniyambadi. This study shows that contamination was high in certain parts of Vellore District and the quality of water must be maintained by resorting to appropriate treatment and management strategies.     

Inferring the chemical parameters for the dissolution of fluoride in groundwater

Geochemical study of groundwater from 58 selected fluoride-rich areas in different parts of India that includes eight states indicates that: 1. These groundwaters are alkaline in pH (7.4-8.8) and their electrical conductivity varies from 530-2,680 µS/cm and fluoride concentration from 1.7-6.1 mg/l. Presence of fluoride-bearing minerals in the host rocks and their interaction with water is considered to be the main cause for fluoride in groundwater. 2. The decomposition, dissociation and dissolution are the main chemical processes for the occurrence of fluoride in groundwater. During rock-water interaction, concentration of fluoride in rock, aqueous ionic species and residence time of interaction, etc. are also important parameters. 3. This study indicates that 85% groundwater samples have EC: 1,000-2,000 µS/cm, pH: 7.5-8.5, and HCO₃/Ca (epm ratio): 0.8-2.3. 4. The Ca and HCO₃ contents of groundwater samples have shown good correlation with fluoride.     

化隆—循化盆地不同类型含水层组高氟地下水的分布及形成过程

天然成因的高氟地下水是世界范围内备受关注的环境问题和饮用水安全问题。前人对高氟地下水的形成过程已开展了大量研究,但是对于高原盆地复杂水文地质条件下不同类型含水层组(第四系松散层含水层、基岩裂隙或岩溶含水层以及新生代古近纪以来的碎屑岩含水层)高氟地下水的分布和形成过程尚不明确。本文以化隆—循化盆地为研究区,通过采集、测试研究区内的各类地下水样品,分析研究区内不同类型含水层中地下水的化学特征及同位素特征。结果表明,高氟地下水(1.007.73 mg/L)主要分布在沿黄河的河谷区域和巴燕低山丘陵区域的泉水和潜水中以及深部的承压水中,在垂向上高氟地下水无明显分布规律。接受黄河水入渗补给的河谷潜水中氟离子浓度较低,补给黄河的河谷潜水中氟离子浓度较高。贫钙富钠的弱碱性苏打型水有利于地下水中氟的富集。泉水和潜水中氟主要来源于萤石的溶解,而承压水中氟除了来源于萤石外,还来源于其他含氟矿物。对于潜水和第四系松散层泉水,蒸发浓缩作用促进了地下水中氟的富集。另外,阴离子竞争吸附作用、阳离子交换吸附作用是泉水(第四系松散层泉水和基岩裂隙泉水)和潜水中氟元素富集的主要原因,而承压水中氟离子浓度受竞争吸附作用影响较大,阳离子交换吸附作用影响较小。研究成果可为化隆—循化盆地低氟地下水的勘查和开发提供科学依据。     

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.     

Fluoride contamination of groundwater and its seasonal variability in parts of Purulia district,West Bengal,India

The contamination of aquifers by fluoride and arsenic is a major cause of concern in several parts of India. A study has thus been conducted to evaluate the extent and severity of fluoride contamination and also its seasonal variability. Two blocks (Purulia-1 and Purulia-2) were considered for this purpose. Twenty groundwater samples (in each season) were collected from tube wells during the pre-monsoon and post-monsoon seasons. In addition to fluoride, groundwater samples were also analyzed for major cations, anions, and other trace elements. The concentration of fluoride shows significant seasonal variation and ranges between 0.94–2.52 and 0.25–1.43 mg/l during the pre-monsoon and post-monsoon seasons, respectively. In pre-monsoon season, more than 40% of the water samples show fluoride concentrations higher than the WHO limit. However, during the post-monsoon season, none of the groundwater sample shows fluoride concentrations higher than the WHO limit. Lesser concentration during the post-monsoon season is attributed to the dilution effect by the percolating rainwater, which has also been reflected in the form of a decrease in concentrations of other elements. The petrographic studies of the rock samples collected from the study area show that the rocks are mainly composed of plagioclase, orthoclase, and quartz with abundant biotite. The weathering and dissolution of biotite plays an important role in controlling the fluoride concentrations in the groundwater of the study area.     

Regional appraisal of the fluoride occurrence in groundwaters of Andhra Pradesh

Fluoride (F^?) is essential for normal bone growth, but higher concentration in the drinking water causes health problems which are reported in many states of India. Andhra Pradesh is one of the states which suffer from excess fluoride in groundwater particularly in the hard rock terrain. In this context, a study was conducted in Andhra Pradesh based on chemical analysis of water samples from hydrograph net work stations (dug wells) and exploratory bore wells. The concentration of fluoride in groundwaters ranges from traces to 9.75 mg/l. The occurrence of fluoride is mostly sporadic, uneven and varies with depth. The highly affected districts include Nalgonda and Warangal in Telangana region, Prakasam in coastal region, Anantapur and Kurnool in Rayalaseema region. In certain areas of Nalgonda district, 85% of wells have fluoride more than permissible limit (> 1.5 mg/l) for drinking water. High F^? is present in all the geological formations, predominantly in granitic aquifers, compared to the other formations. The average value of fluoride is high in the deeper zone (1.10 mg/L), compared to the shallow zone (0.69 mg/L). The fluoride-rich minerals present are the main sources for fluoride concentrations in groundwater. Residence time, evapotranspiration and weathering processes are some of the other supplementary factors for high fluoride concentrations in groundwater. Long-term data of hydrograph net work stations (dug wells) reveal that fluoride concentrations do not show any marked change of trend with respect to time. The concentration of fluoride is found to increase with increase of Na⁺and HCO ₃ ^? , and decrease with increase of Ca²⁺. Sodium bicarbonate waters are more effective in releasing fluoride from minerals into groundwater. High fluoride waters are of Na⁺ type. The paper presents a brief account of the study and its results.     

Environmental assessment of soil,groundwater, and surface water quality in the south of the Riyadh,Saudi Arabia

To understand the impact of the influence of treated wastewater, a study was undertaken in the downstream side of Wadi Hanifa in the southern part of Riyadh City in Saudi Arabia. Chemical elements from 17 groundwater samples, 9 surface water samples (treated wastewater), and 14 soil samples were analyzed. Water facies analyses showed that both groundwater and surface water belong to the SO₄-Cl class. However, the groundwater is characterized by high salinity (average value of 3547 mg/l), which may be result of the greater rock-water interaction and limited rainfall recharge. The NO₃ values are also high in the groundwater samples (average value of 40 mg/l) and are mainly attributed to the agricultural practices in the study area. The surface water samples (treated wastewater from the plant) shows an average salinity value of 1232 mg/l and is better suited for irrigation purposes. Heavy elements analyzed in the soil samples show high concentrations of all the elements except Mn and Ni as compared to their background concentration. Enrichment factor and index of geoaccumulation calculated from the soil samples indicate that they are severely enriched with respect to Cd and Se. The spatial distribution maps were prepared based on kriging interpolation technique to estimate the concentrations of the analyzed elements at unknown locations. The treated wastewater in the study area is better suited for agricultural and domestic activities as compared to groundwater.     

Integrated use of geophysical, hydrological and geographic information system (GIS) methods in enhancing the groundwater quality in a fluoride-endemic terrain (Andhra Pradesh, India)

The concept of groundwater recharge and quality improvement is often implemented in arid and semi-arid areas with depleted aquifers. Nalgonda district in Andhra Pradesh, India, has endemic fluoride, with concentrations in drinking water varying between 3 and 8?mg/l. Numerous techniques adopted in the recent past for defluoridizing groundwater proved to have limitations. The integrated approach of a geographic information system (GIS) and an analytic hierarchy process (AHP), to identify suitable sites for recharge structures over an area of ??115?km², is highlighted. Further, to validate the delineated sites, a micro-watershed basin (2?km²) was selected for detailed recharge assessment and site feasibility studies through geophysical and tracer tests. Groundwater velocity (7?m/day) and flow direction through fractures in the shallow horizon were established through tracer experiments. The efficacy of the recommended recharge structures and their impact on groundwater quality were assessed over a period of 5?years, from 2002 to 2007, and the mean groundwater fluoride concentration of?>?3.5?mg/l over the study area was brought down to?<?1.5?mg/l.     

Environmental fate and health exposures of the geogenic and anthropogenic contaminants in potable groundwater of Lower Ganga Basin,India

The study evaluated the sources and controlling factors of the groundwater contaminants in an agroeconomic region of Lower Ganga Basin using principal component analysis (PCA), multivariable linear regressions (MLR), correlation analysis, and hierarchical cluster analysis, and evaluated the public health risks using the Latin Hypercube Sampling, goodness-of-fit statistics, Monte Carlo simulation and Sobol sensitivity analysis based on the 1000 samples collected in two sampling cycles (N = 1000). The study reveals that the dissolution of fluoride-bearing minerals and semi-arid climate regulate the fluoride concentrations (0.10–18.25 mg/L) in groundwater. Extensive application of inorganic nitrogenous fertilizers and livestock manure mainly contributed to elevated nitrate levels (up to 435.0 mg/L) in groundwater. The health risks analysis indicates that fluoride exposure is more prevalent in the residents of each age group than the nitrate and both contaminants exhibited higher non-carcinogenic health risks on the infant and child (minor) age groups compared to adolescents and adults. Based on the cokriging interpolation mapping, the minor residents of 17.88%–23.15% of the total area (4545.0 km²) are vulnerable to methemoglobinemia whereas the residents of all age-groups in 38.47%–44.45% of the total area are susceptible to mild to severe dental/skeletal fluorosis owing to consumption of untreated nitrate and fluoride enriched groundwater. The Sobol sensitivity indices revealed contaminant levels, groundwater intake rate and their collective effects are the most influential factors to pose potential health risks on the residents. Artificial recharge and rainwater harvesting practices should be adopted to improve the groundwater quality and the residents are advised to drink purified groundwater.