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,NaCO_3 and Na-Cl.The aqueous concentrations of F~- and CO_3~(2-) show positive correlation whereas F~- and Ca~(2+) 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-HCO_3 to Na-HCO_3) 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.     

Geochemical (process based) characterization of groundwater along the KT boundary of South India

A study has been carried out in KT (Cretaceous-Tertiary) boundary along the contact zones of hard rock, limestone and sedimentary formations to discern the geochemical processes governing the groundwater chemistry. A total of sixty-three groundwater samples were collected from the handpumps covering the entire study area and measured for hydrochemical species. Principal component analysis of the hydrochemical data inferred three major processes governing the geochemistry of the groundwater of the region as leaching, ion exchange and weathering. It was also inferred that there are few samples depicting the mixtures of these processes (what are they mention it) and few samples not representing any of these processes with adequate statistical significance. Hence, in order to know the geochemical behaviour of the samples representing each process, their combinations along with the samples which are not- representative samples of these processes were inferred using various standards plots to get an insight into their geochemical characteristics and affinity. This also inferred the samples representing different processes have a significant signature of geochemical facies. The major ions and the stable isotopes of groundwater were used to understand these processes. The carbonate and sulphate saturation states of these samples were calculated by PHREEQC and compared with major variations with the identified three geochemical processes. The state of saturation of Halite, Anhydrite, Gypsum, Aragonite, Dolomite, Calcite, Talc and Chrysolite were determined in all the samples. Inverse modeling was carried out considering the non-representative samples as initial solution and the samples representing each factor as final solution to understand the phase mole transfer in each process. An attempt was also made in this study to compare the geochemical behaviour of groundwaters from different KT boundaries. The samples representing these processes were plotted on an integrated map representing lithology, lineaments, drainage and elevation to determine their interrelationships. The study groups the samples into anthropogenic or geogenic. The leaching process is controlled by lithology and landuse, ion exchange processes is influenced by lithology and drainage patterns whereas weathering processes were controlled by lithology, drainage and lineaments. Non representation of samples (NRS) were mainly controlled by drainage and lineaments of the region.     

The impact of paleo-channel on groundwater contamination,Andhra Pradesh,India

 Nakka vagu, a tributary of the River Manjira in the Medak district of Andhra Pradesh, has a catchment area of ∼500 km². Patancheru is an industrial development area (IDA) near the vagu. There are about 350 industries of varied nature (pulp, plastic, bulk drugs, pharmaceuticals, paints and steel rolling mills) that are engaged in the manufacture/processing of their respective products and that use water extensively. The hydrogeological setup has a bearing on the widespread contamination in the area because of discharge of industrial effluents into open land and streams. Several dug wells and boreholes situated in the study area have been monitored for water level fluctuations and quality variations. Pumping tests have been conducted to evaluate aquifer parameters. The geology, drainage, chemistry and other related anthropogenic factors play a major role in the spread of pollution in the area. Hence, it is very important to determine the degree of vulnerability to pollution based on hydrogeological factors. Amidst the granite terrain, the Nakka vagu has been identified as a paleo-channel (composed of clay–silt–sand facies); its presence in the area has immensely increased the spread of groundwater contamination. The transmissivity of the alluvial aquifer varies from 750 to 1315 m²/day. The adjoining granite has a transmissivity that varies from 30–430 m²/day. The thickness of the valley fill in the discharge region is about 10–12 m, with a lateral spread of 500–700 m, east of Nakka vagu. Received: 17 November 1999 · Accepted: 14 March 2000     

区域地下水污染调查取样点布设量化分配方法

在区域尺度、有限样品的地下水污染调查中,密度控制可以计算区域总样品数量,但取样点布设应综合考虑地质环境、人类活动等方面的差异性。目前,样点布设主要依赖技术人员经验,存在较强的不确定性,如何科学布设取样点是需要解决的一个科学问题。针对这个问题,文章基于实际工作创建了“区域预分配、单元再优选”的解决方法。在区域上,基于层次分析法构建量化分配模型,以背景控制因素和潜在污染因素建立分配因子组合,运用指数标度量化定性因子、标度函数计算定量因子,通过矩阵运算获取每个分配单元的样品预分配数量;在单元内,按照分段控制、条件优选的方法提高取样点针对性和代表性。利用构建的分配方法,以拉萨河流域地下水水质调查为案例进行了取样点布设分配应用,确定了各单元样品分配数量。结果表明:考虑背景控制和潜在污染的层次分析模型及量化计算平衡了拉萨河流域不同分配单元对样品的实际需求,解决了城关区面积小样品需求多、当雄县面积大样品需求少等问题;分段控制、条件优选的方法明确了分配单元内取样点选择依据。本方法的构建为地下水污染调查取样点布设提供了必要的方法支撑。     

Geochemical characterization of groundwater from an arid region in India

A study on the geochemical processes in arid region of western India (Kachchh district) was carried out using major, minor, trace metal data and isotopic composition (δ²H, δ¹⁸O) of groundwaters. Results indicate that the distribution of chemical species in groundwater of this district is controlled by leaching of marine sediments, dissolution of salts in root zone and incongruent dissolution of carbonate minerals. Common inorganic contaminants such as fluoride, nitrate and phosphate are within drinking water permissible limits. However, most of the samples analyzed contain total dissolved salts more than desirable limits and fall in doubtful to unsuitable category with regard to irrigational purpose. Trace metal data indicates no contamination from toxic elements such as arsenic and lead. An increased salt content is observed in groundwater at shallower depths indicating mixing with surface water sources. The chemical characteristics of the groundwater have found to be strongly dependent on the local lithological composition. Environmental isotopic data indicates that the groundwater is of meteoric origin and has undergone limited modification before its recharge. The processes responsible for observed brackishness are identified using chemical and isotope indicators, which are in agreement with subsurface lithology and hydrochemistry. These data though represent hydrochemical scenario of 2001 can still be used for understanding the long-term fluctuations in water chemistry and would be quite useful for the planners in validating groundwater quality models.     

Nitrate contamination in groundwater of Sopore town and its environs,Kashmir, India

An attempt has been made in this research work to evaluate the concentration of nitrate in groundwater and its management in Apple town and its environs. Groundwater pollution has been reported in many aquifers because of high concentration of nitrate in ground water, which is the result of excessive use of fertilizers to cropland. Systematic sampling was done, with a view to understand the source of nitrate concentration in the study area. Fifteen sample sites were selected and the samples were taken for a baseline study to understand the geochemistry of the study area and to assess its physicochemical characteristics. The water quality parameters were investigated for summer (May, 2007) and winter (December, 2007) seasons and were compared with the standard values given by ICMR / WHO. The hydrochemical data of 15 samples indicates that the concentration of almost all parameters fall within the permissible limits except nitrate. Linear Trend Analysis on seasonal and annual basis clearly depicted that nitrate pollution in the study area is increasing significantly. About 85% of samples during summer season and 67% of the samples during winter season were showing a high concentration of nitrate, exceeding permissible limit of WHO (50 mg/l), which is due to the use of nitrogenous fertilizers in the study area. Appropriate methods for improving the water quality and its management in the affected areas have been suggested.     

Assessment of groundwater quality in and around Vedaraniyam,South India

Groundwater from 47 wells were analyzed on the basis of hydrochemical parameters like pH, electric conductivity, total dissolved solids, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, CO₃ ^2?, HCO₃ ^?, NO₃ ^?, PO₄ ^3? and F^? in the Cauvery delta of Vedaraniyam coast. Further, water quality index (WQI), sodium percentage (Na %), sodium absorption ratio, residual sodium carbonate, permeability index and Kelley’s ratio were evaluated to understand the suitability of water for drinking and irrigation purposes. The result shows significant difference in the quality of water along the coastal stretch. The order of dominance of major ions is as follows: Na⁺ ≥ Mg²⁺ ≥ Ca²⁺ ≥ K⁺ and Cl^? ≥ HCO₃ ^? ≥ CO₃ ^2? ≥ PO₄ ^3? ≥ F^?. Na/Cl, Cl/HCO₃ ratio and Revelle index confirmed that 60–70 % of the samples were affected by saline water intrusion. WQI showed that 36 % of the samples were good for drinking and the remaining were poor and unsuitable for drinking purpose. The degradation of groundwater quality was found to be mainly due to over-exploitation, brackish aquaculture practice, fertilizer input from agriculture and also due to domestic sewage.     

Geochemical assessment of groundwater contamination with special emphasis on fluoride concentration, North Jordan

The concentrations of fluorine in groundwater of North Jordan range from 0.009 to 0.055 mg/l. Other chemical parameters, e.g. pH, EC, TDS, Cl, TH, HCO₃, PO₄, SO₄, NO₃, NH₄, K, Ca, Mg, and NO₃ have been studied and showed higher concentrations in HCO₃⁻ and NO₃⁻ of 307 and 51 mg/l, respectively. Thermodynamic considerations show that almost all the analyzed samples are undersaturated with respect to calcite and fluorite. This undersaturation is probably due to their low availability in the locations. Fluoride concentration shows a positive relation to pH and HCO₃, whereas Cl, Mg, Ca, and Na initially increase and then decrease with increasing fluoride in the water. Saturation indexes of fluorite and calcite are estimated. The chemistry of the groundwater is controlled by the fluorite and calcite solubility. The topography of the area has exerted control on the aerial extent of fluoride concentration.     

Hydrogeological investigation of a groundwater contamination site in southern Taiwan

 Groundwater samples taken from wells adjacent to a food machinery manufacturing plant in southern Taiwan indicate that there is a serious phenolic contamination. To understand the hydrogeological properties, and to prepare for remedial action, a series of hydrogeological investigations were conducted. Investigative work included collecting background information, analyzing existing data, measuring the groundwater, and conducting a slug test, pumping and recovery test, aerial photography analysis and electrical resistivity survey. Results from these investigations show that the local groundwater aquifer may be classified as an unconfined or confined formation, depending on the thickness of the interbedded clay layer. The direction of local groundwater flow is from southwest to northeast, with high transmissivity. The contaminant moves much more slowly than the average groundwater velocity, and it is limited to an area centered around the plant. The local geology of the contaminated area exhibits significant heterogeneity; it is not likely to have been formed by natural sedimentation. Data from the field aerial photography analysis and electrical resistivity survey also suggest that this shallow formation may result from artificial back-filling. Received: 1 September 1994 · Accepted: 28 December 1995     

Hydrogeochemical assessment of groundwater in Neyveli Basin, Cuddalore District, South India

In the light of progressive depletion of groundwater reservoir and water quality deterioration of the Neyveli basin, an investigation on dissolved major constituents in 25 groundwater samples was performed. The main objective was detection of processes for the geochemical assessment throughout the area. Neyveli aquifer is intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural area. Besides semi-aridity, rapid social and economic development stimulates greater demand for water, which is gradually fulfilled by groundwater extraction. Groundwaters of the study area are characterized by the dominance of Na?+?K over Ca?+?Mg. HCO₃ was found to be the dominant anion followed by Cl and SO₄. High positive correlation was obtained among the following ions: Ca–Mg, Cl–Ca,Mg, Na–K, HCO₃–H₄SiO₄, and F–K. The hydrochemical types in the area can be divided into two major groups: the first group includes mixed Ca–Mg–Cl and Ca–Cl types. The second group comprises mixed Ca–Na–HCO₃ and Ca–HCO₃ types. Most of the groundwater samples are within the permissible limit of WHO standard. Interpretation of data suggests that weathering, ion exchange reactions, and evaporation to some extent are the dominant factors that determine the major ionic composition in the study area.     

Geochemical characterization and heavy metal contamination of groundwater in Satluj River Basin

Groundwater, a renewable and finite natural resource, vital for man’s life, social and economic development and a valuable component of the ecosystem, is vulnerable to natural and human impacts. The aim of present study is to evaluate hydrogeochemical parameters and heavy metals in groundwater and to study their spatial distribution in the Rupnagar District of Punjab. The spatial distribution of physico-chemical parameters were studied using Arc GIS 9.2. It was observed that the concentration of parameters, such as NO₃, Cd, Cr, Mn and Pb was above permissible limit (World Health Organization, WHO) in southern part of the study area. The heavy metal pollution index (HPI) was calculated for all sampling locations and it was found much above the critical limit of pollution. Geochemical reaction models of selected water groups were constructed using Phreeqc. Geochemical modeling suggests that sodium has source other than halite-albite and calcium has alternate source other than gypsum-carbonate or silicates. It also suggests that evaporites, ion exchange, dissolution along with anthropogenic activities are controlling the hydro-geochemistry of groundwater in the region. Various indices, such as heavy metal pollution index, permeability index, sodium adsorption ratio, were studied to verify suitability of groundwater for drinking and irrigation.     

Geochemical characterization of groundwater from northeastern part of Nagpur urban,Central India

Hydrogeochemical investigations are carried out in the northeastern part of Nagpur urban to assess the quality of groundwater for its suitability for drinking and irrigation purposes. Groundwater samples are collected from both shallow and deep aquifers to monitor the hydrochemistry of various ions. The groundwater quality of the area is adversely affected by urbanization as indicated by distribution of EC and nitrate. In the groundwater of study area, Ca²⁺ is the most dominant cation and Cl⁻ and HCO₃ ⁻ are the dominant anions. Majority of the samples have total dissolved solids values above desirable limit and most of them belong to very hard type. As compared to deep aquifers, shallow aquifer groundwaters are more polluted and have high concentration of NO₃ ⁻. The analytical results reveal that most of the samples containing high nitrate also have high chloride. Major hydrochemical facies were identified using Piper trilinear diagram. Alkaline earth exceeds alkalis and weak acids exceed strong acids. Shoeller index values reveal that base-exchange reaction exists all over the area. Based on US salinity diagram most of samples belong to high salinity-low sodium type. A comparison of groundwater quality in relation to drinking water standards showed that most of the water samples are not suitable for drinking purpose.     

Assessment of groundwater contamination from a hazardous dump site in Ranipet, Tamil Nadu, India

Tanneries located in an industrial development area of Ranipet (India) manufactured chromate chemicals during 1976?C1996. A large quantity of associated hazardous solid wastes has been stacked about 5-m high above ground level, spread over 3.5?ha inside one of the factory premises. The study area receives an average annual rainfall of 1,100?mm. The granitic formation in the northern part of Palar River catchment has high infiltration rates and has resulted in fast migration of the contamination to the water table. Chromium levels in the groundwater were found up to 275?mg/l. The available hydrogeological, geophysical and groundwater quality data bases have been used to construct a groundwater flow and mass transport model for assessing the groundwater contamination and it has been calibrated for the next 30?years. The migration has been found to be very slow, with a groundwater velocity of 10?m/year. This is the first field-scale study of its kind in this industrial area. The findings are of relevance to addressing the groundwater pollution due to indiscriminate disposal practices of hazardous waste in areas located on the phreatic aquifer. Further, it has been reported that the untreated effluent discharge adjacent to the chromium dump site is most influential in the migration of contaminants.     

Migration and contamination of major and trace elements in groundwater of Madras city,India

Groundwater samples collected from both open and bore wells in an area of about 270 km² from Madras City, India, have been analyzed for major ions (HCO₃, Cl, Si, Na, Ca, and Mg) and trace elements (As, Se, B, V, Cr, Fe, Co, Pb, Cu, Zn, Cd, Mn, Ni, Mo, and Ba). The study reveals that the quality of potable water has deteriorated to a large extent. Seawater intrusion into the aquifer has been observed in nearly 50 percent of the study area. The toxic elements (As and Se) have already exceeded the maximum permissible limits of drinking water in almost the entire city. A positive correlation of As and Se with other toxic metals such as V, Cr, Fe, B, etc., indicates that all these elements are anthropogenic in origin. Applying multivariate analysis, the source for trace elements in groundwater has been grouped into two major factors: pollution and mobilization factors. The groundwater in the study area is largely contaminated by organic effluents and reflects the intensity of pollution caused by the overlying soil sediment and rapid infiltration of the pollutants.     

Preliminary geochemical evidence of groundwater contamination in coral islands of Xi-Sha,South China Sea

Geochemical data on dissolved major, minor and trace constituents in groundwater samples from Xi-Sha coral islands (Paratas Islands) reveal the main processes responsible for their geochemical evolution. Multivariate statistical analysis indicates four sources of solutes: (1) seawater intrusion due to limited groundwater recharge; (2) leaching of heavy metals from imported granite soil; (3) leaching of toxic elements such as As due to guano-soil erosion and historical phosphatic guano mining; and (4) local and regional contamination characterized by high loadings of Cu, Ag and Hg. Although process 1 dominates the geochemical characteristics of the groundwater, process 4 indicates the significant role of anthropogenic impact by local (e.g., Cu) and regional (e.g., Hg) sources. Such contamination in groundwater will potentially impose adverse effects on the fragile ecosystem of the coral islands. It is necessary to monitor microorganisms associated with human feces in the nearshore water column as well as nutrient levels in coastal waters in order to further assess the impact of human activities on the ecosystem of these islands.