Deterioration of coastal groundwater quality in Island and mainland regions of Ramanathapuram District, Southern India

A study was carried out in the Island and mainland regions of Ramanathapuram District to characterize the physico-chemical characteristics of 87 groundwater samples in Island and 112 groundwater samples in mainland which include pH, EC, TDS, salinity, total alkalinity, calcium hardness, magnesium hardness, total hardness, chloride and fluoride. Heavy inorganic load in majority of the groundwater samples has been estimated due to the salinity, TDS, TH and chloride beyond the threshold level which substantiates the percolation of sea water into the freshwater confined zones. Although the groundwater sources are available in plenty, the scarcity of potable water is most prevalent in this coastal area. The Water Quality Index (WQI) and Langeleir Saturation Index (LSI) have also been calculated to know the potable and corrosive/incrusting nature of the water samples. The statistical tools such as principal component analysis, box plots and correlation matrix have also been used to explain the influence of different physico-chemical parameters with respect to one another among the groundwater samples. The percentage of groundwater samples in mainland was more than that in Island with respect to the acceptable limit of WHO drinking standard, especially in TDS, CH, TH and chloride but the converse is observed in the case of fluoride. About 8 % of the mainland aquifers and 42 % of Island aquifers were identified to have fluoride greater than 1.5 mg/l. The signature of salt-water intrusion is observed from the ratio of Cl/CO ₃ ^2? ?+?HCO₃ and TA/TH. A proper management plan to cater potable water to the immediate needs of the people is to be envisaged.     

An investigation on the pollution status of holy aquifers of Rameswaram, Tamil Nadu, India

The Study area is the sacred Ramanathasamy temple and selected for the characterization of physico-chemical parameters viz., pH, EC, TDS, Salinity, TA, TH, Ca( + 2), Mg( + 2), Chloride and Fluoride for 22 groundwater samples and the impact of pre- and post-monsoon on the groundwater quality was also studied. The study area is well known for the chronic fresh water shortage and the locals depend mostly on springs for their fresh water needs. The Water Quality Index (WQI) computed shows the transfer of samples under unacceptable quality to acceptable quality. The Langelier Saturation Index (LSI) reflected that majority of the samples have the tendency to form scale. The Karl Pearson correlation matrix has approved the maximum relationship of calcium and chloride with respect to the total dissolved solids (TDS). It is interesting to conclude that the groundwater in the study area has very hard nature, especially of non-carbonate type.     

MONITORING OF SPATIAL AND TEMPORAL HYDROCHEMICAL CHANGES IN GROUNDWATER UNDER THE CONTAMINATING EFFECTS OF ANTHROPOGENIC ACTIVITIES IN MERSIN REGION, TURKEY

The development of groundwater resources for water supply is a favored way in Turkey. The Berdan alluvial aquifer in Mersin is particularly productive, but little is known about the natural phenomena that govern the groundwater quality and the contamination sources in this region. During 2001 and 2002, water samples for chemical analysis were obtained from 27 wells and from two points of Berdan River and analyzed by ICP. Main chemical characteristics of sampled groundwater define two aquifers, which were also determined by hydrogeological investigations. The groundwater produced from some of the wells was affected by anthropogenic activities temporally and spatially by seawater intrusion. Berdan River is polluted with the wastewater discharges and river water also influences the groundwater quality.     

Hydrogeochemical study of shallow carbonate aquifers, Rameswaram Island, India

Groundwater quality assessment has been carried out based on physicochemical parameters (pH, EC, TDS, CO(3), HCO(3), Cl, SO(4), PO(4), NO(2), Ca(+2), Mg(+2), Na(+) and K(+)) and metal concentration in the Rameswaram Island from 25 bore wells. The Langelier Saturation Index of the groundwater shows positive values (63% samples) with a tendency to deposit the CaCO(3) in the majority of water samples. Scatter plot (Ca + Mg/HCO(3)) suggests carbonate weathering process, which is the main contributor of Ca(2+), Mg(2+) and HCO(3) ions to the water. Gibbs diagram suggests rock-water interaction dominance and evaporation dominance which are responsible for the change in the quality of water in the study area. NaCl and mixed CaNaHCO(3) facies are two main hydrogeochemical facies of groundwater. Mathematical calculations and graphical plots of geochemical data reveal that the groundwater of Rameswaram Island is influenced by natural weathering of rocks, anthropogenic activities and seawater intrusion due to over exploitation. Weathering and dissolution of carbonate and gypsum minerals also control the concentration of major ions (Ca(+2), Mg(+2), Na(+) and K(+)) in the groundwater. The nutrient concentration of groundwater is controlled to a large extent by the fertilizers used in agricultural lands and aquaforms. Comparison of geochemical data shows that majority of the groundwater samples are suitable for drinking water and irrigation purposes.     

The occurrence and hydrochemistry of fluoride and boron in carbonate aquifer system, central and western Estonia

Silurian–Ordovician (S–O) aquifer system is an important drinking water source of central and western Estonia. The fluoride and boron contents of groundwater in aquifer system vary considerably. The fluoride concentration in 60 collected groundwater samples ranged from 0.1 to 6.1 mg/l with a mean of 1.95 mg/l in the study area. Boron content in groundwater varied from 0.05 mg/l to 2.1 mg/l with a mean value of 0.66 mg/l. Considering the requirements of EU Directive 98/83/EC and the Estonian requirements for drinking water quality, the limit value for fluoride (1.5 mg/l) and for boron (1.0 mg/l) is exceeded in 47 and 28 % of wells, respectively. Groundwater with high fluoride and boron concentrations is found mainly in western Estonia and deeper portion of aquifer system, where groundwater chemical type is HCO₃–Cl–Na–Mg–Ca, water is alkaline, and its Ca²⁺ content is low. Groundwater of the study area is undersaturated with respect to fluorite and near to equilibrium phase with respect to calcite. The comparison of TDS versus Na/(Na?+?Ca) and Cl/(Cl?+?HCO₃) points to the dominance of rock weathering as the main process, which promotes the availability of fluoride and boron in the groundwater. The geological sources of B in S–O aquifer system have not been studied so far, but the dissolution of fluorides from carbonate rocks (F?=?100–400 mg/kg) and K-bentonites (F?=?2,800–4,500 mg/kg) contributes to the formation of F-rich groundwater.     

Evaluation of groundwater quality and its suitability for drinking and agricultural use in Thanjavur city, Tamil Nadu, India

As groundwater is a vital source of water for domestic and agricultural activities in Thanjavur city due to lack of surface water resources, groundwater quality and its suitability for drinking and agricultural usage were evaluated. In this study, 102 groundwater samples were collected from dug wells and bore wells during March 2008 and analyzed for pH, electrical conductivity, temperature, major ions, and nitrate. Results suggest that, in 90% of groundwater samples, sodium and chloride are predominant cation and anion, respectively, and NaCl and CaMgCl are major water types in the study area. The groundwater quality in the study site is impaired by surface contamination sources, mineral dissolution, ion exchange, and evaporation. Nitrate, chloride, and sulfate concentrations strongly express the impact of surface contamination sources such as agricultural and domestic activities, on groundwater quality, and 13% of samples have elevated nitrate content (>45 mg/l as NO₃). PHREEQC code and Gibbs plots were employed to evaluate the contribution of mineral dissolution and suggest that mineral dissolution, especially carbonate minerals, regulates water chemistry. Groundwater suitability for drinking usage was evaluated by the World Health Organization and Indian standards and suggests that 34% of samples are not suitable for drinking. Integrated groundwater suitability map for drinking purposes was created using drinking water standards based on a concept that if the groundwater sample exceeds any one of the standards, it is not suitable for drinking. This map illustrates that wells in zones 1, 2, 3, and 4 are not fit for drinking purpose. Likewise, irrigational suitability of groundwater in the study region was evaluated, and results suggest that 20% samples are not fit for irrigation. Groundwater suitability map for irrigation was also produced based on salinity and sodium hazards and denotes that wells mostly situated in zones 2 and 3 are not suitable for irrigation. Both integrated suitability maps for drinking and irrigation usage provide overall scenario about the groundwater quality in the study area. Finally, the study concluded that groundwater quality is impaired by man-made activities, and proper management plan is necessary to protect valuable groundwater resources in Thanjavur city.     

Assessment of groundwater quality and <Superscript>222</Superscript>Rn distribution in the Xuzhou region,China

Evaluation of groundwater quality represents significant input for the development and utilization of water resources. Increasing exploitation of groundwater and man-made pollution has seriously affected the groundwater quality of the North China Plain, such as in the Xuzhou region which is the target of this investigation. The assessment of the groundwater quality and sources in the region was based on analyses of water chemistry and ²²²Rn activity in samples collected from wells penetrating unconfined and confined aquifers. The results indicate that most of the untreated groundwater in the region is not suitable for the long-term drinking based on permissible limits of the Chinese Environmental Agency and the World Health Organization. However, the groundwater can be used as healthy source of drinking water when they can pass the biological test and softening water treatment. Most of the groundwater is suitable for irrigation. Excessive amounts of SO₄^2? and NO₃^? are attributed to mainly influence of wastewater, irrigation, and dissolution of sulfate minerals in local coal strata. The major source of the groundwater is meteoric recharge with addition from irrigation and wastewater discharges. Variability of the water quality seems to be also reflecting the type of aquifers where the highest concentration of HCO₃^? occurs in water of the carbonate fractured aquifer, while the highest Cl^? concentration in the unconfined aquifer. Source of ²²²Rn activity is mainly related to the rock-water interaction with possible addition from the agricultural fertilizers. Protection of groundwater is vital to maintain sustainable drinking quality through reducing infiltration of irrigation water and wastewater.     

NITRATE CONCENTRATIONS IN RIYADH, SAUDI ARABIA DRINKING WATER SUPPLIES

Riyadh, Saudi Arabia is supplied with drinking water fromboth desalinated sea water and treated groundwater sources. Sampleswere analysed for NO₃ from selected deep and shallow wells, two locations within the city's six groundwater treatment plants, thedesalinated sea water and distribution network. Average nitrateconcentrations (as NO₃) were 8.2 and 15.8 mg/L for deep andshallow well waters, respectively. The average nitrate concentrations (asNO₃) in the groundwater treatment plants influent waters and thefinal product water were 16.2 and 8.5 mg/L, respectively. Due toblending of the plants' product water with the desalinated sea water, theaverage network nitrate concentration was 4.4 mg/L. The scheduledwater interruption does not seem to cause any appreciable change in thenitrate levels in the distribution network.     

Hydrogeochemistry and Groundwater Quality Assessment of Lower Part of the Ponnaiyar River Basin, Cuddalore District, South India

The Lower Ponnaiyar River Basin forms an important groundwater province in South India constituted by Tertiary formations dominated by sandstones and overlain by alluvium. The region enjoyed artesian conditions 50 years back but at present frequent failure of monsoon and over exploitation is threatening the aquifer. Further, extensive agricultural and industrial activities and urbanization has resulted in the increase in demand and contamination of the aquifer. To identify the sources and quality of groundwater, water samples from 47 bore wells were collected in an area of 154 km² and were analysed for major ions and trace metals. The results reveal that the groundwater in many places is contaminated by higher concentrations of NO₃, Cl, PO₄ and Fe. Four major hydrochemical facies Ca–Mg–Cl, Na–Cl, Ca–HCO₃ and Na–HCO₃ were identified using Piper trilinear diagram. Salinity, sodium adsorption ratio, and sodium percentage indicate that most of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standards. The most serious pollution threat to groundwater is from nitrate ions, which are associated with sewage and fertilizers application. The present state of the quality of the lower part of Ponnaiyar River Basin is of great concern and the higher concentration of toxic metals (Fe and Ni) may entail various health hazards.     

Groundwater depth and elevation interpolation by kriging methods in Mohr Basin of Fars province in Iran

Prediction of groundwater depth and elevation is important in quantitative water management especially in arid areas. There are several basins in southwest of Iran, in Zagross Mountain, in which the water wells are distributed along a narrow elliptic ring band around the region. To find the most applicable interpolation method, both of the groundwater depth and elevation are predicted by different kriging methods. It is found that the groundwater elevation and depth can be predicted by different methods. Furthermore, it is found that the methods in which the trend is eliminated predicted the groundwater elevation and depth in central part of the region is with less standard error. Furthermore, the methods with no trend elimination, predicted the groundwater depths with less error near the water wells. Dividing the area to hydro-geologically homogeneous sub-areas improved the interpolation precision.     

Earth-tide-induced fluctuations in the salinity of an inland river,New South Wales,Australia: a short-term study

Wybong Creek discharges salts into the agriculturally and industrially important Hunter River in New South Wales, Australia. Abrupt increases in salinity occur periodically in the mid-Wybong Creek catchment. In order to understand the processes which cause these abrupt increases, changes in surface and groundwater were investigated. It is shown that salinity increases can be attributed to highly discrete groundwater discharge directly into the river from below. Hourly electrical conductivity data measured in the river showed regular, diurnal electrical conductivity fluctuations of up to 350 μS cm^?1. These fluctuations could not be attributed to barometric pressure, temperature, or evapotranspiration. Instead, a similar periodicity in surface water electrical conductivity and groundwater height in nearby groundwater wells was found. Fluctuations were of similar periodicity to the orthotides which cause fluctuations in surface water height and are induced by Earth tides. The geology in the mid-catchment area indicates conditions are optimal for Earth tides to impact groundwater. The reporting of orthotidal changes in water chemistry in this article is believed to be the first of its kind in the scientific literature, with the large fluctuations noted having important implications for water monitoring and management in the catchment. Further research investigating Earth-tide-induced phases of groundwater heights will better constrain the relationships between surface water chemistry and groundwater height.     

GIS-based assessment and characterization of groundwater quality in a hard-rock hilly terrain of Western India

The growing population, pollution, and misuse of freshwater worldwide necessitate developing innovative methods and efficient strategies to protect vital groundwater resources. This need becomes more critical for arid/semi-arid regions of the world. The present study focuses on a GIS-based assessment and characterization of groundwater quality in a semi-arid hard-rock terrain of Rajasthan, western India using long-term and multi-site post-monsoon groundwater quality data. Spatio-temporal variations of water quality parameters in the study area were analyzed by GIS techniques. Groundwater quality was evaluated based on a GIS-based Groundwater Quality Index (GWQI). A Potential GWQI map was also generated for the study area following the Optimum Index Factor concept. The most-influential water quality parameters were identified by performing a map removal sensitivity analysis among the groundwater quality parameters. Mean annual concentration maps revealed that hardness is the only parameter that exceeds its maximum permissible limit for drinking water. GIS analysis revealed that sulfate and nitrate ions exhibit the highest (CV?>?30%) temporal variation, but groundwater pH is stable. Hardness, EC, TDS, and magnesium govern the spatial pattern of the GWQI map. The groundwater quality of the study area is generally suitable for drinking and irrigation (median GWQI?>?74). The GWQI map indicated that relatively high-quality groundwater exists in northwest and southeast portions of the study area. The groundwater quality parameter group of Ca, Cl, and pH were found to have the maximum value (6.44) of Optimum Index factor. It is concluded that Ca, Cl, and pH are three prominent parameters for cost-effective and long-term water quality monitoring in the study area. Hardness, Na, and SO₄, being the most-sensitive water quality parameters, need to be monitored regularly and more precisely.     

Groundwater quality and its suitability for domestic and agricultural use in Tondiar river basin,Tamil Nadu,India

Assessment of suitability of groundwater for domestic and agricultural purposes was carried out in Tondiar river basin, Tamil Nadu, India. The study area covers an area of 315 km² and lies in a semiarid region. Groundwater is the major source for domestic and agricultural activity in this area. Groundwater samples were collected from 45 wells during pre-monsoon and post-monsoon period in the year 2006. The water samples were analysed for physical and chemical characteristics. Suitability of groundwater for irrigation was evaluated based on salinity hazard, sodium percent, sodium adsorption ratio, residual sodium carbonate, US salinity diagram, Wilcox’s diagram, Kelly’s ratio and permeability index. Ca-HCO₃, mixed Ca–Mg–Cl and Na–Cl were the dominant groundwater types. High hardness and electrical conductivity in this area makes the groundwater unsuitable for drinking and agricultural purposes. Concentration of trace elements (Mn, Cu, Zn, Pb and Ni) did not exceed the permissible limit for drinking and agricultural purposes. Majority of the groundwater samples were unsuitable for domestic and agricultural purposes except for 31% and 36%, which were suitable for drinking and irrigation purposes, respectively.     

A pragmatic approach to study the groundwater quality suitability for domestic and agricultural usage,Saq aquifer,northwest of Saudi Arabia

The present study deals with detailed hydrochemical assessment of groundwater within the Saq aquifer. The Saq aquifer which extends through the NW part of Saudi Arabia is one of the major sources of groundwater supply. Groundwater samples were collected from about 295 groundwater wells and analyzed for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dissolved solids (TDS), Na⁺, K⁺, Ca²⁺, Mg²⁺, CO₃ ^?, HCO₃ ^?, Cl^?, SO₄ ^2?, and NO₃ ^?. Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 284 and 9,902?μS/cm with an average value of 1,599.4 μS/cm. The groundwater is highly mineralized with approximately 30 % of the samples having major ion concentrations above the WHO permissible limits. The NO₃ ^? concentration varies between 0.4 and 318.2 mg/l. The depth distribution of NO₃ ^? concentration shows higher concentration at shallow depths with a gradual decrease at deeper depths. As far as drinking water quality criteria are concerned, study shows that about 33 % of samples are unfit for use. A detailed assessment of groundwater quality in relation to agriculture use reveals that 21 % samples are unsuitable for irrigation. Using Piper’s classification, groundwater was classified into five different groups. Majority of the samples show Mix-Cl-SO₄- and Na-Cl-types water. The abundances of Ca²⁺ and Mg²⁺ over alkalis infer mixed type of groundwater facies and reverse exchange reactions. The groundwater has acquired unique chemical characteristics through prolonged rock-water interactions, percolation of irrigation return water, and reactions at vadose zone.     

Assessment of groundwater corrosiveness for unconfined aquifer system at Kalpakkam

Groundwater samples from the shallow unconfined aquifer were collected from fifteen borewells in Kalpakkam nuclear plant site and were analysed for various physico-chemical parameters. The pH, temperature, salinity, TDS and EC were measured in the field. The borewell samples were analysed in the laboratory for Ca(2+), Mg(2+), Na(+), Cl(-), [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. The Piper Trilinear diagram showed that majority of the borewell samples fall in Na - Cl +SO(4) type and Na - CO(3)+HCO(3) type. The Cl: HCO3 ratio of some borewell samples are categorized under injuriously contaminated to highly injurious type. The higher salinity levels encountered in some borewells emphasized the need for better understanding of groundwater corrosiveness. Accordingly, the Langeliar saturation Index (SI), Aggressivity index (AI) and Larson ratio (LnR) were evaluated for assessing the corrosive nature of the groundwater. The saline water incursion in the southern part of the study area increased the ionic concentration of Cl(-) and [Formula: see text] that made the groundwater corrosive.     

基于VOCs浓度反演的地下水中含油物质泄漏原位在线监测方法的建立及应用

石油石化企业的含油物质泄漏进入地下水,会对生态环境造成负面影响。通过构建地下水井模型,比选不同原理的挥发性有机物(VOCs)检测传感器,建立了基于VOCs浓度反演的地下水中含油物质泄漏原位实时在线监测方法。研究发现,常规水质六参数传感器对含油物质泄漏的响应会产生滞后现象,在实时预警监测地下水井中含油物质时可不安装常规水质六参数传感器,节约企业污染防控监测成本。将该方法应用于企业现场进行原位实时监测,当实时监测值超过数据监控平台预警阈值时,系统会发出警报,实现了地下水井中含油物质泄漏实时预警监测。该监测方法具有响应速度快、准确性高、成本低、监测过程简单等优势,将帮助企业实时掌握地下水污染状况,提高地下水污染防控预警效率。     

Design of National Groundwater Quality Monitoring Network in Egypt

In the Nile Valley and Delta the protection of groundwater resources is high priority environmental concern. Many groundwater quality problems are already dispersed and may be widespread and frequent in occurrence. Examples include problems associated with the extensive application of chemical fertilizers in agricultural specially in the new reclaimed areas, leaks in sewers, septic tanks, the aggregate effects of many different points source pollution in urban areas and natural, geologically related water quality problems. A national groundwater quality monitoring has been designed and implemented based on the stepwise procedure. The national groundwater quality monitoring network is used to quantify the quality changes in long run, either caused by pollution activities or by salt water intrusion and to describe the overall current groundwater quality status on a national scale of the main aquifers. The monitoring tools and methodologies developed in this research can be used to assure protection of public health and determine the sustainability of groundwater in various purposes. This national monitoring network plays important roles for decision makers in developing the groundwater resources management plans in different aquifers systems in Egypt.     

A novel high-frequency groundwater quality monitoring system

High-frequency, long-term monitoring of water quality has revolutionized the study of surface waters in recent years. However, application of these techniques to groundwater has been limited by the ability to remotely pump and analyze groundwater. This paper describes a novel autonomous groundwater quality monitoring system which samples multiple wells to evaluate temporal changes and identify trends in groundwater chemistry. The system, deployed near Fresno, California, USA, collects and transmits high-frequency data, including water temperature, specific conductance, pH, dissolved oxygen, and nitrate, from supply and monitoring wells, in real-time. The system consists of a water quality sonde and optical nitrate sensor, manifold, submersible three-phase pump, variable frequency drive, data collection platform, solar panels, and rechargeable battery bank. The manifold directs water from three wells to a single set of sensors, thereby reducing setup and operation costs associated with multi-sensor networks. Sampling multiple wells at high frequency for several years provided a means of monitoring the vertical distribution and transport of solutes in the aquifer. Initial results show short period variability of nitrate, specific conductivity, and dissolved oxygen in the shallow aquifer, while the deeper portion of the aquifer remains unchanged—observations that may be missed with traditional discrete sampling approaches. In this aquifer system, nitrate and specific conductance are increasing in the shallow aquifer, while invariant changes in deep groundwater chemistry likely reflect relatively slow groundwater flow. In contrast, systems with high groundwater velocity, such as karst aquifers, have been shown to exhibit higher-frequency groundwater chemistry changes. The stability of the deeper aquifer over the monitoring period was leveraged to develop estimates of measurement system uncertainty, which were typically lower than the manufacturer’s stated specifications, enabling the identification of subtle variability in water chemistry that may have otherwise been missed.     

Probability-based nitrate contamination map of groundwater in Kinmen

Groundwater supplies over 50 % of drinking water in Kinmen. Approximately 16.8 % of groundwater samples in Kinmen exceed the drinking water quality standard (DWQS) of NO₃ ^?-N (10 mg/L). The residents drinking high nitrate-polluted groundwater pose a potential risk to health. To formulate effective water quality management plan and assure a safe drinking water in Kinmen, the detailed spatial distribution of nitrate–N in groundwater is a prerequisite. The aim of this study is to develop an efficient scheme for evaluating spatial distribution of nitrate–N in residential well water using logistic regression (LR) model. A probability-based nitrate–N contamination map in Kinmen is constructed. The LR model predicted the binary occurrence probability of groundwater nitrate–N concentrations exceeding DWQS by simple measurement variables as independent variables, including sampling season, soil type, water table depth, pH, EC, DO, and Eh. The analyzed results reveal that three statistically significant explanatory variables, soil type, pH, and EC, are selected for the forward stepwise LR analysis. The total ratio of correct classification reaches 92.7 %. The highest probability of nitrate–N contamination map presents in the central zone, indicating that groundwater in the central zone should not be used for drinking purposes. Furthermore, a handy EC–pH-probability curve of nitrate–N exceeding the threshold of DWQS was developed. This curve can be used for preliminary screening of nitrate–N contamination in Kinmen groundwater. This study recommended that the local agency should implement the best management practice strategies to control nonpoint nitrogen sources and carry out a systematic monitoring of groundwater quality in residential wells of the high nitrate–N contamination zones.