大庆西部地下水位降落漏斗区水资源人工调蓄方案

对地下水资源的长期大量集中开采形成了区域性地下水位降落漏斗,地下水的超采引发了一系列环境地质问题。利用降落漏斗区腾空的地下储水空间进行水资源的人工调蓄可使地下水位得到恢复。以地下水为主要供水水源的大庆市目前已形成了东西两个大的区域性地下水位降落漏斗,必须进行地下水人工调蓄。设计并模拟了现状开采、逐年压缩分别在现采和压采基础之上进行人工回灌等4种人工调蓄方案,对大庆西部地下水位降落漏斗区进行水资源人工调蓄。结果表明,压缩开采和人工回灌均可加速降落漏斗区地下水位的恢复,在逐年压缩地下水开采量5%的情况下实施人工回灌（0.45×10⁸m³/a）,地下水位恢复效果最明显,到2010年末,漏斗中心地下水位可回升7.7~10.3 m。     

Optimization of water resources management using SWOT analysis: the case of Zakynthos Island, Ionian Sea, Greece

Zakynthos, an island of 408 km² in the Ionian Sea, is completely dependent on its groundwater resources for fulfilling the demands of the water supplies. The use of groundwater resources has become particularly intensive during the last decades because of the intense urbanization, the tourist development and the irrigated land expansion that took place. The main aquifers are developed in limestones (karstic), sandstones of neogene deposits (confined) and alluvial deposits (phreatic). This paper focuses on the assessment of their hydrogeological characteristics and the groundwater quality. For this investigation, groundwater level measurements, drilling data, pumping tests and chemical analyses of groundwater samples were used. The average annual consumption that is abstracted from the aquifer systems, is 4.9 × 10⁶ m³ year⁻¹. The exploitable groundwater reserves were estimated to be 3.3 × 10⁶ m³ year⁻¹. In the last decades, the total abstractions exceed the natural recharge, due to the tourist development; therefore the aquifer systems are not used safely. The results of chemical analyses showed a deterioration of the groundwater quality. According to the analyses the shallow alluvial aquifer and the confined aquifer are polluted by nitrates at concentrations in excess of 25 mg L⁻¹. High sulphate concentrations might be related to the dissolution of gypsum. Seawater intrusion phenomena are recorded in coastal parts of aquifer systems. The increased Cl⁻ concentrations in karstic aquifer indicate signs of overexploitation. Strengths, weaknesses, opportunities and threats (SWOT) analysis was applied in order to evaluate the SWOT of the groundwater resources. Moreover, some recommendations are made to assist the rational management that aim at improving the sustainability of the groundwater resources of Zakynthos Island.     

Seasonal variation of groundwater quality in a part of Guntur District, Andhra Pradesh, India

The area in Guntur district, Andhra Pradesh, India, is selected to discuss the impact of seasonal variation of groundwater quality on irrigation and human health, where the agriculture is the main livelihood of rural people and the groundwater is the main source for irrigation and drinking. Granite gneisses associated with schists and charnockites of the Precambrian Eastern Ghats underlie the area. Groundwater samples collected seasonally, pre- and post-monsoons, during three years from forty wells in the area were analyzed for pH, EC, TDS, TA, TH, Ca²⁺, Mg²⁺, Na⁺, K⁺, CO₃²⁻, HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻and F⁻. The chemical relationships in Piper’s diagram, Chebotarev’s genetic classification and Gibbs’s diagram suggest that the groundwaters mainly belong to non-carbonate alkali type and Cl⁻ group, and are controlled by evaporation-dominance, respectively, due to the influence of semi-arid climate, gentle slope, sluggish drainage conditions, greater water–rock interaction, and anthropogenic activities. A comparison of the groundwater quality in relation to drinking water quality standards proves that most of the water samples are not suitable for drinking, especially in post-monsoon period. US Salinity Laboratory’s and Wilcox’s diagrams, and %Na⁺ used for evaluating the water quality for irrigation suggest that the majority of the groundwater samples are not good for irrigation in post-monsoon compared to that in pre-monsoon. These conditions are caused due to leaching of salts from the overlying materials by infiltrating recharge waters. A management plan is suggested for sustainable development of the area.     

Stable isotope geochemistry of dissolved chloride in relation to hydrogeology of the strongly exploited Quaternary aquifers,North China Plain

Deep Quaternary groundwater is the main source for industrial, domestic, and agricultural water supply in the North China Plain (NCP). There is currently a regional decline of groundwater levels, deterioration of water quality and environmental geological problems induced by increasing exploitation of the NCP Quaternary aquifer system. To trace sources and transport processes of dissolved Cl⁻ in a regional aquifer system and to reveal hydrogeological characteristics of Quaternary complexes, δ³⁷Cl, δ¹⁸O and δD, and chemical compositions (including F⁻, Cl⁻, Br⁻) of the deep groundwater sampled from the northern flow system of the NCP were measured along the west–east groundwater flow paths. The measured δ³⁷Cl values decreased from 0.39‰ to −2.22‰ (SMOC) along the groundwater flow direction, with increasing Cl⁻ concentrations. Marine aerosol input via rainfall is the main source of Cl⁻ in the deep groundwater near the recharge areas, and subsequent evaporation/evapotranspiration appears to be responsible for Cl⁻ accumulation. Mixing of recharge water with water of high-Cl⁻ and low-δ³⁷Cl accounts for the pattern of δ³⁷Cl and Cl⁻ concentration observed in Aquifer-3 along the west–east transect. The water with high-Cl and low-δ³⁷Cl is likely from pore water released from compacted clays induced by over-exploitation of deep groundwater, suggesting that clay is a dominant subsurface source of Cl⁻ for groundwater where a regional depression cone is present in the Quaternary aquifers. The groundwater of Aquifer-4 in the Huang-Hua depression is potentially mixed with an upward flux of Cl⁻ from the Neogene aquifer through subvertical faults. Diffusion and ion filtration are two mechanisms invoked to explain the highly negative δ³⁷Cl data for groundwater of Aquifer-4 in the Yanshan–Haixing areas, which provides new insight into solute migration and the hydraulic relationship in the strongly exploited groundwater system. This study using the conservative solute Cl⁻ provides additional important information for further investigations of the geochemistry of a wide range of reactive solutes in the Quaternary aquifer system, so guiding water resource management.     

The hydrogeochemistry of a heavily used aquifer in the Mexican wine-producing Guadalupe Valley, Baja California

The Guadalupe Valley aquifer is the only water source for one of the most important wine industries in Mexico, and also the main public water supply for the nearby city of Ensenada. This groundwater is monitored for major ion, N-NO₃, P-PO₄, Fe, As, Se, Mo, Cd, Cu, Pb, Zn and Sb concentrations, as well as TDS, pH, dissolved oxygen and temperature. High concentrations of N-NO₃ (26 mg l⁻¹), Se (70 μg l⁻¹), Mo (18 μg l⁻¹) and Cu (4.3 μg l⁻¹) suggest that groundwater is being polluted by the use of fertilizers only in the western section of the aquifer, known as El Porvenir graben. Unlike the sites located near the main recharge area to the East of the aquifer, the water in El Porvenir graben has low tritium concentrations (<1.9 TU), indicating a pre-modern age, and thus longer water residence time. No significant variations in water quality (generally <10%) were detected throughout 2001–2002 in the aquifer, suggesting that reduced rainfall and recharge during this dry period did not significantly affect water quality. However, the wells nearest to the main recharge area in the Eastern aquifer show a slight but constant increase in TDS with time, probably as a result of the high (∼200 L S⁻¹) uninterrupted extraction of water at this specific recharge site. Relatively high As concentrations for the aquifer (10.5 μg l⁻¹) are only found near the northern limit of the basin associated with a geological fault.     

Characterization of chloride transport in the unsaturated zone near salted road

The application of road salts as deicing agents contributes to the anthropogenic loading of chloride (Cl⁻) on the environment. Using a 2D solute model, the potential of the unsaturated zone to serve as a reservoir and the mechanisms controlling the movement of Cl⁻ were examined. Physical properties and initial pore-water Cl⁻ concentrations were derived from an array of soil borings. Initial pore-water concentrations show the presence of a Cl⁻ “slug” approximately 0.75 m below the surface. Simulations show that within the unsaturated zone, Cl⁻ transport is predominantly vertical, driven by molecular diffusion. After a 1-year simulation, a Cl⁻ slug similar to the background observation was noted. While Cl⁻ is retained in the unsaturated zone, a net loss of Cl⁻ from the unsaturated zone was simulated for the first 10 years. In year 11, an equilibrium between the Cl⁻ input and output is achieved. The presence of Cl⁻ in the unsaturated zone becomes a long-term source of chloride to the groundwater, which eventually discharges into the surface water. Historically, surface water chemistry data support the continual discharge of chloride to the surface water in the area, further supporting the hypothesis that the unsaturated zone serves as a Cl⁻ reservoir.     

Groundwater chemistry and occurrence of arsenic in the Meghna floodplain aquifer,southeastern Bangladesh

Dissolved major ions and important heavy metals including total arsenic and iron were measured in groundwater from shallow (25–33 m) and deep (191–318 m) tube-wells in southeastern Bangladesh. These analyses are intended to help describe geochemical processes active in the aquifers and the source and release mechanism of arsenic in sediments for the Meghna Floodplain aquifer. The elevated Cl⁻ and higher proportions of Na⁺ relative to Ca²⁺, Mg²⁺, and K⁺ in groundwater suggest the influence by a source of Na⁺ and Cl⁻. Use of chemical fertilizers may cause higher concentrations of NH₄⁺ and PO₄³⁻ in shallow well samples. In general, most ions are positively correlated with Cl⁻, with Na⁺ showing an especially strong correlation with Cl⁻, indicating that these ions are derived from the same source of saline waters. The relationship between Cl⁻/HCO₃⁻ ratios and Cl⁻ also shows mixing of fresh groundwater and seawater. Concentrations of dissolved HCO₃⁻ reflect the degree of water–rock interaction in groundwater systems and integrated microbial degradation of organic matter. Mn and Fe-oxyhydroxides are prominent in the clayey subsurface sediment and well known to be strong adsorbents of heavy metals including arsenic. All five shallow well samples had high arsenic concentration that exceeded WHO recommended limit for drinking water. Very low concentrations of SO₄²⁻ and NO₃⁻ and high concentrations of dissolved Fe and PO₄³⁻ and NH₄⁺ ions support the reducing condition of subsurface aquifer. Arsenic concentrations demonstrate negative co-relation with the concentrations of SO₄²⁻ and NO₃⁻ but correlate weakly with Mo, Fe concentrations and positively with those of P, PO₄³⁻ and NH₄⁺ ions.     

Hydrochemical characteristics of groundwater in the Zhangye Basin, Northwestern China

The Zhangye Basin, located in arid northwest China, is an important agricultural and industrial center. In recent years rapid development has created an increased demand for water, which is increasingly being fulfilled by groundwater abstraction. Detailed knowledge of the geochemical evolution of groundwater and water quality can enhance understanding of the hydrochemical system, promoting sustainable development and effective management of groundwater resources. To this end, a hydrochemical investigation was conducted in the Zhangye Basin. Types of shallow groundwater in the Zhangye Basin were found to be HCO₃ ⁻, HCO₃ ⁻–SO₄ ²⁻, SO₄ ²⁻–HCO₃ ⁻, SO₄ ²⁻–Cl⁻, Cl⁻–SO₄ ²⁻ and Cl⁻ . The deep aquifer groundwater type was found to be HCO₃⁻–SO₄²⁻ throughout the entire area. Ionic ratio and saturation index calculations suggest that silicate rock weathering and evaporation deposition are the main processes that determine the ionic composition in the study area. The suitability of the groundwater for irrigation was assessed based on the US Salinity Laboratory salinity classification and the Wilcox diagram. In the study area, the compositions of the stable isotopes δ¹⁸O and δD in groundwater samples were found to range from −4.00 to −9.28‰ and from −34.0 to −65.0‰, respectively. These values indicate that precipitation is the main recharge source for the groundwater system; some local values indicate high levels of evaporation. Tritium analysis was used to estimate the ages of the different groundwaters; the tritium values of the groundwater samples varied from 3.13 to 36.62 TU. The age of the groundwater at depths of less than 30 m is about 5–10 years. The age of the groundwater at depths of 30–50 m is about 10–23 years. The age of the groundwater at depths of 50–100 m is about 12–29 years. For groundwater samples at depths of greater than 100 m, the renewal time is about 40 years.     

Hydrochemical characterization of groundwater in the Accra plains of Ghana

Chemical and isotopic analyses are used to characterize and identify the relevant water-rock interactions, which are responsible for the poor groundwater quality in the Accra Plains. Four main water types are identified. Processes that singly or in combination influence the chemical composition of each water type include halite dissolution carbonate dissolution and precipitation, seawater intrusion, cation exchange, evaporative concentration of solutes and aluminosilicates dissolution. These processes contribute considerably to the concentration of major ions in the groundwater. Stable isotope contents of the groundwater suggest mainly direct integrative recharge. A few samples plot along the meteoric-seawater mix line which is coincidentally the evaporative line. The Cl⁻/Br⁻ ratios of some of these are close to 300 confirming marine origin, others probably concentrated by evaporation have their Cl⁻/Br⁻ ratios significantly lower than 300. Groundwater is qualitatively good for drinking purposes only along the foothills of the Akwapim Togoland ranges.     

Response of groundwater chemistry to water deliveries in the lower reaches of Tarim River,Northwest China

In this paper, we analysed the monitored data from nine groundwater-monitoring transects in the lower reaches of Tarim River during the five times of stream water deliveries to the river transect where the stream flow ceased. The results showed that the groundwater depth in the lower reaches of Tarim River rose from −9.30 m before the conveyances to −8.17 and −6.50 m after the first and second conveyances, −5.81 and −6.00 m after the third and fourth the conveyance, and −4.73 m after the fifth. The horizontal extent of groundwater recharge was gradually enlarged along both sides of the channel of conveyance, i.e., from 250 m in width after the first conveyance to 1,050 m away from the channel after the fourth delivery. With the rising groundwater level, the concentrations of major anions Cl⁻, SO₄²⁻ and cations Ca²⁺, Mg²⁺, Na⁺, as well as total dissolved solids (TDS) in groundwater underwent a significant change. The spatial variations in groundwater chemistry indicated that the groundwater chemistry at the transect near Daxihaizi Reservoir changed earlier than that farther from it. In the same transect, the chemical variations were earlier in the monitoring well close to watercourse than that farther away from the stream. In general, the concentration of the major ions and TDS at each monitoring well increased remarkably when the water delivery started, and decreased with the continued water delivery, and then increased once again at the end of the study period. Hence, the whole study period may be divided into three stages: the initial stage, the intermediate stage and the later stage. According to the three stages of groundwater chemistry reaction to water delivery and the relationships between groundwater chemical properties and groundwater depths, we educe that under the situation of water delivery, the optimum groundwater depth in the lower reaches of the Tarim River should be −5 m.     

Hydrogeochemical processes in the groundwater environment of Heihe River Basin,northwest China

The Heihe River Basin is a typical arid inland river basin for examining stress on groundwater resources in northwest China. The basin is composed of large volumes of unconsolidated Quaternary sediments of widely differing grain size, and during the past half century, rapid socio-economic development has created an increased demand for groundwater resources. Understanding the hydrogeochemical processes of groundwater and water quality is important for sustainable development and effective management of groundwater resources in the Heihe River basin. To this end, a total of 30 representative groundwater samples were collected from different wells to monitor the water chemistry of various ions and its quality for irrigation. Chemical analysis shows that water presents a large spatial variability of chemical facies (SO₄ ²⁻–HCO₃⁻, SO₄ ²⁻–Cl⁻, and Cl⁻–SO₄ ²⁻) as groundwater flow from recharge area to discharge area. The ionic ratio indicates positive correlation between the flowing pairs of parameters: Cl⁻ and Na⁺(r = 0.95), SO₄ ²⁻ and Na⁺ (r = 0.84), HCO₃ ⁻ and Mg²⁺(r = 0.86), and SO₄ ²⁻ and Ca²⁺ (r = 0.91). Dissolution of minerals, such as halite, gypsum, dolomite, silicate, and Mirabilite (Na₂SO₄·10H₂O) in the sediments results in the Cl⁻, SO₄ ²⁻, HCO₃ ⁻, Na⁺, Ca²⁺ and Mg²⁺ content in the groundwater. Other reactions, such as evaporation, ion exchange, and deposition also influence the water composition. The suitability of the groundwater for irrigation was assessed based on the US Salinity Laboratory salinity classification and the Wilcox diagram. The results show that most of the groundwater samples are suitable for irrigation uses barring a few locations in the dessert region in the northern sub-basin.     

Geochemistry characterization of groundwater in an agricultural area of Razan,Hamadan, Iran

This study was conducted to evaluate factors regulating groundwater quality in an area with agriculture as main use. Thirty groundwater samples have been collected from Razan area (Hamadan, Iran) for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater. The chemical compositions of the groundwater are dominated by Na⁺, Ca²⁺, HCO₃ ⁻, Cl⁻ and SO₄ ²⁻, which have been derived largely from natural chemical weathering of carbonate, gypsum and anthropogenic activities of fertilizer’s source. The production of SO₄ ²⁻ has multiple origins, mainly from dissolution of sulphate minerals, oxidation of sulphide minerals and anthropogenic sources. The major anthropogenic components in the groundwater include Na⁺, Cl⁻, SO₄ ²⁻ and NO₃ ⁻, with Cl⁻ and NO₃ ⁻ being the main contributors to groundwater pollution in Razan area.     

Correlative and comparative characterization of main ion concentrations in laterite groundwater in semi-arid northern Burkina Faso

About 24 samples from hand-dug wells and boreholes were used to characterize concentrations of the main inorganic ions in a laterite environment under semi-arid climatic conditions in Tikaré, northern Burkina Faso. It was found that the most represented groundwater anion in groundwater was HCO₃ ⁻ with average levels of 49.1 mg/L in the dry season and 33.5 mg/L in the rainy season. The most represented cation was Ca²⁺ with mean concentrations of 13.7 and 9.5 mg/L, respectively. The main processes, which influence the concentrations of these ions, are evaporation (dry season), local enrichment of recharge water in some elements, ion exchange and fixation by clay minerals (in case of K⁺). The best correlations were found between Ca²⁺ and Mg²⁺ (r = 0.95), Cl⁻ and Na⁺ (r = 0.95), HCO₃ ⁻ and Mg²⁺ (r = 0.89), HCO₃ ⁻ and Ca²⁺ (r = 0.89), and between HCO₃ ⁻ and Na⁺ (r = 0.80). In general, the quality of the groundwater from the different wells sampled for this study was good enough to serve as drinking water. However, there were situations where the quality of water was polluted because of anthropogenic contaminants (mainly NO₃ ⁻, K⁺, Cl⁻) from septic tanks and manure pits located in the vicinity of some sampled wells. In addition, application of fertilizers also represents a potential anthropogenic contamination source with regard to SO₄ ²⁻, Ca²⁺, K⁺, Na⁺, and Mg²⁺. Considering the high concentrations of SO₄ ²⁻, Mg²⁺, Na⁺ and Ca²⁺ found in one borehole, the deeper, fractured aquifers were also likely to be enriched in these elements. In contrast, the shallow aquifers are likely to be contaminated with Cl⁻, NO₃ ⁻ and K⁺. Cl⁻ and K⁺ seem to be locally present in recharge water as shown by their relative higher mean concentrations in the rainy season samples.     

Sustainable groundwater management on the small island of Manukan,Malaysia

Numerical models are capable of simulating various groundwater scenarios and relate it towards groundwater management. This paper focuses on numerical modeling and water balance approaches in the search for a sustainable management plan in Manukan Island. The impacts of pumping and recharge rates represented by groundwater scenarios were investigated by means of hydraulic heads, chloride concentrations and water balance components. Overpumping and inconsistency in recharge rate are the stresses shown in Scenario A. Scenario B involved with reduction pumping rate by 25% has shown an increase in groundwater levels, chloride concentration and groundwater storage. Scenario C showed the most promising finding compared with Scenarios A and B. Highest hydraulic heads, lowest chloride concentration (1,552.2 mg/L) and positive groundwater storage (254.3 m³/day) were obtained in Scenario C. Chloride concentration in pumping wells still exceeds World Health Organization International Standard limit in Scenario C which illustrates an additional water treatment is needed. Nevertheless, in view of a compromise groundwater management plan in study area, Scenario C is the best plan so far to protect the groundwater resources in the study area. More understanding of the artificial recharge method (percolation tank) and study site by means of modeling studies is needed. Additionally, further progress is needed in obtaining the water usage data from each part to determine the best pumping rate. A sustainable groundwater management plan is crucial to maintain the natural resources and social benefits as well as to protect the ecological balance of Manukan Island.     

Statistical analysis of groundwater chemistry of the Tarim River lower reaches,Northwest China

This study applied a comprehensive quantitative approach including statistical, principal component and gray relation analyses to assess the groundwater chemistry based on monitored data from 840 samples collected from the lower reaches of Tarim River from 2000 to 2009. The main findings were: (1) there were six types of groundwater chemistry in the lower reaches of Tarim River where Cl·SO₄–Na·Mg was the dominant type accounting for 73.57% in all samples. There were linear relationships among chemical parameters, where TDS had significant multiple correlations with Na⁺, K⁺, Mg²⁺, Ca²⁺ and Cl⁻, respectively. (2) Three principal components (PC1, PC2 and PC3) were extracted. They included comprehensive measurements for salinization, alkalinity and pH, respectively. Most parameters showed decreasing trends during the period of 2000–2009, as well as the scores on PC1, because the concentrations of various chemical substances were diluted due to the uplift of the groundwater table in the lower reaches and the implementation of the ecological water delivery project in 2000. (3) HCO₃ ⁻ was the most sensitive chemical parameter affected by the groundwater table followed by TA, Mg²⁺, TH, SO₄²⁻, K⁺, TDS and TS. PC2 was the most sensitive principal component to the change of the groundwater table followed by PC1 and PC3.     

Hydrogeochemical investigations and groundwater provinces of the Friuli Venezia Giulia Plain aquifers,northeastern Italy

Water resources are a key factor, particularly for the planning of the sustainable regional development of agriculture, as well as for socio-economic development in general. A hydrochemical investigation was conducted in the Friuli Venezia Giulia aquifer systems to identify groundwater evolution, recharge and extent of pollution. Temperature, pH, electric conductivity, total dissolved solids, alkalinity, total hardness, SAR, Ca²⁺, Na⁺, K⁺, Mg²⁺, Cl⁻, SO₄ ²⁻, NO₃ ⁻, HCO₃ ⁻ _, water quality and type, saturation indexes and the environmental stable isotope δ¹⁸O were determined in 149 sampling stations. The pattern of geochemical and oxygen stable isotope variations suggests that the sub-surface groundwater (from phreatic and shallow confined aquifers) is being recharged by modern precipitations and local river infiltrations. Four hydrogeological provinces have been recognised and mapped in the Friuli Venezia Giulia Plain having similar geochemical signatures. These provinces have different degrees of vulnerability to contamination. The deep confined groundwater samples are significantly less impacted by surface activities; and it appears that these important water resources have very low recharge rates and would, therefore, be severely impacted by overabstraction.     

Desalination of a sedimentary rock aquifer system invaded by Pleistocene Champlain Sea water and processes controlling groundwater geochemistry

The objective of this study was to identify geochemical processes and Quaternary geological events responsible for the variations in groundwater geochemistry observed in a sedimentary rock aquifer system, including brackish to saline groundwater. Inorganic constituents and environmental isotopes were analyzed for 146 groundwater samples. Dissolution of carbonates dominates in recharge areas, resulting in Ca-, Mg-HCO₃ groundwater. Further along flow paths, under confined conditions, Ca²⁺–Na⁺ ion exchange causes groundwater evolution to Na-HCO₃ type. Na-Cl groundwater is also found and it falls on a seawater mixing line. Using conservative tracers, Cl⁻ and Br⁻, the original Champlain Sea water is shown to have been, in the region, a mixture of about 34% seawater and 66% freshwater, a composition still retained by some groundwater. Na-Cl groundwater thus results from mixing with former Champlain Sea water and also from solute diffusion from overlying marine clay. The system is thus found to be at different stages of desalinization, from the original Champlain Sea water still present in hydraulically stagnant areas of the aquifer to fully flushed conditions in parts, where more flow occurs, especially in recharge zones. The geochemical processes are integrated within the hydrogeological context to produce a conceptual geochemical evolution model for groundwater of the aquifer system.     

Hydrochemical and isotopic evidence of recharge,apparent age,and flow direction of groundwater in Mayo Tsanaga River Basin,Cameroon: bearings on contamination

Unplanned exploitation of groundwater constitutes emerging water-related threats to MayoTsanaga River Basin. Shallow groundwater from crystalline and detrital sediment aquifers, together with rain, dams, springs, and rivers were chemically and isotopically investigated to appraise its evolution, recharge source and mechanisms, flow direction, and age which were used to evaluate the groundwater susceptibility to contamination and the basin’s stage of salinization. The groundwater which is Ca–Na–HCO₃ type is a chemically evolved equivalent of surface waters and rain water with Ca–Mg–Cl–SO₄ chemistry. The monsoon rain recharged the groundwater preferentially at an average rate of 74 mm/year, while surface waters recharge upon evaporation. Altitude effect of rain and springs show a similar variation of −0.4‰ for δ¹⁸O/100 m, but the springs which were recharged at 452, 679, and 773 m asl show enrichment of δ¹⁸O through evaporation by 0.8‰ corresponding to 3% of water loss during recharge. The groundwater which shows both local and regional flow regimes gets older towards the basins` margin with coeval enrichment in F⁻ and depletion in NO₃ ⁻. Incidentally, younger groundwaters are susceptible to anthropogenic contamination and older groundwaters are sinks of lithologenic fluoride. The basins salinization is still at an early stage.     

Nitrate pollution of groundwater in Toyserkan,western Iran

A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate (NO₃ ⁻) status of groundwater. The most prevalent water type is Ca–HCO₃ followed by water types Ca–Mg–HCO₃. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l⁻¹ for NO₃ ⁻, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO₃ ⁻ concentration was low (<20 mg l⁻¹), and in 53.7% of samples (51), in the range of 20–50 mg l⁻¹. The samples were classified into four groups based on NO₃ ⁻ and chloride (Cl⁻) concentrations. Of the samples, 40% were classified as group 4 and were relatively high in Cl⁻ and NO₃ ⁻ (Cl⁻ > 47 mg l⁻¹, NO₃ ⁻ > 27 mg l⁻¹). The high correlation between NO₃ ⁻ and Cl⁻ (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation practice.     

Environmental research of groundwater in the urban and suburban areas of Attica region,Greece

In this study, 92 groundwater samples were collected from the Attica region (Greece). Moreover, geographical information system database, geochemistry of groundwater samples and statistics were applied. These were used for studying the chemical parameters (NO₃ ⁻, Mg²⁺, Ca²⁺, Cl⁻, and Na⁺) and conductivity spatial distribution and for assessing their environmental impact. The ranges of chemical parameters of the water samples (in mg L⁻¹) are: NO₃ ⁻ 1–306, Mg²⁺ 2–293, Ca²⁺ 3–453, Cl⁻ 5–1,988, and Na⁺ 4–475. The elevated concentrations of sodium, Mg²⁺, Cl⁻ are attributed to natural contamination (seawater intrusion). On the other hand, NO₃ ⁻ elevated concentrations are attributed to anthropogenic contamination (nitrate fertilizers). The results of the GIS analysis showed that elevated values of Na⁺, Mg²⁺, Cl⁻ are related to shrubby and sparsely vegetated areas, while elevated values of NO₃ ⁻ are connected with urban and agricultural areas.