Assessment of geochemical processes occurring in groundwaters in the coastal alluvial aquifer

Groundwater samples are collected from 30 observation wells in the study area to analyze the hydrochemical quality for determining the seawater encroachment in the part of Central Godavari Delta, Bay of Bengal, India. In order to establish the baseline hydrochemical conditions and processes determining the groundwater quality, an integrated investigation coupled with multivariate statistical analysis and hydrochemical methods are used to identify and interpret the groundwater chemistry of the aquifer system. The major land use is irrigated agriculture and aquaculture in the study area. The ground waters affected by the seawater intrusion featured high levels of sodium (Na⁺), chloride (Ca⁺), and TDS, which are the simplest common indicators for seawater influence. The elevated levels of NO₃–N at some monitoring wells indicate nitrate pollution of groundwater due to anthropogenic origin such as septic effluents or chemical fertilizers. Besides the major chemical compositions, it was also demonstrated that ionic ratios would be useful to delineate seawater intrusion and they include Na⁺/Ca²⁺, Mg²⁺/Ca²⁺, SO₄ ^2?/Ca²⁺, Na⁺/(Na⁺?+?Cl^?), and Ca^?/sum of anions. This paper demonstrates the variations in hydrochemical quality of groundwater and its evolution processes in two different seasons in the coastal aquifer alluvial settings     

Major ion chemistry of shallow groundwater of a fast growing city of Central India

Nagpur City located in semiarid area of central India is a fast-growing industrial centre. In recent years, rapid development has created an increased demand for drinking water, which is increasingly being fulfilled by groundwater abstraction. The present study was undertaken to assess major ion chemistry of shallow groundwater to understand geochemical evolution of groundwater and water quality for promoting sustainable development and effective management of groundwater resources. A total of 47 water samples were collected from shallow aquifer of selected parts of the city and the water chemistry of various ions viz. Ca^2 +, Mg^2 +, Na⁺, K⁺, CO₃  ^2-_{3}^{\ \, 2-}, HCO₃  ^-_{3}^{\ \, -}, Cl⁻, SO₄  ^2-_{4}^{\ \,2-} and NO₃  ^-_{3}^{\ \,-} are carried out. The chemical relationships in Piper diagram identify Ca–HCO₃–Cl and mixed Ca–Na–HCO₃–Cl as most prevalent water types. Alkaline earth exceeds alkalis and weak acids exceed strong acids. Ionic ratios and Gibb’s diagram suggest that silicate rock weathering and anthropogenic activities are the main processes that determine the ionic composition in the study area. The nitrate appeared as a major problem of safe drinking water in this region. We recorded highest nitrate concentration, i.e., 411 mg/l in one of the dug well. A comparison of groundwater quality in relation to drinking water quality standards revealed that about half of the shallow aquifer samples are not suitable for drinking.     

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.     

Evaluation of groundwater suitability for domestic,irrigational, and industrial purposes: a case study from Thirumanimuttar river basin,Tamilnadu, India

The Thirumanimuttar sub-basin forms an important groundwater province in south India, facing serious deficiency in both quality and quantity of groundwater due to increased demand associated with rapid population explosion, agricultural growth and industrial activities. A total of 194 groundwater samples were collected and 15 water quality parameters were analyzed using standard procedures. Na⁺, Cl⁻, Ca^2 +, HCO₃^-_{3}^{-}, Mg^2 + and SO₄^2-_{4}^{2-} concentration ions are more dominant in both seasons. The total dissolved solids and electrical conductivity was observed good correlation with Na⁺, Cl⁻, HCO₃^-_{3}^{-}, Ca^2 +, Mg^2 +, Cl⁻, PO₄^3-_{4}^{3-} and NO₃^- _{3}^{- } ions indicating dominance of plagioclase feldspar weathering, anthropogenic input and over drafting of groundwater irrespective of seasons. The Hill–Piper diagram indicates alkaline earths exceed the alkalis, an increase of weak acids was noted during both the seasons. For assessing the groundwater for irrigation suitability parameters like total hardness, sodium adsorption ratio, residual sodium carbonate (RSC), permeability index, and sodium percentage are also calculated. Permanent hardness was noted in higher during both the seasons due to discharge of untreated effluents and ion exchange process. The RSC indicates 56% of the samples are not suitable for irrigation purposes in both seasons, if continuously used will affect the crop yield. From the results, nearly 72% of the samples are not suitable for irrigation.     

Impacts of urbanization on groundwater hydrodynamics and hydrochemistry of the Toluca Valley aquifer (Mexico)

The Toluca Valley is located on the high plains of Mexico, where there are significant industrial zones and large populations. Water needs are almost exclusively met by groundwater, which has brought about intense exploitation of the aquifer and indication of some contamination. The present study investigates the effect of urbanization, related to industrialization of the region, on groundwater in the central portion of the Toluca Valley aquifer—a zone with high population density and where the largest industrial park is located. A general decline in the groundwater level has been found over the years, at a rate of as much as 2.5 m/year. The appearance of a large drawdown cone was identified, indicating changes in the direction of groundwater flow. Also identified was the presence of several ground fissures, the location of which coincided with the drawdown cone. In hydrochemical terms, the water type is sodium-magnesium bicarbonate and this characteristic has not changed over time, although it has been possible to detect the presence of larger quantities of sulfates (up to 117 mg/L) and nitrates (up to 47 mg/L) in recent years, likely associated with contamination from industrial and urban wastewater. Factor analysis made it possible to identify ions that would characterize natural processes involving the acquisition of salts (HCO₃ ^?, Na⁺, Mg²⁺, and Si), as well as anthropic activities (SO₄ ^2?, NO₃ ^?, Cl^?, Ca²⁺, and K⁺).     

Hydrogeochemical characterization of contaminated groundwater in Patancheru industrial area,southern India

The groundwater is one of the most contaminated natural resources in Patancheru industrial area due to unplanned and haphazard industrial growth and urbanization without following basic pollution control norms. The rapid industrialization initiated in early 1970 has started showing up its after effects few years later in the form of physiochemical contamination of the both surface and groundwater bodies of the area. It has resulted in local people being deprived of safe drinking water, plant and aquatic life has severely affected, and situation is deteriorating over the years in the area in spite of some preventive and remedial measures being initiated. The focus of the present study is to understand the chemical characteristics of groundwater and geochemical processes the contaminant water is undergoing which are normally imprinted in its ionic assemblages. The water samples collected in pre- and post-monsoon seasons from forty two groundwater and four surface water sources were analyzed for major constituents such as Ca²⁺, Mg²⁺, Na⁺, K⁺, CO₃⁻, HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻, and F⁻, and selected samples were tested for ten important trace metals like Fe, Pb, Bi, Mn, Cr, Co, Ni, Cu, Zn, and Cd. Na⁺ among cations and Cl⁻ among anions dominate the water in both the seasons where as Ca²⁺, HCO₃⁻, and Cl⁻ show significant reduction in their ionic strength in post-monsoon. The groundwater in general is of mixed type, but most of it belong to Na⁺–Cl⁻, Na⁺–HCO₃⁻, Ca²⁺–Mg²⁺–HCO₃⁻, and Ca²⁺–Mg²⁺–Cl⁻ facies. The Na⁺ and Ca²⁺ are in the transitional state with Na⁺ replacing Ca²⁺ and HCO₃⁻–Cl⁻ due to physiochemical changes in the aquifer system. The evaluation of hydrochemistry through various ionic indices, ratios, and plots suggest that silicate–carbonate weathering, ion exchange, dissolution, and evaporation processes are responsible for origin of the present chemical status of the groundwater which is also controlled by the contamination from extraneous sources that could have accelerated the dissolution processes. Gibbs plots authenticate that the evolution of water chemistry is influenced by interaction of percolating water with aquifer matrix apart from anthropogenic enrichment of elements which get over concentrated due to evaporation.     

Groundwater quality and its suitability for drinking and agricultural use in the Yanqi Basin of Xinjiang Province, Northwest China

The Yanqi Basin in Xinjiang Province is an important agricultural area with a high population density. The extensive agricultural activities in the Yanqi Basin started in the 1950s with flood irrigation techniques. Since then, the groundwater table was raised because of the absence of an efficient drainage system. This obstacle is a crucial factor that restricts sustainable socioeconomic development. Hydrochemical investigations were conducted in the Yanqi Basin, Northwestern China, to determine the chemical composition of groundwater. Sixty groundwater samples were collected from different wells to monitor the water chemistry of various ions. The results of the chemical analysis indicate that the groundwater in the area is generally neutral to slightly alkaline and predominantly contains Na⁺ and Ca²⁺ cations as well as HCO₃ ^? and SO₄ ²⁺ anions. High positive correlations between HCO₃ ^?–Mg²⁺ + Ca²⁺, SO ₄ ^2?–Mg²⁺, SO₄ ^2?–Na⁺ + K⁺, and Cl^?–Na⁺ + K⁺ were obtained. The total dissolved solids (TDS) mainly depend on the concentration of major ions such as HCO₃ ^?, SO₄ ^2?, Cl^?, Ca²⁺, Mg²⁺, and Na⁺ + K⁺. The dominant hydrochemical facies for groundwater are Ca²⁺–Mg²⁺–HCO₃ ^?, Mg²⁺–Ca²⁺–SO₄ ^2?–Cl^?, Na⁺–K⁺–Cl^?–SO₄ ^2?, and Na⁺–K⁺–Mg²⁺–Cl^?–HCO₃ ^? types. The hydrochemical processes are the main factors that determine the water quality of the groundwater system. These processes include silicate mineral weathering, dissolution, ion exchange, and, to a lesser extent, evaporation, which seem to be more pronounced downgradient of the flow system. The saturation index (SI), which is calculated according to the ionic ratio plot, indicates that the gypsum–halite dissolution reactions occur during a certain degree of rock weathering. SI also indicates that evaporation is the dominant factor that determines the major ionic composition in the study area. The assessment results of the water samples using various methods indicate that the groundwater in the study area is generally hard, fresh to brackish, high to very high saline, and low alkaline in nature. The high total hardness and TDS of the groundwater in several places indicate the unsuitability of the groundwater for drinking and irrigation. These areas require particular attention, particularly in the construction of adequate drainage as well as in the introduction of an alternative salt tolerance cropping.     

Factors controlling the salinity in groundwater in parts of Guntur district, Andhra Pradesh, India

Groundwater chemistry has been studied to examine the associated hydrogeochemical processes operating for the development of salinity in the groundwater in parts of Guntur district, Andhra Pradesh, India. The study area is underlain by charnockites and granitic gneisses associated with schists of the Precambrian Eastern Ghats. Groundwater is the main resource for irrigation besides drinking. Chemical parameters, pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, , , Cl⁻, , , F⁻ and SiO₂, are taken into account. Groundwater is of brackish type. Na⁺−Cl⁻ facies dominates the groundwater. Examination of compositional relations and mineral saturation states shows that the ion exchange of Ca²⁺ for adsorbed Na⁺, evapotranspiration, dissolution of soil salts, dissolution of NaCl and CaSO₄, and precipitation of CaCO₃ are the dominant hydrogeochemical processes associated with the groundwater composition in the area. Evapotranspiration causes accumulation of salts in the soil/weathered zone. These salts reach the water table by leaching through infiltrating recharge water. A positive relation between depth to water table and TDS with season supports this inference. The effects of human activities, such as intensive and long-term irrigation, irrigation-return-flow, application of unlimited agricultural fertilizers and recycling of saline groundwater, act to further increase the salinity in the groundwater. Therefore, the groundwater quality increases towards the flow path, while the post-monsoon groundwater shows higher concentrations of TDS, Na⁺, Mg²⁺, Cl⁻, , , F⁻ and SiO₂ ions. The study could help to understand the hydrogeochemical characteristics of the aquifer system for taking effective management measures to mitigate the inferior groundwater quality for sustainable development.     

Water Quality Assessment of Osun River: Studies on Inorganic Nutrients

The present investigation provides data of some ions, namely Na⁺, Ca²⁺, NH₄ ⁺,Cl^-, NO₃ ^-,CN^- and PO₄ ^3- on water samples of river Osun,selected rivers in the region and groundwaters. The pH,temperature, electrical conductivity (EC), total dissolvedsolids (TDS), total hardness (TH) and total carbon (IV) oxide(TCO₂) have also been determined to asses the chemicalstatus and pollution levels of these water sources. The highervalues of certain parameters with respect to the acceptablestandard limits for drinking water indicate the pollution inboth groundwater and river water samples of the study area, and make the waters unsuitable for various applications. Thehigh pollution river water source showed higher levels ofphosphate, nitrate and ammonium ions (P < 0.05). There is nosignificant difference (P < 0.05) between the meanconcentrations of other inorganic nutrients in the high and lowpollution water source types. The correlation coefficientbetween quality parameter pairs of river water and groundwatersamples are determined and the significance of these parametersin both types of water sources are discussed.     

Identification of the hydrogeochemical processes in groundwater using major ion chemistry: a case study of Penna–Chitravathi river basins in Southern India

Hydrogeochemical studies were carried out in the Penna–Chitravathi river basins to identify and delineate the important geochemical processes which were responsible for the evolution of chemical composition of groundwater. The area is underlain by peninsular gneissic complex of Archaean age, Proterozoic meta-sediments, and strip of river alluvium. Groundwater samples were collected covering all the major hydrogeological environs in pre- and post-monsoon seasons. The samples were analyzed for major constituents such as Ca^2?+?, Mg^2?+?, Na^?+?, K^?+?, CO₃ ^???, HCO₃ ^???, Cl^???, SO₂ ^???4, NO₃ ^???, and F^???. The groundwater in general is of Na^?+?–Cl^???, Na^?+?–HCO₃ ^???, Ca^2?+?–Mg^2?+?–HCO₃ ^???, and Ca^2?+?–Mg^2?+?–Cl^??? types. Na^?+? among cations and Cl^??? and/or HCO₃ ^??? among anions dominate the water; Na^?+? and Ca^2?+? are in the transitional state with Na^?+? replacing Ca^2?+? and HCO₃ ^??? Cl^??? due to physiochemical changes in the aquifer and water–rock interactions. The Ca^2?+?–Mg^2?+?–Cl^??? HCO₃ ^??? type water in one third samples suggest that ion exchange and dissolution processes are responsible for its origin. Change in storage of aquifer in a season does not influence the major geochemical makeup of groundwater. Gibbs plots indicate that the evolution of water chemistry is influenced by water–rock interaction followed by evapotranspiration process. The aquifer material mineralogy together with semiarid climate, poor drainage system, and low precipitation factors played major role in controlling groundwater quality of the area.     

Groundwater Quality Monitoring in Shallow and Deep Aquifers in Saidabad Tahsil Area, Mathura District, India

Water availability in arid regions is both sporadic and highly variable in quantity. If the water quality shows large variations of salinity and concentration of other chemical constituents with depth and time span, it has considerable effect on the entire hydrological set up of the area. In the Saidabad tahsil area, the deep aquifers that supply water to borewells in the alluvial plain of the Mathura region, Uttar Pradesh, have higher salinity than those of the dugwells from the shallow aquifers. The excessive drilling of tubewells and high yield tubewells are resulting in deterioration of water quality of the shallow aquifers. On the contrary, the chemical constituents such as, Na⁺, K ⁺, Cl ^-, andHCO ₃ ^- show higher concentration in shallow aquifers than deep aquifers. A study carried out to monitor water quality in this region reveals that the groundwater quality varies with depth and time span in shallow and deep aquifers. Factors controlling variations in salinity and concentration of chemical constituents of the water in the two types of aquifers are discussed. The relative merits of the shallow water for potability are pointed out with respect to salinity concentrations and public health.     

Hydrogeochemical characteristics and assessment of drinking water quality in Zeuss�CKoutine aquifer, southeastern Tunisia

Zeuss?CKoutine aquifer, located in southeastern Tunisia, has been used intensively as a primary source to meet the growing needs of the various sectors. 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 and statistical investigation was conducted. Groundwater samples have been collected from 13 wells from 1995 to 2005; to understand the sources of dissolved ions and assess the chemical quality of the groundwater. Results demonstrate that among the cations, only the mean concentrations of Na^?+? exceed guideline values set by the World Health Organization (WHO). Regarding the analyzed anions, the concentration of SO $_{4}^{2-}$ and Cl^??? are above the WHO allowable concentrations. Total dissolved solids in most groundwater samples are greater than 1,000 mg l^???1, the limit set by the WHO, indicating slightly saline or moderately saline water. In general, a significant increase in the degree of water mineralization was observed in the direction of southwest to northeast following the regional flow direction. Calculated saturation indices show that all water samples were oversaturated with respect to aragonite, calcite, and dolomite, and undersaturated with respect to anhydrite, gypsum, and halite. Based on hydrochemical facies, two types of water predominate in the study area. The first is Ca?CNa?CSO₄?CCl in type and located in the southwest which corresponds to the recharge part of the aquifer. The second type is Na?CCa?CCl?CSO₄ and located in the east, which corresponds to the discharge part.     

Physicochemical quality evaluation of groundwater and development of drinking water quality index for Araniar River Basin, Tamil Nadu, India

Groundwater is the most important natural resource which cannot be optimally used and sustained unless its quality is properly assessed. In the present study, the spatial and temporal variations in physicochemical quality parameters of groundwater of Araniar River Basin, India were analyzed to determine its suitability for drinking purpose through development of drinking water quality index (DWQI) maps of the post- and pre-monsoon periods. The suitability for drinking purpose was evaluated by comparing the physicochemical parameters of groundwater in the study area with drinking water standards prescribed by the World Health Organization (WHO) and Bureau of Indian Standards (BIS). Interpretation of physicochemical data revealed that groundwater in the basin was slightly alkaline. The cations such as sodium (Na⁺) and potassium (K⁺) and anions such as bicarbonate (HCO₃ ^?) and chloride (Cl^?) exceeded the permissible limits of drinking water standards (WHO and BIS) in certain pockets in the northeastern part of the basin during the pre-monsoon period. The higher total dissolved solids (TDS) concentration was observed in the northeastern part of the basin, and the parameters such as calcium (Ca²⁺), magnesium (Mg²⁺), sulfate (SO₄ ^2?), nitrate (NO₃ ^?), and fluoride (F^?) were within the limits in both the seasons. The hydrogeochemical evaluation of groundwater of the basin demonstrated with the Piper trilinear diagram indicated that the groundwater samples of the area were of Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2?, Ca²⁺-Mg²⁺-HCO₃ ^? and Na⁺-K⁺-Cl^?-SO₄ ^2? types during the post-monsoon period and Ca²⁺-Mg²⁺-Cl^?-SO₄ ^2?, Na⁺-K⁺-Cl^?-SO₄ ^2? and Ca²⁺-Mg²⁺-HCO₃ ^? types during the pre-monsoon period. The DWQI maps for the basin revealed that 90.24 and 73.46 % of the basin area possess good quality drinking water during the post- and pre-monsoon seasons, respectively.     

Geostatistical Evaluation of Spatial Variation Related to Groundwater Quality Database: Case Study for Arak Plain Aquifer,Iran

Geostatistical methods are one of the advanced techniques to interpolate groundwater quality data. Geostatistical interpolation techniques employ both the mathematical and the statistical properties of the measured points. Compiling the data distribution on spatial and temporal domain is of crucial importance in order to evaluate its quality and safety. The main purpose of this paper is to assess groundwater quality of Arak plain, Iran, by an unbiased interpolated method so called Kriging. Therefore, seven quality variables of Arak plain aquifer including TDS, SAR, EC, Na⁺, TH, Cl^?, and SO₄ ^2? have been analyzed, studied, and interpreted statistically and geostatistically. Utilized data in this study were collected from 97 water well samples in Arak plain, in 2012. After normalizing data, variogram as a geostatistical tool for defining spatial regression was calculated and experimental variograms have been plotted by GS⁺ software, then the best theoretical model was fitted to each variogram based on minimum RSS error. Cross validation was used to determine the accuracy of the estimated data. The uncertainty of the method could be well assessed via this method since the method not only gave the average error (around 0 in this study) but also gave the standard deviation of the estimations. Therefore, more than 3800 points were estimated by ordinary Kriging algorithm in places which have not been sampled. Finally, estimation maps of groundwater quality were prepared and map of estimation variance, EV, has been presented to assess the quality of estimation in each estimated point. Results showed that the Kriging method is more accurate than the traditional interpolation algorithms not honoring the spatial properties of the database.     

Leachate Characterization and Assessment of Groundwater Pollution Near Municipal Solid Waste Landfill Site

Leachate and groundwater samples were collected from Gazipur landfill-site and its adjacent area to study the possible impact of leachate percolation on groundwater quality. Concentration of various physico-chemical parameters including heavy metal (Cd, Cr, Cu, Fe, Ni, Pb and Zn) and microbiological parameters (total coliform (TC) and faecal coliform (FC)) were determined in groundwater and leachate samples. The moderately high concentrations of Cl⁻, NO⁻ ₃, SO²⁻ ₄, NH⁺ ₄, Phenol, Fe, Zn and COD in groundwater, likely indicate that groundwater quality is being significantly affected by leachate percolation. Further they proved to be as tracers for groundwater contamination. The effect of depth and distance of the well from the pollution source was also investigated. The presence of TC and FC in groundwater warns for the groundwater quality and thus renders the associated aquifer unreliable for domestic water supply and other uses. Although some remedial measures are suggested to reduce further groundwater contamination via leachate percolation, the present study demand for the proper management of waste in Delhi.     

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.     

上海青浦地区大气降水的化学特征

利用上海青浦地区2003—2014年观测的大气降水监测资料,分析该区域12 a以来大气降水的酸化程度、化学组成特征,探讨降水中化学成分的不同来源及相对贡献。结果表明:降水pH年均值为4.43~6.33,酸雨频率为2.6%~86.8%,降水酸化程度大致经历了明显恶化和波动变化2个阶段。降水电导率年均值为1.77~4.01 m S/m,呈下降趋势。降水中各离子雨量加权平均当量浓度顺序为SO_4~(2-)NH_4~+Ca~(2+)NO_3~-Cl~-Na~+Mg~(2+)F-K~+,SO_4~(2-)、NH+4、Ca~(2+)和NO_3~-是降水中的主要离子,占离子总量的83.0%;降水类型由硫酸型向硫酸和硝酸混合型转变。降水离子中的二次组分SO_4~(2-)、NO_3~-和NH_4~+绝大部分来源于人为源,Ca~(2+)、Mg~(2+)和K+主要来自于土壤源和人为源的贡献,Cl~-主要来自海洋源,同时人为源的影响也不可忽视。     

Assessment of geospatial and hydrochemical interactions of groundwater quality,southwestern Nigeria

Groundwater pollution resulting from anthropogenic activities and poor effluent management is on the rise in Nigeria. Hence, groundwater used for domestic purposes is questionable and therefore calls for scientific scrutiny. Investigation of hydrochemical interactions and quality of groundwater resource is essential in order to monitor and identify sources of water pollutants. As a result, groundwater samples were collected from 21 locations in Abeokuta South, Nigeria and analyzed for physicochemical parameters using standard methods. Results obtained were subjected to hydrochemical and geospatial analyses. Water quality parameters investigated exhibited wide variations from location to location. Fe²⁺, Mg²⁺, SO₄^2?, Cl^?, total hardness (TH), Mn, Na⁺, NO₃^?, SiO₂, and alkalinity exhibited the highest levels of variation with coefficients of variation of 131.3, 92.8, 83.9, 76.7, 65.9, 64.3, 57.6, 57.2, 57.0, and 52.5, respectively. The average pH value was 6.76 with 71% of the water samples being slightly acidic. Na²⁺, Mg²⁺, Fe²⁺, and EC contents exhibited the most violation of drinking water standards with percent violations of 100, 52.4, 47.6, and 47.6%, respectively. Parameters, such as Mn, Ca²⁺, NO₃^?, and CO₃^2?, were within the WHO guideline values for drinking water in all the samples. The highest level of significant correlation was found to exist between Na⁺ and Cl^? (r?=?0.84, α?=?0.01). Six principal components, which explained 83.5% of the variation in water quality, were extracted with the first (34.1%) and second components (15.7%) representing the influence of mineral dissolution and anthropogenic practices, respectively, on the hydrochemistry of the area. Four hydrochemical clusters were identified with distinctly partitioned water quality. Further analysis revealed that 38, 29, 24, and 9% of the samples were the Na-K-HCO₃, Na-K-Cl-SO₄, Ca-Mg-HCO₃, and Ca-Mg-Cl-SO₄ types, respectively. Anthropogenic activities are increasing threat to groundwater quality in the study location and therefore call for urgent attention. There is also a need for routine monitoring of groundwater in Abeokuta.     

A hydrochemical and geological investigation on the Mambakkam mini watershed,Kancheepuram District,Tamil Nadu

The hydrochemical characterization of groundwater is important to bring out its nature and usefulness. The main objective of this paper was to discuss the major ion chemistry of groundwater in the Mambakkam mini watershed. Besides its semi-arid nature, rapid socioeconomic development encourages a greater demand for water, which leads to uncontrolled groundwater development. The groundwater of the study area is characterized by the dominance of alkaline earth (Ca²⁺, Mg²⁺) and strong acids (Cl⁻, SO₄⁻) over alkalies (Na⁺, K⁺) and weak acids (HCO₃⁻, CO₃⁻) during both post-monsoon and pre-monsoon seasons of the year 2010, based on the hydrochemical facies. These have been probably derived from natural chemical weathering of rock minerals, ion exchange and anthropogenic activities of the fertilizer source. The classification based on the total hardness reveals that a majority of groundwater samples fall in the hard to very hard category during the pre-monsoon season. Based on the values of EC, SAR and RSC and the diagrams of USSL and Wilcox, most of the groundwater samples range from excellent to permissible for irrigation purposes, with a low alkalinity and high salinity hazard, except for a few samples in the study area.     

Occurrence of Acid Rain over Delhi

Precipitation samples were collected as wet-fall only andprimarily on event basis in Delhi during the monsoon period of1995. Concentrations of major anions (SO₄ ^2-,NO₃ ^- and Cl^-) andcations (Ca²⁺, Mg²⁺,Na⁺ and K⁺) were determined. The pH of the rain waterwas found to be more than 5.6, showing alkalinity during theearly phase of monsoon, but during the late phase of monsoon pHtendency was towards acidity due to lack of proper neutralizationof acidic ions. Neutralization is not only due to the localprocess but also due to the pre-monsoon Andhi which bringsSuspended Particulate Matter (SPM) containing Ca²⁺,Mg²⁺, Na⁺ and K⁺ as well as the local emission ofNH₃. In the late monsoon the concentration of cations getsreduced because of heavy rainfall and relatively unfavourablecondition for their transport from the adjoining areas, whereasthe anion concentrations remain unchanged owing to theircontinuous emission.