Geochemical Evolution Of Groundwater Research Articles

Groundwater geochemical evolution, origin and quality in the Lower Pra Basin, Ghana: Insights from hydrogeochemistry, multivariate statistical analysis, mineral saturation indices, stable isotopes (δ2H and δ18O) and geostatistical analysis

Groundwater geochemical evolution, origin and quality in the Lower Pra Basin, Ghana: Insights from hydrogeochemistry, multivariate statistical analysis, mineral saturation indices, stable isotopes (δ2H and δ18O) and geostatistical analysis

Geochemical evaluation and the mechanism controlling groundwater chemistry using chemometric approach and groundwater pollution index (GPI) in the Kishangarh city of Rajasthan, India.

This study is primarily focused on delving into the geochemistry of groundwater in the Kishangarh area, located in the Ajmer district of Rajasthan, India. In pursuit of this research goal, the sampling locations were divided into three parts within the Kishangarh region: Badgaon Rural (KSGR), Kishangarh Urban (KSGU), and the Kishangarh RIICO marble industrial area (KSGI). Various analytical methods have been executed to assess the suitability of groundwater for various purposes based on pH, electric conductivity, total dissolved solids, hardness, salinity, major anions, and cations. The ionic trend of anions and cations was found as HCO3- > Cl- > SO42- > NO3- > Br- > NO2- > F- and Na+ > Ca2+ > Mg2+ > K+, respectively. Applying statistical techniques such as principal component analysis (PCA) and Pearson correlation matrix analysis (PCMA) makes it evident that the physicochemical attributes of water sourced from the aquifers in the study area result from a blend of diverse origins. In addition, Gibbs, Piper, Durov, and scatter plots were used to assess groundwater's geochemical evolution. Piper plot demonstrated the two types of groundwater facies, Na-HCO3- and Na-Cl, implying significant contributions from evaporitic dissolution and silicate weathering. Also, the scatter plots have evaluated the impression of mine acid leachate, evaporitic dissolution, and silicate weathering to upsurge salt formation in the groundwater. The pollution risk evaluation within the study area was conducted using the groundwater pollution index (GPI). This index revealed a prominent concern for pollution, particularly in the northern segment of the study region. As a result, it can be inferred that the fine aeolian sand and silt formations in the northern part are relatively more vulnerable to contamination.

Integrated approach to understand the multiple natural and anthropogenic stresses on intensively irrigated coastal aquifer in the Mediterranean region

Understanding the major factors influencing groundwater chemistry and its evolution in irrigation areas is crucial for efficient irrigation management. Major ions and isotopes (δD-H2O together with δ18O–H2O) were used to identify the natural and anthropogenic factors contributing to groundwater salinization in the shallow aquifer of the Wadi Guenniche Plain (WGP) in the Mediterranean region of Tunisia. A comprehensive geochemical investigation of groundwater was conducted during both the low irrigation season (L-IR) and the high irrigation season (H-IR). The results show that the variation range and average concentrations of almost all the ions in both the L-IR and H-IR seasons are high. The groundwater in both seasons is characterized by high electrical conductivity and CaMgCl/SO4 and NaCl types. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, and Na–Ca exchange are the main chemical reactions in the geochemical evolution of groundwater in the Wadi Guenniche Shallow Aquifer (WGSA). Stable isotopes of hydrogen and oxygen (δ18O–H2O and δD-H2O) indicate that groundwater in WGSA originated from local precipitation. In the H-IR season, the δ18O–H2O and δD-H2O values indicate that the groundwater experienced noticeable evaporation. The enriched isotopic signatures reveal that the WGSA's groundwater was influenced by irrigation return flow and seawater intrusion. The proportions of mixing with seawater were found to vary between 0.12% and 5.95%, and between 0.13% and 8.42% during the L-IR and H-IR seasons, respectively. Irrigation return flow and the associated evaporation increase the dissolved solids content in groundwater during the irrigation season. The long-term human activities (fertilization, irrigation, and septic waste infiltration) are the main drives of the high nitrate-N concentrations in groundwater. In coastal irrigation areas suffering from water scarcity, these results can help planners and policy makers understand the complexities of groundwater salinization to enable more sustainable management and development.

Long-term groundwater geochemical evolution induced by coal mining activities-a case study of floor confined limestone aquifer in Yaoqiao Coal Mine, Jiangsu, China.

Groundwater chemical composition can be changed due to long-term coal mining activities, but it was unclear how it was induced in Taiyuan Formation limestone (TFL) regarding the lack of relevant quantitative studies. The aim of this research is to improve understanding of the chemical composition changes in groundwater of L4 limestone in the coal mining area based on the available hydrochemical and hydrodynamical reports and studies during the period 1978-2020. The systematical analysis of the groundwater composition and field allows to make the hydrogeological characterization with the relatively independent blocks by the factor groups "Planar division & Vertical zonation" and "High water pressure, Poor recharge & Little water inflow," which determines different hydrochemical types and high TDS concentration. The long-term groundwater drainage has caused the eastern and southern limestone aquifer to demonstrate a wide range of depression cones and depletion of groundwater resources, the majority areas were dewatered, and the karstification process changed significantly. An analysis of chemical compositions changes due to extensive permanent drainage of L4 limestone water revealed the decrease in the TDS concentration. The solubility of calcite, dolomite, and gypsum changed, which resulted in the decreasing tendency of Ca2+ + Mg2+ ions. Evaporation and concentration were found to be the main factors determining the L4 limestone water composition, whereas ion exchange was the primary factor for rock-water interaction. These findings are helpful for mine enterprises to take necessary measures for preventing and controlling the groundwater quality degradation from the extensive coalmine drainage.

Characterization of drinking groundwater quality and assessment of human health risk in Xin’an spring basin, a typical mining and karst area of the northern China

Groundwater is an important natural resources of drinking water in mining area in Xin’an spring basin, northern China. To foster the sustainable development and utilization of groundwater, a total of 332 groundwater samples, including 147 pore groundwater, 95 fissure groundwater and 90 karst groundwater, were collected and hydrochemical parameters were applied to assess the groundwater quality and human health risks caused by oral ingestion. The results showed that the major chemical components of groundwater in Xin’an spring basin were HCO3−, SO42−, NO3−, Cl−, Ca2+, Mg2+, Na+, total hardness (TH), and total dissolved solids (TDS). The contents of TDS, TH, SO42−, NO3−, F−, Fe, Mn, Pb, and As in groundwater were exceed the standard of groundwater quality (SGQ) limits. The main hydrochemical types of groundwater were HCO3-Ca·Mg and SO4·Cl–Ca·Mg. The factors controlling the groundwater chemistry mainly were mineral weathering, evaporation, cation exchange, and anthropogenic input. The results of water quality assessment showed that the karst and fissure groundwater in study area was mainly excellent-good quality water, while pore groundwater was mainly good-medium quality water. The poor and extremely poor quality water was mainly distributed in Changzhi basin, and the greater contribution made by Pb, Mn, NO3−, Fe, SO42−, TH and TDS. The range of hazard index (HI) values of groundwater was 0.28 to 27.79, and the HI values mainly contributed by NO3−, F−, As, ingestion rate (IR) and exposure duration (ED). The cumulative carcinogenic risk (CCR) values ranged from 1.5 × 10–7 to 2.78 × 10–3, and the greater contribution made by Cr, As, Cd, IR and ED. The results of health risk assessment suggested that some parts of the study region may pose a significant non-carcinogenic risk and a high probability in developing cancer to local residents, and infants were at greatest risk to health, followed by children and adults, while teenagers were at least at risk. This study will provide a deeper insight into the water quality situation and geochemical evolution of groundwater in Xin’an spring area, and will assist decision-makers to formulate management strategies of drinking water safety for the study area.

Evolution of Hydrogeochemistry in the Haolebaojinao Watershed of the Ordos Basin, China

The exploitation of groundwater in arid and semi-arid areas, especially in basins where groundwater is intensively exploited, is likely to have adverse effects on the originally fragile ecological environment, which also greatly alter the hydrogeochemical evolution process. Over-abstraction of groundwater in the Haolebaoji watershed of the Ordos Basin located in the semi-arid regions has led to a series of changes in the groundwater system, which has attracted considerable attention from environmental protection organizations. However, the origin and geochemical evolution of groundwater in the Haolebaoji watershed have not been revealed. In this study, the Haolebaoji watershed is selected as the typical study area to investigate hydrogeochemical evolution under the intensive groundwater exploitation. Groundwater samples were collected and tested for major ions and stable isotopes (δ18O, δD). Various approaches including the ion proportional relationship diagram, chlor-alkali index, saturation index, Gibbs diagram, and principal factor analysis were used to reveal the hydrogeochemical processes regulating the groundwater geochemistry. The groundwater in the study area is divided into five hydrochemical types according to the Piper diagram. It was found that the chemical composition of groundwater in the study area is mainly controlled by the dissolution of calcite, dolomite, gypsum, and halite. The cation exchange intensity gradually increased with the flow of groundwater from the recharge to the discharge area. Rock weathering plays a controlling role in the formation of groundwater geochemistry, but it is also controlled by evaporative crystallization in some runoff and discharge areas. Groundwater is predominantly recharged by modern local atmospheric precipitation, and deep wells receive water supply during cold periods. The study findings provide important information for the development of sustainable groundwater management strategies for the Ordos Energy Base.

Hydrogeochemical characteristics and health risk assessment of potentially toxic elements in groundwater and their relationship with the ecosystem: case study in Tunisia.

Sidi Bouzid basin knows for several decades a fast-growing anthropogenic activity and, consequently, an increase in groundwater pollution which attracted researcher attention. For this task, we performed an exhaustive study to evaluate groundwater geochemical evolution. Our research begins with analyzing the geochemical process, then determining the water quality indices and their impact on the ecosystem, and after that correlating between different compartments, and ends with the assessment of the human health risk toward NO3-, Fe, Mn, Zn, Cd, and Pb. The dominant facies of the groundwater in the study area are Ca-Mg-SO4 and Ca-Mg-HCO3 and are mainly influenced by evaporite deposits (CaSO4, CaSO4·2H2O, and NaCl). The pollution index of groundwater (PIG) displays values ranging between 0.5 and 4.5 indicating four classes of pollution (insignificant, low, moderate, and high). More than half of the samples (55%) belong to the low and moderate PIG classes. However, the results show elevated values of NO3- concentration; 76% of samples exceed 30mg/L. Among the studied contaminants, the highest carcinogenic and non-carcinogenic risks in study areas were related to NO3-. For all water samples, the risk levels for children were greater than those for adults. Lastly, the partial least square-structural equation modelling (PLS-SEM) shows that the chemical elements do not have a short-term potential impact of pollutants on ecosystems.

Effects of precipitation, irrigation, and exploitation on groundwater geochemical evolution in the people’s victory canal irrigation area, China

The People's Victory Canal Irrigation Area is a large gravity irrigation area in the middle and lower reaches of the Yellow River. Groundwater hydrochemistry is controlled by geochemical weathering, precipitation, irrigation from the Yellow River diversion, and artificial exploitation. The Piper diagram, hierarchical cluster analysis, Gibbs diagram, and ion proportion coefficient were applied to improve our understanding of the hydrogeochemical evolution. Our results indicated that groundwater ion concentration has prominent spatial zonation characteristics in the study area. The groundwater ion components in the low salinity area are mainly a result of silicate and carbonate weathering, with the major hydrochemical type being HCO3·Cl–Na·Mg and HCO3–Na·Ca. The soil salt content in the low salinity area is low. The main effect of precipitation on groundwater chemical composition is a reduction in groundwater ion concentration by recharge. The groundwater ion concentration near the canal is similar to the Yellow River water. The groundwater ionic components in the high salinity area are mainly affected by weathering, silicate dissolution, and evaporative salt rocks. The water chemical type is SO4·Cl–Na·Mg. Expectedly, the soil salt content is high in the high salinity area. The Yellow River recharge decreased the ion concentration of groundwater near the canal. In addition, the groundwater exploitation increase results in a change in the flow field, affecting the local groundwater chemistry. The groundwater ion concentration increases as the groundwater flow from the high salinity area to the low salinity area. In contrast, the groundwater ion concentration in the high salinity area decreases. We further discuss these results in the context of the complex influence of precipitation, Yellow River diversion irrigation, and artificial exploitation on the hydrogeochemical evolution.

Geochemical Evolution of Groundwater in the Quaternary Aquifer in Beni Suef area, Egypt

Geochemical Evolution of Groundwater in the Quaternary Aquifer in Beni Suef area, Egypt

Understanding the geochemical evolution of groundwater in Central Gujarat, India: an integrated hydrogeochemical and multivariate statistical approach

Understanding the geochemical evolution of groundwater in Central Gujarat, India: an integrated hydrogeochemical and multivariate statistical approach

Geochemical evolution of groundwater under the influence of human activities： A case study in the southwest of Poyang Lake Basin

Groundwater quality continues to be threatened globally by anthropogenic activities including excessive use of chemical fertilizers and sewage discharge. However, few studies on the evolution of groundwater chemistry have systematically characterized human and natural effects, while which is of great importance for sustainable water resources management. In this study, hydrochemical data and multiple tracers (δ15N–NO3-, δ18O–NO3-, and 87Sr/86Sr) were employed to elucidate the geochemical evolution of groundwater in an intensive human activity area - the southwest of Poyang Lake Basin where is characterized by the highly complex hydrogeological environment with the diversity of aquifer types and lithology. Combining fuzzy c-means (FCM) clustering with natural background levels (NBLs) analyses, groundwater was divided into four groups with hydrological and statistical significance: groundwater in recharge zones (group 2-1 and group 3), transition zones (group 2-2) and discharge zones (group 1). Using the ions relations and 87Sr/86Sr, we found that the dissolved components of groundwater in recharge zones were controlled by natural processes (water-rock interactions and groundwater runoff conditions), and human activities have altered the natural geochemical evolution of groundwater in transition zones and discharge zones. Multi-tracer approach (δ15N–NO3-, δ18O–NO3-, and 87Sr/86Sr) were used to analyze the sources of nitrate in groundwater. The results showed that the high nitrate load in groundwater was predominately from sewage, and the groundwater quality in local areas was also influenced by NH4+ fertilizer and manure. In addition, nitrate in groundwater was controlled by land use types that groundwater flows through, depending on hydrogeological conditions and soil properties. Inverse geochemical models were developed and constrained to evaluate the relative contributions of natural and anthropogenic sources and to establish a conceptual model of groundwater geochemical evolution in the study area. This study provides a way to evaluate the relative contributions of natural and anthropogenic sources on groundwater quality and explore the geochemical evolution of groundwater in human activity areas.

Recharge and Geochemical Evolution of Groundwater in Fractured Basement Aquifers (NW India): Insights from Environmental Isotopes (δ18O, δ2H, and 3H) and Hydrogeochemical Studies

Considering water as a limiting factor for socio-economic development, especially in arid/semi-arid regions, both scientific communities and policymakers are interested in groundwater recharge-related data. India is fast moving toward a crisis of groundwater due to intense abstraction and contamination. There is a lack of understanding regarding the occurrence, movement, and behaviors of groundwater in a fractured basement terrane. Therefore, integrated environmental isotopes (δ18O, δ2H, and 3H) and hydrogeochemical studies have been used to understand the recharge processes and geochemical evolution of groundwater in the fractured basement terranes of Gujarat, NW India. Our results show that the relative abundance of major cations and anions in the study basin are Ca2+ > Na+ > Mg2+ > K+ and HCO3− > Cl− > SO42− > NO3−, respectively. This suggests that the chemical weathering of silicate minerals influences the groundwater chemistry in the aquifer system. A change in hydrochemical facies from Ca-HCO3 to Na-Mg-Ca-Cl. HCO3 has been identified from the recharge to discharge areas. Along the groundwater flow direction, the presence of chemical constituents with different concentrations demonstrates that the various geochemical mechanisms are responsible for this geochemical evolution. Furthermore, the chemical composition of groundwater also reflects that the groundwater has interacted with distinct rock types (granites/granulites). The stable isotopes (δ18O and δ2H) of groundwater reveal that the local precipitation is the main source of recharge. However, the groundwater recharge is affected by the evaporation process due to different geological conditions irrespective of topographical differences in the study area. The tritium (3H) content of groundwater suggests that the aquifer is mainly recharged by modern rainfall events. Thus, in semi-arid regions, the geology, weathering, and geologic structures have a significant role in bringing chemical changes in groundwater and smoothening the recharge process. The findings of this study will prove vital for the decision-makers or policymakers to take appropriate measures to design water budgets as well as water management plans more sustainably.

Hydrogeochemical characteristics and processes of groundwater in an over 2260 year irrigation district: A comparison between irrigated and nonirrigated areas

A comprehensive understanding of groundwater chemistry and its evolution in irrigation districts is essential for irrigation management. In this study, with emphasis on a comparison between irrigated and nonirrigated areas, the groundwater chemistry and hydrogeochemical processes of a typical irrigation district with an irrigation history of over 2260 years were studied to clarify the effects of long-term irrigation on groundwater quality. Based on 107 water samples collected from across the study area, a comprehensive analysis was conducted using multivariate statistics, stable isotope analysis, and hydrogeochemical modeling. The results showed that the variation range and average concentrations of almost all the ions in the irrigation district are much greater than those in the nonirrigated areas. The groundwater in the nonirrigated areas could be characterized by low TDS and HCO3 or HCO3·SO4 types, whereas the groundwater in the irrigation district could be characterized by complex water types and high TDS. Stable isotopes of hydrogen and oxygen indicated that the groundwater in the irrigation district experienced strong evaporation. The calculated groundwater residence time showed that it takes approximately 2180 years for the groundwater to flow through the irrigation district. Some old irrigation water was present, and it influenced the current groundwater chemistry in the study area. The processes forming the current groundwater chemistry in the irrigation district can be formulated as: mixing → evaporation → water–rock interaction. For mixing, the proportions of rainfall, irrigation water from the Jing River, and lateral recharge from the nonirrigated areas were found to be approximately 30%, 49%, and 21%, respectively. For evaporation, the ratio based on the TDS was 3.83 when comparing the groundwater in the irrigation district with the mixed water after evaporation. Hydrogeochemical modeling showed that the irrigation area is a potential carbon source. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, CO2 degassing and Na-Ca exchange are the main chemical reactions in the geochemical evolution of groundwater. The lesson learned from this irrigation district is that long-term irrigation will lead to salinization and complexity of the groundwater. Hence, in the water resource management of irrigation districts, attention should not only be paid to the balance of water quantity, but also to the balance of salts and the hydrochemical evolution of groundwater.

Investigating the Potential Role of Geological Context on Groundwater Quality: A Case Study of the Grenville and St. Lawrence Platform Geological Provinces in Quebec, Canada

The hydrogeochemical study of the Lanaudière and Eastern Mauricie regions (Canada) demonstrates that trace elements appear to be better tracers of geological influence on groundwater chemistry than major elements. Isotopic ratios and the similar chemical composition of groundwater suggest that the physicochemical parameters of groundwater have a greater effect on hydrogeochemical mechanisms than the immediate geological environment The results allow us to propose a conceptual model of groundwater geochemical evolution with the aim to guide the protection and sustainable management of regional groundwater resources in the Lanaudière and Eastern Mauricie regions. These regions were selected because of their location at the boundary of the Grenville and St. Lawrence Platform geological provinces, representing two distinct geological contexts (Precambrian crystalline rocks and Paleozoic sedimentary rocks). Regional-scale hydrogeochemical and isotopic groundwater characterization was carried out to identify the role of the differences in regional geology on groundwater quality. Our analyses included major and trace elements, stable isotopes, and multivariate statistics. Similar processes are at the origin of dissolved major chemical elements and suggest that soluble minerals common to both geological provinces control groundwater chemistry. If differences exist, they are due to the hydrogeological conditions of the samples, such as residence time or groundwater entrapment at the time of the postglacial marine incursion of the Champlain Sea, rather than the geological context. Some differences, sometimes significant, were observed for some minor elements (F−, Mn2+, H2S), which implies a more comprehensive knowledge of the chemistry of the stratigraphic units within the Lanaudière and Eastern Mauricie aquifers.

Groundwater Origin and Dynamics on the Eastern Flank of the Colorado River Delta, Mexico

Isotope data and major ion chemistry were used to identify aquifer recharge mechanisms and geochemical evolution of groundwaters along the US–Mexico border. Local recharge originates as precipitation and occurs during winter through preferential infiltration pathways along the base of the Gila Range. This groundwater is dominated by Na–Cl of meteoric origin and is highly concentrated due to the dissolution of soluble salts accumulated in the near-surface. The hydrochemical evolution of waters in the irrigated floodplain is controlled by Ca–Mg–Cl/Na–Cl-type Colorado River water. However, salinity is increased through evapotranspiration, precipitation of calcite, dissolution of accumulated soil salts, de-dolomitization, and exchange of aqueous Ca2+ for adsorbed Na+. The Na–Cl-dominated local recharge flows southwest from the Gila Range and mixes with the Ca–Mg–Cl/Na–Cl-dominated floodplain waters beneath the Yuma and San Luis Mesas. Low 3H suggests that recharge within the Yuma and San Luis Mesas occurred at least before the 1950s, and 14C data are consistent with bulk residence times up to 11,500 uncorrected 14C years before present. Either the flow system is not actively recharged, or recharge occurs at a significantly lower rate than what is being withdrawn, leading to aquifer overdraft and deterioration.

Groundwater sources, flow patterns, and hydrochemistry of the Central Yinchuan Plain, China

Groundwater in the Yinchuan Plain (China) is a critical domestic resource that is also used for agricultural irrigation and to maintain ecological environments, among other purposes. Recent research has shown that ineffective planning of water resources, along with large-scale groundwater pumping (mining) has led to ecological problems. To further analyze the characteristics of the regional groundwater flow patterns, and guide the development and utilization of water resources, potentiometric, hydrochemical, and isotopic data were collected along a 60-km transect that crosses the middle Yinchuan Plain. The data were used to develop a two-dimensional conceptual model of the sources, flow patterns, and geochemical evolution of groundwater from the Helan Mountains in the west across the Yellow River in the east. An important component of the model is that in the process of groundwater flow from west to east, the flow direction changes due to the influence of a thick fine-grained sandy-clay unit and long-term groundwater pumping. Local lakes and the shallow groundwater system are recharged by water from the Yellow River. Geochemically, water within the proluvial deposits exhibits relatively low concentrations of total dissolved solids. Further east, the water gradually becomes brackish. The geochemical composition of the shallow groundwater beneath the fluviolacustrine plain west of the Yellow River is also controlled by evaporation, precipitation and cation exchange processes. In other areas, groundwater chemistry is mainly controlled by water–rock interactions and cation exchange. This study enhances understanding of groundwater flow in the region, and provides information critical to water resources development and management.

Analysis of mining effects on the geochemical evolution of groundwater, Huaibei coalfield, China

Investigations were undertaken at the Xutuan and Renlou coal mines in Huaibei coalfield, Anhui Province, China to determine the effects of mining on the geochemical evolution of groundwater in the area. A total of 77 samples were collected between 1999 and 2017 from Neogene, Permian, and Carboniferous aquifers in two coal mines for hydrogeochemical analysis. The variation of hydrochemical types and the difference of Cl− and TDS suggest that the groundwater in the Neogene aquifer flow from the Xutuan coal mine to the Renlou coal mine. The high concentrations of chloride in groundwater in the Permian aquifer may be associated with recharge from the Neogene aquifer under the effects of mining. Principal component analysis and the results of chemical analysis of water samples were used to explore the water–rock processes in the three aquifers. The results suggest that the main controlling process of the Xutuan coal mine is ion exchange between Na+ and Ca2+, while the principal chemical processes in the Renlou coal mine are likely to be ion exchange and reverse ion exchange between Na+ and Ca2+. Mining will lead to the decline of the Neogene aquifer potentiometric heads and the compaction of aquifer sediments. This, in turn, could lead to the development of fissures caused by mining which could increase the hydraulic connection between the Neogene and the Permian aquifer, and increase the ion-exchange intensity of the Permian aquifer. The inverse geochemical modeling results of groundwater flow-paths in the Neogene and Carboniferous aquifers suggest that reverse ion-exchange process is taking place in these aquifers, which provides additional evidence for geochemical evolution. This combined method of using various lines of evidences from hydrogeology, multivariate statistical analysis, hydrogeochemical research, and geochemical models can explain the hydrogeochemical evolution processes of groundwater at a deeper level.

Hierarchical Cluster Analysis as an Indicative of the Hydrogeochemical Evolution of Ground Water in a Shallow Aquifer System

The use of the Hierarchical Cluster Analysis (HCA) in conjunction with a multi-sample graphical technique offers a robust indicator of geochemical evolution of ground water. HCA applied to identify geochemical processes controlling the ground water geochemistry of shallow aquifer system in the outer plains of Jammu and Kashmir State. HCA has good agreement with hydro chemical facies to reflect the process and pattern of the ground water flow in geological formation and it explains the distribution and genesis of ground water. Majority of the collected water samples have higher HCO3- than alkaline earth metals thus indicating base exchange-softened water

Geochemical evolution of the Thriassion Plain groundwaters, Attica, Greece.

The geochemical evolution of groundwater in the coastal area of the Thriassion Plain, Attica, Greece, has been investigated using major and trace elements of chemical analyses. The groundwater of good quality (total dissolved solids TDS between 400 and 1100 mg/l) has been found in the Plio-Pleistocene sediments up to the depth of 90 m below sea level. Moreover, the existing contamination of groundwater in the Pleistocene-Holocene sediments possibly originates from the pumping of the old brackish water of the upper aquifers and the returns of the irrigation water as well as the possible occurrence of palaeo-seawater in the aquifers. A five-stage conceptual model is suggested for groundwater geochemical evolution from the main recharge area to the main discharge area. Limestone and dolomite dissolution in the recharge area leads to one end member of the Ca-Mg-HCO3 type. These waters evolve to Ca-Mg-Cl-HCO3 along their flow path possibly due to the dissolution of relics of evaporites, as well as mixing with seawater that is Na-Cl type, the other end member. Two more hydrogeochemical processes have also been identified; possibly gypsum, anhydrite, halite and fluorite dissolution; calcite, aragonite and dolomite precipitation.

Geochemical evolution of groundwater in hard-rock aquifers of South India using statistical and modelling techniques

ABSTRACTMultivariate statistical analysis and inverse geochemical modelling techniques were employed to deduce the mechanism of groundwater evolution in the hard-rock terrain of Telangana, South India. Q-mode hierarchical cluster analysis (HCA) and principal component analysis (PCA) were used to extract the hydrogeochemical characteristics and classify the groundwater samples into three principal groups. Use of thermodynamic stability diagrams and inverse geochemical modelling in PHREEQC identified the chemical reactions controlling hydrogeochemistry of each of the groups obtained from statistical analysis. The model output showed that a few phases are governing the water chemistry in this area and the geochemical reactions responsible for evolution of groundwater chemistry along the flow path are (i) dissolution of evaporite minerals (dolomite, halite); (ii) dissolution of primary silicate minerals (albite, anorthite, K-feldspar, biotite); (iii) precipitation of secondary silicate minerals (kaolinite, quartz, gibbsite, Ca-montmorillonite) along with anhydrite and calcite; and (iv) reverse ion exchange processes.