Chemical Composition Of Groundwater Research Articles

Evaluation on quality and health risk of groundwater in a highly urbanized watershed, China.

Urbanizations and industrializations may accelerate the contamination and deterioration of groundwater quality. This study aimed to evaluate the quality and potential human health risks associated with shallow groundwater in Shenzhen, China, a city characterized by high levels of urbanization and industrialization. The hydrochemistry characteristics, water quality levels, and human health risks of main ions, nutrient elements, and metals in 220 samples collected from Maozhou River Basin (MRB) located in the northwest of Shenzhen were investigated. It showed that chemical constituents of the groundwater were further complicated by seawater intrusion and urbanization expansion. Water quality evaluated by fuzzy comprehensive method showed that 21.05% of samples distributed around reservoirs were classified into grade II or better. Nearly 79% of samples distributed in the densely populated urban land were classified into grade III or worse, indicating pollution from anthropogenic factors cannot be ignored. For the river tidal reach where river stage fluctuated about 0.5 to 1.5 m within a tidal cycle, the chemical composition of groundwater was influenced by frequent water exchange with the river. The carcinogenic and non-carcinogenic health risks for different age groups, from the high to the low, were children, adult women, adult men, adolescent women, and adolescent men, respectively. Approximately 39% of groundwater samples distributed around the densely populations area with health risk larger than 5 × 10-5 were unacceptable for children. This investigation would be helpful for improving groundwater management and as a practical reference for sustainable groundwater exploitation in the MRB.

Historical and ecological aspects of hydro-reclamation research at the Kirov Meadow-Swamp Experimental Station (<i>to the 105th anniversary of the Station's formation</i>)

The article presents the history of the origin and development of hydromodule research at the Kirov Meadow-Swamp Experimental Station, their practical implementation and ecological significance in the development of the principles of a saving, soil-protective and environment-forming system of agriculture on organic soils in the conditions of the North-East of the European part of the Russian Federation. The main object of long-term research is a typical lowland peatland «Gadovskoye», located on the territory of the Kotelnich peat base of the Kirov region. Special attention is paid to the search for the most effective ways to regulate the water regime of drained swamps used in feed production. It has been established that the most operational, efficient and environmentally friendly method is sluicing, when additional moisture is supplied to the root layer from below. The most optimal range of groundwater regime for annual and perennial forage grasses is shown. The correlation dependence of yield on the degree of drainage of peat deposits is presented. A significant contribution to the reclamation science was made by hydromodule studies on the cutover bogs of the Kirov region. The chemical composition of groundwater and waste swamp waters has been studied on the «Gadovskoye», «Zenginskoye», «Bakhtinskoye», «Pishchalskoye» peatlands, and others, the relationship of the water-physical properties and water regime of the residual deposit with food and temperature regimes, as well as with the coefficient of water consumption of plants and the bearing capacity of the soil of cutover bogs has been established. Agroecological monitoring of the developed peatlands, which have been in culture for more than 40−60 years, shows that during the operation of these facilities there is a gradual decrease in their productivity, due to a decrease in the total agricultural background, partial and even complete violation of the hydrological functions of the drainage network. In order not to completely lose these anthropogenic formations from the sphere of cultural nature management, it is necessary, first of all, periodic repairs of the entire drainage system. Further restructuring within the landscape shell will make it possible to construct fundamentally new post-swamp forest-meadow agroecosystems, where other alternative fields to forage production (hunting, forestry activity, berry-officinal, mushroom, etc.) can be provided.

Identification of hydrochemical fingerprints, quality and formation dynamics of groundwater in western high Himalayas.

Identifying hydrochemical fingerprints of groundwater is a challenge in areaswith complex geological settings. This study takes the Gilgit-Baltistan, a complex geological area in west high Himalayas, Pakistan, as the study area to get insights into the hydrochemcial genesis and quality of groundwater in complex geological mountainous regions. A total of 53 samples were collected across the area to determine the hydrochemical characteristics and formation of groundwater. Results revealed groundwater there is characterized by slightly alkaline and soft fresh feature. Groundwater is dominated by the hydrochemical facies of HCO3·SO4-Ca·Mg type. The factor method yields three components (PCs) of principal component analysis, which together explain 75.71% of the total variances. The positive correlation of EC, TDS, Ca2+, SO42-, K+ in PC1, and NO3-, Cl- in PC2 indicate that a combination of natural and anthropogenic activities influences groundwater hydrochemistry. Water-rock interaction is the main mechanism governing the natural hydrochemistry of groundwater. The negative correlation of Cl-, SO42-, Ca2+, and Na+ with NDVI attributes to inorganic salt uptake by plant roots. Groundwater chemical composition is also affected by the type of land use. Groundwater is characterized as excellent and good water quality based on the entropy-weighted water quality index assessment, and is suitable for drinking purposes except for very few samples, while aqueous fluoride would pose potential health threats to water consumers in western high Himalayas, and infants are most at risk compared to other populations. This study will help to deepen the hydrochemial formation mechanism and exploitation suitability of groundwater resources in the mountainous areas that undergone the combined actions of nature and human activities, and provide insights into the characteristics of water environmental quality in western Himalayas area.

Groundwater quality constrains and new opportunities for water supply from hard rock aquifers in a fast-expanding city of Sub-Saharan Africa, Yaoundé-Cameroon

Expanding cities and their water utilities face a significant challenge ensuring safe and sufficient water supply within a context of great uncertainty. Population growth, urbanisation and economic fluctuation coupled with climate variability further exacerbate these problems in Sub-Saharan Africa (SSA).The study focusing in Yaoundé-Cameroon, Central Africa demonstrates quality constrains and new opportunities of water supply from hard rock aquifers. Stable isotopes and hydrochemical parameters of 56 boreholes, 57 dug wells, 31 springs and 22 rivers, sampled in the dry and wet seasons were used to provide visibility of the groundwater system in addition to its interaction with surface water. Stable isotope results of δ18O and δ2H show uniform mixing of the groundwater masses from rainwater infiltration. Groundwater chemical compositions show variable mineralisation, linked to the environment in which water circulates and the land use change, reflecting classical polluted NaK–NO3 urban groundwater type and CaMg–HCO3 natural water quality in the peri-urban area. The enriched shallow urban groundwater is further reflected in surface water indicating interaction of the two water masses. Hydrochemical processes reveal pollution constrains in urban groundwater uses and the importance of rock-water interaction and residence time in the peri-urban groundwater. The defined NBL/TV coupled with the new water supply scheme could be helpful in the land use management practices, monitoring of the natural water quality and improving access to safe drinking water in SSA.

Chemical Characteristics and Genetic Analysis of Karst Groundwater in the Beijing Xishan Area

As an important water supply source in Beijing， karst groundwater has played an irreplaceable role in the security of urban water supply and ecological environment protection in the past 70 years. The Xishan karst groundwater system， located in the upper reaches of western Beijing， belongs to ecological conservation areas. There are several centralized water supply fields in this area. In this study， the Xishan karst groundwater system was taken as the research object. A total of 120 karst groundwater samples in this area were investigated by using statistical analysis， ion ratio， and principal component analysis （PCA） methods to explore the spatial distribution characteristics and formation mechanism of groundwater hydrochemistry. The research results showed that： ① the groundwater quality of the Xishan system was generally good， with the characteristics of neutral pH and low salinity. A total of 84.17% of the water samples were classified as hard water. The chemical type of groundwater was mainly HCO3-Ca·Mg. ② The chemical composition of groundwater was mainly affected by the water-rock interaction， and the weathering source of rock was mainly the dissolution of carbonate. ③ The results of principal component analysis showed that 34.41% of the chemistry formation of groundwater could be explained by carbonate dissolution， 27.33% by rock salt and evaporate dissolution， 11.76% by aquifer sediment dissolution， and 10.30% by domestic sewage discharge. From the recharge area to the runoff area and then to the discharge area， the TH and TDS gradually increased. Coal mining drainage and human activities were the main factors that caused groundwater degradation and variable hydrochemical types in the piedmont. In the future， it is necessary to further strengthen environmental governance， control point and non-point source pollution， and continuously monitor key areas to provide scientific support for ecological and environmental protection.

Anthropogenic load effect on formation of hydrogeological conditions of the Shirvan steppe of the Kura-Aras lowland in Azerbaijan

Relevance. Azerbaijan water and soil resources are limited and subject to technogenic impacts more and more every year. Use of water and demand for water in the republic are growing at a higher rate every year. On the other hand, global climate changes have a serious impact on formation of hydrogeological processes. In such circumstances, it is very important to study the formation situations of hydrogeological conditions under the influence of natural and anthropogenic factors, to use the available water resources efficiently and economically, and to take preventive measures against negative processes. Aim. To study the regularity of formation of the hydrogeological conditions of the Shirvan steppe of the Kura-Araz lowland in the Republic of Azerbaijan under the influence of natural and anthropogenic processes over a long period time. Object. Subsoil waters of the Shirvan steppe of the Kura-Araz Lowland in the Republic of Azerbaijan. Methods. Based on the results of the studies (1977 to 2020) of perennial average level of groundwater and degree of mineralization, the rate of soil salinization, the regime of groundwater and based on the materials collected in this direction, the regime types of groundwater were separated and correlative dependence was found by the method of least squares between regime types and regime-shaping factors – atmospheric sediments, river networks, irrigation water, irrigation canals, drainage, etc. The genetic types of the regime were selected according to the factors creating the regime and the synchronicity of the groundwater level change. Results. Under the influence of natural and anthropogenic factors, the level of groundwater, degree of mineralization, chemical composition, salinity and chemical composition of soils have changed. From 1958 to 2020, due to the irrigation melioration, the groundwater level of the area rose by 4.1 m, due to the infiltration of surface water and removal of mineralized water through drainage, their mineralization rate decreased by 16.2 g/l. Based on the results of the research on changes in the level, degree of mineralization and chemical composition of groundwater, soil salinity and chemical composition, and based on the analysis of archival materials collected in this direction, groundwater regime types were selected and correlative dependence between regime types and regime-creating factors by the method of least squares was defined. Due to the synchronicity of regime-creating factors and groundwater level changes, the genetic types of the regime were selected – climate, hydrological, irrigation, irrigation-watering, drainage, irrigation-watering and the fields of their distribution areas were determined.

Geochemical Characteristics and Controlling Factors of Groundwater Chemical Composition in the Zihe River Source Area, Shandong, China

The geochemical characterization and evolution of shallow groundwater in the Zihe River source area is a key issue that needs to be addressed. In this study, a combination of traditional geochemical techniques and geochemical modeling was used to explain the geochemical processes and major ion sources in the chemical evolution of shallow groundwater in the Zihe River source area, Northeast China. Fifty-seven water samples were collected in June 2020 for chemical analysis, and the results showed that the main groundwater chemistry types in the three major aquifers are HCO3·SO4-Ca·Mg-type pore water from loose quaternary rocks, HCO3·SO4-Ca·Mg-type karstic fissure water from carbonate rocks, and HCO3·SO4-Ca-type weathered fissure water from massive rocks. Water–rock interactions in alkaline environments were the main causes of changes in groundwater chemistry. Rock weathering dominated the geochemical evolution of each aquifer. The analysis of ion concentration ratios and modeling revealed that the aquifer’s chemical components are mainly derived from the dissolution of dolomite and calcite and partly from the infiltration of pollutants containing Cl− and NO3−, as well as from the dissolution of quartz. Mg2+ is derived from the dissolution of dolomite. HCO3− is primarily derived from the co-dissolution of calcite and dolomite, and to a lesser extent, its content is also influenced by the recharge of rainfall. SO42− has two sources: it mainly originates from the dissolution of gypsum and the anhydrite layer, followed by atmospheric precipitation. The synthesis showed that the groundwater quality in the source area of Zihe River is good, all the indices reached the standard of class III groundwater quality, and the overall degree of human pollution is low. The results of this research will provide a scientific basis for the local authorities to delineate karst groundwater protection zones in the Zihe River source area and to formulate resource management strategies for the development, utilization, and protection of karst groundwater.

Evaluating the groundwater quality in Northern Tarim Basin by resistivity inverted from magnetotelluric data

Groundwater is a potentially significant resource for agricultural and industrial uses in Tarim Basin, the largest arid endorheic basin in China. Hydrogeochemical and hydrogeologic researches have provided detailed information of groundwater chemical type, composition, ion content and flow. However, there is lacking in quantitative estimation of groundwater in whole basin scale subject to the limits of samples as well as the unclear underground structure. To address the problem, 3-D electrical resistivity model constructed from inversion of magnetotelluric (MT) data was used to calculate the Total Dissolved Solids (TDS) of groundwater based on previous experimental studies and empirical equations. The TDS model shows relatively high value in the east of the study area and in deep, primarily controlled by depth, flow direction, stratigraphy, and water table gradient. Groundwater can be classified into five categories in terms of TDS range in Standard for Groundwater Quality. Finally, the volume of each type and average available quantity of Classes I ∼ III (TDS < 1 g/L) per person were estimated by taking account of population distribution. Mapping groundwater TDS and volume reveals that human activities also play a role in groundwater salinity. The evaluation of groundwater quality and volume based on TDS provides a basis for future urban construction and development as well.

Analysis on the Chemical Characteristics and Genesis of Drinking Groundwater in Rural Areas of Suihua City, Northeast China

People living in the rural areas of Suihua City rely mainly on groundwater. Determining the chemical characteristics of groundwater and its impact on human health is very important to support drinking water safety engineering. We conducted a systematic study of water chemistry and human health by using software such as SPSS, SQLEVAL, MapGIS, and other methods such as statistical analysis, correlation analysis, Shukarev analysis, Piper’s trilinear plot analysis, scale factor analysis, and N.L. Nemerow index analysis. It is concluded that the cation in the groundwater is mainly of calcium type, and the anion is of mixed type of chloride, sulfate, and bicarbonate. The four types of water chemistry that account for greater than 10% of the total are 11-A, 4-A, 8-A, and 22-A. The chemical composition of groundwater is mainly controlled by rock weathering; Na+ and K+ come from rock salt and silicate rock; while Ca2+ and Mg2+ mainly come from carbonate rock. Cation Exchange interaction occurs in shallow groundwater. Fe and Mn in groundwater are mainly influenced by geological and lithological factors, while NO3 − and F− are mainly influenced by anthropogenic activity. This study is of great significance for the management of healthy drinking water in rural areas of Suihua City.

Variation of groundwater and mineral composition of in situ leaching uranium in Bayanwula mining area, China.

The reaction between the lixiviant and the minerals in the aquifer of In-situ uranium leaching (ISL) will result mineral dissolution and precipitation. ISL will cause changes in the chemical composition of groundwater and the porosity and permeability of aquifer, as well as groundwater pollution. Previous studies lack three-dimension numerical simulation that includes a variety of minerals and considers changes in porosity and permeability properties simultaneously. To solve these problems, a three-dimensional reactive transport model (RTM) which considered minerals, main water components and changes in porosity and permeability properties in Bayanwula mine has been established. The results revealed that: (1) Uranium elements were mainly distributed inside the mining area and had a weak trend of migration to the outside. The strong acidity liquid is mainly in the mining area, and the acidity liquid dissolved the minerals during migrating to the outside of the mining area. The concentration front of major metal cations such as K+, Na+, Ca2+ and Mg2+ is about 150m away from the boundary. (2) The main dissolved minerals include feldspar, pyrite, calcite, sodium montmorillonite and calcium montmorillonite. Calcite is the most soluble mineral and one of the sources of gypsum precipitation. Other minerals will dissolve significantly after calcite is dissolved. (3) ISL will cause changes in porosity and permeability of the mining area. Mineral dissolution raises porosity and permeability near the injection well. Mineral precipitation reduced porosity and permeability near the pumping well, which can plugging the pore throat and affect recovery efficiency negatively.

Impact of ground adsorption capacity on the change in chemical composition of groundwater

Impact of ground adsorption capacity on the change in chemical composition of groundwater

Deriving groundwater major ions from electrical conductivity using artificial neural networks supported by analytical hydrochemical solutions

Tracing groundwater chemistry requires broad and continuous sampling campaigns to keep track of groundwater deterioration. The need is pressing in coastal aquifers due to high water demand to meet rapid population growth. This paper uses artificial intelligence (AI) to develop an algorithm capable of predicting seven major chemical ions in water (Ca2+, Mg2+, Na+, K+, HCO3−, Cl− and SO42−) from electrical conductivity (EC), a single input that can be easily acquired manually or via automated monitoring programs. The algorithm mainly relied on artificial neural network (ANN) to tackle complex and nonlinear relationships. It included a set of procedures among others, Levenberg-Marquardt back propagation multilayer perceptron (MLP), conjugate gradient back propagation with Fletcher-Reeves updates MLP, and support vector regression. The low accuracy of ANN models in predicting Ca2+ and HCO3− concentrations justified their calculation via advanced hydrochemical analytical solutions that were embedded in one AI scheme. The full scheme was trained and tested over an EC20 range of 400–3000 μS/cm, and then validated for new measurements elsewhere. It showed <15% discrepancy for the four ions that constitute the majority of groundwater chemical composition (Cl−, Na+, HCO3− and Ca2+). Higher uncertainties were associated with concentrations derived for EC values outside the training limits. The developed algorithm can save time and money in return of labor and laboratory work. It is an open source code publicly available for further improvements by training it on additional data covering a wider EC range.

Chemical composition of groundwater and its controlling factors in the Liuzhuang coal mine, northern Anhui Province, China

Abstract Identification of the hydrochemical characteristics of the groundwater system in the mining area and the controlling factors of the water's chemical components is necessary to protect groundwater resources. In this study, 80 sets of groundwater samples were collected from three aquifers of the Liuzhuang coal mine (northern Anhui Province, China), and a total of eight indicators were selected for quantitative analysis of the chemical components of water. Conventional mathematical and statistical methods and Piper trilinear diagrams show that the cations in the groundwater samples of the mine area are mainly K+ + Na+ (92.4%), while the anions in the Cenozoic and Carboniferous aquifers are mainly Cl−, reaching 57.2% and 55.2%, respectively, and the anions in the Permian aquifer are mainly HCO3- (52.6%). Most of the water chemistry types are Cl-Na, HCO3-Na, and HCO3-Cl-Na. Analysis on the basis of Gibbs plots showed that the aquifer system in the mine area is primarily controlled by the water–rock interaction. The results of ion ratio analysis, principal component analysis, and cluster analysis showed that the dissolution of hydrochloric acid and alternating cation adsorption is more prominent in the Cenozoic and Carboniferous aquifers, while desulfurization is more significant in the Permian aquifer.

Hydrogeochemical evolution of groundwater impacted by acid mine drainage (AMD) from polymetallic mining areas (South China)

Mining activities have long-term impacts on the groundwater of surrounding areas and deserve in-depth analysis and study. Herein, the geochemical mechanisms of acid mine drainage (AMD)-affected groundwaters were examined, and groundwater quality was assessed through water quality indices. 15 water samples from 7 domestic and 4 groundwater monitoring wells were tested for physical and chemical parameters in 2022, and multivariate statistical analysis was carried out with monitoring data from 21 domestic wells in 2010. The groundwater chemical composition varied from a predominantly Ca-HCO3 type in 2010 to a Ca-SO4 type in 2022. The isotopic values of δ18O and δD indicate that groundwater has not been significantly affected by evaporation. Changes in groundwater sulfate and total dissolved solids (TDS) levels over the twelve-year period confirmed the AMD infiltration impact on groundwater quality. The groundwater chemical properties changed more slowly than those of surface waters affected by AMD based on a cumulative increase in sulfate concentration of 29.94 mg/L. Changes in groundwater quality were investigated, namely, the spatiotemporal distribution of potentially toxic elements (PTEs), including Fe, Mn, Cd, Pb, and As. Mn concentrations in upstream groundwater areas near the mine decreased by 61.8% between 2010 and 2022. Conversely, groundwater in midstream areas had Mn concentrations of 2.25 mg/L and arsenic concentrations of 11.8 μg/L, both exceeding the WHO, 2022 standard. According to multivariate statistical analysis, Mn, Cd, and Pb originated from polymetallic minerals, whereas As was likely derived from the reduction of Fe/Mn hydroxyl oxides. AMD remediation improved contaminated upstream groundwater quality over 12 years, with a 36.8% improvement in WQI values. PTE distribution determined water quality changes; therefore, PTE contamination should be treated in mid- and downstream regions while contaminated groundwater should be treated upstream.

Controls of groundwater mineralization assessment in a mining catchment in the Upper West Region, Ghana: Insights from hydrochemistry, pollution indices of groundwater, and multivariate statistics

Natural and anthropogenic activities have proven to be the main sources of contaminants in groundwater. Hence, the need for continuous evaluation of the controlling factors of groundwater mineralization for monitoring purposes. The study assessed the controls of the groundwater mineralization in the Julie gold belt of the Upper West Region of Ghana using hydrochemistry, pollution index of groundwater (PIG), percentage of pollution index (PPI), factor analysis, and a multivariate linear regression model. TDS ​> ​HCO3− ​> ​NO3− ​> ​Ca2+ ​> ​Mg2+ ​> ​Na+ ​> ​Cl− ​> ​SO42− ​> ​K+ ​> ​CO32− ​> ​F− are the trends in the abundance of the hydrochemical parameters and are generally within WHO acceptable limits, with the exception of F− and NO3− contents in 5 and 32 communities, respectively. Waters containing Mg2+, Na+, HCO3−, and SO42− evolved into Mg–HCO3–Na–SO4. The PIG indicated pollution levels of 73.3% and 26.7% from mineral dissolution and agricultural activities, respectively, from the PPI values. From the indices, shallow meteoric water (r2 ​> ​1 values), factor analysis, and regression model approaches, anthropogenic activities, and mineral dissolution are the main controlling factors for the groundwater chemical composition in the area.

Assessing the intensity of reduction and restoration of irrigated lands’ state in the Republic of Bashkortostan

AbstractBackgroundIrrigation of lands over time leads to such negative processes as land salinization and waterlogging, reduction of soil fertility, changes in the chemical composition of groundwater, and the emergence of linear and irrigation erosion. The land improvement (ameliorative) categories adopted in Russia and several post‐Soviet countries determine their suitability for agricultural use and the focus of measures to preserve potential soil fertility.AimsThe study aims to build a mathematical model to assess the intensity of the reduction and restoration of irrigated lands’ state in the Republic of Bashkortostan.MethodsThe methods of the theory of random processes are proposed to estimate the intensity of reduction and restoration of irrigated lands’ state on the territory of the Republic.ResultsAs a result of the calculations, the values of intensities characterizing changes in the state of land in the region were obtained. The practical significance of the developed model consists of the possibility of short‐term forecasting and determination of the necessary intensity of land quality restoration taking into account planned values during the given period.ConclusionsThe offered indicator of intensity and the method of its definition can be used in research of similar processes proceeding on agricultural lands within the limits of large spatial units.

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.

Traceability and Biogeochemical Process of Nitrate in the Jinan Karst Spring Catchment, North China

Accurate identification of nitrate (NO3−) sources is critical to addressing groundwater pollution, especially in highly vulnerable karst aquifers. The groundwater hydrochemistry and δ15NNO3 and δ18ONO3 isotopes were analyzed in samples taken from the Jinan Spring Catchment, which has been affected by urbanization and agricultural activities. The study highlighted the use of hydrochemistry, environmental isotopes, and a multisource linear mixed model for NO3− source identification and apportionment. The results showed that, controlled by carbonate rocks, the hydrochemical types in both rainy and dry seasons were highly consistent, and HCO3·SO4−Ca was the dominant type, accounting for 60%. Except for Ca2+, Mg2+ and HCO3−, the coefficients of variation of other ions were all greater than 0.5 in rainy and dry seasons. The chemical composition of groundwater was mainly controlled by water–rock interaction. Ca2+ and HCO3− were mainly derived from carbonate rock dissolution; K+, Na+, SO42−, NO3− and Cl− were partially derived from atmospheric precipitation. The IsoSource model quantitatively revealed that the majority of the groundwater and surface water was influenced by manure and sewage (M&amp;S) contributing 39.3% and 52.3% in the rainy season, and 37.1% and 56.9% in the dry season, respectively. The NO3− source fraction rates were in the order M&amp;S &gt; SON &gt; AF &gt; CF &gt; AD. In addition, nitrate pollution control measures and suggestions for different areas are put forward. In rural residential areas, the free discharge of livestock manure and sewage should be strictly controlled. In agricultural planting areas, chemical fertilizers and pesticides should be used rationally to prevent non-point source pollution. In urban areas, the centralized treatment of industrial and residential sewage should be strengthened to prevent point source pollution.

Hydrogeochemical fingerprint, driving forces and spatial availability of groundwater in a coastal plain, Southeast China

Groundwater is a critical water source, and was investigated from a coastal plain of southern China to reveal its hydrochemical constrains on water supply from phreatic aquifers of humid regions. Groundwater is dominantly fresh but with a relatively large TDS variation of 59-5,800 mg/L. Groundwater chemical composition is complex and presents variable hydrochemical facies from HCO3-Ca to ClNa type. Nitrogen and trace elements in groundwater exceed the desirable drinking limits and may pose health risks to all populations through oral pathways. Nitrogen and Mn are the dominant health threats. Groundwater has a large variation of integrated water quality with the EWQI in the range of 11–1179, but is predominantly (84.78%) excellent to medium quality and suitable for domestic usages. The piedmonts are the ideal areas for groundwater exploitation as groundwater presenting good to poor quality trend from the piedmont downstream-wards. Groundwater hydrochemistry is naturally governed by rock-water interactions, and sporadically regulated by evaporation. Agricultural practices and sporadic municipal sewages input nitrogen and major chemicals into groundwater and result in salinity and quality deterioration. Groundwater exceeding F, I, Fe and Mn are derived from geogenic sources. Both anthropogenic and geogenic toxic substances should be concerned in long-terms groundwater supply

The influence of tectonic setting on groundwater chemical composition in the Peshkopi gypsum karst area, Korab Mountains, Eastern Albania

The influence of tectonic setting on groundwater chemical composition in the Peshkopi gypsum karst area, Korab Mountains, Eastern Albania