Ions In Groundwater Research Articles

Identification of seawater intrusion in Gapura Sub-district, Sumenep Regency, East Java, Indonesia

Gapura sub-district is located in the Sumenep Regency, Madura Island, that also recognized as the center of salt production. Due to not availability of a clean water network from the municipal water network (PDAM), the daily water need of the community is provided by groundwater. Local people have reported several brackish waters in the wells since a few years ago. Therefore, the purpose of this research is to identify seawater intrusion potential in this area. The seawater intrusion is analyzed based on the value of electrical conductivity (EC) and groundwater hydrochemistry. From the analysis of EC values, it can be concluded that there are two out of thirty groundwater samples classified as moderately saline water, while in the study of groundwater ion values, both two samples have chloride values that are more than 240 mg/L. However, the Cl and HCO3 ratio show that the two samples will only have a small effect on seawater. Therefore, it can be concluded that the Gapura sub-district does not have seawater intrusion. High salinity in some wells is mostly coming from salt production in this area.

Understanding the hydrogeochemical processes and physical parameters controlling the groundwater chemistry of a tropical river basin, South India.

Detailed investigation on hydrogeochemistry of hard rock terrains is important to identify the major geochemical processes and the source of ionic constituents in groundwater. The present study is carried out to understand the hydrogeochemistry of groundwater resources and the major hydrogeochemical processes, controlling the concentration of major ions in groundwater in the Kallada River Basin (KRB), South India. About 166 groundwater samples were collected from KRB during pre- and post-monsoon of 2016 for hydrogeochemical analysis. Most of the groundwater samples in KRB were within permissible limits of drinking water quality. The dominant groundwater types during pre-monsoon were Ca2+-Mg2+-Cl- which was changed to Na+-Cl- during post-monsoon. This is supported bythe inverse relationship of depth of wells and change in EC during pre- and post-monsoon periods. Rock-water interaction processes such as reverse ion exchange and silicate weathering are major geochemical processes responsible for the hydrogeochemical signatures of KRB. The shallower wells (< 10 m) show strongest relation with the water types Na+-HCO3- and Ca2+-Mg2+-Cl- which have been changed to Na+-Cl- and Ca2+-Mg2+-HCO3- during post-monsoon. However, in deeper wells, Na+-Cl- is the dominant type of water during both seasons. The hierarchical cluster analysis displays different hydrogeochemical associations representing diverse physicochemical parameters both spatially and temporally. This study could shed light on diverse hydrogeochemical processes which are responsible for the hydrogeochemistry in KRB. Major hydrogeochemical processes in the Kallada River Basi.

Full-scale testing and numerical modelling of segmental-joint performance with corroded bolt

Water leakage through segmental joints often occurs for shield tunnels built under groundwater. Chloride ions in groundwater can cause the corrosion of steel bolts in segmental joints, reducing the rigidity of the tunnel lining and endanger the operation safety of tunnels. In this paper, the impact of the corrosion of the steel bolt on the structural performance of segmental joint was investigated using six full-scale segmental joint tests and a series of numerical simulation. Both the experimental and numerical results indicate that the segmental-joint performance can be divided into three stages under different loading and corrosion states. The bolt corrosion can reduce the waterproof ability, bending stiffness, and ultimate bearing capacity of the segmental joint. The impact of the bolt corrosion is most significant in the second stage. Furthermore, the bolt corrosion has a larger impact on segmental-joint performance under a positive bending moment than under a negative bending moment, owing to the configuration of the joint. The impact of the bolt corrosion is strongly dependent on the loading state of the tunnel joint and the corrosion ratio of the bolt.

Nitrate in groundwater of the west side Magelang Regency, Central Java, Indonesia

Nitrate (NO3-) pollution in groundwater is generally caused by chemical fertilizers from the agricultural sector and wastewater from onsite sanitation. Magelang Regency, Central Java, Indonesia, is a large food estate that has 206 km2 paddy fields. In addition, this area is inhabited by 1.3 million people who produce onsite sanitary waste every day. Due to the concentration and intensity of fertilization and sanitary waste, which are quite high, Magelang Regency is susceptible to groundwater pollution by nitrate. This study aims to determine the characteristics of nitrate in the groundwater of the west side Magelang Regency, Central Java, Indonesia. The research was carried out by testing groundwater samples taken from several springs, dug wells, and drilled wells used by society for their daily needs. Groundwater sampling was carried out in the wet season and tested using the ion chromatography method to determine the level of nitrate in groundwater and know the chemical characteristics to analyze dominant ions in groundwater. The results showed that the average nitrate was 3.9 mg/l; the deviation standard was 5.12; minimum nitrate was 0 mg/l; and maximum nitrat was 20.78 mg/l. The origin of nitrate content may come come from feces but still in small quantities. Facies of groundwater are Ca-HCO3 and Na-Cl. It can be concluded that the groundwater of the west side Magelang Regency is not yet polluted by nitrate. However, there is still a possibility in the future, so that necessary to apply for groundwater protection immediately.

Source apportionment and natural background levels of major ions in shallow groundwater using multivariate statistical method: A case study in Huaibei Plain, China

Understanding the sources, natural background levels (NBLs), and threshold values (TVs) of the major ions in groundwater is essential for the effective protection of water resources. In this study, a total of 70 shallow groundwater samples were collected in Suzhou, Huaibei Plain, China. A variety of statistical methods and cumulative probability distribution techniques were performed to identify the sources, NBLs, and TVs of the major ions. The major ion concentrations found in decreasing order as follows: HCO3− > SO42− > NO3− > Cl− and Na+ > Ca2+ > Mg2+. Piper diagram for hydrochemical types shows that groundwater types were Mg–HCO3 (36%), Ca–HCO3 (34%), and Na–HCO3 (30%). According to the factor and the Unmix model analysis, anthropogenic (agriculture-related) and geogenic source (water–rock interactions-related) were identified to be responsible for the chemical composition of the groundwater in the study area, and their mean contributions for the major ion concentrations are 47.9% and 52.1%, respectively. The NBLs for Na+, Ca2+, Mg2+, Cl−, SO42−, and NO3− were determined to be 29.5–44.2, 26.2–38.9, 18.9–39.5, 1.0–9.9, 12.9–19.4, and 2.1–16.5 mg/L, respectively, and the TVs were calculated as 122.1, 169.5, 39.5, 129.6, 134.7, and 18.3 mg/L, respectively. Moreover, this study shows the feasibility and reliability of using these multivariate statistical methods and natural background levels to evaluate the status of groundwater quality.

Correlation of hexavalent chromium concentration to groundwater hydrochemical zones chemistry

The origin of hexavalent chromium in groundwaters can be anthropogenic and/or geogenic. The natural occurrence of Cr6+ in groundwater has been reported in many regions of the world and occurs by oxidation of Cr3+ to Cr6+ in the presence of Mn oxides of ultramafic rocks and serpentinites in ophiolite complexes. Pumping and intensive use of groundwater is an anthropogenic activity with effect on water vulnerability and Cr6+ formation. The chemistry of groundwater zonation can be helpful in determining the vulnerability of groundwater to contamination. Depending on the geological background, the water in the deeper aquifer levels has a clearly different composition from the water in the shallow aquifer levels. In this work, five neighboring aquifer systems of different geological background are simultaneously examined targeting to identify the origin of the Cr6+ in the different aquifer hydrochemical zones and the impact of groundwater use on contamination levels. Correlation of separate clusters of Cr6+ concentration to representative groundwater ions or ion ratios from water-rock interaction, at different sampling periods, has been applied for the first time. There is a strong positive correlation of nitrates only to low concentrations of Cr6+. These results indicate the leaching in the shallow zone of Cr6+, formed in the unsaturated zone, together with high content in NO3− precipitated water and/or return irrigation water. High concentrations of Cr6+ present no correlation to nitrates and positive correlation to both Mn2+ and Fe2+ indicating its geogenic formation in the ophiolite sediments of the deep aquifer.

Hydrochemical Characteristics and Evolution of Groundwater in the Alluvial Plain (Anqing Section) of the Lower Yangtze River Basin: Multivariate Statistical and Inversion Model Analyses

The alluvial plain (Anqing section) of the lower reaches of the Yangtze River basin is facing increasing groundwater pollution, not only threatening the safety of drinking water for local residents and the sustainable development and utilization of groundwater resources but also the ecological security of the Yangtze River Basin. Therefore, it is necessary to conduct a preliminary analysis on the hydrochemical characteristics and evolution law of groundwater in this area. This study aimed to evaluate potential hydrogeochemical processes affecting the groundwater quality of this area by analyzing major ions in groundwater samples collected in 2019. Compositional relationships were determined to assess the origin of solutes and confirm the predominant hydrogeochemical processes controlling various ions in groundwater. Moreover, factors influencing groundwater quality were evaluated through the factor analysis method, and the control range of each influencing factor was analyzed using the distribution characteristics of factor scores. Finally, reverse hydrogeochemical simulation was carried out on typical profiles to quantitatively analyze the hydrochemical evolution process along flow paths. The Piper trilinear diagram revealed two prevalent hydrochemical facies, Ca-HCO3 type (phreatic water) and Ca-Na-HCO3 type (confined water) water. Based on the compositional relationships, the ions could be attributed to leaching (dissolution of rock salt, carbonate, and sulfate), evaporation and condensation, and cation exchange. Four influencing factors of phreatic water and confined water were extracted. The results of this study are expected to help understand the hydrochemical characteristics and evolution law of groundwater in the alluvial plain (Anqing section) of the lower Yangtze River basin for effective management and utilization of groundwater resources, and provide basic support for the ecological restoration of the Yangtze River Basin.

Groundwater Chemistry at Deep Aquifer in Koyra: Khulna, Bangladesh

Koyra (Khulna District) is the coastal Upazila of Bangladesh and is very susceptible to salinity intrusion. The surface and shallow tube well water in the Upazila is naturally saline. The quality of subterranean tube well water in the deliberate area is hardly presented for different Unions of Koyra. Dakshin Bedkashi Union of Koyra is very saline prone. Therefore, the groundwater chemistry of Dakshin Bedkashi Union was determined to legalize if the groundwater is fit for drinking and irrigation or not. Spatially dispersed 30 water samples were collected from the deep aquifer (550 to 700 feet depth) in December, 2016 and analyzed for physico-chemical properties. The outcomes were compared with WHO, USEPA and BBS drinking water quality standard and with FAO standard for irrigation purpose. The pH varied from 6.73 to 8.33, indicating that the water samples were within the WHO drinking water quality standard. The TDS showed a long range variation (230.5 to 2052.0 ppm) with an average of 841.23 ppm, of which 33% of water sources exceeded BBS standard value. The mean value of salinity was 0.65 (±0.43) ppt and EC was 1,400.9 (±904.18) µS cm-1. The loads of key ions were ranked as Na+&gt; Ca2+&gt; Mg2+&gt; K+ and HCO3-&gt; Cl-&gt; SO42-&gt; NO3-&gt; PO4-. The Piper diagram demonstrated that the existing hydro-chemical facies of groundwater were Na+-Cl--HCO3- and Na+-Ca2+-HCO3- type. The Gibbs diagram illustrated that the chemical arrangement of groundwater is mainly misrepresented by rock weathering. Silicate weathering was the profuse process along study area. The Wilcox diagram proved that the greater water sources were allowable to suspicious for irrigation. The core component analysis ensured that rock suspension and sea water intrusion was the primary source of ions in groundwater. The controlling factors of groundwater chemistry were typically related to geologic factors, while the anthropogenic factors have not any momentous effects.

Hydro-chemical Characteristics and Ion Origin Analysis of Surface Groundwater at the Shengjin Lake and Yangtze River Interface

The interface between Shengjin Lake and Yangtze River was selected as the study area. The water chemical composition and hydrogen and oxygen isotope values of different types of water bodies were tested, and their seasonal variation characteristics were analyzed to explore the sources of chemical ions in the surface and groundwater. Finally, the contribution of mixed water sources to chemical ions in groundwater was estimated. The results show the following ① The concentration of chemical ions in the surface and groundwater of the study area is higher than that of atmospheric precipitation, and the physical and chemical parameters exhibit seasonal variation. ② Surface water mainly belongs to the Ca-HCO3 type, but the proportion of the Ca-SO4 type in summer is significantly lower than that in other seasons; Groundwater primarily belongs to Ca-HCO3 and Ca-SO4 types, with proportions of 46% and 27%, respectively, and the seasonal difference is not significant. ③ Ca2+ and Mg2+ in the surface and groundwater mainly come from the dissolution of carbonate rocks, carbonic acid and sulfate ions participate in the dissolving process of carbonate minerals. Na+and Cl- are partly derived from atmospheric precipitation and partly sourced from agricultural fertilization and manure sewage. ④ Mixed water sources is also an important source of chemical ions in groundwater, with the average contribution 28% to Cl-, showing a seasonal trend.

Preseismic Groundwater Ion Content Variations: Observational Data in Flowing Wells of the Kamchatka Peninsula and Conceptual Model

Repeated manifestations of hydrogeochemical anomalies in groundwater ion content variations before local strong earthquakes were recorded in three flowing wells of the Petropavlovsk-Kamchatsky test site. A model of changes in chemical composition of groundwater is considered using observational data and modeling of two waters mixing with contrasting composition in a zone of increased permeability in aquifer. Hydrodynamic parameters of the model—relaxation time of water pressure impulses and the time of mixed water movement in aquifer and wellbore—can vary from days to hundreds of days in individual wells. These parameters determine the duration and morphological features of anomaly in mixed water from a well. Using observational data from self-flowing well M-1, an assessment was made of chemical composition and mineralization of two mixing waters and their ratio in mixed water under background conditions and during the preparation of earthquake on 2 March 1992, Mw = 6.9.

Risk factors for endemic chronic kidney disease of unknown etiology in Sri Lanka: Retrospect of water security in the dry zone

The prevalence of chronic kidney disease of unknown etiology (CKDu) is receiving considerable attention due to the serious threat to human health throughout the world. However, the roles of geo-socio-environmental factors in the prevalence of the CKDu endemic areas are still unknown. Sri Lanka is one of the countries most seriously affected by CKDu, where 10 out of 25 districts have been identified as the areas with the high prevalence of CKDu (10–20%). This review summarizes the geographical distribution of CKDu and its probable geochemical, behavioral, sociological, and environmental risk factors based on research related to hydrogeochemical influences on CKDu in Sri Lanka. More than 98% of CKDu patients have consumed groundwater as their primary water source in daily life, indicating the interactions of geogenic contaminants (such as F−, total dissolved solids, Hofmeister ions) in groundwater is responsible for the disease. Apart from the hydrogeochemical factors, mycotoxins, cyanotoxins, use of some herbal medicines, dehydration, and exposure to agrochemicals were alleged as risk factors. Sociological factors, including poverty, living habits and anthropogenic activities, may also provoke the emergence of CKDu. Therefore, the interaction of geo-socio environmental risk factors should be sociologically and scientifically considered to prevent the prevalence of CKDu. Future in-depth studies are required to reveal the individual role of each of the postulated etiological factors, possibly using machine learning and advanced statistics.

Hydrogeochemical characterization of Tai’an Pumped Storage Power Station reservoir and the implications for Reservoir Water Leakage

Reservoir leakage is typically a potential risk to reservoir operation in the world. In this study, Tai’an pumped storage power station reservoir was selected as an example to analyze the chemical characteristics of various waters in detail. The results showed that silicate rock weathering was the main source of water chemical ions of reservoir water, groundwater and Bashangoue water. Hydrogeochemical analysis showed that the water samples of the right bank gallery and measuring weir behind dam came from the reservoir water leakage, measuring weir of bottom gallery, B2 branch pipe gallery and No.6 construction hole water samples did not originate from reservoir water but from groundwater. The research results are of great guiding significance for guiding the diagnosis and control of reservoir leakage.

Hyporheic zone geochemistry of a multi-aquifer system used for managed aquifer recharge in Beijing, China

Hyporheic groundwater geochemistry evolution depends on the interactions of surface water and groundwater (SW–GW). Hydrodynamic variations driven by the long-term managed aquifer recharge (MAR) practice could change hyporheic geochemical processes, which requires a better understanding for groundwater management. In this work, a geochemical survey was conducted in a multi-aquifer MAR system. The results showed great impact of the MAR practice on the hydrodynamics and major ion chemistry of groundwater in the hyporheic zone compared to natural recharge. Besides, related geochemical processes including rock weathering and ion exchange showed increased effect on hyporheic hydrochemistry with aquifer depth, depending on hydrogeological conditions in addition to river water infiltration. Combined with hydrochemical indicators and the end-member mixing model, the relative contribution of precipitation to groundwater was estimated to be 5% for the 30-m aquifer, 16% for the 50-m aquifer, and 64% for the 80-m aquifer. However, precipitation made small contributions (<5%) to the major ions of groundwater regardless of depth. Conversely, the relative contributions of river water infiltration decreased with aquifer depth (95%→84%→36%), and its proportional contributions to major ions showed a similar trend (90%→84%→39%), which suggests reduced SW–GW interaction intensity with depth in the hyporheic zone. The major ion compositions of hyporheic groundwater tend towards river water after the long-term MAR practice, reflecting comprehensive effect of mixing and related geochemical processes. This study demonstrates the relevance of detailed studies at regional scale to understand anthropogenic effects from projects such as MAR on groundwater geochemistry especially in multi-aquifer systems.

Hydrochemical evolution and assessment of groundwater quality in fluorosis-affected area, Mandla District, central India

Deterioration of groundwater quality is a matter of serious concern today. In Mandla region of central India, fluorosis is common among the local people due to consumption of fluoride-contaminated groundwater. It is, therefore, important to understand the hydrochemical process of contamination and assess the groundwater quality of this region. A total of 173 samples (pre-monsoon and post-monsoon) were collected from borewells and dug wells of different depths for major ions analysis: K+, Na+, Ca2+, Mg2+, Cl−, CO32−, HCO3−, NO3−, SO42−, and F−; along with pH, temperature, TH (as CaCO3), TDS and EC. Broadly, three hydrogeologic units have been identified, viz. Deccan lava flows, infratrappean Lameta and Archean granite and gneiss. In Deccan, two distinct hydrostratigraphic units are Mandla and Dhuma. Mandla is the most prominent and extensive aquifer having hydraulic conductivity 5–15 mday-1 and yield 10–50 m3day−1. Water quality data vis-à-vis well-depth data indicate that Mandla aquifer, lying at a lower elevation than 500 m amsl, is fluoride-contaminated and harmful for human health. Fluoride (41.0% of total samples) and bicarbonate (54.9% of total samples) concentrations in analyzed water are above the global standard for drinking purpose. However, above 500 m msl groundwater is not contaminated with fluoride and is suitable for drinking and irrigation purpose. Fluoride concentration maps depict spatial and seasonal variation. Spatial variation of fluoride in groundwater is due to change in aquifer lithology, varying degree of rock weathering and orientation of structural lineaments. In fluoride concentration map of post-monsoon season, broadening of contour of uncontaminated zone indicates groundwater recharge, which corroborates with water fluctuation map. The fluoride-contaminated water and low-fluoride water are mainly Na–HCO3 and Ca–HCO3 type, respectively. The hydrochemical processes suggest pre-dominance of rock-water interaction; contribution of Na+ and K+ ions in groundwater is due to silicate weathering, whereas Ca2+ and Mg2+ ions are derived due to both silicate and carbonate weathering. Saturation index calculation point towards calcite-dolomite supersaturation and consequent precipitation, along with fluorite dissolution under alkaline condition.

Fluoride ions in groundwater of the Turkana County, Kenya, East Africa

Groundwater samples were evaluated throughout Turkana County (Kenya, East Africa) while looking for drinking water sources. Some samples showed high concentrations of fluoride with values in the range of 0.15–5.87 mg/L. Almost 50% of the samples exceeded the WHO and Kenyan potable water standard guideline value of 1.5 mg/L for drinking water quality. The hydrogeochemical studies revealed that the dominant cation in water is Na+ and the dominant anion is HCO3− resulting in Na-HCO3 type of groundwater, followed by Ca/Mg-HCO3 or Na-SO4 and Na-Cl in a few cases. Speciation modelling revealed that the groundwater is undersaturated with respect to gypsum and anhydrite, mostly undersaturated with respect to fluorite (6 samples are at equilibrium), and supersaturated or at equilibrium with respect to calcite (CaCO3). Precipitation of calcite favours the dissolution of F-rich minerals in the alkaline medium. Simultaneously, groundwater is enriched with sodium and bicarbonate, probably as a result of chemical weathering of Na-feldspar. Investigated groundwater can be presumably used for drinking purposes from 17 wells, but a detailed investigation of other trace element concentrations is necessary.

Hydrochemistry and Its Controlling Factors and Water Quality Assessment of Shallow Groundwater in the Weihe and Jinghe River Catchments

The Weihe and Jinghe Rivers catchments are important tributaries of the Yellow River, where it is of great significance to evaluate groundwater hydrochemistry and quality for ecological protection and sustainable development. Piper diagrams, Gibbs, Na-normalized molar ratios, and ion correlation methods were used to analyze the chemical composition of groundwater in these two catchments. Furthermore, the WQI method, Wilcox diagrams, USSL diagrams, and Doneen diagrams were used to evaluate the suitability of groundwater quality for drinking and irrigation. The results showed that the Weihe and Jinghe River catchments are dominated by fresh and weakly alkaline water. Groundwater ion concentration in the Weihe River are higher than in Jinghe River except for Na+, and the major groundwater types are HCO3-Ca-Mg(accounted for 50%), and HCO3-Ca-Mg and HCO3-Na-K (accounted for 32.5%), respectively. The hydrochemistry of the Weihe and Jinghe River catchments is mainly controlled by rock weathering, primarily silicate weathering. Moreover, the groundwater chemistry in the research area is affected by mining and chemical fertilizer application for agriculture. Furthermore, the hydrochemistry of the Weihe River catchment is affected by cation exchange, although this was not obvious in some regions of the Jinghe River catchment. The overall groundwater quality of the two catchments was good, with the Jinghe River water quality being better than in the Weihe River catchment. Based on SSP, SAR, and PI, the groundwater in some parts of the study area cannot be directly used for irrigation as this would result in salinization and, thus, inhibit plant growth. Overall, the groundwater quality in the south of the study area is better than in the north, and is better in the Jinghe River catchment than in the Weihe River catchment according to these three indicators. This study provides a basis for the sustainable development of two catchments, providing baseline data for groundwater quality management.

Discrete geochemical behavior of Sr and Ba in the groundwater of Southern Mor Range, Balochistan, a tracer for igneous and sedimentary rocks weathering and related environmental issues

A comparative study of Strontium (Sr) and Barium (Ba) along with associated major ions of groundwater was made from the Southern Mor Range, Balochistan, where both igneous and sedimentary rocks are exposed. In the studied samples, Sr2+ varies from 237 to 6,723 with a mean of 1,688 μg/l, while Ba2+ ranged from 40 to 1,332 μg/l with a mean of 207 μg/l. TDS and Sr2+ displayed moderate positive, while Ba2+ showed a slight negative relation. Majority (80.85%) of the samples have existed in the narrow pH range (7.5–8.5). The impact of water-rock interaction is evidenced from the Gibbs diagram; showed influence of igneous and sedimentary rocks on the release of Sr2+ and Ba2+. It is also evidenced from molar ratio of Sr2+/Ca2+, Mg2+/Ca2+, Na+/Cl−, Mg2+/Cl− of the groundwater. Strontium possessed fairly high relative mobility (RM, av. 0.349) and mobility index (MI, av. 4.38), while RM (av. 0.003) and MI (av. 0.04) of Ba2+ was very low. The saturation indices (SI) plots barite vs. celestite, showed saturation of Ba, while Sr2+ ions are unsaturated. The low Ba2+/Sr2+ (av. 0.208) indicated the existence of aquifer in low elevation areas and the HCO3−/Cl− ratio (>1) demonstrated a short flow path and speedy flow. The suitability of groundwater was assessed for drinking purpose as per World Health Organization (WHO) and Expanded Programme on Immunization (EPI) guidelines and possible environmental issues were discussed.

Evaluating the genesis and dominant processes of groundwater salinization by using hydrochemistry and multiple isotopes in a mining city

The increasing salinization of groundwater renders it challenging to maintain the water quality. Moreover, knowledge regarding the characteristics and mechanism of groundwater salinization in mining areas remains limited. This study represents the first attempt of combining the hydrochemical, isotope (δD, δ18O, δ37Cl, and 87Sr/86Sr) and multivariate statistical analysis methods to explore the origin, control, and influence of fluoride enrichment in mining cities. The TDS content of groundwater ranged from 275.9 mg/L to 2452.0 mg/L, and 54% of the groundwater samples were classified as class IV water according to China's groundwater quality standards (GB/T 14848–2017), indicating a decline in the water quality of the study area. The results of the groundwater ion ratio and isotope discrimination analysis showed that dissolution and evaporation involving water-rock interactions and halite were the main driving processes for groundwater salinization in the study area. In addition to the hydrogeological and climatic conditions, mine drainage inputs exacerbated the increasing salinity of the groundwater in local areas. The mineral dissolution, cation exchange, and evaporation promoted the F− enrichment, while excessive evaporation and salinity inhibited the F− enrichment. Gangue accumulation and infiltration likely led to considerable F− enrichment in individual groundwater regions. Extensive changes in the groundwater salinity indicated differences in the geochemical processes that controlled the groundwater salinization. Given the particularity of the study area, the enrichment of salinization and fluoride triggered by mining activities cannot be ignored.

Study on the Effect of Applied Pressure on Iron and Manganese Rejection by Polyamide and Polypiperazine Amide Nanofiltration Membranes

The aim of this research is to investigate the removal behavior of iron and manganese that naturally exist as divalent ions in groundwater by using nanofiltration membranes. The main focus of this study is to better understand the effect of applied pressures during the rejection of these metallic ions from synthetic groundwater in order to achieve drinking water standard. Polyamide and polypiperazine amide nanofiltration membranes denoted as PA-NF and PPA-NF were selected to investigate the iron and manganese rejection at low applied pressures (1-5 bar). In single solute solution with feed concentration at 10 mg/L and initial pH of 6.8 ± 0.5, the rejection of iron was ≥96% by PA-NF membrane at applied pressure of 2 bar. However, the rejection percentage by PPA-NF was 86.6% whereby this membrane unable to remove iron to the allowable drinking water standard. The rejection of manganese with single solute at concentration of 1 mg/L with initial pH of 6.8 ± 0.5 by using the PA-NF membrane was ≥98% and almost all of dissolved manganese were rejected at 5 bar. However, manganese removal by PPA-NF membrane was found less than 70% for all of the applied pressures. Findings from this work showed that the removal of iron and manganese were dependent on the applied pressures. PA-NF membrane able to remove both metallic ions that comply with the drinking water standard. The increased of applied pressure contributed to concentration polarization effect on the membrane surfaces leading to a decrease in solute rejection by decreasing the charge effect mainly for the iron removal from synthetic groundwater.

The effect of pH, calcium, phosphate and humic acid on cadmium availability and speciation in artificial groundwater

The interface between the ions in groundwater affects the biogeochemical behaviour of metal, and metal bioremediate by bacteria. Therefore, this study was aimed to predict the influence of pH, calcium, phosphate and humic acid on cadmium availability in artificial groundwater (AGW). Speciation and the thermodynamic calculation (MINTEQ program) were used to predict this in AGW theoretically. In results, cadmium availability diminished with an increase in pH, increase of calcium concentration and the addition of phosphate and humic acid of AGW. According to MINTEQ program, cadmium binds to some cations leaving fewer free cadmium ions available in AGW such as CdHCO3 +, Cd(SO4)2 2-, CdCl+, CdHPO4, HA1-Cd, FA1-Cd, FA2-Cd, and HA2-Cd. It is suggested though that pH in AGW is maintained at pH 4.00 for best availability of cadmium and bioremediate by bacteria.