Showing papers in "Chemie Der Erde-geochemistry in 2020"

Groundwater chemistry and groundwater quality index incorporating health risk weighting in Dingbian County, Ordos basin of northwest China

Abstract: Groundwater is essential to secure the safety of water supply in the Ordos basin, China. In this study, 35 groundwater samples were collected from part of the Dingbian County, a significant part of the Ordos energy base in China, and were analyzed for 17 physicochemical parameters. The health risk was quantified through the model recommended by the United States Environmental Protection Agency (USEPA). In addition, water quality index (WQI), which is incorporated with human health risk weighting, was adopted to evaluate the overall groundwater quality. The results show that groundwater in the study area is slightly alkaline water, and the hydrochemical types of groundwater is mainly HCO3-Na, HCO3-Na·Mg·Ca and mixed SO4·Cl-Na types. The non-carcinogenic health risks follow the order: NO3−>F−>Cr6+>As>NO2−>Mn, and the carcinogenic risks is mainly contributed by Cr6+. Children face higher risks than adults, and most groundwater samples are associated with unacceptable health risks for both adults and children. WQI results show that poor quality water and very poor quality water account for 11.43 % and 17.14 % of all sampled groundwater, respectively, which are not suitable for drinking. In terms of sodium hazard, nearly half of the groundwater samples are not suitable for irrigation. The results of this study will be helpful in groundwater management and protection in this area, and the health risk weighting method can be referenced by international scholars.

Mineralogy and geochemistry of sedimentary rocks and eolian sediments in Gale crater, Mars: A review after six Earth years of exploration with Curiosity

Abstract: The Mars Science Laboratory Curiosity rover arrived at Mars in August 2012 with a primary goal of characterizing the habitability of ancient and modern environments. Curiosity was sent to Gale crater to study a sequence of ∼3.5 Ga old sedimentary rocks that, based on orbital visible and near- to short-wave infrared reflectance spectra, contain secondary minerals that suggest deposition and/or alteration in liquid water. The sedimentary sequence in the lower slopes of Mount Sharp in Gale crater preserves a dramatic shift on early Mars from a relatively warm and wet climate to a cold and dry climate, based on a transition from smectite-bearing strata to sulfate-bearing strata. The rover is equipped with instruments to examine the sedimentology and identify compositional changes in the stratigraphy. The Chemistry and Mineralogy (CheMin) instrument is one of two internal laboratories on Curiosity and includes a transmission X-ray diffractometer (XRD) and X-ray fluorescence (XRF) spectrometer. CheMin measures loose sediment samples scooped from the surface and drilled rock powders, and the XRD provides quantitative mineralogy to a detection limit of ∼1 wt.% for crystalline phases. Curiosity has traversed >20 km since landing and has primarily been exploring an ancient lake environment fed by streams and groundwater. Of the 19 drilled rock samples analyzed by CheMin as of sol 2300 (January 2019), 15 are from fluvio-lacustrine deposits that comprise the Bradbury and Murray formations. Most of these samples were drilled from units that did not have a clear mineralogical signature from orbit. Results from CheMin demonstrate an astounding diversity in the mineralogy of these rocks that signifies geochemical variations in source rocks, transportation mechanisms, and depositional and diagenetic fluids. Most detrital igneous minerals are basaltic, but the discovery in a few samples of abundant silicate minerals that usually crystallize from evolved magmas on Earth remains enigmatic. Trioctahedral smectite and magnetite at the base of the section may have formed from low-salinity pore waters with a circumneutral pH in lake sediments. A transition to dioctahedral smectite, hematite, and Ca-sulfate going up section suggests a change to more saline and oxidative aqueous conditions in the lake waters themselves and/or in diagenetic fluids. Perhaps one of the biggest mysteries revealed by CheMin is the high abundance of X-ray amorphous materials (15–73 wt.%) in all samples drilled or scooped to date. CheMin has analyzed three modern eolian sands, which have helped constrain sediment transport and mineral segregation across the active Bagnold Dune Field. Ancient eolian sandstones drilled from the Stimson formation differ from modern eolian sands in that they contain abundant magnetite but no olivine, suggesting that diagenetic processes led to the alteration of olivine to release Fe(II) and precipitate magnetite. Fracture-associated halos in the Stimson and the Murray formations are evidence for complex aqueous processes long after the streams and lakes vanished from Gale crater. The sedimentology and composition of the rocks analyzed by Curiosity demonstrate that habitable environments persisted intermittently on the surface or in the subsurface of Gale crater for perhaps more than a billion years.

Solute geochemistry and groundwater quality for drinking and irrigation purposes: a case study in Xinle City, North China

Abstract: Xinle City is located in the upper reaches of the Daqing River basin, north China. Influenced by intense and extensive industrial and agricultural activities, sodium and nitrate pollution of the groundwater is becoming more and more serious in the study area. With an effort to quantitatively describe the present situation of groundwater and analyze the specific sources of the main ingredients, 32 well samples were collected and analyzed for understanding the hydrochemical characteristics and the suitability for drinking and irrigation purposes. Gibbs diagrams, Piper diagrams, solubility diagram, and ionic correlation analysis were used to assess the groundwater formation process. Drinking water quality index (DWQI) based on TDS, pH, K+, Ca2+, Na+, Mg2+, Cl−, HCO3−, SO42− and NO3− was used to evaluate the quality for drinking, while irrigation water quality index (IWQI) based on EC, Na%, permeability index (PI), sodium adsorption ratio (SAR), residual sodium bicarbonate (RSBC) and magnesium (MH) were used to assess the water quality for irrigation. The results demonstrated that the groundwater hydrochemical type in Xinle City is mainly dominated by the typical Ca∙Na-HCO3 and Ca-HCO3. Groundwater in the study area was found to be suitable for long-term drinking and irrigation. The abundances of ions are Ca2+>Na+>Mg2+>K+ for cations, and HCO3−>SO42−>NO3−>Cl−>F− for anions. The concentrations of Na+ and NO3− in groundwater are high in the study area. Particularly, the value of NO3− in some water samples far exceeds the WHO and Chinese standard limits. Na+ and NO3− are mainly of anthropogenic source, and they are from industrial pollution and agricultural pollution, respectively. Therefore, reducing the concentrations of Na+ and NO3− in groundwater is essential for the sustainable utilization of groundwater resources in the study area. The recommendations suggested in this research may provide insights for decision makers to make sound groundwater quality policies, and thus could be helpful to prevent further groundwater pollution in the study area.

Fluoride contamination in groundwater of the Shanmuganadhi River basin (south India) and its association with other chemical constituents using geographical information system and multivariate statistics

Abstract: Contamination of fluoride in drinking water affects human health, and its reduction is essential for the safe utilization of groundwater for domestic and agricultural uses. Groundwater in the ephemeral (monsoonal) Shanmuganadhi River basin, situated at rain shadow of the Western Ghats (south India), is indiscriminately utilized for rural water supply and agricultural activities. Fluoride contamination in groundwater of the river basin was evaluated using geochemical characteristics of sixty-one groundwater samples collected from the observation wells. Groundwater quality evaluation was attempted by estimating pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), and concentrations of Ca2+ Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3-, PO43- and F-. Multivariate statistical techniques helped to identify the factors responsible for fluoride enrichment. The fluoride ion ranges from 0.01 to 2.5 mg/l with 77 % of the samples having less than 1.5 mg/l. Groundwater samples (23 %) with more than 1.5 mg/l of F- are unsuitable for consumption. Fluoride vulnerable zones were mapped using the Geographical Information System (GIS) in which fourteen villages of the basin are with risk category for dental fluorosis among children. The multivariate statistical techniques (including correlation matrix) highlight the relationship among various geochemical parameters, and the cluster analysis apprehends the sources/processes contributing the chemical variables. Based on this study, it is recommended to adopt natural remediation technique like Managed Aquifer Recharge (MAR) for the enhancement of groundwater quality in this basin.

A MATLAB based graphical user interface (GUI) for quickly producing widely used hydrogeochemical diagrams

Abstract: Hydrogeochemical diagrams are powerful tools facilitating hydrogeochemical research, among which Piper diagram, Gibbs diagrams, USSL diagram, Wilcox diagram and PI classification diagram are widely applied. However, it is usually tedious and time-consuming to draw these diagrams, not only because of the complex procedures to treat input data, but also due to the different software used. It is always required that several pieces of software should be used for a single hydrochemical study. Therefore, this study reported a MATLAB based graphical user interface (GUI) to overcome these shortages. Three simple steps are included in the GUI to draw a diagram. The frame of the diagram to be drawn is first selected from the database of the GUI, after which the input data (water sample data) are imported into the GUI and the properties of the points such as the sizes, colors and shapes are set. Finally, the diagrams produced can be exported from the GUI as images. This MATLAB based GUI is capable of generating quickly five types of diagrams that are commonly used in hydrogeochemical research. The codes of the GUI and related functions can be adjusted according to the user’s needs. It is helpful to reduce the time spent in drawing these hydrochemical diagrams.

Mechanisms controlling groundwater chemistry and assessment of potential health risk: A case study from South India

Abstract: Protection and management of groundwater resources depends on full understanding of the processes controlling the groundwater chemistry and associated health risks. In view of this, the rural part of Wanaparthy district, Telangana State, India was chosen for the present study and the groundwater samples collected from there were chemically analyzed. Quality of groundwater is of alkaline nature and mostly fresh water type. According to Trilinear Diagram, the change of groundwater quality from Ca2+- HC O 3 − type to Na+- C l − type through mixed water type suggests the gradual influence of anthropogenic activities on the aquifer system. Gibbs Diagrams demonstrate that the chemistry of groundwater is mainly controlled by rock-water interactions and the rest by evaporation due to impact of anthropogenic sources. Bivariate Diagrams (Na+ vs C l − , Ca2++Mg2+ vs S O 4 2 − + HC O 3 − and Ca2++Mg2+- S O 4 2 − - HC O 3 − vs Na+- C l − ) clearly specify that the processes of weathering and dissolution of minerals, and ion exchange are the dominant controlling factors of groundwater chemistry. Hierarchical R-type Cluster Analysis illustrates that Group I ( C l − - Na+ and HC O 3 − ) is considered natural contribution, Group 2 ( S O 4 2 − - Mg2+- Ca2+) is natural or anthropogenic source and Group 3 ( N O 3 − - K2+ - F − ) is anthropogenic influence. As per the estimation of sources of ions in the groundwater body by Unmix Model, the Source 1 ( N O 3 − , C l − , S O 4 2 − and Na+) is related to the anthropogenic activities; Source II (Ca2+, HC O 3 − , Na+, S O 4 2 − , Mg2+ and C l − ) to the weathering of silicate minerals, dissolution of chloride and sulfate minerals; and Source III (K+, F − , Ca2+, HC O 3 − and Mg2+) to the weathering of fluoride, calcium, magnesium and potassium bearing minerals or the application of chemical compounds of potassium and fluoride ions. These sources lead to groundwater contamination in some locations, thereby causing unfit for drinking purpose. Health Risk Assessment with respect to N O 3 − and F − ions suggests that the Total Hazard Index of non-carcinogenic risk (> 1.0) is observed from 26.67%, 26.67% and 43.33% of the total groundwater samples and the threat is to children compared to men and women due to their smaller body weights. Therefore, the health risk reduction measures are recommended to improve the groundwater quality in the study region.

Prediction of arsenic vulnerable zones in the groundwater environment of a rapidly urbanizing setup, Guwahati, India

Abstract: The present study, through a multi model assessment approach emphasizes the relevance of prior urban settlement planning with respect to the changing land use pattern. A coupled approach integrating satellite data products of Land Use and Land Cover (LULC) change along with chemical evaluation of As toxicity were modelled to evaluate the groundwater vulnerability. Change detection analysis was incorporated using the satellite images of 2013 and 2016 which shows 10 % increase in the buildings as compared to the total area of the study in given period. The LULC class that has been most compromised in this expansion and got reduced were the vegetation (∼6 %) and the barren areas (∼4 %) and the total surface water sources (0.5 %), all contributing in increased urban sprawl. As per the origin of As contamination in the area it seems that high sediment deposition along the braided Brahmaputra River stretch leads to As contamination which was associated with Fe-(oxy)-hydroxide dissolution. The vulnerability assessment using Artificial Neural Network technique in this region shows that As is present relatively in lesser concentration in the east direction. The continuous expansion of the urban habitation towards the greater As concentration zone will further make the situation critical for the people dependent on groundwater. The study suggests that prior settlement planning must be carried out in accordance to the presence of any toxic constituent in drinking water source to avoid future crisis for potable water.

Factors determining the hydrogeochemical processes occurring in shallow groundwater of coastal alluvial aquifer, India

Abstract: A hydrochemical study on the coastal aquifers were collected initiated to determine the factors affecting the groundwater chemistry in South India. 48 groundwater samples from bore wells during post monsoon period. The samples were measured for in situ parameters and major ions following the standard procedures. The analyzed results were further interpreted using geochemical plots, ionic ratios, water quality indices, geochemical modeling and statistics. pH values in the groundwater ranged from 6.6 to 8.0 and alkaline in nature. The average value of EC was 7155 μS/cm and higher values were mostly distributed along the coastal region of the study area. From the Piper plot, hydrochemical evolution path was identified, from Ca−HCO3 (recharge waters) to mixed Ca-Mg-Cl (reverse ion exchange waters) through Ca-Cl types (leachate waters), indicating the reverse ion exchange and seawater intrusion. Saturation index reflected that Calcite was oversaturated due to availability of Ca and HCO3 ions. Factor analysis further improved the understanding of the major controlling hydrochemical processes for groundwater chemistry. The hydrochemistry of the coastal aquifer was affected by several factors such as dissolution, water-rock interaction, reverse ion exchange, seawater intrusion, and influence of minor agricultural. The water quality assessment showed that the concentration of most of the parameters exceeded the standards limit, and considered as unsuitable for drinking purposes. But they are inferred to be suitable for agricultural purposes according to SAR, Na%, RSC and PI.

Spatial distribution and health risk assessment of fluoride contamination in groundwater of Telangana: A state-of-the-art

Abstract: The groundwater of Telangana province is well known for its very high fluoride concentration. The main aim of this review is to assess the fluoride contamination, understand the spatial distribution pattern and also evaluate the potential human health risk for adults and children in the Telangana. Fluoride contamination in groundwater is the principal threat to public health in Telangana state in India. It is observed that the mean fluoride concentration in groundwater of ten districts in Telangana showed a decreasing trend: Nalgonda > Warangal > Ranga Reddy > Adilabad > Medak > Khammam > Karimnagar>Hyderabad > Mahabubnagar > Nizamabad. The high fluoride concentration is observed in Nalgonda where the mean fluoride is 5.76 times higher than the recommended limit of 1.5 mg/L for drinking purposes. The fluoride concentration in groundwater derives mainly from the weathering and dissolutions of fluoride bearing minerals. Nalgonda region, the hazard quotient (HQFluoride) for adults and children ranged from 0.79 to 6.54 and 1.07 to 8.84 with an average of 3.01 and 4.07, respectively. In Warangal region, the non-carcinogenic health risk in terms of HQFluoride was found in the range of 0.77 to 2.63 and 1.04 to 3.55 with a mean of 1.46 and 1.97 for adults and children, respectively. Furthermore, children are at highly prone to health risk when compared to adults in the Telangana. Therefore, special care and pure drinking water should be supplied to the rural regions of Telangana.

Detailed geochemical assessment & indexing of shallow groundwater resources in metropolitan city of Nagpur (western Maharashtra, India) with potential health risk assessment of nitrate enriched groundwater for sustainable development

Abstract: Identification of complex processes controlling the groundwater chemistry and the indexing of urban groundwater for drinking were carried out with special emphasis on health risk associated with nitrate contamination in the urban areas of Nagpur City in western India. The hydrochemical facies of forty-seven samples collected from shallow aquifers were of Ca–HCO3 and mixed Ca–Na–HCO3 type indicating a transition from pure recharge water to mixed type water. 75% of the samples were very hard water. Geochemical signatures evaluated from the Na+-Cl− plot, Na+:Na+ + Cl−, Ca2+ + Mg2+ vs. HCO3− + SO42− plot, (Na++ K+ - Cl−)/(Na++ K+ - Cl− + Ca2+), Ca2+/Na+ vs. Mg2+/Na+, SO42−/Cl− signposted the collective contribution of calcite, dolomite, silicate, and gypsum weathering on groundwater geochemistry. The dominancy of cation exchange followed by reverse ion exchange, anthropogenic inputs, and mineral dissolution are resolved based on bivariate plots. The supersaturated thermodynamic states of calcite and dolomite minerals played a major factor for low Ca2+ in some samples. Nitrate higher than the drinking-water thresholds of 50 mg/L (as per WHO) in around 51.1% of the samples reflected the consequences of urbanization on shallow aquifers. The EWQI method ranked 74.5% of the urban groundwater as moderately suitable and remaining samples are not suitable for drinking. The non-carcinogenic risk (HI Total) were computed as 1.82, 2.16, and 2.47 for an adult male, adult female, and children of Nagpur urban region. The non-carcinogenic risk was higher in children as compared to the adult residents. The noteworthy finding of the study may help in building effective policies and enhancing individual cooperation for the sustainable development of groundwater reservoirs in this region.

Combined zircon U-Pb dating and chemical Th─U─total Pb chronology of monazite and thorite, Abu Diab A-type granite, Central Eastern Desert of Egypt: Constraints on the timing and magmatic-hydrothermal evolution of rare metal granitic magmatism in the Arabian Nubian Shield

Abstract: We present the first chemical age determination of monazite from a geochemically-specialized rare metal granite of the Central Eastern Desert (CED), Egypt. The Abu Diab composite A-type granite of the CED divides into three co-magmatic phases: two mica granite (TG), garnet-bearing muscovite granite (GMG), and muscovite granite (MG). The GMG granitic phase is a typical example of a rare metal, volatile-rich aqueous silicate magma. Its zircon has extremely high U-concentration (up to 45,000 ppm) and intense metamictization, resulting in significant radiogenic Pb-loss, as well as common Pb contamination, along fractures and other imperfections. Laser ablation (LA-ICP-MS) zircon U-Pb results yield imprecise to meaningless dates. On the other hand, the GMG exhibits two texturally and chemically distinct varieties of monazite, pristine (Mnz1) and altered (Mnz2), that yield similar electron microprobe (EMP) chemical ages of 587 ± 8 Ma (2σ) for Mnz1 and 587 ± 9 Ma (2σ) for Mnz2. These ages, combined with the inferred alteration temperature (T > 400 °C), indicate monazite alteration/replacement occurred during or soon after crystallization of the pluton, in response to expelled magmatic-hydrothermal fluids inferred to be F-rich, late-staged deuteric fluids. The alteration and elemental substitution of zircon and monazite reflect coupled dissolution-recrystallization processes during late-staged deuteric alteration when zircon and thorite were relatively vulnerable to post-magmatic hydrothermal effects because of their extremely metamict state. The ca. 587 Ma age is typical of A-type granite intrusion across the CED and the post-collisional stage of the Arabian Nubian Shield (ANS; 610 – 560 Ma), and is within analytical error of associated magmatic thorite (592 ± 8 Ma). These two ages agree with the timing of rare metal-rich intrusions (0.6−0.4 Ga) related to the Pan-African orogeny. Future research using the monazite chronometer may better constrain the timing of rare metal granitic magmatism of the ANS.

Seasonal changes in groundwater composition in an industrial center of south India and quality evaluation for consumption and health risk using geospatial methods

Abstract: Effluents from leather tanneries and other small-scale industries have caused groundwater contamination in one of the biggest industrial centers (i.e. Vellore) of south India. This study evaluated quality of 70 different open and tube wells for consumption and health risks by collecting groundwater samples in four different seasons between 2017−2018. We compared physicochemical parameters of the groundwater samples with international drinking water standards (World Health Organization) to know their suitability for human consumption. Piper’s trilinear diagram classified most of them as Ca-Cl and mixed Ca-Mg-Cl types. Inverse Distance Weighted (IDW) spatial interpolation showed the spatial distributions of different groundwater quality parameters. These parameters, including the Water Quality Index (WQI), indicated that most of the samples collected during the non-rainfall seasons (post-NE monsoon: 82.8 %; pre-SW monsoon: 78.6 %) were ‘poor’ for consumption. However, the qualities of 40–44.3 % of samples collected during both the rainfall seasons (NE and SW monsoon) were “good”. We evaluated non-carcinogenic health risks for children and adults from consumption of the nitrate-rich groundwater by estimating the Hazard Quotient (HQ). Our results did not suggest any health risk for children and adults during both the rainfall seasons. In the non-rainfall seasons, about 59–63 % of samples posed health risk to children and 37–39 % caused possible health risk to the adult population.

Hydrogeological and hydrochemical investigation in the Burdur Saline Lake Basin, southwest Turkey

Abstract: The Burdur Saline Lake Basin is semi-closed and it is situated in the southwest of Turkey. This saline and highly alkaline lake has a tectonic origin. Alluvium represents the most important aquifer and other aquifer is granular and karstic in nature. In the present study, we collected 35 groundwater samples and analyzed them to characterize the groundwater chemistry and investigate hydrogeochemical processes. Na+, Ca2+, Mg2+, HCO32− and SO42− are the dominant ions and the samples are grouped into different hydrochemical facies such as Ca–HCO3, Ca–Mg–HCO3, Mg-Ca-HCO3, Na-Mg-SO4 and Na-SO4-HCO3. Limestone, silicate and gypsum controlled the groundwater chemistry through reverse ion exchange, dissolution of carbonates and silicate weathering. Presence of more iron, arsenic and boron in the groundwater is geogenic. The statistical analysis, i.e. R-mode factor, determined interrelationships within the chemical data through five factors accounting 85.32 % of the total variance of the dataset. Factor 1 is represented by strong loadings of EC, TDS, Mg2+, Na+, SO42−, As and B, and moderate loadings of K+ and Cl-. Factor 2 has strong positive loadings for Ca and CO3-, and moderate negative loading for pH. Factor 3 has strong positive loadings for Zn and has moderate positive loading for Cl-. Factor 4 has strong negative loadings for T (°C), and has moderate positive loadings for pH and K+. Factor 5 has strong positive loadings for HCO3- and has moderate positive loading for Fe. Geochemical variables of Factors 1, 2, 4 and 5 represented the natural hydrogeochemical processes like water-rock interaction. The variables present in factor 3 reflected the anthropogenic effects in the Burdur Lake Basin.

Removal of uranium from aqueous solution by a permeable reactive barrier loaded with hydroxyapatite-coated quartz sand: Implication for groundwater remediation

Abstract: Uranium (U) contamination has been widely found in groundwater and greatly threatens human health. The present study investigated U removal from aqueous solution using a permeable reactive barrier (PRB) with hydroxyapatite as a reactive material under appropriate conditions. Different-size hydroxyapatites were loaded to quartz sand and the mineral composition of the composite materials was identified by XRD before being applied to column experiments and after adsorption U. Results showed that U removal processes were influenced by sorbent particle size, initial U concentration and hydraulic loading, and initial U concentration exerted the greatest effect on U removal efficiency. Uranium sorption data were fitted to Thomas and Yoon-Nelson models. The fitting results indicated that Thomas model was better than Yoon-Nelson model for description of U sorption characteristics in this study, which had higher correlation coefficients (>0.97). Adsorbed U formed plate-like crystals and occurred widely on the surface of hydroxyapatite, as visualized by SEM. Determination of XPS and EDS in samples with high U concentration implied that U adsorption was achieved via either dissolution-precipitation reactions involving low-solubility U-bearing minerals or surface complexation with reactive function groups on the surface of hydroxyapatite, which was supported by U speciation calculated at equilibrium atmospheric CO2 and U solid phases. The findings suggest that the hydroxyapatite-based PRB can serve as an effective treatment technique for remediation of U contaminated groundwater.

Groundwater vulnerability to pesticide pollution assessment in the alluvial aquifer of Western Bengal basin, India using overlay and index method

Abstract: The groundwater of the Western Bengal basin is found to be polluted by various non-point sourced contaminants. A significant increase in anthropogenic activities subsequently affects water quality. This study is the first attempt to evaluate the groundwater vulnerability to pesticide pollution due to anthropogenic activities across the Western Bengal basin. Pesticide concentration of 141 wells for three consecutive years (2012 - 2014) was collected and data were acquired from West Bengal Pollution Control Board (WBPCB). Based on seven hydrogeological parameters groundwater specific vulnerability was assessed. The vulnerability to pesticide pollution across the Western Bengal basin was again validated with analyzed pesticide concentration for 235 wells for 2014–2016. The agricultural prone region of the study area is highly susceptible to pesticide pollution. The spatiotemporal trend of different pesticides suggests the basin is more vulnerable to insecticides such as malathion than that of herbicides. The application of pesticides influences mostly the spatio-temporal variability of pesticide concentration in groundwater of shallow aquifer across Western Bengal basin; however, the natural hydrogeological setting of this area is one of the most influential parameters which impact the pesticide infiltration onto aquifer. Depth to the water table is the most sensitive parameter which showed a significant impact on pesticide concentration in groundwater. Vulnerability assessment across different land-uses helps the decision-makers to improve water quality.

Variations of water quality deterioration based on GIS techniques in surface and groundwater resources in and around Vembanad Lake, Kerala, India

Abstract: This study evaluated the status of deteriorating water quality around the Vembanad Lake of Kerala State in India. A total of 40 water samples from lake (L, n = 5), river (R, n = 6), open well (W, n = 26), and bore well (BW, n = 9) and were analysed for major ions as per the APHA methods. Different concentrations of Ca (10–190 mg/L), Mg (2–220 mg/L), Na (10–216 mg/L), K (2–50 mg/L), HCO3 (20–400 mg/L), CO3 (10–50 mg/L), Cl (46.5–950 mg/L), NO3 (0.62–19.75 mg/L), SO4 (20.8–423 mg/L) and PO4 (1.63–16.18 mg/L) represent the three different water types: Ca HCO3, Na Cl and mixed type of Ca Na HCO3. Strong connection between the host rock and groundwater quality indicated substantial water-rock interaction. Factor analysis helped to understand the associations of chemical parameters and their sources. TDS, TH, calcium, magnesium, sodium, potassium and chloride exceeded the BIS (2010) based on desirable drinking water and irrigational quality standards in SE, W, and NW directions due to man-made bunds, industrial wastes, agricultural wastes, household sewages, tourism, lime shell, and sand mining. All point and non-point sources of pollution adversely affected water in and around the Vembanad Lake system and caused by water quality deterioration.

Gold–sulphide deposits of the Russian Arctic zone: Mineralogical features and prospects of ore benefication

Abstract: In this study, the forms of silver occurrence and behaviour during extraction from primary gold–sulphide deposits in the carboniferous strata of the Arctic zone of Russia are analysed. Detailed mineralogical and technological studies reveal that the silver is concentrated in tetrahedrites, whereas deposits of this geological–industrial type are usually characterised by other silver-bearing minerals. The silver content in the tetrahedrite varies from 12 to 22 wt.%; silver is also found as an isomorphic impurity in native gold and as a solid solution in sulphide minerals. Moreover, the possibility of implementing a combined gravity–flotation scheme with ore production is discussed. The final concentrates from this process are shown to be suitable for subsequent autoclave oxidation and cyanidation of refractory gold-bearing ores. The aim of the new reagent addition is to enhance the comprehensive usage of ores.

Hydrogeochemical and isotopic study for evaluation of seawater intrusion into shallow coastal aquifers of Udupi District, Karnataka, India

Abstract: Groundwater is the major source of drinking in coastal areas and the gradual decline in its quality is a major concern. The present study was aimed to evaluate the groundwater quality and its deterioration in coastal aquifer in the Udupi district of Karnataka state (southwest India) by studying the hydrogeochemical characteristics and salinization processes. We collected 49 groundwater samples from open well to shallow bore wells apart from one surface water sample and one seawater sample during the pre-monsoon season. Samples were analyzed for major ions and oxygen isotopes (δ18O) and the results reveal that the water is generally acidic to mild alkaline in nature, and the total dissolved solids (TDS) vary from 40 to 12,100 mg/l. δ18O values (−2.73‰ to −0.6‰) indicate highly saline nature of the groundwater. Widely accepted plots such as Piper plot and Gibbs plot and ratios such as sodium/chloride, chloride/bicarbonate, and calcium/magnesium were used to identify the intrusion of saltwater into the coastal aquifers. The total hardness, Piper plot, and Gibbs plot suggest that the groundwater samples are brackish, mixed, and saline in nature. Based on the seawater percentage (SW%) to quantify the salinization of groundwater, we conclude that the saline water intrusion into the shallow aquifers from seawater is a threat in this region.

The Renazzo-like carbonaceous chondrites as resources to understand the origin, evolution, and exploration of the solar system

Abstract: We present here a review of the characteristics of CR carbonaceous chondrite meteorites. Over the past three decades, our knowledge and understanding of the scientific value of the CR chondrites have increased dramatically, as more samples from cold and hot deserts have become available for analysis. Based on a variety of compositional, mineralogical, isotopic, and spectroscopic studies, we have come to understand that CR chondrites are excellent samples of asteroidal meteorites to look for virtually unaltered solar nebula material and to observe asteroidal processes in progress. This paper summarizes these investigations, their similarities, and differences with other chondritic groups, their relationships to asteroids, and the questions yet to be addressed.

Water-rock interactions in the Acoculco geothermal system, eastern Mexico: Insights from paragenesis and elemental mass-balance

Abstract: Geochemical mass balances, supported by mineral characterization and whole-rock elemental analyses, were used to decipher the alteration paragenesis and to understand the elemental mobility related to the interaction of hydrothermal fluids with volcanic rocks (ignimbrites and lavas ranging from rhyolite to dacite) from the Acoculco geothermal system, in the eastern portion of the Trans-Mexican Volcanic Belt. Three extensive events of hydrothermal alteration were distinguished, from earliest to latest: (1) selective silicification and argillization, (2) hydraulic brecciation by silica-rich fluid, and (3) acid-sulfate (vuggy and argillic advanced) alteration. According to the Gresens-Grant mass-balance method, the altered volcanic rocks of Acoculco are generally enriched in Ti and Si and depleted in the rest of major elements; this chemical behavior is striking in the case of vuggy and silicic altered rocks. Small changes in some element concentrations calculated by the Gresens-Grant method may be due to chemical heterogeneity between the rock chosen to be the reference (“fresh rocks”) and the protolith of the altered ones. The chondrite-normalized REE gave different patterns for distinct types of alteration; vuggy and silicified rocks present low LREE and high HREE in opposition to the advanced argillic alteration. Boiling, primarily related to the last alteration event, may have happened at variable depths (825, 325 and 102 m below present surface); it produced changes fluid composition, resulting in acidic pH surface alterations.

The Paleozoic Jalal Abad mafic complex (Central Iran): implication for the petrogenesis

Abstract: The Jalal Abad magmatic rocks are located at the southeastern edge of the Kashmar-Kerman tectonic zone, which includes Cadomian magmatic rocks and sedimentary strata intruded by several Silurian alkaline plutons and associated dikes. They have typical alkaline kaersutite and alkaline to per-alkaline pyroxene and are characterized geochemically by enrichment in LREE, Nb and Ta, and high concentrations of incompatible trace elements, demonstrating alkaline features with typical ocean island basalt signatures. Chondrite-normalized REE and multi-element spider diagrams along with High 206Pb/204Pb ratios (18.46–19.83) for the Jalal Abad gabbro, diorite, and dibasic dikes indicate involvement of an OIB-like source during the formation of these rocks. Modeling of bulk–rock trace elements and Sr–Nd isotopes suggest that magmas were generated by a pair of HIMU-EM1- like mantle source, consistent with a plume mantle origin in a within-plate rift zone. The melting took place in garnet stability field and the fractional crystallization played a major role in magmatic evolution of the mantle-derived parental magma. The Jalal Abad mafic rocks have U–Pb zircon ages of 425.5 ± 8.6 Ma and along with other Ordovician to Silurian rocks in different parts of the Iranian plate are related to the extensional tectonic regime responsible for the rifting of Cadomian fragments from northern Gondwana and the opening of Paleo-Tethys. Our findings indicate that the rifting and seafloor spreading of Paleo-Tethys and the formation of its oceanic crust were intensely influenced by a mantle plume activity in the early Paleozoic.

Conditions for the crystallization of fluorite in the Mushgai-Khudag complex (Southern Mongolia): Evidence from trace element geochemistry and fluid inclusions

Abstract: The Mushgai-Khudag complex is part of the Late Mesozoic Central Asian carbonatite province. Fluorite mineralization is manifested throughout the province, including the Mushgai-Khudag complex. We have investigated the geochemical features and fluid inclusions of fluorites from different types of fluorite-bearing rocks. Fluorite from quartz-fluorite rocks has rare earth element (REE) concentrations in the range of 10500−144300 ppm and the highest light REE contents, with (La/Yb)N = 56−960. Fluorite from the fluorite-apatite-celestine rocks has slightly lower REE enrichment, especially light REE content, with concentrations of 200−5900 ppm and (La/Yb)N = 18−204. Fluorite from the fluorite-calcite rocks is characterized by REE contents of 22−1100 ppm and a variable (La/Yb)N of 0.6−59. These variations in the fluorite REE composition from different types of rocks were probably caused by the fact that at elevated temperatures, fluorine-containing light REE complexes are more stable than fluorine-containing heavy REE complexes. The progressive enrichment of medium and heavy REEs in the latter fluorite is related to fluid evolution. The homogenization temperature and salinity values of fluid inclusions in the Mushgai-Khudag fluorites vary between 550 and 185 °C and from rather high to 2 wt.%, respectively. The parental fluids of the fluorite-bearing rocks evolved from quartz-fluorite rocks to fluorite-apatite-celestine rocks to fluorite-calcite rocks. The key component was changed from sulfate to carbonate-chloride along with the high to medium temperature decrease (∼500−245 °C).

Habitability of Hydrothermal Systems at Jezero and Gusev Craters as Constrained by Hydrothermal Alteration of a Terrestrial Mafic Dike.

Abstract: NASA’s search for habitable environments has focused on alteration mineralogy of the Martian crust and the formation of hydrous minerals, because they reveal information about the fluid and environmental conditions from which they precipitated. Extensive work has focused on the formation of alteration minerals at low temperatures, with limited work investigating metamorphic or high-temperature alteration. We have investigated such a site as an analog for Mars: a mafic dike on the Colorado Plateau that was hydrothermally altered from contact with groundwater as it was emplaced in the porous and permeable Jurassic Entrada sandstone. Our results show evidence for fluid mobility removing Si and K but adding S, Fe, Ca, and possibly Mg to the system as alteration progresses. Mineralogically, all samples contain calcite, hematite, and kaolinite; with most samples containing minor anatase, barite, halite, and dolomite. The number of alteration minerals increase with alteration. The hydrothermal system that formed during interaction of the magma (heat source) and groundwater would have been a habitable environment once the system cooled below ∼120 °C. The mineral assemblage is similar to alteration minerals seen within the Martian crust from orbit, including those at Gusev and Jezero Craters. Therefore, based on our findings, and extrapolating them to the Martian crust, these sites may represent habitable environments which would call for further exploration and sample return of such hydrothermally altered igneous materials.

Petrogenesis of early Cretaceous granitoids in the southern Great Xing'an Range, NE China: Constraints from the Haliheiba pluton

Abstract: Early Cretaceous granitoids are widespread in the southern Great Xing’an Range. However, the petrogenesis of these rocks is poorly understood. We therefore present field investigations, petrological observations, zircon U–Pb ages, whole-rock geochemistry and Hf isotope compositions for the Haliheiba pluton. The pluton comprises fine-grained biotite granite, medium- to coarse-grained biotite granite and porphyritic biotite granite, and mafic microgranular enclaves (MMEs) are unevenly distributed within the host granites. Zircon LA-ICP-MS U–Pb dating yields emplacement ages of ∼139 Ma for the three units. The host granites are characterized by high SiO2 contents (73.16–76.55 wt%) and alkali concentrations (7.92–8.62 wt%), enrichment in light rare earth elements (LREEs), Rb, U, Th, K, and Pb, depletion in heavy rare earth elements (HREEs), Sr, Ba, Ti, and P, and intensely negative Eu anomalies with δEu values from 0.14 to 0.47. The zircons in the host granites yield positive eHf(t) values of +5.0 to +11.2 and fairly young Hf model ages of 408 Ma to 731 Ma. These results indicate that the host granites have high-K calc-alkaline, metaluminous to weakly peraluminous A-type affinity and were mainly derived from partial melting of juvenile crustal materials originated from the depleted mantle, and fractional crystallization was involved in magma evolution. The MMEs have SiO2 contents of 63.45–64.14 wt% and have higher MgO, CaO, tFe2O3 and TiO2 contents than the host granites. The MMEs are enriched in LREEs relative to HREEs with slightly negative Eu anomalies (δEu values of 0.77–0.79) and are slightly enriched in Rb, U, Th, K, Sr, Pb and strongly to slightly depleted in Nb, Ta, Ti and P. These results, together with field investigations and petrological observations, indicate that crust-mantle magma mixing played an important role during the petrogenesis. Furthermore, the MMEs were intermediate members after magma mixing between mafic end-member magmas derived from lithospheric mantle and felsic end-member magmas derived from juvenile crustal materials. Combined with regional geology, our results suggest that a substantial crustal accretion in the southern Great Xing’an Range that occurred during the Neoproterozoic–Carboniferous, and the formation of the Early Cretaceous granitoids in this region was closely related to the lithospheric delamination triggered by the subduction of the Paleo-Pacific Ocean beneath Eurasia.

The impact of Mg2+ ions on equilibration of Mg-Ca carbonates in groundwater and brines

Abstract: At temperatures below 50 °C, the log10 (aMg2+/aCa2+) values in groundwater and brines, irrespective of their origin – either carbonaceous or siliceous rocks/sediments – cover the range between −1.5 and +1.0. Calculations of thermodynamic equilibria between the minerals calcite, aragonite, dolomite and huntite suggest a spread of log10 (aMg2+/aCa2+) between minus infinity and +2.3. Log10(aMg2+/aCa2+) in solution of dissolving ordered dolomite at 25 °C fits the thermodynamical equilibrium between disordered dolomite and calcite and nearly corresponds to that of pure calcite with a dolomitic surface layer due to exchange of Ca2+ against Mg2+ in Mg2+-containing solutions. This observation suggests that the solubility of Mg-Ca carbonates is controlled by the composition of their monomolecular surface layers in equilibrium with the ambient aqueous phase. Incongruently dissolving minerals such as dolomite attain equilibrium between individual surface compositions of different carbonates. The bulk composition of these carbonates hardly if ever equilibrates with the ambient solution due to extremely low ion mobility in the lattice. Because the thermodynamical equilibria are based on the composition of bulk minerals, their estimates of equilibria between carbonates, i.e., log10 (aMg2+/aCa2+) in solution, differ significantly from values established by the chemical composition and structure of the surface layer of carbonates.

Geochemical evidence for seabed fluid flow linked to the subsea permafrost outer border in the South Kara Sea

Abstract: Driven by rising bottom water temperatures, the thawing of subsea permafrost leads to an increase in fluid flow intensity in shallow marine sediments and results in the emission of methane into the water column. Limiting the release of permafrost-related gas hydrates and permafrost- sequestered methane into the global carbon cycle are of primary importance to the prevention of future Arctic Ocean acidification. Previous studies in the South Kara Sea showed that abundant hydro-acoustic anomalies (gas flares) induced by seafloor gas discharge into the water column occur in water whose depth is ≥20 m. This distribution of gas flares could indicate the outer extent to which continuous permafrost restricts upward fluid flow. This paper reports on a geochemical analysis of a 1.1 m long sediment core located in an area of shallow fluid flow off of the Yamal Peninsula coast (South Kara Sea) using high-resolution seismic data. Our results reveal a thin zone of Anaerobic Oxidation of Methane (AOM), a sharp shallow sulfate-methane transition (SMT) located at a sub-bottom depth of 0.3 m, and significant temporal variation in methane discharge confirmed by the pyrite (FeS2) distribution in the core sample. A concave up pore water chloride profile depicts upward fresh/brakish water advection in subsurface sediments. The terrestrial/fresh water genesis of methane from the sampled core is deduced from the stable isotopic signatures (δ13 C and δD). We propose two mechanisms for the observed fluid flow: i) convection of thaw water from subsea permafrost; and/or ii) lateral sub-permafrost ground water discharge marking the outer extent of continuous permafrost off of the central Yamal Peninsula coast at ˜45 m water depth.

Rare earth elements geochemistry of groundwater from Shanmuganadhi, Tamilnadu, India: Chemical weathering implications using geochemical mass-balance calculations

Abstract: Groundwater samples were collected from Shanmughanadhi in Dindigul district of Tamilnadu, India, to determine the concentration and fractionation of REEs during chemical weathering Groundwater samples collected from aquifers hosted in weathered and fractured crystalline formations were analyzed by ICP-MS for Rare earth elements (REEs) after filtering by 045 μm membrane filters ΣREEs in Charnockite accounts 849 × 10−4mgL−1 and 108 × 10−3mgL−1 in hornblende biotite gneiss signifying higher REEs in Gneiss than Charnockite, due to higher flushing rates in gneiss and relatively shorter water residence time in Charnockite aquifer Higher LREEs were observed upstream in the study area, followed by enrichment of MREEs and HREEs in midstream and discharge areas, respectively Irrespective of lithology, the groundwater samples mostly exhibited a positive europium anomaly, which might be due to higher dissolution and mobilization of europium from plagioclase group minerals through rock-water interaction The plagioclase feldspar, orthopyroxene, and alkali feldspars mineral weathering rates were 124, 175, and 200 mol/hectare/year The rare earth minerals enriched in the host rocks provided the referenced material for the REE enrichment in the groundwater Variations in pH and redox conditions in groundwater environments have influenced the enrichment of REE aided by continuous aquifer residence time, chemical weathering, and groundwater flow path

Hydrogeochemical investigation of an epithermal mineralization bearing basin using multivariate statistical techniques and isotopic evidence of groundwater: Kestanelik Sub-Basin, Lapseki, Turkey

Abstract: This study investigates hydrogeochemical processes controlling the groundwater quality using 64 groundwater samples in the epithermal mineralization bearing Kestanelik Sub Basin, NW Turkey. The groundwater dominantly exhibits a mixed-ion hydrochemical facies characterized by Ca-Mg-HCO3, Mg-Ca-HCO3, Ca-Mg--HCO3-SO4 and Ca-Mg-Na-HCO3 reflecting weakly mineralized waters circulating within calcareous sandstone and colluvium. The molar ratios of (Ca2++Mg2+)/(SO42-+HCO3-) and Na+/Cl-ratios and the linear plot between (Na++K+)-Cl- and (Ca2++Mg2+)-(HCO3-+SO42-) indicate that of dissolution of carbonates and silicate weathering, ion and reverse ion exchange processes influence the hydrogeochemistry of groundwater sources. Three and four factors account with 84.48 and 75.27 % of the total variance for spring and well waters, respectively. FC1 in the groundwater samples is described by strong loadings of TH, Ca2+, Mg2+, HCO3-, Ba, TDS, Cl-, EC and SO42-, and moderate loading of Na+, Mn, K+, TDS, pH. FC2 in the samples has strong positive loadings on Al, Fe, Zn, Na+, SO42-, Cl- and moderate positive loadings on B, TDS and K+. FC3 shows strong positive loading on Cu, Al, DO and moderate factor loadings for Fe in the well water samples. FC4 exhibits high positive loadings for As, Zn, and moderate positive loading for EC. Geochemical variables of FC 1, 2, 3 and 4 for the groundwater indicates mixed geogenic source of groundwater contamination through water-rock interaction processes dominantly from (i) the calcareous sandstone, serpentinite and colluvium lithologies and (ii) quartz, illite, pyrite and iron oxide minerals sourced from epithermal mineralization in the area. pH and As values exceed the desirable limits of WHO and TSE 266 guidelines for drinking purpose. The tritium levels show that some well waters have experienced longer water-rock interaction and residence time and are thus recharged from older groundwater sources compared to other well and spring waters.

Multiple sulfur sources for the volcanic hosted massive sulfides in Betul Belt, Central India: Evidence from the sulfide ore chemistry and sulfur isotope geochemistry

Abstract: This work provides an overview of the geological, petrological, and geochemical data available on the three volcanic-hosted massive sulfides (VHMS) deposits (Ghisi, Biskhan, and Jangaldehri) in Betul Belt, Central Indian Tectonic Zone. Sulfur isotope geochemistry was used for the first time from the Betul Belt to constrain the source of sulfur for a better understanding of the ore genesis process. Mineralization is hosted in a felsic dominant bimodal volcano-sedimentary sequence associated with syn-genetic hydrothermal alteration, i.e., intense Mg–Ca alteration (actinolite-tremolite-anthophyllite) and Al–Fe alteration zone (gahnite-garnet-biotite-staurolite) followed by regional metamorphism. Field observations, drill core logging, and petrography studies reveal different modes of mineralization, i.e., dissemination, stringers, and semi-massive sulfides vein, comprises of chalcopyrite, sphalerite, pyrite, galena with lesser pyrrhotite, are paragenetically distinct in three deposits. The petrography, SEM-EPMA studies show the presence of chalcopyrite disease in Fe-rich sphalerite at Biskhan and Jangaldehri in the east and absence of the same texture at Ghisi in the west. This difference reveals the variable physio-chemical nature of the hydrothermal fluid and partial melting of sulfides during subsequent metamorphism. Cu–Fe mineralization was deposited from high-temperature hydrothermal fluids with less sulfur activity at Biskhan-Jangaldehri. Later Zn–Cu–Pb mineralization was formed from lower temperature hydrothermal fluids with higher sulfur activity. The δ34S values of sulfides (sphalerite, chalcopyrite, and pyrite) from three deposits show a wide range of sulfur values (δ34S) from −12.87 to + 19.31‰ (n = 27), consistent with heterogeneous sourcing of S, probably combining magmatic source along with the reduction of seawater sulfate. Variation in the sulfur isotopic compositions of sulfide was the result of dilution and cooling of the metalliferous fluid at different stages after interaction with meteoric, seawater and hydrothermal fluids, which caused the deposition of base metal sulfides. Sulfides from Ghisi in the west display both +ve and −ve values (−12.88 to + 0.38‰; n = 10), suggest sulfur predominantly derived by thermochemical reduction of seawater sulfate with minor input of magmatic sulfur reduction lead to polymetallic Zn–Cu–Pb mineralization. The gradual increasing in the δ34S values (more + ve values +18.65 to +19.31‰; n = 8) from west to east at Biskhan and Jangaldehri (+ 5.01 to + 8.3‰, n = 9) may be due to involvement of both the leaching of igneous basement rocks and chemical process of seawater sulfates by thermochemical reduction (TSR) from deep water levels lead to Zn–Cu mineralization. This δ 34S variation occurs in three deposits of the Betul Belt due to modifications of the primary mineralization during subsequent stages of ore formation and metamorphism, indicating a complex fluid evolution history for VHMS deposits in Betul Belt, Central India, where S derived from a heterogeneous source by multiple geological processes. This situation is more akin to many established VHMS deposits of ancient and modern submarine hydrothermal systems.

Geochemical and 13C trends in sedimentary deposits of coastal Pondicherry region, East coast of India ─ Insights from a borehole study

Abstract: Major, trace, rare earth elements and 13C isotope results of sediments collected up to the depth of 150 meter below ground level (m bgl) have been interpreted in relation to the provenance, weathering and deposition conditions of a multi layered sedimentary formation of Pondicherry region located in East Coast of India. The samples fall in the coarse to medium grain size range (mean Mz: 0.29 – 1.32) and the sorting values (mean SD: 0.29 – 1.04) mostly infer very well sorted nature of sediments. Skewness (mean Ski: 0.09-0.99) shows the domination of very fine skew while the kurtosis (mean KG: 0.76-7.73) shows sediments from extremely lepto kurtic to platy kurtic nature. Micro-structural studies infer that sediments are derived from multiple sources and transported towards the littoral zone through the fluvial processes. Relatively depleted elemental concentrations with respect to upper continental crust (UCC) (elemental ratios