Cl Type Research Articles

Hydrogeochemical and isotopic signatures for the identification of seawater intrusion in the paleobeach aquifer of Cox's Bazar city and its surrounding area, south-east Bangladesh

In order to better understand the encroachment of seawater into the groundwater system a total 115 groundwater samples were collected in an area of ∼7 km2 in Cox's Bazar paleobeach and its vicinity, from different types of tubewells, which included hand pump fitted bore wells (<50 m depth), moderately deep energized bore wells (50 m–100 m depth) and deep bore wells (>100 m depth) during June 2013. A combined hydro-geochemical indicators, selected trace elements (Sr and B) and in addition to δ18O and δ2H were used in this study. Results show that the high values of EC (202 μS/cm to 6730 μS/cm) and TDS (135 mg/L to 4509 mg/L) are found in groundwater of wells closer to the coast and few wells from the northern and central part of the study area. The cross plot of HCO3/Cl and TDS shows that groundwater along the paleobeach and some isolated areas are saline with TDS > 1000 mg/L, associated with high ratios of Cl/TDS (0.065). The groundwater facies generally evolves from freshwater (Ca-Mg-HCO3) to saline water (Na- Cl) type with an intermediate Ca-Mg-Cl type indicating that the aquifer system interacts with seawater and undergoes cation exchange. Results also reveal that the area affected by marine water intrusion has ionic ratios of Br/Cl (0.0006–0.0021) similar to seawater (0.0015) with some higher values. Groundwaters along the paleobeach and some isolated areas, low ionic ratios of SO4/Cl (0.01–6.53) and Na/Cl (0.20–152.09), relative to marine ratios (0.05 and 0.86 respectively), are also observed. Groundwaters with Seawater Mixing Index >1.0 and TDS >1000 mg/L constitute about 20% of the studied groundwaters and have relatively high δ18O (>- 4.0‰) values and the linear relationships between TDS and most of the ions, including B and Sr, and the chemical signature of the saline plumes (e.g., marine SO4/Cl, Na/Cl and Br/Cl ratios) suggest that mixing processes control the chemical composition of the seawater within the aquifers. However, these geochemical variations also reveal that the quality of potable water has deteriorated to a large extent due to seawater intrusion along the paleobeach, migrating inland toward the heavily groundwater exploited areas from the coast line and may entail various future health hazards.

Characterization of a novel cytochrome cGJ as the electron acceptor of XoxF-MDH in the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV

Methanotrophs play a prominent role in the global carbon cycle, by oxidizing the potent greenhouse gas methane to CO2. Methane is first converted into methanol by methane monooxygenase. This methanol is subsequently oxidized by either a calcium-dependent MxaF-type or a lanthanide-dependent XoxF-type methanol dehydrogenase (MDH). Electrons from methanol oxidation are shuttled to a cytochrome redox partner, termed cytochrome cL. Here, the cytochrome cL homolog from the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV was characterized. SolV cytochrome cGJ is a fusion of a XoxG cytochrome and a periplasmic binding protein XoxJ. Here we show that XoxGJ functions as the direct electron acceptor of its corresponding XoxF-type MDH and can sustain methanol turnover, when a secondary cytochrome is present as final electron acceptor. SolV cytochrome cGJ (XoxGJ) further displays a unique, red-shifted absorbance spectrum, with a Soret and Q bands at 440, 553 and 595 nm in the reduced state, respectively. VTVH-MCD spectroscopy revealed the presence of a low spin iron heme and the data further shows that the heme group exhibits minimal ruffling. The midpoint potential Em,pH7 of +240 mV is similar to other cytochrome cL type proteins but remarkably, the midpoint potential of cytochrome cGJ was not influenced by lowering the pH. Cytochrome cGJ represents the first example of a cytochrome from a strictly lanthanide-dependent methylotrophic microorganism.

Assessment of corrosion and scaling potential of the groundwater in the Thanjavur district using hydrogeochemical analysis and spatial modeling techniques

In this study, corrosiveness and scaling potential of groundwater in the Thanjavur district are evaluated based on the chemical analyses of 34 groundwater samples and GIS-based geostatistical mapping techniques. Total dissolved solid values show that six out of 34 samples exceeded the WHO drinking water standard 1000 mg/L. Piper plot shows that majority of the samples are mixed Ca–Mg–Cl type, Ca–HCO3 type and Na–Cl. The results of the physicochemical parameters were used to calculate the most popular corrosion and scaling indices such as Langelier index (LI), aggressive index (AI), Ryznar index (RI), Puckorius index (PI) and Larson–Skold index (LS). Results of LI show that 41% samples have corroding tendency (LI 0). AI has the same result as 41% of the water is moderately corrosive and the remaining has scaling tendency. RI suggests that 88% of the samples have corrosive tendency and 12% have rigorous corrosive tendency. Values of the PI suggest that all the samples were corrosive. Finally, the LS values show that 62% of the samples have scaling tendency and the remaining have corrosion tendency. In general, groundwater in the Thanjavur district shows both corrosive and scaling tendencies, which can cause severe damage to the machineries in the industries. Spatial variation of the corrosive and scaling indices suggests that the central region of the district has more corrosive tendencies and the western and eastern regions have more scaling tendencies.

CO2 Flux from Volcanic Lakes in the Western Group of the Azores Archipelago (Portugal)

Here, we present the first detailed study on diffuse CO2 degassing in the lakes in the Western Group (Corvo and Flores islands) of the Azores archipelago. This research is of interest in order to determine (1) the overall CO2 emission from such lakes, as volcanic lakes are often underrepresented in the databases of these water bodies, and (2) the diffuse CO2 degassing estimates in active volcanic areas such as the Azores. The lake waters on Corvo and Flores islands are mainly of the Na–Cl type, which is likely caused by the lakes’ sea salt signatures, arising from nearby seawater spraying; however, a few samples show evidence of slight alkali earth metal and bicarbonate enrichments in the lake waters, suggesting a contribution of water–rock interaction. In this study, diffuse CO2 flux measurements were taken using the accumulation chamber method, and statistical analyses utilizing the graphical statistical approach (GSA) and sequential Gaussian simulation (sGs) were conducted on the CO2 flux data, showing that the CO2 flux values measured in these lakes were relatively low (0.0–18.6 g m−2 d−1). The results seem to indicate that there is a single source of CO2 (a biogenic source), which is also supported by the waters’ δ13C isotopic signatures. Significant differences in the final CO2 output values were verified between surveys (e.g., 0.16 t d−1 in R1; 0.32 t d−1 in R2), and these differences are probably associated with the monomictic character of the lakes. CO2 emissions ranged between 0.18 t d−1 (CE1) and 0.50 t d−1 (CW1) for the Corvo lakes and between 0.03 t d−1 (P1) and 0.32 t d−1 (R2) for the seven lakes studied on Flores Island. The presence of a dense macrophyte mass in a few of the lakes appears to enhance the CO2 flux in these lakes.

The Effect of Recipient Holstein heifers’ Corpus Luteum Type, Diameter and Secretory Potential on their Pregnancy Rate during Routine ET program in Egypt

The objective: of this study was to find the correlation between the pregnancy rate of Holstein recipient heifers and their corpus luteum type, diameter and its secretary competence at the day of embryo transfer. Methods: A total of (92) recipients were selected after estrus synchronization by prostaglandin. Fresh embryos were collected from (12) donors. Corpus luteum type and diameter were determined at transfer date using transrectal ultrasound. Serum samples were collected at transfer day (7th day post heat/luteal phase) for progesterone and Estradiol-17s assessment. Results: Current study revealed non-significant difference between pregnant and non-pregnant recipients concerning CL diameters; regardless CL type either compact (24±0.83 and 24±0.58mm, respectively) or cavitary (26±1.1 and 27±1.4mm, respectively); however there was significant difference (P<0.05) between compact and cavitary CL diameters in non-pregnant recipient. Concerning, the relationship between CL type and pregnancy rate: thirteen pregnancies (39.39* %) had cavitary CL; whereas, twelve pregnancies (20.34%) had compact CL. Cavitary CL secreted progesterone (5.9 ± 1.7ng/ml) and estradiol (43±1.9 pg/ml). Compact CL recorded low level of progesterone (4.4±0.96 ng/ml), and high estradiol concentration (49±1.4 pg/ml). The percentage of cavitary CL in Holstein breed was (35.87%) versus (64.13%) for compact ones. Ratio of luteal cavity/luteal tissue was (0.48%) for Holstein recipients heifers. Conclusion: Corpus luteum type not diameter was a decisive factor in recipient selection. Luteal phase estradiol concentration was a crucial in recipient selection and should be at the lowest concentration. The percentage of cavitary CL for Holstein recipients was (35.87%), and the ratio of luteal cavity to the luteal tissue was (0.48%).

Copper(II) complex with L-arginine – Crystal structure, DFT calculations, spectroscopic, thermal and magnetic properties

Abstract Complex of formula [Cu(L−Arg)(phen)Cl]Cl·2H2O (1) was synthesized in crystalline form (triclinic crystal system, P1 (No. 1) space group with a = 9.376(1) A, b = 10.415(1) A, c = 12.209(2) A and Z = 2). The relations between the crystal structure, DFT calculations, spectroscopic properties (FT−IR, FT−Raman, NIR−Vis−UV, EPR) as well as the parameters of magnetic data were investigated. The square pyramidal geometry around copper (II) cations is very slightly distorted toward bipyramid geometry. The DFT-calculated interaction energies (ΔE) for the L−Arg zwitterion and phen ligands are −135.31 and −54.17 kcal mol−1, respectively. The g tensor diagonal components obey the relationship g|| > g⊥ (g⊥ = 2.063, g|| = 2.23) which suggested the pure dx2-y2 ground state orbital. Analysis of the crystal structure shows two possible magnetic exchange pathways: the neighboring [Cu( l −Arg)(phen)Cl]+ cations are linked in dimeric units by the N−H⋯Cl type hydrogen bonds, and almost parallel phenanthroline molecules provide π–π stacking interaction between the dimers. Analysis of the magnetic data, using an alternating ferro− and antiferromagnetic chain model for S = 1/2 spins, reveals the existence of weak antiferromagnetic coupling within the dimers (JAF = −0.23 cm−1) and weak ferromagnetic interaction between dimers (JF = 0.11 cm−1).

Sonochemical synthesis, characterization, biological applications, and DFT study of new nano-sized manganese complex of azomethine derivative of diaminomaleonitrile

The characterization of a new, synthesized Mn(II) Schiff base complex of the [MnL2Cl]Cl type (where L = 2-((pyridine-4-yl)metheleneamino)-3-aminomaleonitrile) was carried out by FT-IR, UV–Vis, DRS, GC–Mass, photoluminescence spectroscopy (PL) and elemental analysis. The production of Mn3O4 nanoparticles using thermal decomposition and its spectral properties in the current study is being checked. The nano compounds were characterized by X-ray diffraction, scanning electron microscopy (SEM), and the X-ray energy-dispersive spectrometry analyses. Synthesized manganese oxide nanoparticles have a tetragonal structure with the average size of 25–150 nm. The results of SEM showed that the morphology of [MnL2Cl]Cl was rod-like while the morphology of the Mn3O4 was rod-like as well as spherical. Also, the metal complexes’ antibacterial and antifungal activities were evaluated. The results of the microbiology activities indicated that the metal compounds exhibited stronger microbiology efficiencies than the ligand did.

Characteristics and causes of hydrochemical evolution of deep groundwater in the Luanhe Delta

Analyses of hydrochemical evolution of groundwater can provide a scientific basis for conservation and sustainable development of groundwater recourses. The third aquifer in the Luanhe delta region is taken as an example, and two hydrogeological profiles are selected to analyze the characteristics of hydrochemical constituents. Piper diagram is used to examine the hydrochemical differences in groundwater from upstream to downstream. Hydrochemical types change from Ca·Na-HCO3 type in the upstream to Na·Ca-HCO3·SO4 and Na-HCO3·Cl types in the downstream. In the upstream, incongruent dissolution mainly occurs along the groundwater flow direction, causing simultaneous increases in concentrations of HCO-3 and Ca2+ + Mg2+, as well as simultaneous increases in concentrations of Cl-+SO2-4 and Na+. In the downstream, in addition to incongruent dissolution, cation exchange and desulphidation may also occur, leading to decreases in concentrations of Ca2+, Mg2+ and SO2-4, and increases in concentrations of Cl- and Na+. This research provides a better understanding of the hydrochemical evolution of deep groundwater from the piedmont to the coastal region.

Primary data on the impact from trap magmatism on the hydrogeochemistry of brines in the southwestern part of the Kureyka syncline (Siberian Platform)

The new data on the trap magmatism affecting the hydrogeochemistry of brines in southwestern Kureyka syncline in the west of the ancient Siberian platform are presented. The brines occurring in Paleozoic and Proterozoic deposits have salinity (total dissolved solids) varying broadly: from 30.2 to 469.6 g/dm3 for Na Cl, Na-Ca Cl, Ca-Na Cl, Ca-Mg Cl and Ca Cl types, among which the mixed types (Ca-Na Cl and Na-Ca Cl) are found prevailing. The activity of intrusive trap magmatism in the contact zone (with a strike length of up to 400 m) facilitated the disintegration of organic compounds in the free and water-dissolved form (CH4, C2H6, C3H8, iC4H10, nC4H10, iC5H12, nC5H12, C6H14, I, B, NH4). The reaction of the intruding traps brines interaction significantly affected the initial composition of brines, showing a shift towards their saturation with iron, aluminum, silica and other components and thus bearing the evidence of possible salt-induced metal extraction from magmatic melts into an ore-bearing fluid.

Hydrochemical assessment with respect to arsenic and other trace elements in the Lower Katari Basin, Bolivian Altiplano

Hydrochemical investigations of groundwater and surface water were carried out to better understand the spatial distribution of As, major ions and trace elements. The study was carried out to evaluate the sources of dissolved species and elucidate the processes that govern the evolution of natural water in the Lower Katari Basin. The study area is close to the Titicaca Lake (Cohana Bay) formed by sediments of the Quaternary system, deposited in the fluvio-glacial to fluvio-lacustrine environment and geologic formations of the Devonian and Neogene system of volcanic origin. The study area has several environmental problems mainly caused by contaminants such as heavy metals, nutrients, and bacteria. These problems are linked to the urban and industrial wastes, natural geologic conditions, and mining activities carried out upstream of the Katari Basin, where rivers discharge into the Cohana Bay.A total of 37 water samples were collected during wet season, 31 groundwater samples including drinking water wells and six surface water samples. The hierarchical cluster analysis and principal component analysis were applied to hydrochemical data. Results show high salinity in groundwater related to the evaporation causing serious problems for the groundwater quality and rendering it unsuitable for drinking. Dissolved As concentration ranges from 0.7 to 89.7 μg/L; the principal source of As could be the alteration of volcanic rocks, more than 48% of the shallow groundwater samples exceeded the WHO guideline value for As and more than 22% for NO3-. Groundwater has neutral to slightly alkaline pH, and moderately oxidizing character. The groundwater chemistry reveals considerable variability, ranging from Na-SO4,Cl type through mixed Na-HCO3 type and Ca,Na-HCO3,Cl type. The distribution of trace elements shows a large range of concentrations. Speciation of As indicates that the predominant oxidation state is As (V). The geochemical modelling indicates that As could be associated with iron oxides and hydroxides which are probably the most important mineral phases for the As adsorption. The spatial distribution and the variation of dissolved As concentration in groundwater is governed by the variability in geological characteristics of the region that raises a significant concern about drinking water quality.

Tracing ionic sources and geochemical evolution of groundwater in the Intermountain Una basin in outer NW Himalaya, Himachal Pradesh, India

The present research aims to identify sources of ions and factors controlling the geochemical evolution of groundwater in an intermountain basin, comprising hill and valley fill region, of Outer Himalaya in Himachal Pradesh, India. The groundwater samples collected from 81 tubewells and handpumps are analyzed for major ions, trace metals and stable isotopes (δ18O and δD). Geochemically the dominant hydrochemical facies in the Una basin are Ca–HCO3, Ca–Mg–HCO3 and Na–Cl types at few locations. A relatively lower ionic concentration in the valley fills indicates dilution and low residence time of water to interact with the aquifer mass due to high porosity and permeability. The ionic ratios of 0.9, 0.8 and 3.8 to 5.7, respectively, for (Ca + Mg): HCO3, (Ca + Mg): (HCO3 + SO4) and Na: Cl, suggests that ionic composition of groundwater is mainly controlled by rock weathering of, particularly by dissolution/precipitation of calcrete and calcite hosted in rock veins and Ca–Na feldspar hosted in conglomerate deposits derived from the Higher and Lesser Himalaya during the formation of Siwalik rocks. Although Na, K, NO3 and SO4 are introduced in the groundwater through agricultural practices, Na has also been introduced through ion exchange processes that have occurred during water–rock interaction, as indicated by negative CAI values. Factor analysis further suggests three major factors affecting the water chemistry of the area. The first two factors are associated with rock weathering while the third is anthropogenic processes associated with high nitrate and iron concentration. High concentrations of Fe and Mn ions that are exceeded that of WHO and BIS standards are also present at few locations. The recharge of groundwater in the Outer Himalaya is entirely through Indian Southwest Monsoon (ISM) and depleted ratios of δ18O/δD in valley region indicate infiltration from irrigation in recharging the groundwater and fractionation of isotopes of precipitation due to evaporation before infiltration. High d-excess values and inverse relation with δ18O are indicative of secondary evaporation of precipitation during recharge of groundwater.

Conjunctive uses of the geothermal water resources from lower cretaceous formations in the Mogilno\u2013Lodz trough, Poland

The geothermal energy sector continues to develop dynamically in the world. Within this work, preliminary feasibilities of different geothermal applications were presented for the Lower Cretaceous formations for wider geothermal uses’ development in the Mogilno–Lodz trough, Central Poland. The Lower Cretaceous formations are one of the most prospective geothermal reservoirs in Central Poland. Geothermal waters that occur within them are mostly of Na–Cl type and contain specific elements like I, Br or Fe. These are low-temperature geothermal resources together with highly variable mineralization, from 0.4 to even more than 90 g/L. A simple estimation procedure for hydrogeological information, such as water and thermal conditions of the reservoir obtained from an archival chemical analysis and borehole temperature loggings was developed. The potential for geothermal applications was estimated for three zones of the Mogilno–Lodz trough. Possibilities of conjunctive geothermal applications, such as space heating, balneotherapy and balneorecreation, mineral extraction, electricity production in binary systems and aquifer thermal energy storage were examined for the Lower Cretaceous formations.

Hydro-geochemical characteristics of the groundwater resources in the southern part of the Red River’s Delta plain, Vietnam

In this study, the origin and recharge areas as well as the chemistry of the groundwater in the southern part of the Red River Delta plain, in Thai Binh, Nam Dinh and Ninh Binh provinces (North Vietnam) was investigated by using isotopic techniques combined with geochemical analysis. Groundwaters under the study were those that are available in the Holocene, Pleistocene, Neogene and Triassic aquifers. Groundwater in the Holocene aquifer is brackish of Na–Cl type with an electric conductivity as high as up to 6000 µS cm−1. The water in the shallow aquifer comprises three end-members: the local precipitation, Red River’s water and intruded seawater. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the Southwest of the study region is fresh containing less than 1 g L−1 of total dissolved solids and is characterized by the Ca–Na–HCO3 type. However, groundwater in the deep aquifers in the Northeast area is brackish of Na–Ca–Cl–HCO3 ion type containing more than 1 g L−1 TDS. The chemistry of groundwater in the study region is controlled by three processes, namely the incongruent dissolution of the biogenic high Mg-calcite, the reduction of sulphate and iron oxyhydroxide with organic matters present in the aquifers. The salinity in deep aquifers in the NE was attributed to the diffusion of saline pore water from aquifer or/and aquitard deposits to the recharge water. Groundwater in the Pleistocene, Neogene and Triassic aquifers in the study region seem to have meteoric origin with long traveling time and it mixed with the saline pore water that migrated from the aquifers sediments, as it was evident from the water isotopic compositions. The isotopic compositions of water (δ2H and δ18O) in the Neogene and Triassic aquifers are similar to that found in the Pleistocene aquifer suggesting the aquifers are hydraulically connected to each other due to the over-extraction rate of fresh water from the latter aquifer. Recharge area of groundwater in the Pleistocene and Neogene aquifers is suggested to be from the NW extension of the region and out crops at a highland at an altitude of 140–160-m above sea level (masl). The recharge water flows from northwesterly towards southeasterly to the sea coast. The results of the 14C-dating for groundwater combined with the hydraulic heads distribution in the deep aquifers revealed that the saline groundwater is flowing from the NE and backwards from the sea side to the production well field in the center of the region due to the high rate of groundwater mining. In order to mitigate the saltwater intrusion and avoid deterioration of the quality of the groundwater that is currently being mined and supplied to the local population, it needs to develop and implement an appropriate strategy for the groundwater resource management in the region.

The use of hydrogeochemical analyses and multivariate statistics for the characterization of thermal springs in the Constantine area, Northeastern Algeria

This paper deals with the results of a hydrogeochemistry study on the thermal waters of the Constantine area, Northeastern Algeria, using geochemical and statistical tools. The samples were collected in December 2016 from twelve hot springs and were analyzed for physicochemical parameters (electric conductivity, pH, total dissolved solids, temperature, Ca, Mg, Na, K, HCO3, Cl, SO4, and SiO2). The waters of the thermal springs have temperatures varying from 28 to 51 °C and electric conductivity values ranging from 853 to 5630 μS/cm. Q-mode Cluster analysis resulted in the determination of two major water types: a Ca–HCO3–SO4 type with a moderate salinity and a Na–K–Cl type with high salinity. The plot of the major ions versus the saturation indices suggested that the hydrogeochemistry of thermal groundwater is mainly controlled by dissolution/precipitation of carbonate minerals, dissolution of evaporite minerals (halite and gypsum), and ion exchange of Ca (and/or Mg) by Na. The Gibbs diagram shows that evaporation is another factor playing a minor role. Principal Component Analysis produced three significant factors which have 88.2% of total variance that illustrate the main processes controlling the chemistry of groundwaters, which are respectively: the dissolution of evaporite minerals (halite and gypsum), ion exchange, and dissolution/precipitation of carbonate minerals. The subsurface reservoir temperatures were calculated using different cation and silica geothermometers and gave temperatures ranging between 17 and 279 °C. The Na–K and Na–K-Ca geothermometers provided high temperatures (up to 279 °C), whereas, estimated geotemperatures from K/Mg geothermometers were the lowest (17–53 °C). Silica geothermometers gave the most reasonable temperature estimate of the subsurface waters overlap between 20 and 58 °C, which indicate possible mixing with cooler Mg groundwaters indicated by the Na–K–Mg plot in the immature water field and in silica and chloride mixing models. The results of stable isotope analyses (δ18O and δ2H) suggest that the origin of thermal water recharge is precipitation, which recharged from a higher altitude (600–1200 m) and infiltrated through deep faults and fractures in carbonate formations. They circulate at an estimated depth that does not exceed 2 km and are heated by a high conductive heat flow before rising to the surface through faults that acted as hydrothermal conduits. During their ascent to the surface, they are subjected to various physical and chemical changes such as cooling by conduction and change in their chemical constituents due to the mixing with cold groundwaters.

Synthesis and structural features of copper(II) complexes of N,N,N′,N′-tetramethylethylenediamine with 2-chlorobenzoate1− and 2-hydroxybenzoate1−

Two copper(II) coordination complexes, formulated as [Cu(tmen)(Clba)2] (1) and [Cu(tmen)(Hsal)2·H2O] (2) (where tmen = N,N,N′,N′-tetramethyl ethylenediamine (C6H16N2), Clba1− = 2-chlorobenzoate (C7H4ClO21−), and Hsal1− (C7H5O31− = monoanion of o-hydroxybenzoic acid (salicylic acid)), have been synthesized and characterized by elemental combustion analysis, spectroscopic techniques, thermal studies, and single crystal X-ray analyses. Complex 1 consists of two distinct monomeric units in which the coordination environment around the central copper(II) ion is a distorted octahedron with a CuN2O4 chromophore, constituted by a chelating tmen molecule, and two 2-chlorobenzoate1− anions coordinated through their carboxylate-O atoms in an asymmetrical bidentate fashion. Complex 2 is also a monomer and consists of an CuN2O3 chromophore, in which tmen is coordinated to Cu(II) through its two N atoms in a chelating bidentate fashion, and an aqua-O and the two o-hydroxybenzoate1− (HSal1−) anions are coordinated through one of their carboxylate-O atoms in a monodentate mode, forming a square pyramidal structure. Hydrogen bonding interactions especially of O–H…O, N–H…O, and C–H…Cl types interweave monomeric units and stabilize the overall crystal structures in both complexes. Thermal analysis and antibacterial activities of 1 and 2 against various bacterial strains were also investigated.

Hydrogeochemical evolution of groundwater in a Quaternary sediment and Cretaceous sandstone unconfined aquifer in Northwestern China

A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for the protection of water resources. To assess groundwater chemistry, groundwater sampling was performed from different representative aquifers in 2012–2013. A Piper trilinear diagram showed that the groundwater types can be classified into Na–SO4 and Na–Cl types. Only one groundwater sample was Na–HCO3 type. The dominant cations for all samples were Na+. However, the dominant anions varied from HCO3− to SO42−, and as well Cl−. The mean total dissolved solid (TDS) content of groundwater in the region was 1889 mg/L. Thus, only 20% of groundwater samples meet Chinese drinking water standards (< 1000 mg/L). Principal component analysis (PCA) combined with hierarchical cluster analysis (HCA) and self-organizing maps (SOM) were applied for the classification of the groundwater geochemistry. The three first principal components explained 58, 20, and 16% of the variance, respectively. The first component reflects sulfate minerals (gypsum, anhydrite) and halite dissolution, and/or evaporation in the shallow aquifer. The second and third components are interpreted as carbonate rock dissolution. The reason for two factors is that the different aquifers give rise to different degree of hydrogeochemical evolution (different travel distances and travel times). Identified clusters for evolution characteristic and influencing factors were confirmed by the PCA–HCA methods. Using information from eight ion components and SOM, formation mechanisms and influencing factors for the present groundwater quality were determined.

Hydrogeological Classification and the Correlation of Groundwater Chemistry with Basin Flow in the South-Western Part of Bangladesh

Attempt has been made to find the relationship between the basin groundwater flow and the current water chemistry of south-western part of Bangladesh considering their lithological distribution and aquifer condition. The correlation of water chemistry and basin groundwater flow is depicted in the conceptual model. The water-types of shallow groundwater are predominantly Mg-Na-HCO3 and Ca- Mg-Na-HCO3 type. In the deep aquifer of upper delta plain is predominately Na-Cl, Ca-HCO3 and Mg- HCO3 type. In the lower delta plain Na-Cl type of water mainly occurs in the shallow aquifer and occasionally Ca-HCO3, Ca-Mg-Na-HCO3 and Mg-HCO3 type may also occur in shallow aquifer of the eastern part of lower delta plain which could have originated from the recent recharge of rain water. Na- Cl type water is also found in the deep aquifer of lower delta plain. The origin of Na-Cl type water in the deep aquifer of lower delta part might be connate water or present day sea water intrusion. Fresh water occurring in the deep aquifer in the lower delta area is mostly of Mg-Ca-HCO3 and Na-HClO3 types. This type of water originate from intermediate or deep basin flow from the northern part of Bangladesh. The probable source of deep groundwater is Holocene marine transgression (Khan et al. 2000) occurred in 3000–7000 cal years BP and the deep groundwater of Upper Delta plain and Lower Delta plain is clearly influenced by deep basin flow coming from north part of BangladeshJournal of Bangladesh Academy of Sciences, Vol. 42, No. 1, 41-54, 2018

Occurrence, health risks, and geochemical mechanisms of fluoride and nitrate in groundwater of the rock-dominant semi-arid region, Telangana State, India

ABSTRACTHighly contaminated groundwater can affect the human health and constrain the economic development of a country. For this study 105 groundwater samples were collected in rock-dominant semi-arid (RDSA) region, India and analyzed for hydrochemical parameters including major ions, fluoride, and nitrate. The human health risks due to groundwater fluoride and nitrate contamination were also assessed. The analysis reveals that most of the groundwater samples are alkaline in nature. Hydrochemical types of groundwater in the study area are mainly Ca∙Mg–HCO3 and Na–HCO3 types and a few samples belong to Ca∙Mg–Cl and Na–Cl types in the RDSA region. Fluoride concentration ranges from 0.5 to 3.5 mg/L, and predominantly eastern part of the study region has higher concentrations of fluoride with comparison to the western part. About 49% of the groundwater samples have fluoride concentration above 1.5 mg/L in groundwater, indicating a high health risk to residents. Eventually, water-rock interactions are the main processes to elevate the fluoride concentration in eastern part of the study area. Nitrate concentration ranges from 12 to 212 mg/L, and northern and southern parts of the study region have much higher nitrate concentrations than the central region of the study area, where nitrate concentration is below 45 mg/L. In terms of nitrate, 55% and 17% of the groundwater samples are under high risk and very high risk categories, respectively, which are not suitable for drinking purposes in the study region. Fertilizer application for crop yields could be one of the reasons for elevated nitrate concentration. The total hazard index for adults ranges from 0.87 to 7.08, and for children 1.17 to 9.57, which suggests that children are at higher health risk than adults in the study region. Therefore, contaminants filters and rainwater harvesting are suggested as measures to reduce the health risk in the area.

Groundwater hydrochemical characterization and quality assessment in the Ghriss Plain basin, northwest Algeria

A base line study involving analysis of groundwater samples from the Ghriss plain plio-quaternary aquifer, in northwest Algeria, was carried out to determine the major elements chemistry and to assess the hydrogeochemical processes and water quality for domestic use. The main groundwater facies in the area belong to the Mg–HCO 3 and Mg–Cl types. Based on TDS classification, 44.5% of the analyzed samples belong to fresh water and the remaining 55.5% to brackish water categories. A comparison of groundwater quality parameters in relation to WHO limits for drinking water shows that the concentrations of TDS, Cl − and NO 3 − exceed the desirable limits in many water samples. The principal component analysis (PCA) technique reveals the contribution of Cl − , Na + , Ca 2+ , K + and Mg 2+ in the salinization process and underlines the contamination of the groundwater with NO 3 − in relation to the widespread application of nitrate fertilizers and/or infiltration of untreated urban wastewater. The groundwater quality index (GWQI) shows that 70.5% of the water samples fall within the excellent-to-good category whereas the remaining samples fall in the poor-to-unsuitable for drinking category.

Atmospheric deposition and exceedances of critical loads from 1800-2025 for the conterminous United States.

Atmospheric deposition of nitrogen (N) and sulfur (S) has increased dramatically over pre-industrial levels, with many potential impacts on terrestrial and aquatic ecosystems. Quantitative thresholds, termed "critical loads" (CLs), have been developed to estimate the deposition rate above which damage is thought to occur. However, there remains no comprehensive comparison of when, where, and over what time periods individual CLs have been exceeded. We addressed this knowledge gap by combining several published data sources for historical and contemporary deposition, and overlaying these on six CL types from the National Critical Loads Database (NCLDv2.5; terrestrial acidification, aquatic acidification, lichen, nitrate leaching, plant community composition, and forest-tree health) to examine exceedances from 1800 to 2011. We expressed CLs as the minimum, 10th, and 50th percentiles within 12-km grid cells. Minimum CLs were relatively uniform across the country (200-400eq·ha-1 ·yr-1 ), and have been exceeded for decades beginning in the early 20th century. The area exceeding minimum CLs peaked in the 1970s and 1980s, exposing 300,000 to 3million km2 (depending on the CL type) to harmful levels of deposition, with a total area exceeded of 5.8million km2 (~70% of the conterminous United States). Since then, deposition levels have dropped, especially for S, with modest reductions in exceedance by 2011 for all CL types, totaling 5.2million km2 in exceedance. The 10th and 50th percentile CLs followed similar trends, but were not consistently available at the 12-km grid scale. We also examined near-term future deposition and exceedances in 2025 under current air quality regulations, and under various scenarios of climate change and additional nitrogen management controls. Current regulations were projected to reduce exceedances of any CL from 5.2 million km2 in 2011 to 4.8million km2 in 2025. None of the additional N management or climate scenarios significantly affected areal exceedances, although exceedance severity declined. In total, it is clear that many CLs have been exceeded for decades, and are likely to remain so in the short term under current policies. Additionally, we suggest many areas for improvement to enhance our understanding of deposition and its effects to support informed decision making.