Low Cl Concentrations Research Articles

A simulation of radiolysis of chloride solutions containing ferrous ion

ABSTRACT To investigate the effect of dissolved species from steels on the radiolysis processes of Cl−, radiolysis simulations of solutions containing both Cl− and Fe2+ were carried out. The results showed that the generation of radiolytic products (H2O2, O2 and H2) increased mainly by the addition of Fe2+, and the concentrations of H2O2 and O2 increased with increasing dose rate. Moreover, radiolysis of Fe2+ solutions also induced noticeable pH drop due to the hydrolysis of Fe3+. This pH drop enhanced the reactivity of Cl− with ∙OH, which induced additional generation of H2O2 and O2. These results show that low concentrations of Cl− (1 × 10−3 mol/dm3 = 35 mg/kg) in the presence of Fe2+ could influence the generation of H2O2 and O2 during water radiolysis. On the other hand, it is considered that these effects of Fe2+ and Cl− on water radiolysis are less important for corrosion of steels due to the low concentrations of H2O2 and O2 generated if the concentrations of these additives and dose rate are sufficiently low. The other process, such as dissolution of iron enhanced by FeOOH, might predominantly induce corrosion under the conditions of solutions with low concentrations of H2O2 and O2.

Halogen Heterogeneity in the Lithosphere and Evolution of Mantle Halogen Abundances Inferred From Intraplate Mantle Xenoliths

AbstractWe present halogen, noble gas, and major and trace element compositions of mantle xenoliths from intraplate settings (Eifel, Kilbourne Hole, San Carlos, and Hawaii). The xenoliths show a wide range of halogen elemental ratios, which form two arrays centered on the halogen composition of mid‐ocean ridge basalts. The samples on the array toward high I/Cl value have relatively low Cl concentration and low ratios of highly incompatible elements relative to heavy rare earth elements, whereas the samples on the array toward low Br/Cl value have higher Cl concentration and trace elements ratios. The detailed mechanisms to account for these signatures are equivocal at present. However, they are most likely to be related to secondary processes of volatile loss during partial melting and secondary phase formation during interaction with melts. The common primary mid‐ocean ridge basalt‐like halogen ratios in mantle xenoliths from different parts of the globe indicate that the mantle itself must have a relatively uniform composition over a wide scale. The mantle has maintained its halogen composition over billion year timescales without being affected by I‐rich halogens being transported into the mantle. Mass balance calculations suggest that, in order to maintain the I/Cl ratio of the convecting mantle over 2 Gyr, the I/Cl ratio of the subducted halogens must be no more than several times higher than the present‐day mantle value.

Influence of Cl- ions on anodic polarization behaviour of API X80 steel in high potential/current density conditions in Na2SO4 solution.

Pipeline steel has considerable risk of corrosion in the high voltage direct current interference cases. Thus, under high potential/current density conditions, the anodic polarization behaviour of X80 steel in Na2SO4 solution and the influence of Cl− ions were investigated using reversed potentiodynamic polarization, the current interrupt method, galvanostatic polarization, scanning electron microscopy, and X-ray photoelectron spectroscopy. In the Na2SO4 solution free of Cl− ions, steel was passivated above 0.120 A cm−2 and the potential increased from −0.32 V to 1.43 V. The passive film was composed of Fe3O4, γ-Fe2O3, and FeOOH. The addition of Cl− ions observably influenced the passivation by attacking the passivate film. Low concentration of Cl− ions (<5 mg L−1 NaCl) could set higher demands of current density to achieve passivation and increase the requirement of potential to maintain passivation. A high concentration of Cl− ions (>5 mg L−1 NaCl) completely prevented passivation, showing strong corrosiveness. Thus, the X80 steel was corroded even under high-current-density conditions. The corrosion products were mainly composed of Fe3O4, α-Fe2O3, and FeOOH.

Identifying multiple deep aquifers in the Bengal Basin: Implications for resource management

AbstractIn the Bengal Basin of Bangladesh and West Bengal (India), where arsenic (As) and salinity adversely affect groundwater in shallow aquifers (&lt;150 m deep), consumers increasingly turn to “the deep aquifer” as a source of low‐As and low‐salinity water. We show that “the deep aquifer,” which has traditionally been regarded as a single entity, can be divided into at least eight deep aquifer units each with distinctive chemical, isotopic, hydraulic, and piezometric characteristics. Except in the rapidly subsiding Sylhet Basin, the deep aquifers are largely As‐safe (&lt;50 μg/L and mostly &lt;10 μg/L) but differ in terms of iron (Fe), manganese (Mn), salinity, stable isotopic composition, groundwater age, and in their piezometric response to pumping. We use isotopic data to identify recharge from five periods, of which two are quantitatively dominant: (a) from the Last Glacial Maximum, isotopically heavy water (δ18O &gt;−3.5‰) with low As, Cl, and Fe concentrations occupies hydraulically trapped positions in the South‐Central, Southeast, Southwest, and Madhupur aquifer units and (b) terminal Pleistocene to Early Holocene recharge of isotopically lighter water (δ18O &lt;−3.5‰) that has high Fe and slightly elevated Cl concentrations and was recharged along palaeochannels that facilitated deep circulation up to the mid‐Holocene. Piezometric responses to development change in style towards the coast. In the north, water levels at all depths tend to be coincident and transition through a seasonally divergent pattern to become parallel in the south with a near constant downward gradient. The delineation of the deep aquifer units provides a practical framework for the assessment and management of groundwater resources for water supply.

Modelling study on the effects of chloride on the degradation of bezafibrate and carbamazepine in sulfate radical-based advanced oxidation processes: Conversion of reactive radicals

The degradation rates of pharmaceuticals contaminants (such as bezafibrate and carbamazepine) in the UV/S2O82− process at different Cl− concentrations (0.01, 0.1, 1.0, 10, and 100 mM) and pH values (3, 5, 7, 9 and 11) were investigated in this study. The degradation rate of bezafibrate showed an upward trend before the critical point (Cl− = 1.0 mM), the maximum enhancement was 51%, then the degradation rate decreased. The degradation rate of carbamazepine increased continuously, and the maximum enhancement was 66% when the Cl− concentration was 100 mM. The degradation rate of bezafibrate showed the maximum value at pH = 7 while the most rapid degradation rate of carbamazepine was observed at pH = 3. To explain these interesting results, a kinetic model was used to investigate the conversion of reactive radicals (such as SO4−, OH, Cl, and Cl2−) at different Cl− concentrations and pH values. Simulation results showed that low concentrations (<1.0 mM) of Cl− transformed SO4− into OH and Cl. With the further increased concentration of Cl− from 1.0 mM to 100 mM, OH and Cl can be converted into Cl2−. Furthermore, Cl2− was the dominant reactive species when pH < 7, whereas OH dominated when pH > 7. Few organic chlorinated products were observed in the UV/S2O82−/Cl− process, indicating that the reactions between bezafibrate/carbamazepine and the reactive chlorine radicals Cl/Cl2− occurred mainly through electron transfer and H-extraction, whereas the substitution reaction leading to the formation of organic chlorinated products was not dominated. This study positively demonstrated the absence of chlorinated product formation during SR-AOPs application.

Enhanced removal of organic contaminants in water by the combination of peroxymonosulfate and carbonate

In this study, a favorable CO32−/PMS system for efficient degradation of organic contaminants (acid orange 7 (AO7), acetaminophen, para-aminobenzoic acid, phenol, methylene orange, methylene blue) in water was firstly reported. Under optimal conditions, the decolorization ration of AO7 was 100% within 40 min. Data fitting showed that the AO7 decolorization could be described by the pseudo-first-order kinetics, and the rates constant values ranging from 0.0006 to 0.2297 min−1 depending on the operating parameters (initial PMS, CO32−, AO7 concentrations). Radical scavenging studies revealed that superoxide anion radical (O2−) and singlet oxygen (1O2) rather than sulfate (SO4−) nor hydroxyl (HO) were the dominant oxidants might be responsible for AO7 degradation. The presence of NO3−, HPO42− and low concentration of Cl−, NO2−, HCO3−, H2PO4−, HA had no significantly effect on the decolorization of AO7. Adding a higher Cl− concentration displayed favorable effects on the removal efficiencies of AO7, but adding a higher NO2−, HCO3−, H2PO4− and HA concentration apparently inhibited this process. The decolorization of AO7 was lower in wastewater in comparison to other natural waters and ultrapure water, which was probably due to the presence of higher concentration of colloids in wastewater. Nevertheless, up to 94.8%, 97.0% and 85.1% of AO7 were degraded from the filtrate, permeate, and retentate phases of wastewater within 60 min, respectively. Consequently, CO32−/PMS would be promising for removal methodology for AO7 in wastewater containing considerable colloids. Finally, three intermediates were identified and degradation pathways of AO7 were proposed.

The pyrethroid λ-cyhalothrin induces biochemical, genotoxic, and physiological alterations in the teleost Prochilodus lineatus

The λ-cyhalothrin (CL) is a globally used pyrethroid insecticide that has been detected in different water bodies worldwide. However, studies on the effects of CL on freshwater fishes are still incipient. In this context, we evaluated the acute effects of a commercial formulation containing CL (Karate Zeon® CS 50) in juveniles of the teleost Prochilodus lineatus exposed for 96 h to four concentrations of the active ingredient (5, 50, 250 and 500 ng.L−1). Biochemical, physiological, and genotoxic biomarkers were evaluated in different organs of the fish. Exposure to CL induced significant changes in the enzymatic profiles of P. lineatus, with specific alterations in biotransformation enzymes and antioxidant defence in different tissues. Lipid peroxidation was observed in fish gills and kidney. Increases in esterases were observed in the liver of fish exposed to all CL concentrations evaluated, whereas acetylcholinesterase activity decreased in the muscles of fish at all concentrations. CL also promoted osmoregulatory disorders, with decreases in calcium and magnesium gill ATPases, with consequent hypocalcaemia, in addition an increase in sodium-potassium ATPase activity was observed in the gills of fish exposed to the highest CL concentration, probably in order to compensate a reduction in plasma sodium. Besides, increases in DNA damage were observed in the erythrocytes of fish exposed to all CL concentrations. Thus, despite the low CL concentrations and the short exposure time, this pyrethroid caused hematological adjustments, oxidative stress, osmoregulatory disorders, and DNA damage in P. lineatus, showing that the species is highly sensitive to the deleterious effects of CL.

Electrochemical behavior of tin anode in ascorbic acid solutions

The anodic behavior of tin in ascorbic acid (AA) solutions was investigated using cyclic and/or linear sweep voltammetry and chronopotentiometry method and complemented by XRD and SEM examination. The results showed that the cyclic voltammetric curves in 0.5 M ascorbic acid at 18 ± 0.5 °C involves active/passive transition followed by pitting corrosion. In the active region, Sn dissolves as Sn2+ and Sn4+ and dissolution process is under diffusion control. Passivation is due to deposition of Sn(OH)4 and/or SnO2 on the electrode surface. Pitting corrosion is attributed to local dissolution of the passive film by the adsorbed AA molecules and initiating of pitting attack at a pitting potential Eb. Increasing the acid concentration and temperature enhances the anodic dissolution and shifts Eb to more active direction. Addition of Cl−, Br− and I− in AA enhances both the anodic dissolution and pitting corrosion of Sn. The extent of enhancements depends upon the type and concentration of halide added. The chronopotentiometry curves at constant current densities revealed that increasing the imposed current density decreases the time needed to passivation tp. Addition of low concentrations of Cl−(<5 × 10−5 M) in 0.5 M AA induces pitting corrosion while higher concentrations of Cl− prevent the passivation and the electrode remains in its active state.

Segregation of chlorine in n-type tin monosulfide ceramics: Actual chlorine concentration for carrier-type conversion

Tin monosulfide (SnS) is an attractive material for photovoltaic cells because of its suitable band-gap energy, high absorption coefficient, and non-toxic and abundant constituent elements. The primary drawback of this material is the lack of n-type SnS. We recently demonstrated n-type SnS by doping with Cl. However, the Cl-doped n-type SnS bulk ceramics exhibited an odd behavior in which carrier-type conversion but not electron carrier concentration depended on the Cl concentration. In this study, the electron probe microanalysis (EPMA) elemental mapping of Cl-doped SnS revealed continuous homogeneous regions with a relatively low Cl concentration along with the islands of high Cl concentration in which Sn/S is far from unity. The difference between the Cl concentration in the homogeneous region (determined by EPMA) and the bulk Cl concentration (determined by wavelength-dispersive X-ray fluorescence spectroscopy) increased with the increasing Cl doping amount. The carrier concentration and the Hall coefficient clearly depended on the Cl concentration in the homogeneous region. Carrier-type conversion was observed at the Cl concentration of 0.26 at. % (in the homogeneous region).

Ionic plasticity and pain: The loss of descending serotonergic fibers after spinal cord injury transforms how GABA affects pain

Activation of pain (nociceptive) fibers can sensitize neural circuits within the spinal cord, inducing an increase in excitability (central sensitization) that can foster chronic pain. The development of spinally-mediated central sensitization is regulated by descending fibers and GABAergic interneurons. In adult animals, the co-transporter KCC2 maintains a low intracellular concentration of the anion Cl−. As a result, when the GABA-A receptor is engaged, Cl− flows in the neuron which has a hyperpolarizing (inhibitory) effect. Spinal cord injury (SCI) can down-regulate KCC2 and reverse the flow of Cl−. Under these conditions, engaging the GABA-A receptor can have a depolarizing (excitatory) effect that fosters the development of nociceptive sensitization. The present paper explores how SCI alters GABA function and provides evidence that the loss of descending fibers alters pain transmission to the brain. Prior work has shown that, after SCI, administration of a GABA-A antagonist blocks the development of capsaicin-induced nociceptive sensitization, implying that GABA release plays an essential role. This excitatory effect is linked to serotonergic (5HT) fibers that descend through the dorsolateral funiculus (DLF) and impact spinal function via the 5HT-1A receptor. Supporting this, blocking the 5HT-1A receptor, or lesioning the DLF, emulated the effect of SCI. Conversely, spinal application of a 5HT-1A agonist up-regulated KCC2 and reversed the effect of bicuculline treatment. Finally, lesioning the DLF reversed how a GABA-A antagonist affects a capsaicin-induced aversion in a place conditioning task; in sham operated animals, bicuculline enhanced aversion whereas in DLF-lesioned rats biciculline had an antinociceptive effect.

U-Th/He dating and chemical compositions of apatite in the dacite from the southwestern Okinawa Trough: Implications for petrogenesis

Apatite has recently gained considerable attention, providing new insight into a wide range of geological processes, such as geochronology, magmatism, metasomatism and metallogenesis. Here, we investigate the U-Th/He dates, in situ major- and trace- element concentrations, and 87Sr/86Sr ratios of apatites in the dacite from the southwestern Okinawa Trough to constrain its eruption age and the petrogenesis. The U-Th/He dating of apatites indicates that the volcanic eruption that formed the dacite was no older than 0.28 Ma and that the eruption was related to the replenishment of mafic magma. Apatites are present in the dacite as inclusions within pyroxene phenocrysts and are protected them from the external melt environment; therefore, they should retain a reliable record of their original chemical composition. In addition, all the apatite grains are fluorapatites with F contents of 1.58–2.54 wt.% and Cl contents of 0.57–0.88 wt.%. These grains are enriched in REEs (∑REE = 3341–5527 ppm) with significant Eu anomalies (Eu/Eu∗ = 0.20–0.24), low Sr/Y radios (0.20–0.35), high 87Sr/86Sr ratios (range from 0.70635 to 0.70697). Based on these characteristics, we propose that the dehydration of subducted slab released fluids into the overlying mantle wedge and triggered mantle melting, which produced primitive mafic magma with high Cl content. Then, the mafic magma ascended into the crust, which has low Cl concentrations and high 87Sr/86Sr ratios. The mixing of a mantle-derived basaltic magma and a crustal felsic magma in a shallow magma chamber diluted the Cl content and elevated the 87Sr/86Sr ratio, thus producing the parental magma of the dacite. When the magma chamber was replenished by mafic magma at approximately 0.28 Ma, the high temperature from the injection would have caused the felsic melt to move upward and finally erupt.

Crystallization and destabilization of eudialyte-group minerals in peralkaline granite and pegmatite: a case study from the Ambohimirahavavy complex, Madagascar

AbstractEudialyte-group minerals (EGM) are very common in highly evolved SiO2-undersaturated syenites and are characteristic minerals of agpaitic rocks. Conversely, they are extremely rare in peralkaline granites, with only a handful of EGM occurrences reported worldwide. Here, we study two new examples of EGM occurrence in two types of peralkaline pegmatitic granites from the Cenozoic Ambohimirahavavy complex, and assess the magmatic conditions required to crystallize EGM in peralkaline SiO2-oversaturated rocks. In the transitional granite (contains EGM as accessory minerals) EGM occur as late phases and are the only agpaitic and major rare-earth element (REE) bearing minerals. In the agpaitic granite (contains EGM as rock-forming minerals) EGM are early-magmatic phases occurring together with two other agpaitic minerals, nacareniobsite-(Ce) and turkestanite. In these granites, EGM are partly-to-completely altered and replaced by secondary assemblages consisting of zircon and quartz in the transitional granite and an unidentified Ca-Na zirconosilicate in the agpaitic granite. Ambohimirahavavy EGM, as well as those from other peralkaline granites and pegmatites, are richer inREEand poorer in Ca than EGM in nepheline syenites. We infer that magmatic EGM are rare in SiO2-oversaturated rocks because of low Cl concentrations in these melts. At Ambohimirahavavy, contamination of the parental magma of the agpaitic granite with Ca-rich material increased the solubility of Cl in the melt promoting EGM crystallization. In both granite types, EGM were destabilized by the late exsolution of a fluid and by interaction with an external Ca-bearing fluid.

Role of Segregated Iron at Grain Boundaries on Mg Corrosion

To elucidate the role of noble metal impurities on corrosion of Mg, 3D time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging in combination with X-ray photoelectron spectroscopy and optical microscopy measurements were carried out on Mg samples (99.9%) before and after Mg polarization at EOCP+0.5 V in 0.1 M NaCl. A significant segregation of Fe (and of Mn and Al) metallic impurities at grain boundaries (GBs) was observed on the Mg surface by 3D ToF-SIMS. A 3-step mechanism of Mg corrosion was proposed, including a catalytic effect of Fe segregated at the GBs on the hydrogen evolution reaction (HER). In the 1st stage, the initiation of Mg corrosion is accompanied by the HER occurring over Fe impurities segregated at GBs leading to formation of small circular defects, and propagation with occurrence of dark filiform-like pattern corrosion enriched in Cl−. In the 2nd stage, segregated Fe metallic particles are released by Mg matrix undermining, and are dissolved into Fe2+ ions and in the 3rd stage a redeposition of Fe in the clear areas of Mg surfaces, corresponding to areas with low concentration of Cl−, takes place.

Morphological and Physiological Responses of Ten Ornamental Taxa to Saline Water Irrigation

Because of limited supply of high-quality water, alternative water sources have been used for irrigation in water-scarce regions. However, alternative waters usually contain high salt levels, which can cause salt damage on salt-sensitive plants. A greenhouse study was conducted to evaluate the relative salt tolerance of 10 common ornamental taxa to saline water irrigation. The 10 taxa studied were Chaenomeles speciosa ‘Orange Storm’ and ‘Pink Storm’ (Chaenomeles Double Take™); Diervilla rivularis ‘G2X885411’, ‘G2X88544’ (Diervilla Kodiak®, Black, Orange, and Red, respectively), and ‘Smndrsf’; Forsythia ×intermedia ‘Mindor’ (Forsythia Show Off®); Hibiscus syriacus ‘ILVOPS’ (Hibiscus Purple Satin®); Hydrangea macrophylla ‘Smhmtau’ and ‘Smnhmsigma’ (Hydrangea Let’s Dance® Blue Jangles® and Rave, respectively); and Parthenocissus quinquefolia ‘Troki’ (Parthenociss quinquefolia Red Wall®). Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) eight times on a weekly basis. The results indicated that the 10 ornamental taxa had different morphological and physiological responses to salinity. The C. speciosa and D. rivularis plants in EC 5 had severe salt foliar damage, whereas those in EC 10 were dead. Hibiscus syriacus ‘ILVOPS’ performed well in EC 5 treatment with a shoot dry weight (DW) reduction of 26%, but those in EC 10 had severe foliar salt damage. Hydrangea macrophylla, F. ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ were the most salt tolerant with minor foliar salt damage. The two H. macrophylla cultivars had the highest shoot sodium (Na) and chlorine (Cl) concentrations with a visual quality of 3 (scale 0 to 5 with 0 for dead plants and 5 for excellent performance), indicating that H. macrophylla plants adapted to elevated salinity by tolerating high Na and Cl concentrations in leaf tissue. Forsythia ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ had relatively low leaf Na and Cl concentration, indicating that both taxa are capable of excluding Na and Cl. Chaenomeles speciosa and D. rivularis were sensitive to salinity with great growth reduction, severe foliar salt damage, and high Na and Cl accumulation in leaf tissue.

Effect of Ammonium Chloride in Plating Baths on Soft Magnetic Properties of Electroplated Fe–Ni Films

We electroplated Fe–Ni films in plating baths with ammonium chloride (NH4Cl) and evaluated the magnetic properties of the films. The amount of NH4Cl did not affect the current efficiency of the plating process and the Fe content in the film. The obtained current efficiency of approximately 95% is much higher than our previous study. The coercivity dramatically decreased with increasing NH4Cl from 0 to 15 g/L, and we obtained Fe22Ni78 films with very low coercivity (10 A/m). The Cl− concentration in the plating bath affected the coercivity, and we found that a plating bath with moderate low concentration of Cl− is preferred for obtaining the Fe22Ni78 films with low coercivity.

Removal of indomethacin using UV–vis/peroxydisulfate: Kinetics, toxicity, and transformation pathways

The extensive production and use of non-steroidal anti-inflammatory drugs (NSAIDs) has increased the volume of downstream residues that contaminate the environment, which pose great threats to ecosystems and human health. The decomposition of peroxydisulfate (PDS), which is activated by UV–vis to produce a potent oxidizing sulfate radical, comprises a new type of advanced oxidation technology. The degradation of indomethacin (IM) by the UV–vis activation of peroxydisulfate was investigated. The results demonstrated that IM degradation followed pseudo-first-order reaction kinetics. UV–vis irradiation led to the direct albeit slight photolysis of IM, whereas the addition of an oxidant significantly enhanced the removal efficiency. The IM degradation efficiency was increased when the pH was elevated from 5 to 7; however, the elimination of IM was reduced when the pH was elevated from 7 to 9 due to the conversion of SO4− to HO. A low concentration of Cl− had a dual effect, while a high concentration led to a dramatic inhibitory effect. Fulvic acid (SRFA) inhibited the decomposition of IM through the light screening effect and the quenching of radicals. A quenching experiment revealed that SO4− was the primary free radical, which is confirmed by electron spin resonance spectroscopy. The second-order rate constants of IM and SO4− were also determined. The luminescent bacteria Vibrio fischeri was selected to assess the toxicity of the transformation products, which was further confirmed by quantitative structure-active relationship analysis. The cleavage of the bond between C on the benzene ring and N on the indole group, the hydroxylation of the benzene ring, and the decarboxylation of the aliphatic chain were the main pathways for the degradation of IM in the UV–vis/peroxydisulfate system.

Hydrochemical evaluation and identification of geochemical processes in the shallow and deep wells in the Ramganga Sub-Basin, India.

Groundwater samples were collected from 44 wells in the Ramganga Sub-Basin (RSB), India, and analysed for major ions, nutrients and trace metals. The primary goal of this study is to evaluate the hydrochemistry and to identify the geochemical processes that govern the water chemistry in the shallow and deep tube wells in the study area using geochemical methods. The knowledge of changes in hydrochemistry of the aquifers is important for both groundwater recharge and use in the region. This study found that there are substantial differences of water chemistry between shallow and deep wells. In the shallow wells, the average concentrations of total dissolved solid (TDS), Na, K, Ca, Mg, HCO3, Cl, SO4, NO3, PO4, F, Cu, Mn, Fe and Cr are twofold higher than the deep wells. The concentrations of dissolved silica in the groundwater do not vary with the depth, which implies that the variation in the water chemistry is not due to mineral dissolution alone. Major ion ratios and saturation indices suggest that the water chemistry is predominantly controlled by dissolution of carbonate minerals, silicate weathering and ion exchange reactions. Thermodynamic evaluation (ion activity ratios and stability filed diagrams) indicates that the kaolinite and gibbsite controlled the water chemistry in the both shallow and deep wells. In addition, the groundwater chemistry in the shallow wells is affected by the vertical infiltration of contaminated water from surface contamination sources and nitrification process. In the deep wells, absence of NO3 and low concentrations of Cl, SO4, PO4 and F imply the role of regional flow and denitrification in the groundwater. Results concluded that proper management plan is necessary to protect the shallow aquifer in the RSB since shallow aquifer pumping is less expensive than the deeper one.

First-principles modeling of layer-defect of Al2O3 surface eroded by H2O and Cl−

First-principles calculations have been performed on the layer-defect Al2O3 surface to model the interaction and erosion by water molecules (H2O) and chloride ions (Cl−). The results evidence that for the Al-defect surface, prefer to react with H2O and Cl−, which not be found for O-defect surface systems. For the adsorption energy and binding energy calculations, the Al-defect surface has larger value than O-defect surface. The DOS results show that the hydrolysis reactions of the first adsorbed layer of H2O only happen on the Al-defect surface because of the strong orbital hybridization between O atoms and Cl−. And when low concentrations of Cl− reach the surface, they prefer to erode the Al-defect surface with producing Al-Cl compounds, while they prefer to interact with H2O upon the O-defect surface. Furthermore, the electron density and population data are calculated for more information to analysis the effect of surface corrosion by Cl−.

Yaochong Mo deposit, a low-F porphyry Mo deposit from the Qinling-Dabie orogenic belt

The Qinling-Dabie orogenic belt is the largest Mo mineralization belt in the world. The Yaochong porphyry Mo deposit is located in the northwest Dabie Mountains, with a proven reserve of 51kt Mo metal at an average grade of 0.058%. Here we report geochronology and geochemistry results of the Yaochong porphyry Mo deposit. Zircon U-Pb LA-ICP-MS dating shows that the Yaochong porphyry dykes and a hidden intrusion formed at 135Ma and 140Ma, respectively, which are consistent with Early Cretaceous Mo mineralization events in the Qinling-Dabie orogenic belt. Zircon grains from the Yaochong porphyry dikes (2–1788) and the hidden intrusion from drill holes (41–1940) have highly variable Ce4+/Ce3+ values. It is very likely that both the intrusion and the dikes have experienced high oxygen fugacity, but was partially reduced through assimilation. Apatite grains from the Yaochong porphyry and the intrusion are characterized by high but variable F concentrations and low Cl concentrations, suggesting that they formed in an F-enriched environment with high F/Cl components in the magma source. The Ti-in zircon temperatures of the porphyry dikes range from 700 to 710°C, whereas the average temperature of the buried intrusion nearby is 675°C. Yaochong porphyry shows geochemical and petrologic characteristics similar to those of low F stockwork type porphyry Mo deposit in North America, which may be inherited from the Dabie suture zone.

Geochemical signatures and processes in a stream contaminated by heavy mineral processing near Ipoh city, Malaysia

The environmental impacts of a heavy mineral processing involving rare earth elements (REEs) in the Kinta River and its tributaries near Ipoh city in Malaysia is investigated using geochemical and isotopic signatures and geochemical modeling. Analysis of water, sediment, suspended particulate matter, and rock samples reveals that stream waters close to the heavy mineral processing plant site are anthropogenically influenced, as indicated by slightly low pH (4.98–6.24) and elevated concentrations of Fe (up to 129 mg/L), Cl− (1540 mg/L), total REEs (1580 μg/L), U (17.2 μg/L), and Th (0.33 μg/L). REE patterns and Pb isotope ratios of waters and sediments from a tributary are similar to those of tailings pond seepage and sediments, suggesting that not only these elements but also U and Th are derived from heavy mineral processing. The δ56Fe values of water in the tributary decrease downstream, accompanied by a decrease in Fe concentration, which is likely due to isotope fractionation via oxidative precipitation of Fe hydroxides. The concentrations of REEs, U, and Th decrease downstream, accompanied by an increase in pH, with different removal factors (Th > U > REEs). The influence of contamination is confined to within ∼1.5 km downstream of the source. Tamm's acid oxalate extraction (to dissolve only low crystalline phases) showed that Th and Al concentrations were lower while U and Fe concentrations were higher in downstream suspended particulate samples, suggesting that Th and U may be removed by different mechanisms from stream water. The results of geochemical modeling suggest that Th precipitated as a solid phase, such as an intermediate between ThO2 and Th(OH)4, with increasing stream water pH. In contrast, U may have been removed by adsorption onto Fe hydroxides, as supported by surface complexation modeling. The geochemical signatures and processes discussed in this study may be applicable for environmental assessment of REE processing.