Low Cl Concentrations Research Articles

Geochemistry and Hydrothermal Contamination of the Atemajac-toluquilla Groundwater System (Guadalajara, Mexico)

Chemical and isotopic data were used to explain the geochemistry and the hydrothermal influence in a groundwater system in Guadalajara, México. According to the measured parameters and the characteristics of the groundwater, four water groups were identified: i) thermal waters with high temperatures and high concentrations of Cl, Na, HCO3 and the presence of Li, Mn, F and Mg, apparently of old age with a long residence time; ii) mixed waters of Na-HCO3 to HCO3 water type, which represent a mixture of cold water and thermal water; iii) polluted water characterized by high concentrations of nitrate and sulfate derived from urban and agricultural return flow; iv) cold water characterized by low temperature values, low concentration of Cl, Na and salinity, of Na-HCO3 type. This last group represents modern water located in the recharge zone. Finally, major proportions of hydrothermal fluids are largest in the well waters of the first group varying from 1.9 to 12.5%. The other groups show hydrothermal fractions below 1.7%. Groundwater with elevated hydrothermal proportions is located to the southeastern area of the Toluquilla aquifers. This study identifies some processes that govern the groundwater and hydrothermal mixing.

Differences in loam water retention and shrinkage behavior: Effects of various types and concentrations of salt ions

Soil shrinkage and cracks commonly occur during soil water characteristic curve (SWCC) measurement. These are caused by the capacity of saline soil to retain water, which varies with the type and concentration of salt ions within the soil. A laboratory study was therefore conducted to investigate the effects of four salt cations (K+, Na+, Ca2+, and Mg2+) and anions (Cl−, HCO3−, CO32−, and SO42−) on water retention in loam saturated by salt solutions (5, 30, and 100gL−1) and on soil shrinkage and cracking during dehydration. The van Genuchten model accurately fit with the SWCCs (R2>0.99) obtained. The salt cations generally reduced the soil water-retention capacity, but an extremely low concentration of Na+ slightly increased it. Increasing salt ionic concentrations gradually reduced the soil water-retention capacity. HCO3− and CO32− significantly increased water retention, which gradually decreased as the CO32− concentration increased. As its concentration increased, Cl− reduced water retention. An extremely high concentration of SO42− (100gL−1) also reduced water retention. The observed axial shrinkage was synchronous with radial shrinkage in contraction development. For the cations, K+ and a high concentration of Na+ facilitated the reduction of soil shrinkage, and axial shrinkage strain (δs) was negatively correlated with the K+ and Na+ concentrations. Crack length (CL), crack area (CA), crack length density (CLD), and crack area density (CAD) all decreased with an increase in the concentrations of K+, Na+, and Ca2+ but with a reduction in the concentration of Mg2+. For the anions, HCO3−, CO32−, and a low concentration of Cl− increased soil shrinkage. Moreover, δs was positively correlated with the HCO3− and CO32− concentrations, and negatively correlated with the Cl− concentration. The parameters CL, CA, CLD, and CAD increased with an increase in the concentrations of HCO3−, CO32−, and SO42− but with a reduction in the concentration of Cl−. The present results can serve as a theoretical foundation for additional field studies such as the addition of soil additives (e.g., K2CO3) to improve soil quality.

Fluid geochemical constraints on the heat source and reservoir temperature of the Banglazhang hydrothermal system, Yunnan-Tibet Geothermal Province, China

Longling, located in the Yunnan-Tibet Geothermal Province of China, is characterized by the wide distribution of hydrothermal areas, among which the Banglazhang system is the most geothermally active and marked by intensive hydrothermal activities. There is a lack of neutral Cl waters at Banglazhang, and the geothermal waters are mainly Na-HCO3 type with low but comparable SO4 and Cl concentrations. The SiO2 concentrations of the Banglazhang geothermal waters indicate equilibration in a shallow reservoir with a temperature around 150°C. While dilution by Mg-rich cold groundwaters complicates geothermometry, the Na-K geothermometer suggests that this shallow reservoir is fed by geothermal fluid from a deeper reservoir above 200°C. The geophysical investigations made in the neighboring regions of Banglazhang indicate that the Banglazhang system is likely to be located above the margin of a comparatively shallow-seated magma chamber. However, the hydrochemical and O, H and S isotopic evidence doesn't imply a mixing of magmatic fluid with Banglazhang geothermal waters. The geochemical scenario below Banglazhang is quite different than some typical magmatic-hydrothermal systems in China (such as Yangbajain and Rehai) where the geochemistry of geothermal waters are strongly affected by the input of magmatic fluid. The efforts made in this study might be suggestive for identifying the geothermal and geochemical origin of a large number of unexplored high-temperature hydrothermal systems in remote Yunnan and Tibet of China whose heat sources and geological conditions are unclear.

Generation of Late Mesozoic Qianlishan A2-type granite in Nanling Range, South China: Implications for Shizhuyuan W–Sn mineralization and tectonic evolution

The Late Mesozoic Qianlishan granitic complex in the western Nanling Range, South China is associated with the Shizhuyuan giant W–Sn–Mo–Bi polymetallic deposit. It mainly consists of three phases of intrusions, P-1 porphyritic biotite granite, P-2 equigranular biotite granite and P-3 granite porphyry. All three phases of granite contain quartz, plagioclase, K-feldspar and Fe-rich biotite. They have geochemical affinities of A-type granites, e.g., high FeOT/(FeOT+MgO) ratios (0.84–0.99), total alkali (Na2O+K2O, 7.50–9.04wt.%), high Ga/Al ratios (10,000*Ga/Al>2.6) and high Zr+Nb+Y+Ce concentrations (>350ppm). High Y/Nb ratios (>1.2) suggest that the Qianlishan complex belongs to A2-type granite. Zircon U–Pb ages indicate a short age interval decreasing from 158–157Ma, to 158–155Ma and to 154Ma for the P-1, P-2 and P-3 granites, respectively. These ages are similar to the mineralization age of the Shizhuyuan tungsten polymetallic deposit, within error. The Qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon Ce4+/Ce3+ ratios (1.53–198) and significantly negative Eu anomalies (EuN/EuN*, 0.03–0.13) in apatite. New zircon εHf(t) values for the P-3 granite range from −13.0 to −4.4, similar to those previously obtained for the P-1 and P-2 granites. Both the granite and apatite grains therein are characterized by high F but low Cl concentrations, suggesting the influx of a high F/Cl component. The P-2 granites especially contain higher F contents (1840–8690ppm) and W (7–158ppm) and Sn (6–51ppm) concentrations and with stronger evolution features. Positive trends between F and W and Sn of Qianlishan complex indicate that high F source is crucial for mineralization of W and Sn. We consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the A2 feature of the Qianlishan granite and the fluorine was introduced through breakdown of phengite in the oceanic slab. Partial melting of the lithospheric mantle was induced by upwelling of the asthenospheric mantle as a consequence of slab rollback. Tungsten and tin have been enriched in reduced granitic magmas through fractionation enhanced by high F contents, forming the giant polymetallic deposits.

Decolorization of azo dye by peroxymonosulfate activated by carbon nanotube: Radical versus non-radical mechanism

Carbon nanotube (CNT) has been shown to effectively activate peroxymonosulfate (PMS) to remove contaminants, whereas controversial activation mechanisms (radical vs non-radical mechanism) were previously proposed. Here we report that radical-induced decolorization of acid orange 7 (AO7) dominated in the CNT activated PMS system, but non-radical mechanism was also involved at high Cl⿿ concentration. CNT exhibited high activity in activating PMS to decolorize AO7. The decolorization rate of AO7 increased with increasing PMS dosages and CNT loadings, rising temperature and higher pH. Radical quenching and photoluminescence techniques confirmed the decolorization of AO7 in the CNT/PMS system was caused by the radical oxidation, which dominantly took place on the surface of CNT, rather than the bulk solution. The presence of Cl⿿ exhibited a dual effect on AO7 decolorization. Low concentration of Cl⿿ slightly inhibited AO7 decolorization, but further raising the concentration to above 0.1M significantly accelerated its decolorizaition. Cl⿿ was confirmed to react with PMS to generate HClO, which effectively bleached AO7 through non-radical process rather than radical process. The decolorization of AO7 induced from the non-radical process exhibited different degradation products and less mineralization in comparison to that derived from radical process.

Crack growth behaviour and crack tip chemistry of X70 pipeline steel in near-neutral pH environment

In this paper, crack growth behaviour and the crack tip chemistry of X70 pipeline steel in the near-neutral pH environment were investigated using the in-situ measurements. The stress corrosion crack propagated forward under the cyclic load, with a mean crack growth rate (CGR) of 4.28 × 10–3 mm/cycle. The CGR da/dN obeys well with the stress corrosion fatigue mechanism. During the crack propagation, the crack tip environment differed significantly from the bulk solution. An aggressive electrolyte with low pH (about 4.0) and high concentration of Cl– (about 3.8 M) was produced near the crack tip. These results provided the direct evidence for simulating the crack tip solution and investigating the crack tip anodic dissolution.

A Cation-Chloride Cotransporter Gene Is Required for Cell Elongation and Osmoregulation in Rice.

Rice (Oryza sativa) is characterized by having fibrous root systems; however, the molecular mechanisms underlying the root development are not fully understood. Here, we isolated a rice mutant with short roots and found that the mutant had a decreased cell size of the roots and shoots compared with wild-type rice. Map-based cloning combined with whole-genome sequencing revealed that a single nucleotide mutation occurred in a gene, which encodes a putative cation-chloride cotransporter (OsCCC1). Introduction of OsCCC1 cDNA into the mutant rescued the mutant growth, indicating that growth defects of both the roots and shoots are caused by loss of function of OsCCC1. Physiological analysis showed that the mutant had a lower concentration of Cl(-) and K(+) and lower osmolality in the root cell sap than the wild type at all KCl supply conditions tested; however, the mutant only showed a lower Na(+) concentration at high external Na(+) Expression of OsCCC1 in yeast increased accumulation of K(+), Na(+), and Cl(-) The expression of OsCCC1 was found in both the roots and shoots, although higher expression was found in the root tips. Furthermore, the expression in the roots did not respond to different Na(+), K(+), and Cl(-) supply. OsCCC1 was expressed in all cells of the roots, leaf, and basal node. Immunoblot analysis revealed that OsCCC1 was mainly localized to the plasma membrane. These results suggest that OsCCC1 is involved in the cell elongation by regulating ion (Cl(-), K(+), and Na(+)) homeostasis to maintain cellular osmotic potential.

Initiation of large-volume silicic centers in the Yellowstone hotspot track: insights from H2O- and F-rich quartz-hosted rhyolitic melt inclusions in the Arbon Valley Tuff of the Snake River Plain

During the onset of caldera cluster volcanism at a new location in the Snake River Plain (SRP), there is an increase in basalt fluxing into the crust and diverse silicic volcanic products are generated. The SRP contains abundant and compositionally diverse hot, dry, and often low-δ18O silicic volcanic rocks produced through time during the formation of individual caldera clusters, but more H2O-rich eruptive products are rare. We report analyses of quartz-hosted melt inclusions from pumice clasts from the upper and lower Arbon Valley Tuff (AVT) to gain insight into the initiation of caldera cluster volcanism. The AVT, a voluminous, caldera-forming rhyolite, represents the commencement of volcanism (10.44 Ma) at the Picabo volcanic field of the Yellowstone hotspot track. This is a normal δ18O rhyolite consisting of early and late erupted members (lower and upper AVT, respectively) with extremely radiogenic Sr isotopes and unradiogenic Nd isotopes, requiring that ~50 % of the mass of these elements is derived from melts of Archean upper crust. Our data reveal distinctive features of the early erupted lower AVT melt including: variable F concentrations up to 1.4 wt%, homogenous and low Cl concentrations (~0.08 wt%), H2O contents ranging from 2.3 to 6.4 wt%, CO2 contents ranging from 79 to 410 ppm, and enrichment of incompatible elements compared to the late erupted AVT, subsequent Picabo rhyolites, SRP rhyolites, and melt inclusions from other metaluminous rhyolites (e.g., Bishop Tuff, Mesa Falls Tuff). We couple melt inclusion data with Ti measurements and cathodoluminescence (CL) imaging of the host quartz phenocrysts to elucidate the petrogenetic evolution of the AVT rhyolitic magma. We observe complex and multistage CL zoning patterns, the most critical being multiple truncations indicative of several dissolution–reprecipitation episodes with bright CL cores (higher Ti) and occasional bright CL rims (higher Ti). We interpret the high H2O, F, F/Cl, and incompatible trace element concentrations in the context of a model involving melting of Archean crust and mixing of the crustal melt with basaltic differentiates, followed by multiple stages of fractional crystallization, remelting, and melt extraction. This multistage process, which we refer to as distillation, is further supported by the complex CL zoning patterns in quartz. We interpret new Δ18O(Qz-Mt) isotope measurements, demonstrating a 0.4 ‰ or ~180 °C temperature difference, and strong Sr isotopic and chemical differences between the upper and lower AVT to represent two separate eruptions. Similarities between the AVT and the first caldera-forming eruptions of other caldera clusters in the SRP (Yellowstone, Heise and Bruneau Jarbidge) suggest that the more evolved, lower-temperature, more H2O-rich rhyolites of the SRP are important in the initiation of a caldera cluster during the onset of plume impingement.

Evolution of porewater composition through time in limestone aquifers: Salinity and D/H of fluid inclusion water in authigenic minerals (Jurassic of the eastern Paris Basin, France)

Past water circulations can significantly reduce the porosity and permeability of marine limestones. This is particularly the case in the Middle (Bathonian/Bajocian) to Upper (Oxfordian) Jurassic limestones from the eastern border of the Paris Basin. The knowledge of the timing, the temperature and composition of paleowaters is essential to model the hydrological evolution in this area where the Callovian–Oxfordian claystones are studied for the storage of nuclear wastes. In this way, fluid inclusions hosted in low-temperature (<60°C) authigenic calcite, quartz and celestite crystals were analyzed by Raman spectroscopy and mass spectrometry to determine the chlorinity and D/H ratios. Chlorinity measurements (mmol Cl per liter of water) in fluid inclusions trapped in authigenic crystals during the late Jurassic/early Cretaceous period revealed unexpected high values, up to 3800mmoll−1, indicating that brines were involved in some of the diagenetic crystallization processes. By contrast, fluid inclusions in calcite cements of Cenozoic age within the Oxfordian limestones have low Cl concentration (less than 150mmoll−1), thus showing that a dilution event caused by water infiltrations during the Cretaceous uplift of this part of the basin has flushed out the original saline porewater. By coupling δD of fluid inclusion with δ18O of calcite crystals, we estimate that calcite precipitation occurred at temperatures between 25 and 53°C. The hydrogen isotope composition of calcite-forming water is different between the Middle Jurassic (δD ranging from −20 to −35.8‰V-SMOW) and the overlying Oxfordian limestone (δD from −59.5 to −44.8‰V-SMOW). Present-day groundwaters are also of distinct composition on both sides of the Oxfordian claystones, indicating that limestone aquifers underwent independent hydrologic evolutions since the early diagenetic Jurassic cementation.

Cellular volume regulation by anoctamin 6: Ca²⁺, phospholipase A2 and osmosensing.

During cell swelling, Cl(-) channels are activated to lower intracellular Cl(-) concentrations and to reduce cell volume, a process termed regulatory volume decrease (RVD). We show that anoctamin 6 (ANO6; TMEM16F) produces volume-regulated anion currents and controls cell volume in four unrelated cell types. Volume regulation is compromised in freshly isolated intestinal epithelial cells from Ano6-/- mice and also in lymphocytes from a patient lacking expression of ANO6. Ca(2+) influx is activated and thus ANO6 is stimulated during cell swelling by local Ca(2+) increase probably in functional nanodomains near the plasma membrane. This leads to stimulation of phospholipase A2 (PLA2) and generation of plasma membrane lysophospholipids, which activates ANO6. Direct application of lysophospholipids also activates an anion current that is inhibited by typical ANO6 blocker. An increase in intracellular Ca(2+) supports activation of ANO6, but is not required when PLA2 is fully activated, while re-addition of arachidonic acid completely blocked ANO6. Moreover, ANO6 is activated by low intracellular Cl(-) concentrations and may therefore operate as a cellular osmosensor. High intracellular Cl(-) concentration inhibits ANO6 and activation by PLA2. Taken together, ANO6 supports volume regulation and volume activation of anion currents by action as a Cl(-) channel or by scrambling membrane phospholipids. Thereby, it may support the function of LRRC8 proteins.

Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

Abstract. Groundwater chemistry and isotopic data from 40 production wells in the Atemajac and Toluquilla valleys, located in and around the Guadalajara metropolitan area, were determined to develop a conceptual model of groundwater flow processes and mixing. Stable water isotopes (δ2H, δ18O) were used to trace hydrological processes and tritium (3H) to evaluate the relative contribution of modern water in samples. Multivariate analysis including cluster analysis and principal component analysis were used to elucidate distribution patterns of constituents and factors controlling groundwater chemistry. Based on this analysis, groundwater was classified into four groups: cold groundwater, hydrothermal groundwater, polluted groundwater and mixed groundwater. Cold groundwater is characterized by low temperature, salinity, and Cl and Na concentrations and is predominantly of Na-HCO3-type. It originates as recharge at "La Primavera" caldera and is found predominantly in wells in the upper Atemajac Valley. Hydrothermal groundwater is characterized by high salinity, temperature, Cl, Na and HCO3, and the presence of minor elements such as Li, Mn and F. It is a mixed-HCO3 type found in wells from Toluquilla Valley and represents regional flow circulation through basaltic and andesitic rocks. Polluted groundwater is characterized by elevated nitrate and sulfate concentrations and is usually derived from urban water cycling and subordinately from agricultural return flow. Mixed groundwaters between cold and hydrothermal components are predominantly found in the lower Atemajac Valley. Twenty-seven groundwater samples contain at least a small fraction of modern water. The application of a multivariate mixing model allowed the mixing proportions of hydrothermal fluids, polluted waters and cold groundwater in sampled water to be evaluated. This study will help local water authorities to identify and dimension groundwater contamination, and act accordingly. It may be broadly applicable to other active volcanic systems on Earth.

Molecular Mechanisms That Underlie The [Cl-]I-Sensitive Kinases-Mediated Regulation of Cftr Anion Selectivity

MoleculAr MechAnisMs ThAT underlie The [cl-]i-sensiTive KinAses-MediATed regulATion of cfTr Anion selecTiviTy I. Jun; J. Jang; J. Jung; Y. Kim; and M.G. Lee Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, Seoul 120-752, Korea; and Department of Hematology, Yonsei University College of Medicine, Seoul 120-752, Korea Introduction: CFTR is cAMP activated anion channel which secretes chloride and bicarbonate in airway, exocrine pancreas, intestine, and genitourinary systems. Human pancreas secretes pancreatic juice which contains as much as 140 mM bicarbonate (HCO3-) via CFTR. Recently, we have shown that [Cl-]i-sensitive activation of WNK1OSR1/SPAK pathway plays a critical role in pancreatic HCO3secretion by increasing the bicarbonate permeability (PHCO3/PCl) of CFTR. However, how [Cl-]i-sensitive kinases modulate PHCO3/ PCl of CFTR remains elusive. Material and Methods: Overexpression and knockdown of each kinase in HEK293T cells were performed. Using patch clamp, we measured permeability of bicarbonate and halide ions. We did pulldown assay between truncated WNK1 and CFTR at 150mM and 0mM Clconcentrations. Results: WNK1 affects permeability of other anions as well as bicarbonate in patch clamp recordings. Especially, the interval of relative permeabilities (Px/PCl) between each anion was greatly narrowed by WNK1. Consequently, WNK1 increased the dielectric constant of the hypothetical selectivity filter of CFTR. And we measured the pore size of CFTR at each state. WNK1 makes CFTR pore size larger. We figured out that WNK1 kinase domain binds to CFTR and truncated forms of WNK1 respond to low Clconcentrations. Conclusions: These findings suggest that WNK1 increases the bicarbonate permeability of CFTR by modulating the polarizability of anion selectivity filter and provide insight into the fundamental question of how ion selectivity of anion channels can be regulated by cytosolic signaling at the molecular level. Furthermore, WNK1 senses low [Cl-]i, then kinase domain is exposed and binds to CFTR.

Multiple sulfur isotope systematics of Icelandic geothermal fluids and the source and reactions of sulfur in volcanic geothermal systems at divergent plate boundaries

Multiple sulfur isotope systematics of geothermal fluids at Krafla, Northeast Iceland, were studied in order to determine the source and reactions of sulfur in this system, as an example of a geothermal system hosted on a divergent plate boundary. Fluid temperatures ranged from 192 to 437°C, and the fluids have low Cl concentration between ∼10 and ∼150ppm, with liquid water and vapor being present in the reservoir. Dissolved sulfide (S-II) and sulfate (SVI) predominated in the water phase with trace concentrations of thiosulfate (S2O32-) whereas sulfide (S-II) was the only species observed in the vapor phase. The reconstructed sulfur isotope ratios of the reservoir fluids based on samples collected at surface from two-phase and vapor only well discharges indicated that δ34S and Δ33S of sulfide in the reservoir fluid ranged from −1.5 to +1.1‰ and −0.001 to −0.017‰, respectively, whereas δ34S and Δ33S of sulfate were significantly different and ranged from +3.4 to +13.4‰ and 0.000 to −0.036‰, respectively. Depressurization boiling upon fluid ascent coupled with progressive fluid–rock interaction and sulfide mineral (pyrite) formation results in the liquid phase becoming progressively isotopically lighter with respect to both δ34S and Δ33S. In contrast, H2S in the vapor phase and pyrite become isotopically heavier. The observed Δ33S and δ34S systematics for geothermal fluids at Krafla suggest that the source of sulfide in the reservoir fluids is the basaltic magma, either through degassing or upon dissolution of unaltered basalts. At high temperatures, insignificant SO4 was observed in the fluids but below ∼230°C significant concentrations of SO4 were observed, the source inferred to be H2S oxidation. The two key factors controlling the multiple sulfur isotope systematics of geothermal fluids are: (1) the isotopic composition of the source material and (2) the isotope fractionation associated with aqueous and vapor speciation and how these change as a function of processes occurring in the system, including boiling, oxidation and fluid–rock interaction.

Biochemical Profiles in Freezable and Non-Freezable Ejaculates of Mithun (Bos frontalis) Semen

The present study was undertaken to measure the biochemical profiles of freezable and non- freezable ejaculates of Mithun. Fifty ejaculates (twenty five ejaculates each from freezable and non- freezable ones) were collected from matured Mithun bulls. Biochemical profiles viz., alkaline phosphatase (ALP), acid phosphatase (ACP), aspartate aminotransferase (AST), alanine amino- transferase (ALT), lactic acid dehydrogenase (LDH), calcium (Ca), magnesium (Mg), zinc (Zn), chloride (Cl), citric acid (CA), total seminal plasma protein (TSPP), inorganic phosphorous (IP), fructose and cholesterol concentration in sperm were estimated. The result revealed that these pa - rameters varied significantly (P< 0.05) between the freezable and non-freezable ejaculates. Freezable ejaculates has significantly (P< 0.05) higher ALP, ACP, LDH, Ca, Mg, Zn, citric acid, TSPP, IP, fructose and cholesterol concentration and significantly (P< 0.05) lower Cl concentration than the non- freezable ejaculates. There was a correlation among the biochemicals such as ALP, ACP, LDH, Ca, Mg, Zn, CA, TSPP, IP, fructose, cholesterol and these biochemicals were negatively correlated with AST, ALT and Cl in both freezable and non-freezable ejaculates. It was concluded that most of the biochemical parameters were higher in freezable ejaculates than the non-freezable ejaculates, indicates that freezable ejaculates have has structural stability than the non-freezable ones that leads to freezable sperm has higher functional structures to move faster and in forward direction.

The Effect of WNK4 on the Na+-Cl- Cotransporter Is Modulated by Intracellular Chloride.

It is widely recognized that the phenotype of familial hyperkalemic hypertension is mainly a consequence of increased activity of the renal Na(+)-Cl(-) cotransporter (NCC) because of altered regulation by with no-lysine-kinase 1 (WNK1) or WNK4. The effect of WNK4 on NCC, however, has been controversial because both inhibition and activation have been reported. It has been recently shown that the long isoform of WNK1 (L-WNK1) is a chloride-sensitive kinase activated by a low Cl(-) concentration. Therefore, we hypothesized that WNK4 effects on NCC could be modulated by intracellular chloride concentration ([Cl(-)]i), and we tested this hypothesis in oocytes injected with NCC cRNA with or without WNK4 cRNA. At baseline in oocytes, [Cl(-)]i was near 50 mM, autophosphorylation of WNK4 was undetectable, and NCC activity was either decreased or unaffected by WNK4. A reduction of [Cl(-)]i, either by low chloride hypotonic stress or coinjection of oocytes with the solute carrier family 26 (anion exchanger)-member 9 (SLC26A9) cRNA, promoted WNK4 autophosphorylation and increased NCC-dependent Na(+) transport in a WNK4-dependent manner. Substitution of the leucine with phenylalanine at residue 322 of WNK4, homologous to the chloride-binding pocket in L-WNK1, converted WNK4 into a constitutively autophosphorylated kinase that activated NCC, even without chloride depletion. Elimination of the catalytic activity (D321A or D321K-K186D) or the autophosphorylation site (S335A) in mutant WNK4-L322F abrogated the positive effect on NCC. These observations suggest that WNK4 can exert differential effects on NCC, depending on the intracellular chloride concentration.

Evaluating recharge to an ephemeral dryland stream using a hydraulic model and water, chloride and isotope mass balance

Dewatering associated with mining below water table to achieve dry mining conditions may exert significant pressure on water balance in terms of lowering the water table and change in the dynamics of interactions between surface water and groundwater. The discharge of surplus mine water into ephemeral streams may also affect the water balance, by elevating groundwater levels and altering the exchange rate between streams and underlying aquifers. However, it is unclear whether volumes and recharge processes are within the range of natural variability. Here, we present a case study of an ephemeral creek in the semi-arid Hamersley Basin of northwest Australia that has received continuous mine discharge for more than six years. We used a numerical model coupled with repeated measurements of water levels, chloride concentrations and the hydrogen and oxygen stable isotope composition (δ2H and δ18O) to estimate longitudinal evapotranspiration and recharge rates along a 27 km length of Weeli Wolli Creek. We found that chloride increased from 73 to 120 mg/L across this length, while δ18O increased from −8.2‰ to −7.00‰. Groundwater is directly connected to the creek for the first 13 km and recharge rates are negligible. Below this point, the creek flows over a highly permeable aquifer and water loss by recharge increases to a maximum rate of 4.4 mm/d, which accounts for ∼65% of the total water discharged to the creek. Evapotranspiration losses account for the remaining ∼35%. The calculated recharge from continuous flow due to surplus water discharge is similar to that measured for rainfall-driven flood events along the creek. Groundwater under the disconnected section of the creek is characterised by a much lower Cl concentration and more depleted δ18O value than mining discharge water but is similar to flood water generated by large episodic rainfall events. Our results suggest that the impact of recharge from continuous flow on the water balance of the creek has not extended beyond 27 km from the discharge point. Our approach using a combination of hydrochemical and isotope methods coupled with classical surface flow hydraulic modelling allowed evaluation of components of the water budget otherwise not possible in a highly dynamic system that is mainly driven by infrequent but large episodic floods.

Water chemistry of headwater streams under stormflow conditions in catchments covered by evergreen broadleaved forest and by coniferous plantation

It is important to determine the effects of vegetation on the water chemistry of headwater streams to ensure appropriate water resource management and landscape planning, particularly because vegetation is known to be one of the primary determinants of the chemistry in such streams and is easily altered by silvicultural operations. Previous studies of headwater stream water chemistry have investigated primarily the effects on baseflow. However, the sources and processes involved vary considerably between baseflow and stormflow due to rainfall. Stormflow water is supplied primarily through soil; accordingly, its chemistry is influenced by vegetation. The present study investigates the water chemistry of streams of headwater catchments, six with coniferous plantations and six with evergreen broadleaved forests, under four stormflow events and three times under baseflow conditions. The studied catchments were located in a hilly region in southwestern Japan and covered relatively small areas (0.7–3.6 ha). Inorganic ions, pH, and dissolved organic carbon were analyzed. A higher concentration of dissolved organic carbon and a lower concentration of Cl− were found in the broadleaved catchments compared to the coniferous catchments under stormflow conditions, but no differences were detected under baseflow conditions. For catchments with older forests, the NO3 − concentration was higher in the coniferous catchments than the broadleaved catchments under stormflow conditions. These results indicate that these three constituents were not diluted during stormflow and that their presence in soil water may be affected by the type of vegetation. The observed increased NO3 − concentration under stormflow conditions may result in higher loading downstream.

Constraints on the incorporation mechanism of chlorine in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses

Incorporation mechanisms of Cl in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses as a model system for phonolitic melts were investigated using 35Cl, 23Na, 27Al, and 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The size and large distribution of electric field gradients for 35Cl causes loss of signal in the MAS NMR experiment and this, in combination with the low concentration of Cl and the large chemical shift dispersion, means that even at the highest available fields we are at the limits of MAS NMR. Nevertheless clear differences in the Cl environment in peralkaline and peraluminous glasses can readily be seen. In both glass types Cl exists in relatively symmetric Na-Ca-Cl environments. The 35Cl chemical shift indicates that the Cl environment is dominated by the presence of Na cations, consistent with the Na/Ca ratio of 5/1 in the glasses. 35Cl MAS NMR spectra of the peraluminous glasses show a larger chemical shift distribution and a more positive isotropic chemical shift, ~-75 ppm, than the peralkaline glasses, ~-100 ppm. They also have a larger quadrupole coupling constant with a larger distribution, indicating greater disorder in the peraluminous glasses. It is likely that there are more Ca cations present in the Cl environments in the peraluminous glasses than in the peralkaline glasses despite their having the same Na/Ca ratio. In the peralkaline glasses the formation of Na-Ca-Cl environments leads to a decrease in the number of network-modifying cations, which causes a polymerization of the glass network. No effect on the glass polymerization was observed in the peraluminous glasses. Some 35Cl signal is also lost in the static spectra indicating that ~20% of Cl for a peralkaline glass and more than ~70% for a peraluminous glass must be in environments where there is a large enough electric field gradient that the resulting very broad line is unobservable. These environments could be simply Na-Ca-Cl with higher electric field gradients than those producing the observed 35Cl signal or non-bridging Cl environments like for example Al-Cl. The Cl environment in the present mixed Na2O-CaO aluminosilicate glasses appears to be more disordered than was to be expected from previous NMR spectroscopic studies on simpler glass compositions.

Role of anion polarizability in fluorescence sensitization of DNA-templated silver nanoclusters

Fluorescent silver nanoclusters (Ag NCs) as novel fluorophores have received much attention because of their high brightness, good photostability and widely tunable emissions from the visible to the near-infrared range as a result of their size and existing environment. However, efforts are still needed to find the factors that tune the emission of Ag NCs. In this work, Ag NCs that were size-selectively grown on DNA were used to investigate the effect of the electronic properties of coordinating ligands. Halogen anions were used as the paradigm because of their periodicity in element properties. We found that addition of halogen anions did not alter the emission wavelength of Ag NCs, but the fluorescence intensity showed an initial increase at low concentrations of Cl–, Br– and I– followed by a gradual decrease at high concentrations. No increase in fluorescence was observed for F– at either low or high concentration. Such specific halogen-anion sensitization of the fluorescence of Ag NCs suggests that the binding strength/manner and dipole polarizability of these anions synergistically tune the emission behavior of Ag NCs. Less fluorescence sensitization occurred for the anion having high enough polarizability to form a covalent bond with Ag NCs. The anion polarizability-sensitized fluorescence indicates the role of anion electronic properties in tuning the emission behavior of Ag NCs, which should be seriously considered in designing Ag NC-based sensors and devices.

The Characterization of Wood Species from Mozambique as a Fuel

The efficient utilization of fuelwood as a source of energy is strongly dependent on the properties of the biomass. This study characterizes common hardwood species from Mozambique and evaluates their quality as a fuel. Disc samples, taken at breast height, from Afzelia quanzensis Welwn, Millettia stuhlmannii Taub, Pterocarpus angolensis DC, Sterculia appendiculata K. Schum, Pericopsis angolensis Meeuwen, Acacia nigrescens Oliv., Pseudolachostylis maprounaefolia Pax, and Icuria dunensis Wieringa, were collected from three provinces in Mozambique. Chemical and physical properties were analyzed. The raking of the species as fuel was performed using fuelwood value index. The higher heating value varied between 19.38 and 21.50 MJ/kg dry weight. The concentration of lignin ranged from 21.96 up to 36.69% weight dry basis (wt% d.b.), and ash free. All studied species showed very low concentrations of Si, S, and Cl. Ash content varied between 0.76–3.71 wt% (d.b.), while the basic density ranged from 536 to 1,111 k gm−3. Heavy metals were also determined and their concentrations were below the values reported in the literature. The species Acacia nigrescens had the highest fuelwood value index and it was closely followed by Icuria dunensis and Millettia stuhlmannii. The worst ranked was Sterculia appendiculata.