Low Anion Concentrations Research Articles

Photo-assisted oxygen-rich vacancy copper oxide catalyst to activate peroxymonosulfate (PMS) for efficient degradation of fulvic acid

In this study, novel copper oxide particles-activated peroxymonosulfate (CuO-S/PMS/UV) were employed to degrade fulvic acid(FA). Under the optimal treatment condition, the FA removal of the CuO-S/PMS/UV process was up to 97.74%. The removal rates of SUVA254, UVA365 UVA280 UVA463 and TOC within 40 min in the UV/CuO-S/PMS process were 23.4%, 95.6%, 63.2%, 100% and 40.8% respectively. The three-dimensional fluorescence spectrum analysis of FA during the degradation process revealed the disappearance of FA-associated functional structures. Furthermore, the impact of common anions in the water matrix on the degradation process was investigated, demonstrating that the system remains effective containing low concentrations of anions. Subsequently, mechanism studying showed that SO4•−, 1O2, h+, and •OH species were primarily involved in the degradation of FA, while O2•− has a limited effect in the degradation process. This study can provide valuable insights for the degradation of humic pollutants in the water environment.

Multiple Roles of Anions on the Degradation Efficiency and Mineralization Pathway of Recalcitrant Acetaldehyde by Vacuum Ultraviolet (185 nm) Oxidation.

Vacuum-UV (185 nm, VUV) is widely applied to polish reverse osmosis permeate (ROP), such as the production of electronics-grade ultrapure water. In this study, the VUV oxidation of acetaldehyde, a common carbonyl in ROP, was found to be influenced by anions even at low concentrations. Interestingly, the influencing extent and mechanism varied depending on the anions. Bicarbonate minimally affected the VUV-photon absorption and •OH consumption, but at 5000 μg-C·L-1, it decreased the degradation of acetaldehyde by 58.7% possibly by scavenging organic radicals or other radical chain reactions. Nitrate strongly competed for VUV-photon absorption and •OH scavenging through the formation of nitrite, and at 500 μg-N·L-1, it decreased the removal rate of acetaldehyde degradation by 71.2% and the mineralization rate of dissolved organic carbon by 53.4%. Chloride competed for VUV-photon absorption and also generated reactive chlorine species, which did not affect acetaldehyde degradation but influenced the formation of organic byproducts. The radical chain reactions or activation of anions under VUV irradiation could compensate for the decrease in oxidation performance and need further investigation. In real ROPs, the VUV oxidation of acetaldehyde remained efficient, but mineralization was hindered due to nitrate and chloride anions. This study deepens the understanding of the photochemistry and feasibility of VUV in water with low concentrations of anions.

The suppressive effect of the specific KCC2 modulator CLP290 on seizure in mice

Epilepsy is a chronic neurological disorder characterized by episodic dysfunction of central nervous system. The most basic mechanism of epilepsy falls to the imbalance between excitation and inhibition. In adults, GABAA receptor (GABAAR) is the main inhibitory receptor to prevent neurons from developing hyperexcitability, while its inhibition relies on the low intracellular chloride anion concentration ([Cl-]i). Neuronal-specific electroneutral K+-Cl− cotransporter (KCC2) can mediate chloride efflux to lower [Cl-]i for GABAAR mediated inhibition. Our previous study has revealed that the coordinated downregulation of KCC2 and GABAAR participates in epilepsy. According to a high-throughout screen for compounds that reduce [Cl−]i, CLP290 turns out to be a specific KCC2 functional modulator. In current study, we first confirmed that CLP290 could dose-dependently suppress convulsant-induced seizures in mice in vivo as well as the epileptiform burst activities in cultured hippocampal neurons in vitro. Then, we discovered that CLP290 functioned through preventing the downregulation of the KCC2 phosphorylation at Ser940 and hence the KCC2 membrane expression during convulsant stimulation, and consequently restored the GABA inhibition. In addition, while CLP290 was given in early epileptogenesis period, it also effectively decreased the spontaneous recurrent seizures. Generally, our current results demonstrated that CLP290, as a specific KCC2 modulator by enhancing KCC2 function, not only inhibits the occurrence of the ictal seizures, but also suppresses the epileptogenic process. Therefore, we believe KCC2 may be a suitable target for future anti-epileptic drug development.

Exploring the intensifying effect of periodate/hydroxylamine oxidation process for the effective mineralization of textile dyes effluents with consideration of environmental matrices

AbstractThis study delved into the potential of periodate/hydroxylamine process (PI/HA) as an efficient method for the degradation and mineralization of textile dyes. The PI/HA process generates a range of reactive oxygen species (ROS), which can degrade organic pollutants. The effects of processing conditions, common minerals, organic components, including humic acid and surfactants, and various real environmental matrices, i.e. deionized water, seawater, natural mineral water and treated wastewater effluent, on the PI/HA process efficiency were examined. The results showed that the PI/HA process could remove over 50% of initial dyes concentration in just 10 s, with 80% removal achieved at 10 min using a PI/HA molar ratio of 1 (1.5/1.5 mM). Further adjustments could result in 100% removal in less than 5 min. The process efficiently abated organic matter, with total organic carbon (TOC) reductions exceeding 80% at 60 min and ~90% at 120 min. Radical scavengers showed that •OH played a dominant role (~76%), while 1O2 contributed to a lesser extent (~8.5%). The degradation was more efficient at lower pH, a higher PI to HA molar ratio. The process was unaffected by low concentrations of common mineral anions and surfactants. Higher degradation levels were observed in natural mineral water and seawater.

Pyrene-Based Cationic Fluorophores with High Affinity for BF4-, PF6-, and ClO4- Anions: Detection and Removal.

Anions play an indispensable role in the balance and regulation of the ecological environment and human health; however, excess anions can cause serious ecological and environment problems. Therefore, the detection and removal of excess anions in aqueous solution is not only a technological problem but also crucial for environmental protection. Herein, a set of water-soluble pyrene-based cationic fluorophores were synthesized, which exhibit high sensitivity for the detection of the anions BF4-, PF6-, and ClO4- via electrostatic interactions. Such fluorescent probes exhibit "turn-on" emission characteristics even at low concentrations of anions due to anion-π+ interactions. Moreover, these fluorescence probes act as efficient precipitating agents for the removal of the BF4-, PF6-, and ClO4- anions from an aqueous environment. This work opens up new avenues for future research on pyrene-based fluorophores as turn-on fluorescence probes for anion detection and as excellent precipitating agents in environmental settings.

Valorisation of the residual aqueous phase from hydrothermally liquefied black liquor by persulphate-based advanced oxidation

Hydrothermal liquefaction of Kraft black liquor is a promising method for the production of valuable organic chemicals. However, the separation of the biochar and biocrude leaves a residual aqueous phase in large volumes, which needs to be properly managed to make the process profitable. In this work, the persulphate-based advanced oxidation was assessed, for the first time ever, as a pretreatment of this aqueous phase to reduce its content of phenolic compounds and alcohols, which hinder further valorisation strategies. Results revealed that the phenolic compounds and the alcohols were oxidised in presence of low persulphate anion concentrations (<50 mM), mainly to quinone-like compounds and organic acids. At higher oxidant concentrations, these intermediates were subsequently oxidised to valuable acetic acid. When Fe (II) was added as the catalyst, low concentrations (<9 mM) enhanced the degradation of both phenolic compounds and alcohols due to the increase of the sulphate radicals, consequently reducing persulphate requirements for their removal. Nevertheless, higher Fe (II) doses produced the sequestration of sulphate radicals, thus decreasing the oxidation performance and generating undesired parallel reactions.

A highly selective superphane for ReO4− recognition and extraction

Highly selective anion recognition and extraction is challenging and yet critical for removal of pollutants from the environment and the effective recovery of valuable chemicals from low-content (at sub-ppm or ppb level) sources. In this paper, we detail the gram-scale synthesis of a superphane 2 , an anion receptor that selectively binds ReO 4 − . Superphane 2 can extract perrhenate from solid mixtures containing traces of ReO 4 − anion (as low as 200 ppb) and aqueous media with near 100% selectivity over large excesses of competing anions. Meanwhile, up to 99.99% of ReO 4 − can be separated from complex simulated aqueous waste streams containing ppm-level perrhenate via either liquid-liquid extraction or simple column adsorption. Importantly, after extraction or adsorption, superphane 2 can be recycled and reused by simple treatment with aqueous NaHCO 3 . • A superphane for highly selective recognition of ReO 4 − is synthesized in gram scale • Over 99.99% of ReO 4 − can be separated from complex simulated waste streams • Rapid removal of ppb-level ReO 4 − is achieved via extraction or column adsorption • The superphane for ReO 4 − extraction/adsorption can be recycled and reused Extraction of low concentrations of rhenium anions from waste streams is important industrially. Zhou et al. present the facile and gram-scale synthesis of a superphane via dynamic imine chemistry coupled with NaBH 4 reduction, which can separate perrhenate from low-content mixtures and simulated Hanford waste streams with exceptionally high efficiency and selectivity, along with good recyclability and reusability.

Furosemide prevents membrane KCC2 downregulation during convulsant stimulation in the hippocampus.

In adults, γ-aminobutyric acid (GABA) type A receptor (GABAAR)-mediated inhibition depends on the maintenance of low intracellular chloride anion concentration through neuron-specific potassium-chloride cotransporter-2 (KCC2). KCC2 has been widely reported to have a plasticity change during the course of epilepsy development, with an early downregulation and late recovery in neuronal cell membranes after epileptic stimulation, which facilitates epileptiform burst activity. Furosemide is a clinical loop diuretic that inhibits KCC2. Here, we first confirmed that furosemide pretreatment could effectively prevented convulsant stimulation-induced neuronal membrane KCC2 downregulation in the hippocampus in both in vivo and in vitro cyclothiazide-induced seizure model. Second, we verified that furosemide pretreatment rescued KCC2 function deficits, as indicated by EGABA depolarizing shift and GABAAR inhibitory function impairment induced via cyclothiazide treatment. Further, we demonstrated that furosemide also suppressed cyclothiazide-induced epileptiform burst activity in cultured hippocampal neurons and lowered the mortality rate during acute seizure induction. Overall, furosemide prevents membrane KCC2 downregulation during acute seizure induction, restores KCC2-mediated GABA inhibition, and interrupts the progression from acute seizure to epileptogenesis.

Soil salinity indicators and salinity build-up on saline water irrigation in seed spices

Context Soil salinity is a major constraint in crop production in arid and semiarid regions where saline water is the main irrigation source affecting soil quality and crop productivity. Aims A pot experiment was conducted to study the impact of alternate application of saline water (electrical conductivity (EC): 6.0 dS m−1) and fresh water on soil salinity indicators and salinity build-up under four seed spices (Anethum graveolens L., Nigella sativa L., Pimpinella anisum L. and Trachyspermum ammi L.). Methods Soil samples were collected from a pot experiment (0–15 cm depth) conducted at ICAR-Central Soil Salinity Research Institute, Karnal, Haryana, and analysed for different physicochemical properties (pH and EC), cationic (Ca2+, Mg2+, Na+ and K+) and anionic (CO32−, HCO3−, Cl−, SO42−) concentration and their contribution to salinity build-up in soil. Key results Soil EC varied between 0.45 and 8.27 dS m−1 (EC1:2) and between 1.20 and 24.90 dS m−1 (ECe) irrespective of the seed spice species. The application of saline water in the early stages of growth followed by fresh-water irrigation resulted in a comparatively low ECe, and cation and anion concentrations over continuous saline-water irrigation irrespective of the seed spice crop. ECe, sodium adsorption ratio, potassium and pHs are the important indicators identified by principal component analysis and better explained soil salinity under this situation. Conclusions Keeping these in view, there is a need for cyclic use of saline and fresh water in growing seed spice crops to prevent soil degradation. Study recommends that these four seed spice crops should be irrigated with fresh water during crop establishment and flowering stage, whereas, in between, saline water can be applied. Implications Such management of saline water irrigation could help to reduce salinity and maintain soil health for sustaining crop productivity, specifically for seed spices, in arid and semiarid regions.

Mg/Al and Mg/Fe layered double hydroxides derived from magnesite and chemicals: The effect of adsorbent features and anions chemistry on their removal efficiency

Owing to their anion exchange properties, layered double hydroxides (LDH) are promising candidates as adsorbents for the anions removal from industrial wastewaters. Therefore multiple attempts were made in order to substantially lower their production costs. In this work, LDH obtained via transformation of magnesite were compared to conventionally obtained LDH in terms of their affinity towards As(V), Cr(VI), P(V), Mo(VI), Se(VI) and V(V). The materials with different chemical compositions (Mg/Al and Mg/Fe) were tested in aqueous systems with different parameters such as initial concentration and pH. The minimum doses of adsorbents required for the efficient treatment were determined in the range of 0.1–4.0 g/L. The influence of the competitive anions (sulphates and nitrates) on removal efficiency and kinetics of the reaction was investigated and indicated the negative influence of sulphates. The results revealed, that the LDH obtained with the use of magnesite shows high efficiency and selectivity for the removal of low concentrations of anions (Cin = 0.05 mmol/L). Moreover, the tested LDH are effectively removing anions at low pH conditions.

An Ion Chromatography Method for Simultaneous Quantification of Chromate, Arsenate, Selenate, Perchlorate, and Other Inorganic Anions in Environmental Media.

Chromium (Cr) (VI) is a toxic, mutagenic, and carcinogenic water pollutant. The standard ion chromatography (IC) method for quantification of Cr (VI) in water samples is Environmental Protection Agency Method 218.7, which requires postcolumn derivatization with 1,5-diphenylcarbazide and UV-Vis spectroscopy detection. Method 218.7 is Cr (VI) specific; thus, it does not allow detection of co-occurring natural and anthropogenic anions in environmental media. In this study, we developed an isocratic IC method with suppressed conductivity detection, a Metrohm Metrosep A Supp 7 column, and sodium carbonate/acetonitrile as mobile phase for simultaneous quantification of Cr (VI), , As (V) as arsenate, Se (VI) as selenate, and the common anions F–, Cl–, , , and . The determination coefficient for every analyte was >0.99 and the method showed good accuracy in quantification. Cr (VI), As (V), Se (VI), and limit of detection and limit of quantification were 0.1–0.6 μg/L and 0.5–2.1 μg/L, respectively. Recovery of Cr (VI) in various aqueous samples (tap water, surface water, groundwater, and wastewater) was between 97.2% and 102.8%. Overall, most analytes showed acceptable recovery (80–120%) in the environmental samples tested. The IC method was applied to track Cr (VI) and other anion concentrations in laboratory batch microcosms experiments with soil, surface water, and anaerobic medium. The IC method developed in this study should prove useful to environmental practitioners, academic and research organizations, and industries for monitoring low concentrations of multiple anions in environmental media, helping to decrease the sample requirement, time, and cost of analysis.

Ion effects on the extraction of cesium (I) by 1,3-Diisopropoxycalix [4] arenecrown-6(BPC6) and the highly efficient extraction under neutral conditions

ABSTRACT The effect of ion species and concentration on the extraction percent of Cs+ by 1,3-Diisopropoxycalix [4] arenecrown-6 (BPC6) in octanol/water solvent extraction system has been studied by molecular dynamics simulations and experiments. The results show that the anionic species play an important role on the enhancement of the extraction percent of Cs+. Specifically, the order in which anions promote the extraction percent is different at different total anion concentrations. At a relatively low anion concentration of 0.5 M, the extraction percent follows the sequence: ClO4 −> I−> NO3 −> Br−> Cl−> SO4 2−> F−. At a relatively high concentration of 2 M, the extraction percent of Cs+ follows the following sequence: I−> ClO4 −> Br−~ NO3 −> Cl−> SO4 2−> F−. It is indicated that the extraction percent is dominated by the anion’s interface propensity, which is the probability of anion distribution in the interface compared to the water phase. However, at low concentration of anions, strong coordination effect of NO3 − promotes the extraction effect compared to Br−. At the high anion’s concentration, the stronger salting-out capacity of Br− leads to a considerable increase of extraction percent. In addition, the cations also slightly affect the extraction percent. The extraction percent is affected by both cations’ concentration and the salt-out effect. On this basis, a neutral Cs+ extraction system has been established, and one stage extraction percent could reach 62.5%.

Structural and Dynamic Insights into the Conduction of Lithium-Ionic-Liquid Mixtures in Nanoporous Metal-Organic Frameworks as Solid-State Electrolytes.

Metal-organic framework (MOF)-based separators in Li-ion batteries (LIBs) have the potential to improve the battery performance. The mobility and conduction of lithium and organic ionic liquids (ILs) in these materials acting as (quasi) solid-state electrolytes are crucial for the battery power output. Here, we investigate the mobility of a Li-based IL in MOF nanopores and unveil the details of the conduction mechanism by molecular dynamics (MD) simulations. A complex conductivity depending on the Li-IL loading and on the IL composition is observed. Most importantly, the presence of Li prevents the collapse of the conductivity at high IL loadings. The fully atomistic MD simulations including guest-guest and guest-host interactions elucidate the competing mechanisms: Li follows a Grotthuss-like conduction mechanism with large mobility. While at small pore fillings, the Li conduction is limited by the large distance between the anions facilitating the Grotthuss-like conduction; the conduction at high pore fillings is governed by field-induced concentration inhomogeneities. Because of the small MOF pore windows, which hinders the simultaneous passage of the large IL cations and anions in opposite directions, the IL shows field-induced MOF pore blocking and ion bunching. The regions of low anion concentration and high cation concentration represent barriers for Li, decreasing its mobility. In comparison to Li-free IL, the IL bunching effect is attenuated by the formation of charge-neutral Li-anion complexes, resulting in a tremendously increased conductivity at maximum pore filling. The exploitation of this mechanism may enhance the development of advanced batteries based on IL and nanoporous separators.

Effects of thiocyanate anions on switching and structure of poly(N-isopropylacrylamide) brushes**Project supported by the Joint Funds of Xinjiang Natural Science Foundation (Grant No. 2019D01C333), the National Natural Science Foundation of China (Grant Nos. 11847610 and 21764015), the National Basic Research Program of China (Grant No. 2015CB857100).

In this work, we investigate the effects of thiocyanate anions on the switching and the structure of poly (N-isopropylacrylamide) (PNIPAM) brushes using a molecular theory. Our model takes into consideration the PNIPAM–anion bonds, the electrostatic effects and their explicit coupling to the PNIPAM conformations. It is found that at low thiocyanate anion concentration, as the anion concentration of thiocyanate increases, thiocyanate anions are more associated with PNIPAM chains through the PNIPAM–anion bonds, which contributes to stronger electrostatic repulsion and leads to an increase of lower critical solution temperature (LCST). By analyzing the average volume fractions of PNIPAM brushes, it is found that the PNIPAM brush presents a plateau structure. Our results show that the thiocyanate anions promote phase segregation due to the PNIPAM–anion bonds and the electrostatic effect. According to our model, the reduction of LCST can be explained as follows: at high thiocyanate anion concentration, with the increase of thiocyanate concentration, more ion bindings occurring between thiocyanate anions and PNIPAM chains will result in the increase of the hydrophobicity of PNIPAM chains; when the increase of electrostatic repulsion is insufficient to overcome the hydrophobic interaction of PNIPAM chains, it will lead to the reduction of brush height and LCST at high thiocyanate anion concentration. Our theoretical results are consistent with the experimental observations, and provide a fundamental understanding of the effects of thiocyanate on the LCST of PNIPAM brushes.

Оценка качества природных вод на научных полигонах Ямало-Ненецкого автономного округа (Пуровский, Тазовский, Шурышкарский, Полярно-Уральский)

Surface water bodies are most vulnerable to chemical pollution. Objective: to study the hydro/chemical indicators of the state of surface waters of the Yamalo-Nenetsk Autonomous District and to assess their quality. In 2018, original studies of water bodies located in scientific testing grounds of the Yamalo-Nenetsk Autonomous District were conducted. The reservoirs are located in the zone of the northern and middle taiga, southern tundra and forest-tundra, on the eastern slope of the Polar Urals. Sampling was carried out according to generally accepted methods. In the surface water samples, the main hydro/ chemical parameters were determined. For an integrated assessment of water quality, the water pollution index (WPI) was used. The surface waters of the examined water bodies belong to low mineralized waters with low concentrations of basic anions and cations. All studied waters in terms of BOD5are classified as dirty and very dirty waters. In the surface water samples of the Polar Urals, high concentrations of benz [a] pyrene were detected. The waters of the Tazovsky landfill belong to moderately polluted waters, the waters of the Purriver are polluted, the waters of the Syny river are dirty. The water bodies of the Polar Urals are very dirty. High values of IZV are associated with elevated concentrations of benz(a)pyrene, BOD5, manganese, copper, zinc, and aluminum. The water pollution index more characterizes the unfavorable biogeochemical situation in the region. An elevated level of technogenic pollution due to benzo(a)pyrene, the source of which is the combustion of fossil fuels (pyrogenic), is established in the water bodies of the Polar Urals. The surface waters of the surveyed water bodies are low-quality waters.

Compartmentalizing acid stress in bacteria.

A Donnan equilibrium causes an influx of chloride ions into the Escherichia coli periplasm when the bacterium finds itself in gastric fluid. The combination of low pH and high anion concentration drives proteins to aggregate, a potentially lethal event unless prevented by specific chaperones.

Ecological classification of the freshwater Ostracoda (Crustacea) based on physicochemical properties of waters and habitat preferences

The relationship between ecological characteristic of freshwater ostracods and their habitat preferences has been a critical issue for understanding of both current and past aquatic conditions. To evaluate this idea, 121 water bodies with 11 different habitat types were randomly sampled in the province of Kütahya. Water quality measurements indicated high to low (Ca2+ &gt; Mg2+ &gt; Na+) cations and relatively low (SO42− &gt; Cl− &gt; F−) anion concentrations with Ca2+ being the dominant ion. Sixteen of 23 species were new reports for the area. Alpha diversity (H′ = 3.64) was found relatively high. Four most abundant species with ca. 93% of similarities contributed highest alpha values in warm to cooler (lower than 25 °C), alkaline (pH 8.22), and fresh to slightly brackish waters. Heterocypris salina and Ilyocypris bradyi also revealed the highest tolerances for electrical conductivity. Based on habitat type, species were clustered into three main groups (I–III). Canonical Correspondence Analyses explained about 57.4% of correlation between species and environmental variables. Redox potential, pH, water temperature and electrical conductivity were found to be the most effective factors on species occurrences while habitat type and dissolved oxygen were not effective. Total number of species showed strong negative and positive relationships with water temperature and dissolved oxygen, respectively. Results clearly showed that cosmopolitan species exhibited relatively wide tolerance ranges to different environmental variables. Accordingly, having wide tolerance ranges seems to provide advantages to cosmopolitan species, increasing their survival chances in a variety of habitats.

Molecular Mechanism for the Hofmeister Effect Derived from NMR and DSC Measurements on Barnase.

The effects of sodium thiocyanate, sodium chloride, and sodium sulfate on the ribonuclease barnase were studied using differential scanning calorimetry (DSC) and NMR. Both measurements reveal specific and saturable binding at low anion concentrations (up to 250 mM), which produces localized conformational and energetic effects that are unrelated to the Hofmeister series. The binding of sulfate slows intramolecular motions, as revealed by peak broadening in 13C heteronuclear single quantum coherence spectroscopy. None of the anions shows significant binding to hydrophobic groups. Above 250 mM, the DSC results are consistent with the expected Hofmeister effects in that the chaotropic anion thiocyanate destabilizes barnase. In this higher concentration range, the anions have approximately linear effects on protein NMR chemical shifts, with no evidence for direct interaction of the anions with the protein surface. We conclude that the effects of the anions on barnase are mediated by solvent interactions. The results are not consistent with the predictions of the preferential interaction, preferential hydration, and excluded volume models commonly used to describe Hofmeister effects. Instead, they suggest that the Hofmeister anion effects on both stability and solubility of barnase are due to the way in which the protein interacts with water molecules, and in particular with water dipoles, which are more ordered around sulfate anions and less ordered around thiocyanate anions.

Deposition, accumulation, and alteration of Cl−, NO3−, ClO4− and ClO3− salts in a hyper-arid polar environment: Mass balance and isotopic constraints

The salt fraction in permafrost soils/sediments of the McMurdo Dry Valleys (MDV) of Antarctica can be used as a proxy for cold desert geochemical processes and paleoclimate reconstruction. Previous analyses of the salt fraction in MDV permafrost soils have largely been conducted in coastal regions where permafrost soils are variably affected by aqueous processes and mixed inputs from marine and stratospheric sources. We expand upon this work by evaluating permafrost soil/sediments in University Valley, located in the ultraxerous zone where both liquid water transport and marine influences are minimal. We determined the abundances of Cl−, NO3−, ClO4− and ClO3− in dry and ice-cemented soil/sediments, snow and glacier ice, and also characterized Cl− and NO3− isotopically. The data are not consistent with salt deposition in a sublimation till, nor with nuclear weapon testing fall-out, and instead point to a dominantly stratospheric source and to varying degrees of post depositional transformation depending on the substrate, from minimal alteration in bare soils to significant alteration (photodegradation and/or volatilization) in snow and glacier ice. Ionic abundances in the dry permafrost layer indicate limited vertical transport under the current climate conditions, likely due to percolation of snowmelt. Subtle changes in ClO4−/NO3− ratios and NO3− isotopic composition with depth and location may reflect both transport related fractionation and depositional history. Low molar ratios of ClO3−/ClO4− in surface soils compared to deposition and other arid systems suggest significant post depositional loss of ClO3−, possibly due to reduction by iron minerals, which may have important implications for oxy-chlorine species on Mars. Salt accumulation varies with distance along the valley and apparent accumulation times based on multiple methods range from ∼10 to 30kyr near the glacier to 70–200kyr near the valley mouth. The relatively young age of the salts and relatively low and homogeneous anion concentrations in the ice-cemented sediments point to either a mechanism of recent salt removal, or to relatively modern permafrost soils (<1millionyears). Together, our results show that near surface salts in University Valley serve as an end-member of stratospheric sources not subject to biological processes or extensive remobilization.

Interaction of an Iridium(III)–Bibenzimidazole Complex with Anions – Implications for Luminescent Sensing

AbstractIridium(III) complex [Ir(ppy)2(tmBBI‐H2)](PF6) (IrBBI‐H2) has been exploited as an anion receptor. In this complex, the cis‐diamine function of the bibenzimidazole is coupled in such a way to the photophysics of the iridium metal core that the photophysics is influenced by hydrogen bonds in the ligand periphery. Systematic studies on the complex reveal that IrBBI‐H2 is a convenient sensor for various anions under aerobic conditions and interacts with Cl–, Br–, I–, and HSO4– by forming hydrogen bonds. Whereas H2PO4– is only capable of mono‐deprotonating IrBBI‐H2, a stepwise process is operative when F– and OAc– are added: formation of the mono‐deprotonated complex IrBBI‐H with a low anion concentration, followed by the appearance of double‐deprotonated complex IrBBI– in the presence of higher anion concentration. The interaction of various anions with IrBBI‐H2 has been investigated by emission spectroscopy or NMR titration. According to the conditions chosen, strong binding interactions in the form of a 2:1 complex/anion ratio between the less basic anions and the complex, and a virtually stoichiometric reaction to their respective ion pairs, were observed.