Concentrations Of Ionic Species Research Articles

Low nitrate under waterlogging triggers exodermal suberization to form a barrier to radial oxygen loss in rice roots.

To acclimate to hypoxic waterlogged conditions, the roots of wetland plants form a radial oxygen loss (ROL) barrier that can promote oxygen diffusion to the root tips. We hypothesized that the low nitrate concentrations that occur after molecular oxygen is consumed in waterlogged soils are an environmental trigger for ROL barrier formation in rice (Oryza sativa). We previously identified 128 tissue-specific up/down-regulated genes during rice ROL barrier formation. The RiceXPro database showed that many of these genes were differentially regulated in response to nitrogen deficiency. Therefore, we assessed changes in the concentrations of ionic species of nitrogen under stagnant conditions, i.e., in a nutrient solution that mimics waterlogged soil conditions, and examined the effects of an increase or decrease of nitrate in the nutrient solution on ROL barrier formation and exodermal suberization. Preventing nitrate deficiency in the stagnant nutrient solution suppressed the formation of an ROL barrier. Conversely, a decrease in nitrate strongly induced ROL barrier formation, even under aerated conditions. In parallel with ROL barrier formation, suberin lamellae formed at the exodermis. Nitrate deficiency also promoted aerenchyma formation and the enlargement of root diameters. These findings suggest that the severe decline of nitrates under waterlogged conditions is an environmental cue for exodermal suberization to form an ROL barrier in rice roots.

Identifying the mechanisms behind the stability of silica nano- and micro-particles: Effects of particle size, electrolyte concentration and type of ionic species

Silica nanofluids have emerged as promising agents for various applications, such as water treatment, CO2 absorption, and chemical enhanced oil recovery (CEOR). However, their effectiveness can be hindered when transported through porous media, especially in challenging downhole environments. Aggregation of nanofluid suspensions can damage formation integrity, and brine fluids may unintentionally transport fine micro silica particles, warranting an in-depth examination of micro-particle behavior and stability. This study synthesized silica particles of different sizes (10 nm, 50 nm, 1 μm and 2 μm) and meticulously characterized them using advanced techniques of transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermal gravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. Subsequently, 560 combinations (in 5 series of 112 experiments) of micro- and nano-fluids in the presence of four different salts (NaCl, CaCl2, MgSO4 and MgCl2) were prepared. The stability and sedimentation of these combinations were investigated based on zeta potential, particle size, pH, electrical conductivity, and UV-spectrophotometry. The results indicated that sodium ions were effective for maintaining suspension stability at lower salt concentrations, while magnesium ions were preferred for higher salinities. Particle size increase led to instability at low salinities but stability at high salinities, where enthalpy dominated over entropy. Derjaguin-Landau-Verwey-Overbeek (DLVO) modeling accurately predicted particle interactions and aggregation tendencies. This investigation enhanced the understanding of the mechanisms governing silica particle stability through diverse analytical methods, addressing their limitations. The analysis of UV data over time revealed insights into sedimentation and aggregation kinetics. In summary, this study comprehensively explored the behavior and stability of silica particles in nano- and micro-fluids, shedding light on their performance in applications ranging from enhanced oil recovery to water treatment.

Transport and retention of silica nanoparticles in glass-bead columns: effects of particle size, type, and concentration of ionic species

Silica nanoparticles (SiO2 NPs) have garnered substantial attention as versatile additives in saline fluids, finding application in areas like environmental remediation, wastewater treatment, enhanced oil recovery, and carbon geo-sequestration. Despite their potential, the intricate interaction between electrolyzed nanoparticles and porous media remains inadequately researched in these contexts. This study delves into the pivotal yet underexplored aspect of silica nanoparticle absorption behavior within porous media, a key determinant of their practical effectiveness. The research focuses on silica particles with dimensions of 10 nm and 50 nm, synthesized via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) in methanol. Employing packed glass bead columns as a surrogate for porous media, the study unravels the complex mechanisms governing nanoparticle transport and deposition. Comprehensive investigations encompass variations in particle sizes, ionic strength, and ionic species, resulting in the examination of 48 distinct flooding scenarios. UV/Vis spectrophotometry is used to quantify nanoparticle concentrations in effluents, elucidating their transport behavior within the porous media. Concurrently, pressure drop alterations across the media serve as indicators of particle plugging and changes in permeability. Intriguingly, specific conditions involving a nanofluid comprising 50 nm silica nanoparticles and 10,000 ppm of magnesium chloride exhibit pronounced permeability reduction, offering potential insights for optimizing applications. Particularly noteworthy is the unique reduction in silica particle retention on glass bead surfaces as salinity increases, especially in the presence of magnesium sulfate. A concentration of 5000 ppm magnesium sulfate induces a log-jamming mechanism, resulting in an amplified final-to-intermediate permeability ratio. Experimental outcomes align with observations from scanning electron microscopy, improving understanding of porous media retention mechanisms. This study contributes to a deeper understanding of interactions between nanoparticles and porous media, paving the way for enhanced application strategies.

A Two-Dimensional Transport Model of Bipolar Membrane Electrodialysis for the Electro-Regeneration of Carbon Capture Solvents

Bipolar membrane electrodialysis (BPMED) is a promising technology that uses an electric field to split water into H+ and OH- ions. A repeating stack of cation selective, anion selective, and bipolar membranes are placed between two electrodes, creating a repeating pattern of acid, base, and diluting flow chambers. A major application of BPMED is the electrochemical solvent regeneration of capture solutions used in CO2 point source (PS) or direct air capture (DAC). Protons generated using BPMED can be used to shift the acid-base equilibria back to CO2, providing a more sustainable alternative to traditional thermal regeneration methods when integrated with renewable electricity sources. This method combines electrosynthesis and separation, producing a pure stream of CO2 for sequestration and a concentrated base stream.Despite its potential, current limitations to BPMED implementation for this application stem from a large power consumption and high membrane costs. In addition, gas bubbles in solution can cause high electrical resistances, and experimental studies of this phenomenon are challenging due to the small scale on which it occurs. To address these challenges, we present a two-dimensional model of BPMED for CO2 capture solvent recovery. This model depicts a single repeating cell triplet and was constructed using COMSOL Multiphysics version 6.1. The Navier-Stokes equations were implemented to compute a convection field, and the ionic species concentration was found by solving the Nernst-Planck equation. A source term in the concentration partial differential equations was implemented to account for ionic speciation and water splitting reactions, captured through kinetic rate expressions.Experimental validation was conducted on a PC Cell BED 1-4 recirculating batch system with a stack of seven cell pairs of PC acid 60 (anion selective), PC SK (cation selective), and PC Bip (bipolar) membranes. Good agreement between the model and experimental results across a range of conditions and variables demonstrates accuracy and robustness. The calculated pH and concentration profiles revealed that the majority of the speciation reaction takes place inside, or directly adjacent to, the bipolar membrane, including bubble nucleation. Bubbles form inside membrane pores and displace the electrolyte, greatly increasing the electrical resistance of the membrane, particularly when membrane porosity is low. However, the reaction plane location where bubbles are generated can be manipulated by increasing the channel width or reducing the applied voltage.Future research will focus on expanding to multiphase CFD simulations to investigate the effect on flow. Our two-dimensional model provides valuable insights into the complex and multifaceted nature of BPMED, offering a powerful tool for investigating small-scale processes and advancing the use of BPMED for CO2 capture solvent recovery. Figure 1

Potential environmental pollution study by leachate generation and health risk assessment in the vicinity of bandhwari landfill disposal site, National Capital Region, India

Effects of fast urbanization and development in metropolitan cities is the production of massive amounts of waste from households and industries. Dumping of waste at an unengineered landfill site creates environmental issues. Generated leachate from such landfill is having potential to pollute the surrounding environment including groundwater. To understand the groundwater pollution by the effect of landfill leachate and health risk assessment for humans, four leachate samples and thirty-six groundwater samples were collected from different sources of groundwater from close proximity of Bandhwari Landfill site located in National Capital Region, Delhi. EC and SO42− values of Leachate samples i. e L-1 and L-2 are 42.5 mS/cm and 55.4 mS/cm; 1916.4 mg/l and 1931 mg/l respectively. Leachate pollution Index (LPI) values signifies that landfill leachate is having moderate potential for contamination. The dominance of average ionic species concentration of major cations in groundwater is given as Ca2+>Na+>Mg2+>K+ and major anion as HCO3− > Cl− > SO42− > NO3− > F−. As per Water Quality Index (WQI), 67% of samples lies in excellent category, 17% of samples falling in good category, whereas around 6% of groundwater samples lies in poor category, very poor category and unsuitable category. Landfill leachate and groundwater sample from North East direction are having high concentration of tritium i.e. 8.11 ± 0.40 TU and 3.03 ± 0.29 TU, respectively. Leachate samples from leachate pond-1 and leachate pond-2 are showing quite high Cl−/Br− ratio i. e 342 and 320. 86 respectively. But groundwater samples are exhibiting Cl−/Br− ratio in the range of 173.68 to 108.75. This represents leaching of salts from solid decomposed waste from landfill. Both non-carcinogenic and carcinogenic risk (CRing) were calculated for children and adult. Hazard Index (HI) values are higher than reference value i. e > 1 in the children (in 23% samples) as compare to the adult. These are mainly associated with Co, Cd and Pb. CRing of groundwater sample due to the presence of As, Ni, Cr and Cd falling in the range of 10−6 and 10−4 showing high risk to cancer per 10, 00, 000 million people by ingestion. However there is no significant cancer risk by dermal exposure by all metals in all groundwater samples. Groundwater pollution appears to be limited to the close vicinity in South and North-East direction.

Electrolysis characterization of saline wastewater discharged from a subsurface pipe in saline-alkali land

We improved the design of an ion membrane electrolysis device to assess its use for electrolytic desalination and hydrogen production utilizing wastewater discharged from a subsurface drainage pipe in saline-alkali land. The device can reduce the waste of water resources and agricultural non-point source pollution. The electrolysis performance is low due to the low concentration of salts and complex ionic species in the drainage water from subsurface pipes of farmland. A one-factor quantitative experimental study was conducted to assess the influence of the electrolysis parameters on the electrolytic characteristics. Multifactor synergistic optimization of the parameters was performed. The results indicate different degrees of linear correlations between the hydrogen and chlorine gas production rates and the current density (CD) for different process parameters. Different factors have different degrees of influence on the electrolysis characteristics, and factor interactions occur. The optimization model describing the effects of multiple factors on the final current density (FCD), pH value after reaction (ARP), and energy consumption rate (ECR) is reliable and stable. The optimized operating parameters included a brine concentration (BC) of 3.6 mol·L−1, before reaction pH (BRP) value of 9, working voltage (WV) of 12.2 V, and electrode immersion depth (EID) of 22.5 cm. Under these conditions, the FCD is 183.03 mA·cm−2, the ARP is 13.99, and the ECR is 24,586.50 kW·h/kg. The proposed method substantially improves the electrolysis performance. The results provide theoretical and technical support for utilizing saline wastewater discharged from saline-alkaline land.

A phase field-based framework for electro-chemo-mechanical fracture: Crack-contained electrolytes, chemical reactions and stabilisation

We present a new theoretical and computational framework for modelling electro-chemo-mechanical fracture. The model combines a phase field description of fracture with a fully coupled characterisation of electrolyte behaviour, surface chemical reactions and stress-assisted diffusion. Importantly, a new physics-based formulation is presented to describe electrolyte-containing phase field cracks, appropriately capturing the sensitivity of electrochemical transport and reaction kinetics to the crack opening height. Unlike other existing methods, this approach is shown to accurately capture the results obtained with discrete fracture simulations. The potential of the electro-chemo-mechanical model presented is demonstrated by particularising it to the analysis of hydrogen embrittlement in metallic samples exposed to aqueous electrolytes. The finite element implementation takes as nodal degrees-of-freedom the electrolyte potential, the concentrations of relevant ionic species, the surface coverage, the concentration of diluted species, the displacement field and the phase field order parameter. Particular attention is devoted to improve stability and efficiency, resulting in the development of strategies for avoiding ill-constrained degrees of freedom and lumped integration schemes that eliminate numerical oscillations. The numerical experiments conducted showcase the ability of the model to deliver assumptions-free predictions for systems involving both free-flowing and crack-contained electrolytes. The results obtained highlight the role of electrolyte behaviour in driving the cracking process, evidencing the limitations of existing models.

Valorisation of original nanostructured lead oxides thin films issued from an innovating electrochemical depollution process: Application to the total electro-mineralisation of glyphosate

Glyphosate is a very problematic pollutant in the world. This study presents a simple treatment to degrade it until total mineralisation with no production of AMPA (aminomethylphosphonic acid), its main by-product more toxic and persistent, by using original nanostructured lead oxides thin films. The synthesis conditions of these materials were determined previously in relation to an innovating electrochemical depollution process of water polluted by soluble lead. Different parameters were evaluated such as pH, initial concentration, lead oxide type and consequently its particular morphology. The solutions were systematically analysed by ion chromatography to determine the concentrations of organic pollutants and ionic species produced, and by UV–visible spectroscopy to quantify released lead during process. The thin films were characterized by XRD, SEM and EDS, before and after interaction. The Pb-04 sample type (pure β-PbO2 with cubic needles nanostructures) seems particularly efficient to obtain a total mineralisation with a mineralisation capacity equal to (1127 ± 56) mg of glyphosate/g of material. Moreover, lead was not released in solution due to a total regeneration with the similar crystalline structure. These results are very promising for potential valorisation of heavy metals wastes for future applications at room temperature and very low electrical inputs.

GHz ultrasonic sensor for ionic content with high sensitivity and localization

Sensing the ionic content of a solution at high spatial and temporal resolution and sensitivity is a challenge in nanosensing. This paper describes a comprehensive investigation of the possibility of GHz ultrasound acoustic impedance sensors to sense the content of an ionic aqueous medium. At the 1.55GHz ultrasonic frequency used in this study, the micron-scale wavelength and the decay lengths in liquid result in a highly localized sense volume with the added potential for high temporal resolution and sensitivity. The amplitude of the back reflected pulse is related to the acoustic impedance of the medium and a function of ionic species concentration of the KCl, NaCl, and CaCl2 solutions used in this study. A concentration sensitivity as high as 1mM and concentration detection range of 0 to 3M was achieved. These bulk acoustic wave pulse-echo acoustic impedance sensors can also be used to record dynamic ionic flux.

Measurement report: Summertime fluorescence characteristics of atmospheric water-soluble organic carbon in the marine boundary layer of the western Arctic Ocean

Abstract. Accelerated warming and a decline in sea ice coverage in the summertime Arctic Ocean can significantly affect the emissions of marine organic aerosols and biogenic volatile organic compounds. However, how these changes affect the characteristics of atmospheric water-soluble organic carbon (WSOC), which plays an important role in the climate system, remains unclear. Thus, to improve our understanding of WSOC characteristics in the rapidly changing Arctic Ocean, including its summertime fluorescence characteristics, we simultaneously measured atmospheric concentrations of ionic species and WSOC, a fluorescence excitation–emission matrix coupled with parallel factor (EEM-PARAFAC) analysis of WSOC, and marine biological parameters in surface seawaters of the western Arctic Ocean during the summer of 2016. WSOC was predominantly present as fine-mode aerosols (diameter <2.5 µm, median =92 %), with the mean concentration being higher in the coastal water areas (462±130 ngC m−3) than in the sea-ice-covered areas (242±88.4 ngC m−3). Moreover, the WSOC in the fine-mode aerosols was positively correlated with the methanesulfonic acid in the fine-mode aerosol samples collected over the sea-ice-covered areas (r=0.88, p<0.01, n=10), suggesting high rates of sea–air gas exchange and emissions of aerosol precursor gases due to sea ice retreat and increasingly available solar radiation during the Arctic summer. Two fluorescent components, humic-like C1 and protein-like C2, were identified by the PARAFAC modeling of fine-mode atmospheric WSOC. The two components varied regionally between coastal and sea-ice-covered areas, with low and high fluorescence intensities observed over the coastal areas and the sea-ice-covered areas, respectively. Further, the humification index of WSOC was correlated with the fluorescence intensity ratio of the humic-like C1 / protein-like C2 (r=0.89, p<0.01) and the WSOC concentration in the fine-mode aerosols (r=0.66, p<0.05), with the highest values observed in the coastal areas. Additionally, the WSOC concentration in the fine-mode aerosols was positively correlated with the fluorescence intensity ratio of the humic-like C1 / protein-like C2 (r = 0.77, p<0.01) but was negatively correlated with the biological index (r=-0.69, p<0.01). Overall, these results suggested that the WSOC in the fine-mode aerosols in the coastal areas showed a higher degree of polycondensation and higher aromaticity compared to that in the sea-ice-covered areas, where WSOC in the fine-mode aerosols was associated with relatively new, less oxygenated, and biologically derived secondary organic components. These findings can improve our understanding of the chemical and biological linkages of WSOC at the ocean–sea-ice–atmosphere interface.

Atmospheric Deposition around the Industrial Areas of Milazzo and Priolo Gargallo (Sicily-Italy)-Part A: Major Ions.

The chemical composition of rainwater was studied in two highly-industrialised areas in Sicily (southern Italy), between June 2018 and July 2019. The study areas were characterised by large oil refining plants and other industrial hubs whose processes contribute to the release of large amounts of gaseous species that can affect the chemical composition of atmospheric deposition As in most of the Mediterranean area, rainwater acidity (ranging in the study area between 3.9 and 8.3) was buffered by the dissolution of abundant geogenic carbonate aerosol. In particular, calcium and magnesium cations showed the highest pH-neutralizing factor, with ~92% of the acidity brought by SO42- and NO3- neutralized by alkaline dust. The lowest pH values were observed in samples collected after abundant rain periods, characterised by a less significant dry deposition of alkaline materials. Electrical Conductivity (ranging between 7 µS cm-1 and 396 µS cm-1) was inversely correlated with the amount of rainfall measured in the two areas. Concentrations of major ionic species followed the sequence Cl- > Na+ > SO42- ≃ HCO3- > ≃ Ca2+ > NO3- > Mg2+ > K+ > F-. High loads of Na+ and Cl- (with a calculated R2 = 0.99) reflected proximity to the sea. Calcium, potassium, and non-sea-salt magnesium had a prevalent crustal origin. Non-sea salt sulphate, nitrate, and fluoride can be attributed mainly to anthropogenic sources. Mt. Etna, during eruptive periods, may be also considered, on a regional scale, a significant source for fluoride, non-sea salt sulphate, and even chloride.

Mathematical and computational modeling of electrohydrodynamics through a nanochannel

Fluid-ion transport through a nanochannel is studied to understand the role and impact of different physical phenomena and medium properties on the flow. Mathematically, the system is described through coupled fourth order Poisson–Nernst–Planck–Bikerman and Navier–Stokes equations. The fourth order-Poisson–Nernst–Planck–Bikerman model accounts for ionic and nonionic interactions between particles, the effect of finite size of the particles, polarization of the medium, solvation of the ions, etc. Navier–Stokes equations are modified accordingly to include both electroviscous and viscoelectric effects and the velocity slip. The governing equations are discretized using the lattice Boltzmann method. The mathematical model is validated by comparing the analytical and experimental ion activity while the numerical model is validated by comparing the analytical and numerical velocity profiles for electro-osmotic flow through a microchannel. For a pressure driven flow, the electroviscous and viscoelectric effects decrease the fluid velocity while the velocity slip enhances it. The acidity of the medium also influences the fluid velocity by altering the ζ potential and ion concentration. The finite size of the particle limits the concentration of ionic species, thus, reducing electroviscous effects. As the external concentration decreases, the impact of finite size of particles also reduces. The inhomogeneous diffusion coefficient also influences electroviscous effects as it changes the concentration distribution. The variation in external pressure does not influence the impact of steric and viscoelectric effects significantly. The maximum impact is observed for ΔP = 0 (electro-osmotic flow).

Ammoniacal nitrogen concentration by osmotically assisted reverse osmosis

Ammoniacal nitrogen is a commonly encountered nitrogenous pollutant produced by industrial processes present in wastewater. In this work, model wastewater containing ammoniacal nitrogen (in the form of NH4Cl) was used as a feed solution in the demonstration of osmotically assisted reverse osmosis (OARO) using a multi-stage hollow fiber membrane module setup. The OARO process aimed to dewater the model wastewater and effectively concentrate the ammoniacal nitrogen in solution for easier recovery. Split feed OARO, wherein the feed stream is split either into the concentrated retentate or refluxed back into the permeate side flowing counter-current with the feed, was conducted and the influence of several operational parameters, such as applied pressure, feed flow rate, reflux ratio, on the concentration process was investigated. Also, the properties of the feed solution, i.e. initial feed concentration and presence of other ionic species, such as NaCl, were also tested. Higher concentration efficiency was observed at the following conditions: higher applied pressure, lower flow rate, and higher reflux ratio. The use of low concentrated feed solutions might be useful to decrease the applied pressure and the occurrence of internal concentration polarization was also avoided. The results in this work show that OARO could be a practical membrane-based process for enrichment and recovery of ammoniacal nitrogen from wastewater to further realize a circular economy, in which waste materials such as ammoniacal nitrogen are recovered and reused to produce valuable products.

Highly Efficient Elimination of Pb+2 and Al+3 Metal Ions from Wastewater Using Graphene Oxide/3,5-Diaminobenzoic Acid Composites: Selective Removal of Pb2+ from Real Industrial Wastewater.

In this study, graphene oxide (GO) was functionalized with 3,5-diaminobenzoic acid (DABA) by a one-step method to produce functionalized graphene oxide (FGO). FGO is a new type of absorbent crystalline substance that has a high surface area and a large porosity site as well as a large number of dentate functional groups which lead to enhanced adsorption performance for heavy metal ions. The adsorption efficiency of FGO for Pb+2 and Al+3 metal ions was extra satisfactory when compared with GO due to the ease of design and the homogeneous structure of FGO. The structure of synthesized GO and FGO was confirmed by different techniques such as FTIR, XRD, TGA, BET nitrogen adsorption-desorption methods, and TEM analyses. The mass of utilized adsorbents, the pH of the medium, the concentration of ionic species in the medium, temperature, and process time were all investigated as variables in the adsorbent procedure. The experimental data recorded that the maximum adsorption efficiency of the 0.5 g/L FGO composite was 99.7 and 99.8% for Pb+2 and Al+3 metal ions, respectively, while in the case of using GO, the maximum adsorption efficiency was 92.6 and 91.9% at ambient temperature in a semineutral medium at pH 6 after 4 h. The adsorption results were in good conformity with the Freundlich model and pseudo-second-order kinetics for Pb+2 and Al+3 metal ions. Also, the reusability study indicates that FGO can be used repeatedly at least for five cycles with a slight significant loss in its efficiency.

Geochemical Modeling of Engineered Water Injection in Carbonates Under Harsh Conditions: New Insights With Ionic Adsorption

Abstract Carbonates are characterized by low oil recovery due to their positive surface charge and consequent high affinity to negatively charged crude oil, rendering them to a state of mixed-to-oil wettability. Thus, a better understanding of the rock/brine/oil interactions and their effect on potential-determining ions (PDIs) adsorption/desorption during engineered water injection is needed for realistic and representative estimations of oil recovery. Therefore, this study reveals a novel approach to capture various interactions and better predict the effect of PDIs adsorption/desorption as well as the concentrations of various ionic species in the effluent using Phreeqc. In this work, we determined the adsorption/desorption of PDIs for the first time using surface-complexation reactions and then we validated our results with experimental data from the literature. Our results revealed that the presence of PDIs and their respective adsorption/desorption results in surface charge decrease and increase in pH. Also, this study found that ionic adsorption depends on ionic strength and species activity where calcium adsorption remained constant while magnesium and sulfate adsorptions varied with ionic strength. Moreover, magnesium ion was found to be the most sensitive ionic species to temperature as opposed to calcium and sulfate ions. In addition, sulfate spiking and dilution decrease the sulfate adsorption since the sulfate starts reacting with magnesium and forming complexes. Additionally, deionized water resulted in the highest charge decrease and pH increase with related incremental oil recovery. The adsorption/desorption of ions is case-dependent and thus, the findings cannot be generalized.

Changes in Inorganic Chemical Species in Fog Water over Delhi

Heavy fogs occur during the winter period over the part of northern India and impact aviation, public transport, the economy, public life, etc. During winter, fog water (FW) and non-monsoonal rainwater (NMRW) samples were collected in Delhi, which is a highly polluted and populated megacity in northern India. The collected FW and NMRW samples were analyzed for their inorganic chemical constituents (F−, Cl−, SO42−, NO3−, NH4+, Na+, K+, Ca2+, and Mg2+). The volume-weighted mean (VWM) pH, conductivity, and total dissolved solids (TDS) of FW were 6.89, 206 μS cm−1, and 107 mg L−1, respectively, indicating the dominance of alkaline species. The total measured ionic constituents (TMIC) in FW and NMRW were 5,738 and 814 μeq L−1, respectively, indicating highly concentrated FW in Delhi. The TMIC in FW were factors of 16 and 7 times more concentrated than MRW and NMRW samples, respectively. The concentrations of inorganic acidic species (SO42− and NO3−) in FW were much higher than in monsoon rainwater (MRW: 3 and 5 times) and NMRW (8 and 12 times), respectively. Also, the concentrations of SO42− and NO3 in NMRW were approximately double compared to MRW indicating higher acidic species concentrations during the winter season over Delhi region. Significant decadal growth in the mean concentrations of ionic species in FW (SO42− - ~9 times; NH4+ - double) were observed between 1985 and 2010. However, the nitrate decreased by ~28%. The higher SO42− is likely from heavy-duty vehicles that burn sulfur-containing fuel. The anions in FW, MRW, and NMRW contributed 20, 42, and 43%. However, the cation contributions were 80, 58, and 57%, respectively. The anion contributions were lower in FW than MRW and NMRW indicating the weak formation of acidic species in fog water. The observed alkalinity suggests that it is unlikely for acid precipitation to be present in this region.

Wet season chemical composition of atmospheric wet deposition at Cape Point

The measurement of precipitation chemistry enables the assessment of the temporal and spatial evolution of the chemical composition of the atmosphere associated with atmospheric physical and chemical mechanisms. The aims of this study were to report the chemical composition of rainwater collected at a marine environment, i.e. the Cape Point Global Atmosphere Watch (CPT GAW) station from 2004 to 2012. As expected, the volume weighted mean (VWM) concentrations of Na+ (298.64 μEq.L-1) and Cl- (354.18 μEq.L-1) were significantly higher compared to the VWM concentrations of other ionic species, as well as compared to the VWM concentrations thereof at the sites in the South African interior. The average pH of rainwater was slightly lower than the pH of unpolluted rainwater, mainly due to NO3- associated with the occasional influence of the Cape Town metropole. In contrast to the sites situated in the north-eastern South African interior, where anthropogenic SO42- was the major constituent in rainwater, SO42- at CPT GAW was entirely associated with marine air with no anthropogenic contribution. It was also indicated that 94% of the chemical content at CPT GAW can be attributed to the marine source.

Resolving the interlayer distance of cationic pyrene clusters embedded in superfluid helium droplets using electron diffraction.

We report the electron diffraction of cationic pyrene (C16H10) clusters embedded in superfluid helium droplets. The diffraction profile contains a significant contribution from helium, but interferences of atomic pairs of pyrene are still recognizable. From least-squares fittings, we determine an interlayer distance of 3.0 Å for the cationic cluster, shortened from 3.5 Å in neutral clusters. The relative contributions of dimers and trimers are about 2:1, in qualitative agreement with the doping statistics. Limited by the detection range of the experimental data, we cannot distinguish further structure details. The predominant contribution of helium also prevents observations of the solvation shell of the ionic cluster. Nevertheless, the success of this experiment demonstrates the feasibility of electron diffraction from an ionic all-light-atom system, dispelling the concern over limited particle concentration of ionic species in the diffraction region, and the need of heavy atoms for diffraction intensity.

Modelling of multi-species transport in concrete under the action of external electric field: Influence of the overpotential at electrode–electrolyte interfaces

• A model describing ionic transport with electrostatic potential effect is presented. • Overpotential at electrodes during ionic transport are examined and demonstrated. • Interaction of ionic transport and electrostatic action is described and demonstrated. • Effects of various processing parameters on ionic transport in concrete are discussed. • Transient chloride binding mechanism is discussed and illustrated. The application of external electrical field on concrete structures is widely used to protect it from chloride attack or to evaluate its resistance to chloride penetration in a short period. During these electrochemical processes, the polarization of electrodes placed inside and/or outside of concrete cannot be ignored. This study proposes a numerical model dealing with the mass transport and electrode polarizing process under an externally applied voltage, in which multi-species electromigration, time-varying overpotential and non-equilibrium binding are involved. The Tafel Equation is adopted to express the overpotential at electrode–electrolyte interfaces. The electro-potential boundary changing with overpotential is reset at each time step to obtain the accurate concentration distributions of ionic species. Additionally, benchmarks against third-party experiments are conducted to verify the reliability of the present model. The effects of externally applied voltage, Tafel parameters and initial ionic species concentration on the interaction of overpotential and chloride penetration are also quantitatively examined. The obtained results show that the potential difference between two concrete surfaces is always lower than that applied on electrodes due to the influence of polarization, which has a further impact on the temporal and spatial concentration distributions of ionic species in the pore solution of concrete.

Cisplatin fastens chromatin irreversibly even at a high chloride concentration.

Cisplatin is one of the most potent anti-cancer drugs developed so far. Recent studies highlighted several intriguing roles of histones in cisplatin's anti-cancer effect. Thus, the effect of nucleosome formation should be considered to give a better account of the anti-cancer effect of cisplatin. Here we investigated this important issue via single-molecule measurements. Surprisingly, the reduced activity of cisplatin under [NaCl] = 180 mM, corresponding to the total concentration of cellular ionic species, is still sufficient to impair the integrity of a nucleosome by retaining its condensed structure firmly, even against severe mechanical and chemical disturbances. Our finding suggests that such cisplatin-induced fastening of chromatin can inhibit nucleosome remodelling required for normal biological functions. The in vitro chromatin transcription assay indeed revealed that the transcription activity was effectively suppressed in the presence of cisplatin. Our direct physical measurements on cisplatin-nucleosome adducts suggest that the formation of such adducts be the key to the anti-cancer effect by cisplatin.