Concentrations Of Ionic Species Research Articles

Features of Electrical Double Layers Formed Around Strongly Charged Nanoparticles Immersed in an Electrolyte Solution. The Effect of Ion Sizes

Using the modified Poisson–Boltzmann (PB) theory, which includes restrictions on the maximum attainable concentration of ionic species in a solution Cmax determined by their effective sizes, the distributions of electrostatic potential φ(r) and ion concentration near a spherical nanoparticle with radius a immersed in a 1 : 1 electrolyte solution have been studied under the conditions of constant surface charge density σs. For weakly charged particles, the φ(r) profiles are almost independent of Cmax and coincide with the profile obtained in terms of the classical PB model. Surface potential |φs| gradually increases with a rise in |σs|. Far from the particle, when the potential becomes lower than its thermal value $${{\varphi }_{{\text{T}}}} = \frac{{kT}}{e}$$ (k is the Boltzmann constant, T is the temperature, and e is the elementary charge), the potential decreases exponentially irrespective of the counterion sizes: $$\psi \left( r \right) = \frac{{\varphi \left( r \right)}}{{{{\varphi }_{{\text{T}}}}}} = {{\psi }_{{{\text{eff}}}}}\frac{a}{r}\exp \left( { - \kappa \left( {r - a} \right)} \right),$$ where r is the distance from the particle center and κ is the reciprocal Debye radius. According to the classical PB theory, the growth of the surface charge leads to the saturation of $$\left| {{{\psi }_{{{\text{eff}}}}}} \right|~\left( { \to 4} \right),$$ with the value of $$\left| {{{\psi }_{{\text{s}}}}} \right|$$ obtained by solving the nonlinear PB equation being higher than $$\left| {{{\psi }_{{{\text{eff}}}}}} \right|.$$ In the modified PB theory, which takes into account the size of electrolyte ions in the simplest form, this effect of saturation is absent. Now, $$\left| {{{\psi }_{{{\text{eff}}}}}} \right|$$ depends on both the value of the surface charge and the sizes of counterions. Moreover, at a large size of counterions, $$\left| {{{\psi }_{{{\text{eff}}}}}} \right|$$ substantially exceeds the corresponding value obtained by solving the nonlinear modified PB equation. The difference between the electrical double layer properties obtained by solving the classical and modified PB equations directly follows from the fact that the modified theory predicts the appearance of a condensed layer at a particle surface, with the concentration of counterions in this layer being equal to Cmax. Therewith, the thickness of the layer grows with increasing |σs| (at a constant size of the ions) and the size of the ions (at constant σs).

Ionic Liquid Analogs of AlCl3 with Urea Derivatives as Electrolytes for Aluminum Batteries

AbstractThe ionic liquid analog, formed through the mixture of urea and AlCl3, has previously shown to serve as a low‐cost electrolyte for an aluminum‐graphite battery, while maintaining good performance and achieving high Coulombic efficiency. Undesirable are the relatively high viscosity and low conductivity of this electrolyte, when compared to chloroaluminate ionic liquids with organic cations. In this work, the fundamental changes to the electrolyte resulting from using derivatives of urea (N‐methyl urea and N‐ethyl urea), again mixed with AlCl3, are examined. These electrolytes are shown to have significantly lower viscosities (η = 45, 67, and 133 cP when using N‐ethyl urea, N‐methyl urea, and urea, respectively, at 25 °C). The associated batteries exhibit higher intrinsic discharge voltages (2.04 and 2.08 V for N‐methyl urea and N‐ethyl urea electrolytes, respectively, vs 1.95 V for urea system@100 mA g−1 specific current for ≈5 mg cm−2 loading), due to changes in concentrations of ionic species. Aluminum deposition is directly observed to primarily occur through reduction of Al2Cl7− when AlCl3 is present in excess, in contrast to previously suggested cationic Al‐containing species, via operando Raman spectroscopy performed during cyclic voltammetry.

Seasonal Variation in the Biological Effects of PM2.5 from Greater Cairo.

Greater Cairo (Egypt) is a megalopolis where the studies of the air pollution events are of extremely high relevance, for the geographical-climatological aspects, the anthropogenic emissions and the health impact. While preliminary studies on the particulate matter (PM) chemical composition in Greater Cairo have been performed, no data are yet available on the PM’s toxicity. In this work, the in vitro toxicity of the fine PM (PM2.5) sampled in an urban area of Greater Cairo during 2017–2018 was studied. The PM2.5 samples collected during spring, summer, autumn and winter were preliminary characterized to determine the concentrations of ionic species, elements and organic PM (Polycyclic Aromatic Hydrocarbons, PAHs). After particle extraction from filters, the cytotoxic and pro-inflammatory effects were evaluated in human lung A549 cells. The results showed that particles collected during the colder seasons mainly induced the xenobiotic metabolizing system and the consequent antioxidant and pro-inflammatory cytokine release responses. Biological events positively correlated to PAHs and metals representative of a combustion-derived pollution. PM2.5 from the warmer seasons displayed a direct effect on cell cycle progression, suggesting possible genotoxic effects. In conclusion, a correlation between the biological effects and PM2.5 physico-chemical properties in the area of study might be useful for planning future strategies aiming to improve air quality and lower health hazards.

Dry, wet depositions for ambient air nitrate, sulfate, and chloride ionic species at mixed (traffic, commercial, and residential) sampling sites in Central Taiwan

This research was focused on the measurements of ambient air pollutants species (Cl−, NO3−, and SO42−) concentrations of wet and dry depositions by using PS-1 (TSP), dry depositions plate and wet depositions tub at mixed (traffic, commercial, and residential) sampling sites. Lu-Liao, characterized by traffic, commercial and residential sites, was selected as the dry deposition measurement site. Hungkuang University, characterized by a traffic site, was selected as the wet deposition collection site. At the Luliao site, the results indicated that the average ionic species (Cl−, NO3−, and SO42−) concentrations were 12.86, 25.58, and 18.37 μg/m3, respectively, in winter and 2.94, 11.37, and 14.09 μg/m3, respectively in spring. The average ionic species (Cl−, NO3−, and SO42−) dry depositions were 284.43, 1808.50, and 412.93 μg/m2 min, respectively, in winter and 147.66, 109.59, and 415.44 μg/m2 min, respectively, in spring. As for the monthly Cl−, NO3−, and SO42− volume weighted mean (VWM) concentrations at the Hungkuang site, the results for January were 5.64, 4.41, and 10.13 mg/L, for May were 0.45, 1.98, and 2.09 mg/L, for June were 0.76, 1.39, and 2.46 mg/L, and for July were 1.83, 2.97, and 5.84 mg/L. The monthly Cl−, NO3−, and SO42− Fw (Fluxwet deposition) at the same site were 355.41, 277.63, and 638.15 mg/m2 month, respectively, for January; 17.01, 99.03, and 362.05 mg/m2 month, respectively, for May; 99.03, 181.18, and 319.45 mg/m2 month, respectively, for June; and 362.05, 587.86, and 1156.49 mg/m2 month, respectively, for July. SO42− had the highest VWM and Fw values when compared with the other ionic species, Cl− and NO3−. The highest VWM values for all ionic species (Cl−, NO3−, and SO42−) all occurred in winter.

Assessing the neutralisation, wet deposition and source contributions of the precipitation chemistry over Europe during 2000\u20132017

BackgroundThe chemical composition of precipitation was assessed in 27 European countries from 2000 to 2017, offering a general point of view on the rainwater chemistry in Europe, contributing to a larger understanding of air pollution and atmospheric chemistry.ResultsThe volume-weighted mean concentrations (VWM) were calculated, showing the relative dominance of SO42− and Cl−, explaining the acidic and slightly acidic pH values that ranged from 4.19 to 5.82 over Europe. The VWM concentrations of ionic species measured in rainwater usually followed the SO42 − > Cl− > Na+ > NH4+ > NO3− > H+ > Ca2+ > Mg2+ > K+ > HCO3− downward order, with small exceptions, depending on the industrial activity or legal framework of a particular area. Fractional acidity showed that ~ 69% of the inorganic acidity in precipitation is neutralised, whilst neutralisation factors showed that Na+ and NH4+ contributed the most to the neutralising process. The relationship between acidic and neutralising compounds was further examined by calculating the ionic ratios. Wet deposition rates showed the dominance of acidic compounds over neutralising ones, reflecting the climatic influences and the local and regional economic characteristics of different regions from Europe. Origins of major ions in rainwater were examined using the sea salt and non-sea salt fractions, crustal and marine enrichment factors, correlation analysis and the Principal Component Analysis, showing the significant influence of anthropogenic sources (industry, agriculture, traffic). Natural sources (maritime, terrestrial) also play a major role in influencing the precipitation chemistry of the European continent.ConclusionsThe main conclusion of this study regarding the precipitation chemistry of the European continent during the studied period is represented by the relative homogenous distribution of the analysed chemical species, which is most likely due to the unitary economic development and to the implementation of common European policies in the field of environmental protection. Since the pH is still acidic due to the anthropogenic emissions, more attention should be given to the implementation of environmental legislation, especially in non-European Union countries or in countries that joined recently.

Environmental impact and durability of carbonated calcium silicate concrete

This paper describes the environment impact of low-lime calcium silicate (Ca2SiO4) cement (CSC) that cures by a reaction with gaseous carbon dioxide (CO2). The production of CSC requires less limestone and lower kiln temperatures than those used for ordinary Portland cement (OPC). This makes it possible to reduce the carbon dioxide emissions at the cement kiln from ∼810 kg/t for OPC to ∼565 kg/t for CSC. The carbon dioxide used in the curing process and captured within CSC-based concrete (CSC-C) is industrial-grade carbon dioxide sourced from waste flue gas streams. The fully hardened CSC-C will contain up to 300 kg of carbon dioxide per tonne of cement used in the concrete formulation. This paper also summarises the performance and durability of CSC-C and OPC concrete (OPC-C). Freeze–thaw and scaling resistance were evaluated as per ASTM C666 and ASTM C672, respectively, the concentrations of ionic species leached from the concretes were measured, efflorescence was evaluated in pavers partially submerged in water, and the expansion and mass changes associated with the exposure to sodium sulfate (Na2SO4) and magnesium (Mg) solutions were measured. In each of the durability tests, the CSC-C specimens, made with commercially produced Solidia Cement, performed equivalently or better than the OPC-C specimens.

Compliance and port air quality features with respect to ship fuel switching regulation: a field observation campaign, SEISO-Bohai

Abstract. Since 1 January 2017, ships berthed at the core ports of three designated “domestic emission control areas” (DECAs) in China should be using fuel with a sulfur content less than or equal to 0.5 %. In order to evaluate the impacts of fuel switching, a measurement campaign (SEISO-Bohai) was conducted from 28 December 2016 to 15 January 2017 at Jingtang Harbor, an area within the seventh busiest port in the world. This campaign included meteorological monitoring, pollutant monitoring, aerosol sampling and fuel sampling. During the campaign, 16 ship plumes were captured by the on-shore measurement site, and 4 plumes indicated the usage of high-SF (SF refers to the sulfur content of marine fuels). The average reduction of the mean ΔNOx∕ΔSO2 ratio from high-sulfur plumes (3.26) before 1 January to low-sulfur plumes (12.97) after 1 January shows a direct SO2 emission reduction of 75 %, consistent with the sulfur content reduction (79 %). The average concentrations of PM2.5 (particulate matter with a diameter less than 2.5 µm), NOx, SO2, O3 and CO during campaign were 147.85 µg m−3, 146.93, 21.91, 29.68 ppb and 2.21 ppm, respectively, among which NOx reached a maximum hourly concentration of 692.6 ppb, and SO2 reached a maximum hourly concentration of 165.5 ppb. The mean concentrations of carbonaceous and dominant ionic species in particles were 6.52 (EC – elemental carbon), 23.10 (OC – organic carbon), 22.04 (SO42-), 25.95 (NO3-) and 13.55 (NH4+) µg m−3. Although the carbonaceous species in particles were not significantly affected by fuel switching, the gas and particle pollutants in the ambient air exhibited clear and effective improvements due to the implementation of low-sulfur fuel. Comparison with the prevailing atmospheric conditions and a wind map of SO2 variation concluded a prompt SO2 reduction of 70 % in ambient air after fuel switching. Given the high humidity at the study site, this SO2 reduction will abate the concentration of secondary aerosols and improve the acidity of particulate matter. Based on the enrichment factors of elements in PM2.5, vanadium was identified as a marker of residual fuel ship emissions, decreasing significantly by 97.1 % from 309.9 ng m−3 before fuel switching to 9.1 ng m−3 after regulation, which indicated a crucial improvement due to the implementation of low-sulfur fuels. Ship emissions were proven to be significantly influential both directly and indirectly on the port environment and the coastal areas around Bohai Bay, where the population density reaches over 650 people per square kilometer. The results from this study report the positive impact of fuel switching on the air quality in the study region and indicate a new method for identifying the ship fuel type used by vessels in the area.

Environmental Gating and Galvanic Effects in Single Crystals of Organic-Inorganic Halide Perovskites.

Understanding the impact of environmental gaseous on the surface of organometal halide perovskites (OMHPs) couples to the electronic and ionic transport is critically important. Here, we explore the transport behavior and origins of the gas sensitivity in MAPbBr3 single crystals (SCs) devices using impedance spectroscopy and current relaxation measurements. Strong resistive response occurs when crystals are exposed to different environments. It was shown that SC response to the environment is extremely different at the surface as compared to the bulk due to the disorder surface chemistry. The nonlinear transport properties studied using ultrafast Kelvin probe force microscopy (G-KPFM) to unravel spatio-temporal charge dynamics at SC/electrode interface. The relaxation processes observed in pulse relaxation and G-KPFM measurements along with gas sensitivity of crystals suggest the presence of a triple-phase boundary between environment, electrode, and crystal. Results indicate that the environment is a nontrivial component in the operation of OMHP devices which is reminiscent of fuel cell systems. Furthermore, the triple-phase boundary can play a significant role in the transport properties of OMHPs due to the possibility of the redox processes coupled to the concentration of bulk ionic species. Although instrumental for understanding the device characteristics of perovskites, our studies suggest a new opportunity of coupling the redox chemistry of the Br2-Br- pair that defines the bulk ionic conductivity of MAPbBr3 with the redox chemistry of gaseous (or liquid) environment via a suitable electrocatalytic system to enable new class of energy storage devices and gas sensors.

Evidence of the production of galactooligosaccharide from whey permeate by the microalgae Tetradesmus obliquus

Galactooligosaccharides (GOS) are prebiotics commonly produced from lactose via an enzymatic reaction catalyzed by β-galactosidase (β-gal) which is present in many organisms, including microalgae. Whey permeate (WP), a major byproduct of the dairy industry rich in lactose, represents an interesting medium for producing GOS as high value-added ingredients. Using the microalgae Tetradesmus obliquus as the enzyme source could be an interesting alternative due to its lower nutritional requirements for growth and its applicability in industry. Therefore, this study investigates the growth of T. obliquus and its potential to produce GOS in WP compared to modified Bold's Basal medium (BBM). The growth kinetics, β-gal activity, and medium composition, such as minerals, lactose, glucose, galactose and GOS concentrations, were evaluated during algal cultivation for up to 21 days. The growth rate of T. obliquus was significantly higher in WP, reaching a biomass concentration 4.5 times higher than when growing in BBM. The growth stimulation in WP is directly proportional to the concentration of minerals and ionic species in WP compared to BBM, except for nitrate. The lactose concentration decreased significantly (by 21%) in WP only, with substantial production of the simple carbohydrates, glucose (3.1 g/L) and galactose (4.1 g/L). The higher degree of lactose hydrolysis in WP was supported by significantly higher β-gal specific activity and volumetric productivity. In addition, we detected, for the first time, the production of a trisaccharide GOS in WP whose concentration increased with time, reaching 4.4 g/L and conversion yield of 8.4% (w/w of initial lactose) after 21 days. Overall, these results hold promise for developing a novel bioprocess for the production of value-added products from WP, but the microalgal enzyme must first be characterized and optimized.

Advanced chemical stability diagrams to predict the formation of complex zinc compounds in a chloride environment.

A chemical stability map is advanced by incorporating ion complexation, solubility, and chemical trajectories to predict ZnO, Zn(OH)2, ZnCO3, ZnCl2, Zn5(CO3)2(OH)6, and Zn5(OH)8Cl2·H2O precipitation as a function of the total Zn content and pH of an NaCl solution. These calculations demonstrate equilibrium stability of solid Zn products often not considered while tracking the consumed and produced aqueous Zn ion species concentrations through chemical trajectories. The effect of Cl-based ligand formation is incorporated into these stability predictions, enabling enhanced appreciation for the local corrosion conditions experienced at the Zn surface in chloride-containing environments. Additionally, the complexation of Cl− with Zn2+ is demonstrated to compete with the formation of solid phases, making precipitation more difficult. The present work also extends the chemical stability diagram derivations by incorporating a Gibbs–Thompson curvature relation to predict the effect of nanoscale precipitate phase formation on species solubility. These thermodynamic predictions correlate well with experimental results for Zn corrosion in full and alternate NaCl immersion, and have far-reaching utility in a variety of fields requiring nanoscale, semiconductor, and/or structural materials.

An Electrical Double Layer between Spherical Particles. The Effect of Ion Sizes

Using the modified Poisson–Boltzmann theory, which includes restrictions on the maximum attainable concentration of ionic species in the solution Cmax, determined by their effective dimensions, the spatial distributions of the electric potential and ions between spherical nanoparticles immersed in a 1 : 1 electrolyte solution have been investigated. It has been found that the pattern of the aforementioned distributions is governed by surface electric potential ψs of the particles, interparticle distance, and maximum concentration Cmax. Between weakly charged particles, the electric potential profiles are almost independent of the value of Cmax. As absolute value $$\left| {{{\psi }_{{\text{s}}}}} \right|$$ increases, an effect associated with the ionic sizes manifests itself; i.e., for high $$\left| {{{\psi }_{{\text{s}}}}} \right|$$ values, the electrical double layer expands into the solution, and, the lower Cmax (the larger the effective size of counterions), the higher the degree of expansion. This behavior is related to the fact that, near a particle surface, the profile of counterion concentration is developed with the following distinctly pronounced regions: the region of a plateau with width lc, which corresponds to the condensed part of the profile with C(x) = Cmax for 0 lc. When highly charged particles approach to each other up to such distances that their electrical double layers appear to be strongly overlapped, coions are completely displaced from the interparticle electrolyte layer, and only counterions are present in the layer.

Hydrochemical evaluation of Lower Niger Drainage Area, southeastern Nigeria

Hydrochemical evaluation of parts of Lower Niger Drainage Area was studied. The distribution and concentration of the major ions were assessed. Atomic absorption spectroscopic and spectrophotometric methods were employed in the analyses of chemical species in water, and Piper, Durov and Schoeller diagrams were used in the processing and interpretation of the results. The results of the hydrochemical analysis show the generalized ionic sequence in the study area as K+ > Ca2+> Na+ > Mg2+ and Mg2+ > Ca2+ > Na+ > K+ in wet season and Cl− > SO42− > HCO3− > NO3− in dry season, respectively. Two major water types predominate: Ca–Mg–HCO3 (17.1%) and Na–K–Cl–SO4 (82.9%). The dominant hydrochemical facies observed include Cl–SO4 and Ca–Mg–HCO3, while Cl–HCO3–NO3 occurs to a lesser degree. The various facies present depict mixing of water from different sources, weathering of carbonates and silicates and ion exchange processes leading to increased concentration of calcium and magnesium ions in relation to sodium and potassium ions. The presence of calcium, chloride and sulphate species indicates the existence of inverse ion exchange. The water in the study area shows variation in the concentration of ionic species with seasons, while the water type is not season dependent.

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence.

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste sample. The pore solution is expressed from a fresh paste sample using a pressurized nitrogen gas system. The pore solution is then immediately transferred to a syringe to minimize evaporation and carbonation. After that, assembled testing containers are used for the X-ray fluorescence (XRF) measurement. These containers consist of two concentric plastic cylinders and a polypropylene film which seals one of the two open sides. The pore solution is added into the container immediately prior to the XRF measurement. The XRF is calibrated to detect the main ionic species in the pore solution, in particular, sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-), to calculate sulfate (SO42-) using stoichiometry. The hydroxides (OH-) can be calculated from a charge balance. To calculate the electrical resistivity of the solution, the concentrations of the main ionic species and a model by Snyder et al. are used. The electrical resistivity of the pore solution can be used, along with the electrical resistivity of concrete, to determine the formation factor of concrete. XRF is a potential alternative to current methods to determine the composition of pore solution, which can provide benefits in terms of reduction in time and costs.

Expression of Cementitious Pore Solution and the Analysis of Its Chemical Composition and Resistivity Using X-ray Fluorescence

The goal of this method is to determine the chemical composition and electrical resistivity of cementitious pore solution expressed from a fresh paste sample. The pore solution is expressed from a fresh paste sample using a pressurized nitrogen gas system. The pore solution is then immediately transferred to a syringe to minimize evaporation and carbonation. After that, assembled testing containers are used for the X-ray fluorescence (XRF) measurement. These containers consist of two concentric plastic cylinders and a polypropylene film which seals one of the two open sides. The pore solution is added into the container immediately prior to the XRF measurement. The XRF is calibrated to detect the main ionic species in the pore solution, in particular, sodium (Na+), potassium (K+), calcium (Ca2+), and sulfide (S2-), to calculate sulfate (SO42-) using stoichiometry. The hydroxides (OH-) can be calculated from a charge balance. To calculate the electrical resistivity of the solution, the concentrations of the main ionic species and a model by Snyder et al. are used. The electrical resistivity of the pore solution can be used, along with the electrical resistivity of concrete, to determine the formation factor of concrete. XRF is a potential alternative to current methods to determine the composition of pore solution, which can provide benefits in terms of reduction in time and costs.

Size-resolved characteristics of inorganic ionic species in atmospheric aerosols at a regional background site on the South African Highveld

Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1 year at Welgegund in South Africa was conducted. SO42− and ammonium (NH4+) dominated the PM1 size fraction, while SO42− and nitrate (NO3) dominated the PM1–2.5 and PM2.5–10 size fractions. SO42− had the highest contribution in the two smaller size fractions, while NO3− had the highest contribution in the PM2.5–10 size fraction. SO42− and NO3− levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO42− was significantly lower due to SO42− being formed distant from SO2 emissions and submicron SO42− having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO42−. PM1 and PM1–2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions.

Characteristics of PM2.5 and its chemical constituents in Beijing, Seoul, and Nagasaki

Ambient fine particulate matter (PM2.5) samples were collected from September 2013 to May 2015 in three cities in East Asian countries (Beijing, China; Seoul, South Korea; and Nagasaki, Japan) in order to analyze the spatiotemporal trends of PM2.5 chemical constituents including organic matter (OM), elemental carbon (EC), water-soluble inorganic ions (NO3−, SO42−, and NH4+), and trace elements. The average PM2.5 mass concentration were 125 ± 6.80 μg m−3, 44.6 ± 0.84 μg m−3, and 17.4 ± 0.37 μg m−3 in Beijing, Seoul, and Nagasaki, respectively. Higher carbonaceous concentrations were observed during winter in Beijing and Seoul, while higher concentrations were found during spring in Nagasaki. The highest seasonal averages of organic carbon (OC) to EC ratios were found during spring in Beijing, winter in Seoul, and fall in Nagasaki. The concentrations of secondary OC and its ratio to OC were high during fall and winter. For ion species, NO3− was dominant in Beijing and Seoul, while SO42− was dominant in Nagasaki. Increased contributions of mobile sources in Beijing and Seoul were observed, with higher NO3−/SO42− ratios than those in Nagasaki. Three groups of air masses were found for the three cities using cluster analyses based on 72-h backward trajectories. The cluster from the Bohai economic zone had the highest concentration of PM2.5 for Beijing. For Seoul, a cluster that originated from the Yellow Sea near an industrial area in Liaoning Province and passed through a highly polluted industrial area in southwestern Seoul had high PM2.5 concentrations. A long-range transported cluster that originated in and crossed through heavily industrialized areas in China and South Korea for Nagasaki had higher ion species concentrations. The results of this study are useful to identify the current levels of PM2.5 and its chemical properties to establish a control plan for PM2.5 for Northeast Asia, including China, South Korea, and Japan.

Source apportionment of fine particulate matter by positive matrix factorization in the metropolitan area of São Paulo, Brazil

Aerosols are generated by a wide variety of sources, have different compositions, and have effects on climate, as well as on human health. Therefore, the analysis of aerosols in urban atmospheres has become increasingly more important. In this study, the sources of fine particulate matter (PM2.5) were analyzed by complementary analytical techniques over a one-year period (November 2014–November 2015) in an area characterized by vehicle and industrial emissions, in the eastern part of the Metropolitan Area of São Paulo, Brazil. The study area is near the largest airport in South America in number of flights. Concentrations of trace elements, ionic species, and black carbon were studied. The annual mean concentration was 22.1 ± 13.2 μg m−3 for PM2.5 and 1.87 ± 1.28 μg m−3 for black carbon. During the study period, the São Paulo State 24-h standard for PM2.5 (60 μg m−3) was exceeded five times. Seasonal variations in PM mass and composition reflected the influence of meteorological conditions and heavy-duty vehicle traffic. A stable atmosphere and a lack of rain are the main meteorological factors contributing to higher concentrations in the winter months. Elemental analysis identified Na, Al, Si, S, Cl, K, Ca, Fe, Zn, nitrate, sulfate, and ammonium as the main components, related to vehicle emissions and resuspension of soil and pavement dust. A Positive Matrix Factorization model revealed 4 p.m.2.5 sources (and their contributions): heavy-duty vehicles (52%), soil dust (26%), light-duty vehicles (18%), and other (probably industrial processes, 4%). Our results suggest a link between PM2.5 concentrations and local emissions, given that the study site is surrounded by major highways. Traffic was found to be the most important source of PM, and more attention should be given to its contribution to PM2.5 concentrations.

Salinity effects on the erosion behaviour of MX-80 bentonite: A modelling approach

Abstract The erosion behaviour of bentonites is influenced by the ions concentration to which they are exposed, which could lead to link the erodibility of bentonite to salinity. However, changes in salinity produce further changes in bentonite hydration and swelling that are not always considered. The aim of this work is to apply a numerical model to inspect the influence of salinity in the erosion behaviour of MX-80 bentonite, analysing the effect of swelling on erosion. To this end, a coupled hydro-chemo-mechanical and erosion model, which considers the expansive behaviour of bentonite as a function of salinity, and a hydro-mechanical model with a salinity-dependent erodibility coefficient are used to simulate pinhole erosion laboratory tests with saline waters. The results of the simulations illustrate that the influence of ion species concentration in the erosion behaviour of bentonites does not need a change in erodibility to be reproduced. On the contrary, they show that hydro-chemo-mechanical effects, and especially the changes that salinity induces in the swelling behaviour of bentonite, play a key role in erosion. Taking them into account leads to a more consistent formulation approach that can explain the observed behaviour, and, for that reason, such an approach is strongly recommended to analyse bentonite erosion processes.

Vertical Distributional Characteristics of Inorganic Ions of PM2.5 at Mt. Huashan, Inland China

PM2.5 was simultaneously collected using a high-volume sampler at 4 h intervals from the mountainside and the foot of the mountain in the Mt. Huashan region, inland China, during the summer of 2016, and the samples were analyzed for inorganic ions, to investigate the chemical characteristics and vertical distribution of the fine particles in the region. The results showed that the concentrations of PM2.5 were (46.9±38.2) μg·m-3 and (76.0±44.3) μg·m-3 on the mountainside and at the foot of Mt. Huashan, respectively. The concentrations of inorganic ions in PM2.5 was higher at the foot of the mountain than on the mountainside, with the order of the mass concentrations of the major ionic species being SO42- > NO3- > NH4+ > Ca2+. Among all the inorganic ions, SO42-, NO3-, and NH4+ are the dominant species, accounting for 89% and 85% of the total, on the mountainside and at the foot, respectively. The fine particulate NH4+ existed mostly in the forms of (NH4)2SO4 and NH4NO3 on the mountainside, and in the forms of NH4HSO4 and NH4NO3 at the foot of the mountain. Mass concentrations of PM2.5 and its major components on the mountainside showed clear diurnal variations, with maximums between 12:00-16:00, mainly due to the transport of the pollutants from the ground surface by the planetary boundary layer height variation and the valley breeze. In contrast, the diurnal variations of PM2.5 and its major components at the foot are characterized with two maxima, peaking between 08:00-12:00 in the daytime and 00:00-04:00 in the nighttime, respectively, mainly due to the increased emissions from both the morning rush-hour traffic and the nighttime on-road heavy-duty vehicles. Acidity of the fine particles was estimated by using the equivalent ratio of anions to cations and the thermodynamic equilibrium model ISORROPIA Ⅱ. Both methods showed that the acidity of PM2.5 at the ground surface site is stronger than that on the mountainside in the Mt. Huashan region.

Numerical assessment of CaOx renal calculi development in space using PBE coupled to urinary flow and species transport

Recently collected astronaut data indicate that space travel has a profound impact on the nephron biochemistry with increasing risk of renal stone development during long duration missions. In this paper, a Population Balance Equation (PBE) model is developed to compute the size distribution of nucleating, growing and agglomerating calcium oxalate (CaOx) renal calculi as they are transported through the different nephron sections. The PBE model is coupled to a Computational Fluid Dynamics (CFD) model that solves for the steady state flow of urine, the concentrations of ionic species, calcium and oxalate, and the transport of the crystals along the nephron using a two-phase interpenetrating Eulerian framework. Simulation are performed based on measured averaged post-flight astronaut 24 h. urine biochemistry to assess the size distribution of the CaOx crystals developed under microgravity conditions. The important effects of agglomeration on the aggregate size distributions and the impact of wall friction on the CaOx volume fraction distributions are carefully examined. Simulations are also presented to indicate the important mixing effect that the cascading nephron configuration may induce during the passage of the particles through the various nephron subsections. Parametric numerical predictions for the microgravity astronaut biochemistry are compared to those for normal and stone-former subjects on Earth. It is concluded that under nominal conditions the largest calcium oxalate aggregate sizes developed in space will be still below the critical range for problematic stone development. However, computations also indicate that in microgravity the highest CaOx volume fractions occur next to the tubule and duct walls. This suggests that there may be an increased potential for wall adhesion and possibility of evolution towards critical stone sizes.