Solution Aerosol Research Articles

Carboxylate Counteranions in Electronic Cigarette Liquids: Influence on Nicotine Emissions.

The wide pH range reported for electronic cigarette (ECIG) liquids indicates that nicotine may be present in one or more chemical forms. The nicotine form affects the bioavailability and delivery of nicotine from inhaled products. Protonated nicotine is normally associated with counteranions in tobacco products. The chemical and physical properties of counteranions may differently influence the nicotine form and emissions in ECIG aerosols. In this study, we examined how these anions influence nicotine emissions and their evaporation behavior and potential decomposition during ECIG operation. ECIG liquid solutions with equal nicotine concentration and pH but different counteranions (formate, acetate, and citrate) were prepared from analytical standards to assess the effect of the counteranion on nicotine partitioning. High performance liquid and gas chromatography methods were developed to determine the counteranions and the two protonated (NicH+) and free base (Nic) forms of nicotine in commercially available and standard solutions of ECIG liquids and aerosols. In commercial samples, acetate and citrate anions were detected. In standard solutions, both formate and acetate ions were found to evaporate intact, but citrate ion decomposed into formic acid and other products. This study also shows that the identity of the counteranion has no effect on total nicotine emission from ECIG in agreement with previous reports on tobacco cigarettes. However, the partitioning of aerosolized nicotine into NicH+ and Nic is anion-dependent even when the parent liquid pH is held constant. These results indicate that the anions found in a given ECIG product may influence the nicotine delivery profile to the user by enriching aerosols with free-base nicotine as in the case of polycarboxylic acids such as citric acid.

Fabrication of Thin Electrodic Films by Solution Aerosol Thermolysis (SAT)

Thin films of ceramic or ceramic-metal (cermet) electrodes with appropriate structure and morphology significantly affect performance of solid oxide fuel cells (SOFCs. Thus, electrode parameters such as thickness, porosity and tortuosity dictate the values of gaseous effective diffusivities that eventually determine the extent of concentration polarization losses in these high temperature ceramic fuels cells1. In addition, electrode thickness is also a factor dictating concentration polarization losses in working fuel cells which should be as low as possible. Furthermore, it was established that, even total ohmic cell polarization in ceramic fuel cells based on conventional yttria stabilized zirconia (YSZ) electrolyte is significantly affected by electrode microstructure to a greater extent than by electrolyte ohmic resistance. This becomes more evident at low electrolyte thicknesses (i.e. <20 μm) and is related to contiguity factors between metal particles in the fabricated cermets2. On the other hand, nanostructured thin film electrodes have shown great potential for operation in fuel cells due to their enhanced conversion efficiencies compared to their bulk materials counterparts essentially leading to low polarization losses3. In these structures, controlling the electrode film thickness, porosity and tortuosity is of crucial importance as these dictate the magnitude of effective gas diffusivities of reactants and products and the subsequent overall polarization losses4. Therefore, for a given set of chosen materials, the fabrication method adopted for the ceramic fuel cell has to be optimized for the above electrode parameters for optimum performance. In general, innovative fabrication methods with the potential of producing nanostructural components in ceramic fuel cells and possessing inherently the capacity of controlling electrode microstructural characteristics such as porosity, pore size, thickness and uniformity have not given much attention in the literature compared to materials research5. The major advantages of these techniques over the conventional ceramic techniques such as tape casting, are their potential on producing very thin layers of components (i.e. < 1 μm) and the reduction of the subsequent sintering temperatures due to their more active precursor components. Another advantage lies in their capacity of producing nanocomposite electrodes that offer enhanced electrochemical performance6. The spray pyrolysis (SP) technique belongs to this family of deposition methods7 and involves spraying of a solution of metal salts onto a heated substrate. It is robust, easily up scalable and with easily controllable processing parameters. It offers the advantage of accurate control of stoichiometry at droplet level and possess the potential of incorporating the sintering step in the process. It has been used for fabrication of a large number of electroceramic materials and progress in solid oxide fuel cell component fabrication has been reviewed recently5. The technique belongs to the family of molecular precursor deposition methods in which the film is formed on a support via a physical and/or chemical process by appropriately tuning the characteristics of the physicochemical processes involved during deposition in order to achieve the desired functional characteristics. In the present work we focus on the optimization of the technique for fabricating electrodic films. In particular, results are presented of the application of air pressurized spray pyrolysis using aqueous solutions for the production of film cermets of Cu-CeO2, and La0.75Sr0.25MnO3 (LSM) onto dense YSZ substrates. The use of aqueous solutions reduce significantly the cost and the risk factors to personnel health and to the environment. Cu-CeO2 constitutes a potential anode that combines the functionalities of copper ( an electronic conductor) and a good oxidation catalyst (i.e. CeO2) for potential hydrocarbon fuels fed into a SOFC while LSM is the typical state of the art cathode used with a YSZ electrolyte8. The films are characterized by X-ray diffraction and scanning electron microscopy (SEM). References 1W. He et al., Journal of Power Sources, 195, 532 (2010) 2F. Zhao, A. V. Virkar, Journal of Power Sources 141, 79 (2005) 3W. Hea et al., , Nano Energy 1, 828, (2012) 4W. He , J. B. Goodenough, Journal of Power Sources 251, 108 (2014) 5N. E. Kiratzis, Ionics 22,751 (2016) 6S.J. Litzelman et al., Fuel Cells 08, 294 (2008) 7E. Papastergiades et al., Ionics 15, 545 (2009) 8N.E.Kiratzis et al., Journal of Electroceramics 24, 270 (2010) Figure 1

Potential effect of atmospheric dissolved organic carbon on the iron solubility in seawater

Atmospheric aerosols are an important source of soluble iron (sol-Fe) to the global oceans. After deposition to seawater, sol-Fe will either complex with Fe-binding marine organic ligands and enter the ocean dissolved Fe (DFe) pool, or form oxyhydroxide particles (PFe) and precipitate out. Since oceanic DFe is commonly assumed to be bioavailable, the importance of atmospheric sources of sol-Fe for ocean biogeochemistry is determined by both: total fluxes of sol-Fe and the fraction of sol-Fe that is converted to DFe in the ocean. The results from these laboratory studies show that in 20 min from the time of mixing with seawater, nearly all sol-Fe gets oxidized and converted to PFe. The addition of dicarboxylic acids (oxalic and malic) had minor influence on the conversion rate of sol-Fe to PFe. However, the addition of α-hydroxy-carboxylic acids (citric and tartaric) to Fe solutions prior to mixing with seawater was found to considerably increase the concentration of seawater DFe. After 10 days of the experiment, 15% and 50% of the sol-Fe in citric and tartaric acid solutions, respectively, remained in a DFe form. Numerical simulations for sol-Fe laden dust deposition events to the ocean show that if α-hydroxy acids are present in aerosol solution upon deposition to the surface ocean, over 95% of sol-Fe can potentially bind with marine organic ligands; this fraction reduces to < 20% in the absence of atmospheric organics. A possible mechanism is provided to explain the differences in binding strength between aerosol sol-Fe and atmospheric dissolved organic carbon species commonly found in maritime aerosols.

Morphology and Structure of Solid Oxide Fuel Cell (SOFC) Components Fabricated by Spray Pyrolysis

The technique of Solution Aerosol Thermolysis (SAT) was applied for fabrication of thin films of electrodes and electrolytes suitable for operation in Solid Oxide Fuel Cells (SOFCs). Anodic electrodes were chosen for their suitability as suitable electrocatalysts for the direct oxidation of hydrocarbons in these high temperature fuel cells. The technique was optimized in terms of process parameters and their effect on film morphology and crystal structure. Major parameters optimized in aqueous solutions were the substrate temperature, solution flowrate, solution total salts concentration and substrate to nozzle distance given the type of a set of precursor salts.

Fabrication of Thin Electrodic Films by Solution Aerosol Thermolysis (SAT)

We present here results of the application and parameter optimization of the technique of solution spray pyrolysis for the fabrication of electrodic films of the type Cu-CeO2 και La0.75Sr0.25MnO3 (LSM) on dense pellets of the solid electrolyte yttria-stabilized zirconia (YSZ). The first type of electrode combines the properties of a good electronic conductor (Cu) and an efficient catalyst while the second constitutes a typical perovskite exhibiting mixed (i.e. ionic and electronic) conductivity. Both types of electrodes find wide use in ceramic fuel cells, gas sensors and catalytic processes.

PM2.5-Induced Oxidative Stress and Mitochondrial Damage in the Nasal Mucosa of Rats.

Exposure to PM2.5 (particulate matter ≤2.5 μm) increases the risk of nasal lesions, but the underlying mechanisms, especially the mechanisms leading to mitochondrial damage, are still unclear. Thus, we investigated the in vivo effects of PM2.5 exposure on the inflammatory response, oxidative stress, the enzyme activities of Na+K+-ATPase and Ca2+-ATPase, and the morphology and function of mitochondria in the nasal mucosa of rats. Exposure to PM2.5 occurred through inhalation of a PM2.5 solution aerosol. The results show that the PM2.5 exposure induced increased levels of malondialdehyde (MDA) and levels of proinflammatory mediators, including interleukin 6 (IL-6), IL-8, and tumor necrosis factor-α (TNF-α). These changes were accompanied by decreases in the activities of total superoxide dismutase (T-SOD), Na+K+-ATPase, and Ca2+-ATPase in rat nasal mucosa. PM2.5 significantly affected the expression of specific mitochondrial fission/fusion genes (OPA1, Mfn1, Fis1, and Drp1) in nasal mucosa. These changes were accompanied by abnormal alterations of mitochondrial structures, including mitochondrial swelling, cristae disorder, and even fission resulting from higher doses of PM2.5. Our data shows that oxidative damage, inflammatory response, and mitochondrial dysfunction may be the toxic mechanisms that cause nasal lesions after exposure to PM2.5.

Study of pH Stability of R-Salbutamol Sulfate Aerosol Solution and Its Antiasthmatic Effects in Guinea Pigs.

Currently, all commercial available nebulized salbutamol in China is in its racemic form. It is known that only R-salbutamol (eutomer) has therapeutic effects, while S-salbutamol (distomer) may exacerbate asthma after chronic use. Therefore, it is an unmet clinical need to develop R-salbutamol as a nebulized product that is more convenient for young and old patients. In our study, a stable aerosol solution of R-salbutamol sulfate was established, and its antiasthmatic effects were confirmed. The decomposition rate and racemization effect of the R-salbutamol sulfate solution were evaluated over a pH range from 1 to 10 (except pH=7, 8) at 60°C. The aerodynamic particle size of the R-salbutamol sulfate solution and commercial RS-salbutamol sulfate solution were both tested in vitro by Next-Generation Impactor (NGI) in 5°C. Laser diffractometer was used to characterize the droplet-size distribution (DSD) of both solutions. We next conducted an in vivo animal study to document the antiasthmatic effect of R-salbutamol aerosol sulfate solution and determine the relationship to RS-salbutamol. The results showed that the R-salbutamol sulfate solution was more stable at pH 6. In vitro comparison studies indicated that there was no distribution difference between R-salbutamol sulfate solution and the commercial RS-salbutamol solution. The animal results showed that R-salbutamol was more potent than RS-salbutamol against the same dose of histamine challenge. Unlike commercial RS-salbutamol, which was acidified to a pH of 3.5 to extend bench life but may cause bronchoconstriction in asthmatic patients, the neutralized R-salbutamol solution was more suitable for clinic use.

Attachment Behavior of Fission Products to Solution Aerosol

Attachment Behavior of Fission Products to Solution Aerosol

Aerosol-Assisted Plasma Deposition of Biocomposite Coatings: Investigation of Processing Conditions on Coating Properties

The aerosol-assisted atmospheric-pressure planar dielectric-barrier-discharge-type plasma deposition (AA-APPD) system can polymerize monomers and immobilize biomolecules simultaneously. In this paper, we used this technology to deposit biocomposite thin films of polyethylene (PE) along with lysozyme (Lyz) under different aerosol solution temperatures and at different coating positions in the discharge region. In addition, we compared the deposition efficacy of two kinds of Lyz solution using deionized (DI)-water and phosphate-buffered saline (PBS) as solvents, respectively. The results show that deposition rate of thin films increases with increasing solution temperature at most coating positions. In addition, coatings from Lyz-PBS perform higher deposition rates, but with weaker Lyz viability as compared with that of Lyz DI-water. Finally, we also verified that this DBD-type AA-APPD system can not only successfully deposit Lyz in PE thin film, but also maintain Lyz viability after plasma process under different solution temperatures and positions.

Elemental and molecular analysis of metal containing biomolecules using laser induced breakdown spectroscopy and sonic spray ionization mass spectrometry: A step towards full integration and simultaneous analysis

A novel methodology is proposed that combines sonic spray ionization (SSI) mass spectrometry (MS) with laser induced breakdown spectroscopy (LIBS) for analyzing metal-containing biomolecules and complexes. Focusing pulses from a nanosecond laser (Nd:YAG, λ=1064nm) in the microdroplet ensemble produced by a pneumatic nebulizer yielded LIBS spectra that enabled highly sensitive detection of several metal ions in aqueous and aqueous methanolic solutions. Based on the calibration curve method, LOD values at the ng/mL level were achieved for Ca (15ng/mL), Ba (27ng/mL), Cu (67ng/mL) and Fe (650ng/mL) with accuracy >90%. LIBS measurements were performed for the first time on aerosols of solutions of known biomolecules such as superoxide dismutase and alpha-lactalbumin, which led to the reliable determination of the concentration of Cu and Ca, respectively, both in the range of a few μg/mL. In parallel, the relative molecular mass of the metalloproteins was determined by separate SSI-MS measurements performed using an identical pneumatic nebulizer based sample introduction system. This is a first step towards the ultimate aim of integrating the two analytical techniques by use of a single pneumatic nebulization system for simultaneous sample introduction for both LIBS and SSI-MS. Such a system is expected to greatly enhance our capabilities to simultaneously acquire molecular and atomic data.

Effects of Astragalus and Codonopsis pilosula polysaccharides on alveolar macrophage phagocytosis and inflammation in chronic obstructive pulmonary disease mice exposed to PM2.5.

Astragalus and Codonopsis pilosula are used for their immunomodulatory and anti-inflammatory effects. Here, we investigated the effects of Astragalus polysaccharides (APS) and Codonopsis pilosula polysaccharides (CPP) on alveolar macrophage (AM) phagocytosis and inflammation in chronic obstructive pulmonary disease (COPD) associated with exposure to particulate matter with a mean aerodynamic diameter ≤2.5μm (PM2.5). A mouse model of COPD was established by cigarette smoke exposure. PM2.5 exposure was performed by inhalation of a PM2.5 solution aerosol. APS and CPP were administered intragastrically. COPD showed defective AM phagocytosis and increased levels of interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α in bronchoalveolar lavage fluid and serum. PM2.5 exposure aggravated the damage, and this effect was reversed by APS and CPP gavage. The results indicate that APS and CPP may promote defective AM phagocytosis and ameliorate the inflammatory response in COPD with or without PM2.5 exposure.

Morphology and Structure of SOFC Components Fabricated By Spray Pyrolysis

Solid oxide fuel cells are expected to play a significant role in the future energy sector mainly due to their inherent high efficiency and low pollutants emissions. These devices typically operate above 800°C by means of a solid oxide electrolyte, typically yttria stabilized zirconia (YSZ) that conducts oxygen ions at sufficiently high conductivities at these temperatures. The cathode is exposed to air or pure oxygen which is reduced to O2 -. State of the art cathodes are based on the perovskite lanthanum strontium manganite La0.9Sr0.1MnO3 (LSM) in a mixture with YSZ which exhibits adequate electronic conductivity at 1000°C, is stable under oxidizing conditions and has a good thermal expansion match with YSZ. The anodic electrode is exposed to the fuel mixture that can even consist of CO which is normally, deleterious for other types of fuel cells. In fact, one major advantage of SOFCs is their suitability to oxidize conventional hydrocarbons and/or biofuels which renders them ideal candidates in connection with renewable sources (see Figure 1). Due to the difference in the oxygen chemical potential between the anode and the cathode, part of the free energy of the oxidation reaction is converted directly to electricity. State of the art anodes, have been based on Ni due to its low cost, again in a mixture with YSZ[i]. Oxidizing directly (i.e. without an intermediate reforming step) conventional hydrocarbons in SOFCs offers a number of advantages that relate to the existing infrastructure for these fuels that in this case, can be used more efficiently and environmentally consciously until their reserves are depleted. Nickel cermets, however, have to be replaced with other types of mixed conducting (i.e. ionic and electronic) electrodes that do not catalyze carbon formation such as composite anodes of the type Cu/CeO2 /YSZ[ii] or materials based on lanthanum chromate such as the perovskite (La0.75Sr0.25)Cr0.5Mn0.5O3 -δ (LSCM)[iii]. High materials and fabrication costs have prevented wide commercialization of these type of fuel cells and, thus, research efforts have been intensified in recent years by many laboratories that address the above issues. Regarding fabrication, there exist two major categories of techniques, namely conventional which are based on a particulate approach and deposition which entail the formation of cell components on a support via a physical and/or chemical process. The latter offer the advantage of in situ and directly controlling final particle size and morphology by appropriately tuning the characteristics of the physicochemical processes involved during deposition. The purpose of this research is to explore the potential of the spray pyrolysis (SP) technique which is a deposition technique for the fabrication of SOFC components of flat plate geometry. It involves spraying of an appropriate solution of ionic salts on a suitable substrate at certain temperature for the production of oxides in film form[iv]. The technique has the potential for the fabrication of electrolytic films with low thickness resulting in lower ohmic losses and for the fabrication of all the cell components in situ. It also offers great flexibility in terms of materials selection and processing parameters to fabricate suitable electrodes and electrolytes for SOFCs. In the present work, we focus on the effect of the substrate temperature and solution concentration on the final morphology of anodic, cathodic and electrolytic films fabricated by SP using environmentally friendly aqueous solutions. Results are presented of the application of this method for the production of anodic film cermets such as Cu-CeO2, Co-CeO2 and Cu-La0.75Sr0.25Cr0.5Mn0.5O3-δ (Cu-LSCM) on dense YSZ substrates. In addition, cathodic electrodes of La0.75Sr0.25MnO3(LSM) on dense YSZ and porous LSM substrates were fabricated. Finally, YSZ films as well as composite structures of the type Cu-LSCM/YSZ were deposited on porous LSM pellets. The effort is concentrated to identify optimized processing conditions that lead to good adhesion. The produced films were characterized by X-ray diffraction and scanning electron microscopy (SEM). [i] Kiratzis N. E., Connor P., Irvine J. T. S.(2010) Preparation and characterization of copper based cermet anodes for use in solid oxide fuel cells at intermediate temperatures. J. Electroceram. 24:270-287. [ii] Park S.D., Vohs J.M., Gorte R.J. (2000) Direct oxidation of hydrocarbons in a solid-oxide fuel cell. Nature 404: 265-267. doi:10.1038/35005040 [iii] Plint S.M., Connor P.A., Tao S., Irvine J.T.S. (2006) Electronic transport in the novel SOFC anode material La1−xSrxCr0.5Mn0.5O3±δ. Solid State Ion. 177: 2005-2008. doi:10.1016/j.ssi.2006.02.025 [iv] Papastergiades E., Argyropoulos S., Rigakis N., Kiratzis N. E. (2009) Fabrication of ceramic electrolytic films by the method of solution aerosol thermolysis (SAT) for solid oxide fuel cells (SOFC). Ionics 15: 545-554. Figure 1

Comparison of Methods for Predicting the Compositional Dependence of the Density and Refractive Index of Organic-Aqueous Aerosols.

Representing the physicochemical properties of aerosol particles of complex composition is of crucial importance for understanding and predicting aerosol thermodynamic, kinetic, and optical properties and processes and for interpreting and comparing analysis methods. Here, we consider the representations of the density and refractive index of aqueous-organic aerosol with a particular focus on the dependence of these properties on relative humidity and water content, including an examination of the properties of solution aerosol droplets existing at supersaturated solute concentrations. Using bulk phase measurements of density and refractive index for typical organic aerosol components, we provide robust approaches for the estimation of these properties for aerosol at any intermediate composition between pure water and pure solute. Approximately 70 compounds are considered, including mono-, di- and tricarboxylic acids, alcohols, diols, nitriles, sulfoxides, amides, ethers, sugars, amino acids, aminium sulfates, and polyols. We conclude that the molar refraction mixing rule should be used to predict the refractive index of the solution using a density treatment that assumes ideal mixing or, preferably, a polynomial dependence on the square root of the mass fraction of solute, depending on the solubility limit of the organic component. Although the uncertainties in the density and refractive index predictions depend on the range of subsaturated compositional data available for each compound, typical errors for estimating the solution density and refractive index are less than ±0.1% and ±0.05%, respectively. Owing to the direct connection between molar refraction and the molecular polarizability, along with the availability of group contribution models for predicting molecular polarizability for organic species, our rigorous testing of the molar refraction mixing rule provides a route to predicting refractive indices for aqueous solutions containing organic molecules of arbitrary structure.

Elemental Detection of Cerium and Gadolinium in Aqueous Aerosol via Laser-Induced Breakdown Spectroscopy.

Laser-induced breakdown spectroscopy (LIBS) was used to detect and measure the concentrations of Ce and Gd in aqueous aerosol solutions. A total of 36 standards, with concentrations of Ce and Gd ranging from 100 parts per million (ppm) to 10 000 ppm, were made to explore the relationship between them. In this study, a Collison nebulizer with an argon carrier gas was used to generate the aerosol droplets. For each liquid sample, ten repetitions of 200 laser shots each were recorded. The percent relative standard deviations (%RSD) were on an average of 7.5% between the ten different sample repetitions. Due to the close proximity of the Ce and Gd lines, it was challenging to identify peaks with low interferences. However, several lines were identified, calibration curves were constructed, and the best curves were generated using the 457.228 nm line for Ce and the 409.861 nm line for Gd. The LODs for these curves were calculated to be 209.7 ppm and 216.4 ppm for the Ce line and Gd line, respectively.

Accurate Measurements of Aerosol Hygroscopic Growth over a Wide Range in Relative Humidity

Using a comparative evaporation kinetics approach, we describe a new and accurate method for determining the equilibrium hygroscopic growth of aerosol droplets. The time-evolving size of an aqueous droplet, as it evaporates to a steady size and composition that is in equilibrium with the gas phase relative humidity, is used to determine the time-dependent mass flux of water, yielding information on the vapor pressure of water above the droplet surface at every instant in time. Accurate characterization of the gas phase relative humidity is provided from a control measurement of the evaporation profile of a droplet of know equilibrium properties, either a pure water droplet or a sodium chloride droplet. In combination, and by comparison with simulations that account for both the heat and mass transport governing the droplet evaporation kinetics, these measurements allow accurate retrieval of the equilibrium properties of the solution droplet (i.e., the variations with water activity in the mass fraction of solute, diameter growth factor, osmotic coefficient or number of water molecules per solute molecule). Hygroscopicity measurements can be made over a wide range in water activity (from >0.99 to, in principle, <0.05) on time scales of <10 s for droplets containing involatile or volatile solutes. The approach is benchmarked for binary and ternary inorganic solution aerosols with typical uncertainties in water activity of <±0.2% at water activities >0.9 and ∼±1% below 80% RH, and maximum uncertainties in diameter growth factor of ±0.7%. For all of the inorganic systems examined, the time-dependent data are consistent with large values of the mass accommodation (or evaporation) coefficient (>0.1).

Applications of the technique of solution aerosol thermolysis (SAT) in solid oxide fuel cell (SOFC) component fabrication

The technique of solution aerosol thermolysis (SAT) for the production of components suitable for operation of solid oxide fuel cells (SOFC) is reviewed. Major advantages of the technique include its versatility, low cost, and control of the product stoichiometry at droplet level. Progress in understanding the major physicochemical parameters that play a role in final film morphology is emphasized.

Aerosol composition and properties variation at the ground and over the column under different air masses advection in South Italy.

Aerosol composition and properties variation under the advection of different air masses were investigated, as case studies, by contemporary measurements over the atmospheric column and at the ground in a semi-rural site in South Italy. The absence of local strong sources in this area allowed to characterize background aerosol and to compare particle mixing effects under various atmospheric circulation conditions. Aerosol optical depth (AOD) and Ǻngström parameters from radiometric measurements allowed the detection and identification of polluted, dust, and volcanic atmospheric conditions. AODs were the input for a suitable model to evaluate the columnar aerosol composition, according to six main atmospheric components (water-soluble, soot, sea salt accumulation, sea salt coarse, mineral dus,t and biological). Scanning electron microscope (SEM) analysis of particulate sampled with a 13-stage impactor at the ground showed not only fingerprints typical of the different air masses but also the effects of transport and aging on atmospheric particles, suggesting processes that changed their chemical and optical properties. Background columnar aerosol was characterized by 72% of water-soluble and soot, in agreement with ground-based findings that highlighted 60% of contribution from anthropogenic carbonate particles and soot. In general, a good agreement between ground-based and columnar results was observed. Under the advection of trans-boundary air masses, water-soluble and soot were always present in columnar aerosol, whereas, in variable percentages, sea salt and mineral particles characterized both dust and volcanic conditions. At the ground, sulfates characterized the amorphous matrix produced in finer stages by the evaporation of solutions of organic and inorganic aerosols. Sulfates were also one of the key players involved in heterogeneous chemical reactions, producing complex secondary aerosol, as such clay-sulfate internally mixed particle externally mixed with soot chains.

Observation of attachment ratio of fission products on solution aerosol

Attachment behavior of fission products to solution aerosols has been observed to elucidate the role of chemical effects in the generation mechanism of fission-product aerosols. Primary aerosols generated from aqueous solution of sodium chloride or ammonium sulfate were passed through a fission-product chamber, and radioactive aerosols were generated by attaching fission products to the primary aerosol particles. Attachment ratios of the fission products on aerosols were estimated from activity measurements. It was found that the attachment ratio of the sodium chloride solution aerosol is larger than that of the ammonium sulfate solution aerosol.

Determination of the filter capture efficiency for safe use of fixative solutions in the biological glove box of the International Space Station

For fixation of biological specimen in the International Space Station (ISS) aqueous solutions of formaldehyde, glutaraldehyde and ethanol are used in a biological glove box (BGB) containment. The air circulated through the BGB unit is filtered over a bank of filters consisting of a packed bed of activated bituminous coal-based granular carbon impregnated with sodium bromate. A procedure was developed to determine the performance of these filters in the case an unexpected spill would occur. In a simulated spill scenario under earth gravity conditions finely dispersed aerosols of the aforementioned aqueous solutions were drawn through the filter unit at a flow of 75 L/min. To determine the filter capture efficiency, glass fiber membrane filters were impregnated with 2,4-dinitrophenylhydrazine (DNPH) to capture formaldehyde and glutaraldehyde by chemical binding. The filters were analyzed for the DNPH-aldehyde complex by HPLC-UV. Ethanol was collected by adsorption on activated coal and subsequently analyzed by gas chromatography flame ionization detection (GC-FID). A challenge with 10.0 mL of test solution resulted in downstream air concentrations of 0.295 ± 0.094 mg/m3 for a solution of 3% of formaldehyde in water and 0.018 ± 0.015 mg/m3 for a solution containing 3.5% of glutaraldehyde in water. For a filter load of 5.0 mL of 70% ethanol in water, the downstream concentration was 19.4 ± 7.8 mg/m3. This corresponds to filter capture efficiencies of 99.5% for formaldehyde, 99.9% for glutaraldehyde, and 97.5% for ethanol. The measured concentrations downstream of the filter unit all remained below the spacecraft maximum allowable concentrations (SMAC) for these substances. Breakthrough tests were performed at tenfold the volume of the simulated spill scenario. Complete breakthrough occurred at 35 ± 14 min for formaldehyde and at 15 ± 2 min for ethanol. For glutaraldehyde breakthrough was not observed within 75 min.

Modelling size and structure of nanoparticles formed from drying of submicron solution aerosols

Drying of submicron solution aerosols, under controlled conditions, has been explored to prepare nanoparticles for drug delivery applications. A computational model of solution drop evaporation is developed to study the evolution of solute gradients inside the drop and predict the size and shell thickness of precipitating nanoparticles. The model considers evaporation as a two-stage process involving droplet shrinkage and shell growth. It was corroborated that droplet evaporation rate controls the solute distribution within a droplet and the resulting particle structure (solid or shell type). At higher gas temperatures, rapid build-up of solute near drop surface from high evaporation rates results in early attainment of critical supersaturation solubility and a steeper solute gradient, which favours formation of larger, shell-type particles. At lower gas temperatures, formation of smaller, solid nanoparticles is indicated. The computed size and shell thickness are in good agreement with experimentally prepared lipid nanoparticles. This study indicates that solid or shell structure of precipitated nanoparticles is strongly affected by evaporation rate, while initial solute concentration in the precursor solution and atomized droplet size affect shell thickness. For the gas temperatures considered, evaporative cooling leads to droplet temperature below the melting point of the lipid solute. Thus, we conclude that control over nanoparticle size and structure, of thermolabile precursor materials suitable for drug delivery, can be achieved by controlling evaporation rates, through selection of aerosol processing conditions.