In the last decade, our research group set up and optimised analytical techniques for the characterisation of the major components of atmospheric aerosol (i.e. secondary inorganic ions and ...carbonaceous material) and source markers (e.g. levoglucosan, carbonates). In this study, we present a complete overview on the most problematic aspects that can be encountered during the quantification of the two main components of aerosol, i.e. the ionic and carbonaceous fractions. More in detail, different liquid chromatographic approaches were set up for main ions and anhydrosugars determination. Quality assurance procedures (i.e. tests on data reliability) were applied during the set-up phase and they are presented in this work. As regards the carbonaceous component characterisation, two evolved gas analysis techniques were set up and applied: the thermogravimetric technique coupled to the Fourier transformed infrared spectroscopy (TGA/FTIR) and the thermal–optical transmittance method (TOT). A suitable protocol for organic and elemental carbon separation was set up for the TGA/FTIR system and a comparison with the results obtained by the TOT method was carried out. Studies on the impact of filter load, field blanks, and sample composition on OC/EC quantification by the TOT method were performed. Moreover, approaches for carbonate carbon quantification on different kinds of filters were developed. It was demonstrated that this approach allows to reach the ionic balance in samples impacted by carbonate compounds. The optimised methods have been applied for the analysis of thousands of PM filters allowing the obtainment of reliable results.
The National Aerosol Facility (NAF) has been built at IIT Kanpur, India for studying the aerosol behavior under simulated severe nuclear reactor accident conditions. Plasma torch aerosol generator ...(PTAG) has been employed in this facility for generating metal oxide particles with desirable properties. Plasma synthesis closely simulates the particle generation characteristics from degraded core during a postulated severe nuclear reactor accident. This study presents the effect of controlling parameters namely electrical power, carrier gas flow rate and powder feed rate of PTAG on the mass characteristics of synthesized metal oxide particles. The structural and morphological information of the synthesized particles has also been obtained via analysis performed using X-ray diffraction (XRD) method and Transmission electron microscopy (TEM). A set of optimized parameters has been finalized based on the outcome of this study. The study aims to standardize the generator system in order to perform future NAF experiments.
Aerosols created by the vaporization of simulated spent nuclear fuel (simfuel) were produced by laser heating techniques and characterised by a wide range of post-analyses. In particular attention ...has been focused on determining the fission product behaviour in the aerosols, in order to improve the evaluation of the source term and consequently the risk associated with release from spent fuel sabotage or accidents. Different simulated spent fuels were tested with burn-up up to 8 at. %. The results from the aerosol characterisation were compared with studies of the vaporization process by Knudsen Effusion Mass Spectrometry and thermochemical equilibrium calculations. These studies permit an understanding of the aerosol gaseous precursors and the gaseous reactions taking place during the aerosol formation process.
Developments in high dose dry powder aerosol delivery will increasingly challenge the applicability of currently used aerosol characterisation techniques. With cascade impaction analysis bounce ...effects can negatively influence stage collection efficiency, especially with increasing impactor loads. In this study the suitability of the multi stage liquid impinger (MSLI) and the Next Generation Impactor (NGI) for the characterisation of dry powder aerosols containing up to 50mg of drug is evaluated. The occurrence of bounce effects is quantitatively assessed by comparison with data obtained from laser diffraction analysis. The liquid based impaction surfaces of the MSLI largely prevent bounce effects, but the low number of cut-off values associated with this impactor hinders accurate data interpretation. With the NGI, a standard high viscosity plate coating insufficiently reduces bounce effects, causing the fraction <1μm to be higher than what can maximally be expected based on the primary particle size distribution (PSD) obtained from RODOS dispersion. With this type of impactor, the use of solvent soaked filters as impaction surface is necessary to eliminate bounce effects.
While the viscosity of sucrose and sodium citrate solutions increased with increasing percentage (w/v) of solute, the surface tension largely remained consistent. Water, sucrose (10–60% w/v) and ...sodium citrate (7–36% w/v) solutions were nebulised in two air-jet nebulisers (Pari LC; Medix A II) operated at 6 1 min
−1 and in an ultrasonic device (Medix Electronic) operated at mid-power setting. A wide variation in nebuliser size and output characteristics existed between the different commercially available models studied. Contrary to atomisation theories for air-jet nebulisation, droplet size was inversely related to solution viscosity (over 1–6 cP). Beyond this critical value droplet size increased as viscosity increased. This anomaly may be due to viscosity acting either directly or through liquid flow-rates. By contrast the ultrasonic device generated droplets of size proportional to viscosity but was unable to nebulise high viscosity fluids (i.e. > 6 cP). The low viscosity solutions offered less resistance to the integral fountain disintegration process, thereby producing smaller droplets and higher outputs.
Therapeutic steroid suspensions are frequently administered via nebulisation to neonates and young children. We sought to investigate how the size and concentration of model-suspended particles ...(latex spheres) would influence the physical characteristics of the nebulised aerosol. Suspensions of monodispersed latex spheres from 0.605 to 11.90μm: diluted 0.1 to 0.01% (w/v) were nebulised in three air-jet nebulisers and one ultrasonic nebuliser. Secondary aerosol characteristics were measured with a Malvern 2600C laser diffraction sizer. The residual volumes and percentage outputs of suspension and latex spheres were determined by weight measurements and Coulter Counter analysis. The choice of nebuliser markedly influenced the size, polydispersity and output of the resultant aerosol. No specific correlation existed between the size and/or concentration of the original latex spheres and the size distribution of the nebulised droplets. There was a higher output of smaller spheres, with little or no release of the spheres whose size exceeded the typical mass median diameter of the aerosols. The latex spheres were generally concentrated in the residual fluid due to solvent evaporation, blockage of nebuliser orifice by spheres and/or the refluxing action of the suspension. The ultrasonic nebuliser was less efficient than the jet devices; it degraded the larger spheres and was unable to atomise the 1.16 μm sphere suspensions.
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