RESUMEN
Laser cladding with H13 steel powders was performed and the related material transformations were studied for the particles emitted during this process. Fractions of various sizes of the aerosol particles formed during the laser cladding were collected on a cascade impactor, while the electromobility and the aerodynamic size of the particles were measured using a scanning mobility particle spectrometer and an aerodynamic particle sizer, respectively. The aerosol particles deposited onto the impactor plates were analyzed using scanning electron microscopy−energy-dispersive X-ray spectroscopy, as well as total-reflection X-ray fluorescence and X-ray absorption near-edge structure spectroscopy. Both the concentration and mean oxidation state of the major components were correlated with the aerosol particle size. The ultrafine aerosol particles (with a diameter less than about 100 nm) were predominantly oxidized and formed as the result of an evaporation−oxidation−condensation process sequence. The larger particles (>200 nm in geometric diameter) were primarily the residues of the original metal powder and exhibited a composition change as compared to the as-received metal powder. Correlations between the changes in the concentration ratio of the components were detected and explained.
RESUMEN
OBJECTIVES: The aim of this study was to provide particle number and mass deposition rates of submicron particles in the human airways as inputs for toxicology and other areas of aerosol science. METHODS: Scanning Mobility Particle Spectrometer was used to measure the number concentrations and size distributions of the ultrafine urban particles during summer and winter in Budapest. The Stochastic Lung Model (SLM) was applied to calculate number and mass deposition rates of the inhaled particles in different anatomical regions of the airways. RESULTS: Our calculations revealed that for the selected days in summer and winter with PM10 values below the health limit 4.7 and 18.4 billion particles deposited in the bronchial region of the lungs. The deposition in the acinar region of the lung was even higher, 8.3 billion particles for the summer day, and 33.8 billion particles for winter day. CONCLUSIONS: Our results clearly demonstrate that large daily numbers of urban UFPs are deposited in the respiratory tract, which may play a key role in the health effects of particulate matter (PM) inhalation. Present results, connecting the ambient exposure parameters with the local burden of the airway epithelium, can be useful inputs of in vitro cell culture experiments. By the combination of urban UFP monitoring and numerical modeling of particle deposition with toxicological studies, the health risks of urban aerosols could be better assessed. The use of UFP data in addition to PM10 and PM2.5 in the epidemiological studies would also be indicated.
