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Experimental Methods to Study Aerosol Nanoparticles.
Ždímal, Vladimír ; Schwarz, Jaroslav ; Ondráčková, Lucie ; Ondráček, Jakub
During the last few decades, the experimental possibilities of studying aerosol particles have grown enormously. Not only is it possible to determine the particle size distribution in different metrics, not only can the chemical composition of the size-resolved aerosol be determined, but methods have been developed over the last two decades that allow all of these tasks to be handled in real time. These methods stem from several basic physical principles: molecular diffusion based on Brownian motion, electrostatic separation of particles with predictable charge, condensational growth of particles, gravitational settling, acceleration of particles in nozzles, inertial impaction, and light scattering on particles.\nHowever, if we are specifically interested in separating particles smaller than 100 nanometers in diameter, the choice of experimental methods would be substantially reduced. In fact, we have only four physical principles that can be utilized in this size range with reasonable degree of uncertainty: Brownian motion, electrostatics, impaction and condensation. For the determination of the chemical composition in a given size range, the most commonly used is a combination of physical / chemical ionization with mass detection, however, the range of quantifiable substances is greatly limited.\nRecently, exposure monitoring of workers in the production of engineered nanoparticles has become increasingly important. Here, the task is further complicated by the fact that it is necessary to sample directly from the vicinity of the worker's mouth to determine personal exposure. As far as the collection of nanoparticles in the respiratory zone is concerned, there is not yet a great choice of options, and experimental methods are still being developed and tested. A promising alternative is a stationary measurement, where state-of-the-art aerosol spectrometers are located close to the working space of the personnel, so that the actual exposure of the worker can be estimated. In this case, however, it is necessary to calibrate the on-line instruments by comparison with simultaneous personal collection.\n
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