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PubMed2002

Hygroscopicity of aerosol particles at low temperatures. 2. Theoretical and experimental hygroscopic properties of laboratory generated aerosols.

A Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) system has been used to measure hygroscopic growth curves and deliquescence relative humidities (DRH) of laboratory generated (NH4)2SO4, NaCl, and NaNO3 particles at temperatures T= 20 degrees C and -10 degrees C. Good agreement (better than 3.5%) between measured growth curves and Köhler theory was found using empirical temperature and concentration dependent values for water activity, solution density, and surface tension. The measured growth curves only experience a small temperature dependence in the observed temperature range. Therefore, to a first approximation, it is possible to neglect the temperature dependence of the water activity for theoretical calculations in the temperature range -10 degrees C < T < 25 degrees C. The small differences between experiment and theory, which were predominantly observed for NaCl particles, are probably caused by a small amount of water adsorbed on the "dry" crystals. It was also observed that these particles experience a significant restructuring at relative humidity RH < DRH, which was also taken into account for a comparison with theoretical curves. If salt particles are used for instrument calibration, precautions regarding the dry particle diameter have to be taken.

Adsorption↗
PubMed2002

[Pneumological diagnostics by means of models aerosols. IV. Clearance of aerosol particles from the pulmonary alveoli. Foundations and first clinical results].

The elimination of deposited particles (inorganic and organic particles, bacteria, viruses) from the periphery of the human lung (alveolar clearance) implies phagocytosis by alveolar macrophages, intracellular digestion, migration and translocation. Alveolar clearance of poorly soluble particles happens very slowly and primarily depends on the function of alveolar macrophages. In humans, the transport of particles to the bronchial tree is of secondary relevance, suggesting that the elimination of particles primarily depends on digestion (dissolution) processes within macrophages. The dissolved material is excreted via urine, if there is no further metabolization within the body. The pathophysiology of the alveolar clearance mechanisms in the human lung can be studied by a magnetic tracer technique (magnetopneumography). Ferromagnetic magnetite test-particles are deposited in the periphery of the lung by controlled inhalation. After magnetization and particle alignment in a strong external magnetic field pulse, the amount of retained particles can be detected by a sensitive magnetic field sensor (SQUID, superconducting quantum interference device). Long lasting cigarette smoking and chronic lung inflammations (sarcoidosis, interstitial lung fibrosis) induce a significant impairment of alveolar clearance capacity, while patients with chronic bronchitis show only a moderate impairment of alveolar clearance.

Aerosols↗