Computation of ammonium bisulfate aerosol deposition in conducting airways

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Abstract
Experimental measurements of the growth of monodisperse dry NH 4 HSO 4 aerosols by H 2 O vapor condensation have been reported in the literature. These data are incorporated into an aerosol deposition model to study the behavior of inhaled NH 4 HSO 4 particles, which is of concern in relation to human health. The tracheobronchial tree is described by Weibel's model A morphology, and Landahl's formulas are used to compute particle deposition efficiencies. Enhanced losses in the trachea due to the action of the laryngeal jet are accounted for by using an empirical deposition efficiency equation. The effect of NH 4 HSO 4 aerosol growth is quantitated by comparisons of total and intrabronchial deposition probabilities with those of a nonhygroscopic aerosol of equal aerodynamic size. Computations indicate that hygroscopic growth effects are a function of the size of the particles inhaled. Total deposition efficiencies of NH 4 HSO 4 ‐H 2 O droplet aerosols are greater than those of nonhygroscopic aerosols only if the former originate from dry NH 4 HSO 4 particles exceeding a critical geometric diameter of 0.3 μm. Growth effects are explained in terms of the relative efficiencies of the dominant deposition mechanisms active in the lung.