Mass Transfer of Uptake Process of Nitrogen Oxides in Respiratory Conducting Airways

NO_x-intake Process by Living Body, Part 5

Abstract

The previous reports presented the application of the double film model to absorption of gaseous pollutants across mucus-tissue boundary in respiratory airways. The model was applied to those gaseous pollutants which dissolve into water at chemical equilibrium at gas-liquid interface. The resent paper aims at an extension of the double film model to uptake of nitrogen oxides. Dissolution of NO₂ into water does not proceed at chemical equilibrium at gas-liquid interface, since the rate of dissolution is slow. The overall mass transfer rate of NO₂ depends not only upon mass transfer process but upon the chemical process, i. e. dissolution. Thus the overall mass transfer coefficient K_a involves the mass transfer coefficients of gas and liquid phase k_g and k_l, and the rate of dissolution k₂. Uptake of nitrogen oxides in human respiratory conducting airways was given in terms of the overall mass transfer coefficient thus determined. The results of calculation are given as below. NO in inspired air is absorbed by 1.2 % in physical dissolution through respiratory conducting airways if NO₂ is not contained. NO₂ is absorbed by 13 %. If both NO and NO₂ are present in inspired air, NO is absorbed not only in physical dissolution but also in equimolar dissolution along with NO₂ (NO+NO₂+H₂O→2NO^-₂+2H⁺). If inspired air contains both NO and NO₂ in the proportion of 10 to 1, the absorption of NO₂ and NO are 13 % and 2.5 % respectively.