Aerosol formation via aqueous-phase chemical reactions

[1] A theoretical study investigating the growth of nano-size particles via aqueous-phase chemical reactions was carried out. These reactions were assumed to involve semivolatile, water-soluble organic compounds and lead to the production of nonvolatile compounds that stay in particles, thereby making them grow effectively. By using a mathematical framework developed earlier, quantitative estimates for the conditions under which the considered mechanism is able to induce a significant particle growth were derived. In addition to the reaction rate itself, important parameters in this respect were the gas/particle-partitioning coefficient of a reacting semivolatile compound, its gas-phase concentration, and mass accommodation coefficient, as well as the particle diameter and chemical composition. For particles <10 nm in diameter, the Kelvin effect supresses effectively the growth via condensation of semivolatile compounds that subsequently react in the particle aqueous phase. Therefore other heterogeneous mechanisms might be more viable for the rapid growth of such small particles; for example, they might involve chemical reactions that take place in the gas-liquid interface. The derived estimates were presented in a form where they can be directly applied to interpret experimental data. As an example of this, results of a recent laboratory study investigating the formation of organic compounds in the aerosol aqueous phase were analyzed.