(232ae) Development of Approaches to Couple Aerosol Charging with Aerosol Coagulation

Authors: 
Tsouris, C., Oak Ridge National Laboratory
Kim, Y. H., Georgia Institute of Technology
Yiacoumi, S., Georgia Institute of Technology
Nenes, A., Georgia Institute of Technology
Aerosol charging can influence the time-evolution of the size distribution of aerosols, which is an important parameter needed to understand their fate in the atmosphere. Electrical charge may be easily accumulated on aerosols through various charging mechanisms, such as ion diffusion. Charge on aerosols can affect their coagulation rates by creating electrostatic interactions. Because the number of elementary charges on aerosols varies, the coagulation rate of aerosols depends not only on their size but also the charge distribution. However, few investigations have been focused on examining the influence of the charge distribution of aerosols on their size distribution, as well as simultaneously tracking both distributions. This study is aimed at developing three modeling approaches to simultaneously investigate charging and coagulation kinetics of aerosols. The modeling approaches are developed on the basis of population balance (PB), but the level of their complexity varies. The first approach is based on bivariate PB equations that have charge and size as variables. For this approach, the bivariate PB model can be used to simultaneously predict the time-evolution of both aerosol charge and size distributions. To reduce computational cost, in the second approach, the bivariate PB equations are replaced by the monovariate PB equations that have particle size as the variable. A set of charge balance (CB) equations is separately derived and then coupled with the monovariate PB equations to include aerosol charging effects. Similarly to the second approach, the last approach includes the monovariate PB equations, but excludes the CB equations by assuming that the charge distribution of aerosols instantaneously reaches steady-state. Case studies using the modeling approaches will be provided and the limitations of each approach will be discussed.