The influence of electric charge on minimum particle scavenging efficiency particle size during below-cloud scavenging processes

Below-cloud wet deposition scavenging processes are important for removing coarse and very fine particles from the atmosphere. This study investigated the influence of electric charge on particle deposition and estimated the scavenging gap particle size (the most penetrating particle size) along with the corresponding minimum collection efficiency and minimum scavenging coefficient particle size by using equations for below-cloud scavenging processes. A harmonic mean type approximation was used for calculations and the Cunningham correction factor was applied to include the slip effect of nuclei mode particles. Results based on the analytically approximated solution compared well with the numerically calculated results and previous studies that did not consider electric charging effects. The results showed that charge effects play an important role in determining the most penetrating particle size. This study also showed that use of the Cunningham correction factor may increase the most penetrating particle size under certain conditions. Subsequently, these results indicate that consideration of the electric charge effect with a Cunningham correction factor is important for estimating the most penetrating particle size.