Simulation of formation and growth of atmospheric sulfate particles

This paper investigates the formation and growth of aerosol sulfate particles in the atmosphere. The evolution of the aerosol size distribution with time was modeled using the aerosol general dynamic equation. This equation was solved numerically using a discrete-nodal point method to describe the particle size distribution. For the initial size distribution we have used an average urban accumulation mode. The first step in our model considers the oxidation of SO2 by OH radicals, producing H2SO4(g). The next step considers the binary nucleation and condensation of the H2SO4---H2O system and its evolution due to coagulation and deposition mechanisms. A detailed description of the model is presented. The mass size distribution at different distances during the transport of the initial aerosol size distribution is also presented. The importance of different mechanisms on the evolution of the aerosol size distribution is discussed. Sensitivity analysis was performed for many model parameters where simulations were made at varying temperature, relative humidity and photo-oxidation rate conditions. Model calculations suggest that condensation growth is the dominant mechanism for the evolution of the size distribution of sulfate particles during moderate relative humidity conditions.