A Model Development To Assess Urban SecondaryAerosol Formation

The diffusion equation that describe chemical composition of the atmospheric fine particles (organic and inorganic) is established. This equation describes the main processes involved in the atmospheric evolution of particles: advection, emission, turbulent diffusion, deposition and gas-to-particle conversion (heterogeneous nucleation). Each term in the equation is discussed, and the methodology of implementation on a Lagrangian air quality model is presented, the Lagrangian air quality model has been used successfully for ozone concentration predictions in the Mexico City Metropolitan Area and still is used widely. The model uses a Operator Splitting approach to solve the diffusion equation, this lead to uncouple (making independent) some processes like advection, vertical diffusion, gas-phase chemistry and aerosol phase processes. The operator splitting makes easy to implement aerosol phase submodel into the numerical scheme. Coagulation and homogeneous nucleation have not taken into account in the model yet, but it is expected that uncertainty introduced would be small with respect to the total mass of the particles.