This work develops a mass transport model coupled with a reactive kinetics model through the Finite element method, to simulate the behavior of pollutants substances in an urban atmosphere. In this work a Symmetrized Strang Split method is used to couple the mass transport model with the reactive kinetics model. This split method solves separately the diffu-sion, advection and reaction effects in a cascade process. The formulation of the mass transport process is showed and its results are compared with a fully coupled finite element method. This comparison is important to show the solution time and computational cost and validity of the split model.