Modeling the Removal of two Gaseous Pollutants and a Mixture of Particulate Matters formed by these Gases in a Rain System

Abstract

In this paper, a nonlinear mathematical model is proposed and analyzed to study the removal of two gaseous pollutants and the
mixture of particulate matters formed separately by these two gases from the atmosphere of a city by rain. It is assumed that particulate matters are formed in the atmosphere by chemical transformations of two gaseous pollutants emitting in the atmosphere in presence of rain. The atmosphere, during rain, is assumed to consist of six interacting phases namely, the raindrops phase, the two phases of gaseous pollutants, their absorbed phases and the phase of the mixture of particulate matters. It is also assumed that gaseous pollutants are removed from the atmosphere by the process of absorption while the particulate matters are removed only by the process of impaction with different removal rates. By analyzing the model, it is shown that under appropriate conditions, these gaseous pollutants and particulate matters are removed from the atmosphere and their equilibrium levels, remaining in the atmosphere, would depend mainly upon the rates of emission of pollutants, growth rate of raindrops and the rate of raindrops falling on the ground, etc. It is found that if the rates of transformations of gaseous pollutants into particulate matters and the rainfall are very large, then these pollutants may be removed completely from the atmosphere. The numerical simulations performed support the analytical findings.