Semi-empirical modeling of CO2 and particles in moving buses

Two semi-empirical time-series mathematical models were developed to describe mass CO2 and PM2.5 concentrations in metropolitan buses under realistic conditions. A CFD (Computational Fluid Dynamics) approach was utilized to ascertain the pressure distribution on a specific bus surface traveling at different speeds. The simulation results indicated that the differential pressure of the front door and the rear door gaps varied from −0.652 Pa to −98.687 Pa and − 0.083 to −13.19 Pa, respectively, under driving speeds ranging from 5 to 60 km/h. To improve accuracy, several modifications were made to the mathematical models using field measurement data. Thus, this study quantified the pressure difference values at different locations and provided an accurate prediction model for typical pollutants by comprehensively considering the influence of multiple factors, thereby allowing for a better understanding of the dispersion and exposure levels of pollutants in buses over time.