Multi-plume aerosol dynamics and transport model for urban scale particle pollution

The Multi-plume Aerosol dynamics and Transport (MAT) model has been developed to study the dynamics of the particle size distribution in urban environments. The MAT model uses a novel multi-plume scheme for vertical dispersion and routines of the aerodynamics models AERO3. It treats the processes: emission from a near ground source, dilution with background air, deposition, coagulation and condensation. The employed plume approach is computationally efficient compared to grid models and is therefore suitable for calculating longer time series. The treatment of the different processes in the model was validated against analytical solutions and literature data and later the full model was applied to a field data set from the Copenhagen area. The range of changes in particle concentration including all processes compared to an inert treatment of particles lies between 13% and 23% of loss in total number concentration and 2% loss and 8% gain for the total volume concentration. This agrees well with measurements in Copenhagen that indicated total number concentration (ToN) losses in the range of 15–30% between kerbside and urban rooftop level. The model also reproduces the shift of the maximum in the size distribution to slightly larger diameters between street and urban rooftop level. Because of the uncertainties in the parameters describing the different processes and their similar influence on the particle size distribution, it is possible to obtain similar results with different parameter combinations. More research and model validation is needed to narrow the range of possible input parameters and model assumptions for this type of modelling.