An urban trajectory model for sulfur in Asian megacities: model concepts and preliminary application

This paper explores the adaptation of a regional Lagrangian approach for making long-term simulations of SO2 and sulfate ambient concentrations at the resolution needed for health effects risk assessment in Asian megacities and their surroundings. A Lagrangian trajectory model (UR-BAT) is described which simulates transport and diffusion of sulfur within and near urban areas, originating from area and major point sources. The long-range contribution is accounted for by the ATMOS model, simulating all Asian sources. The model has been applied to Beijing and Bombay, by using preliminary emission figures, and the results have been compared with available monitoring data. The computed concentrations in different cities are in the correct range, indicating the potential use of the model in an integrated assessment framework such as RAINS-Asia.