Regional Simulation of Atmospheric Pollutants with the CAPITA Monte Carlo Model.

Presented is a Monte Carlo model for the simulation of regional scale transport, transformation, and dry and wet removal. The model was newly re-designed in a modular framework, separating the emissions, transport, and kinetics calculations. The transport module employs a quantized Monte Carlo technique for the simulation of atmospheric boundary-layer physics. Kinetic processes are simulated using rate equations where the rate coefficients are dependent upon meteorological variables, and consequently fluctuate in space and time. The rate coefficient equations are determined via a tuning process comparing simulated to observed measurements. Results from simulations of SO2 and SO42- over the eastern United States during 1992 are presented. Comparisons of simulated daily SO4 2- concentrations to observations had a rate of r2 = 0.35-0.83 depending on season and location. The rate for weekly SO42- wet deposition rates was r2 = 0.5-0.95. The utility of the model to investigate the source receptor relationship is demonstrated by explicitly examining the role of emission rates, transport, and kinetic processes in the attribution of sulfur dioxide and sulfate at a receptor in Massachusetts during the summer of 1992.