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 SO 2 and SO 4 2-over the eastern United States during 1992 are presented. Comparisons of simulated daily SO 4 2-concentrations to observations had a rate of r 2 = 0.35-0.83 depending on season and location. The rate for weekly SO 4 2-wet deposition rates was r 2 = 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.
INTRODUCTIONDuring the 1970's, air quality measurements had shown that pollutant emissions could be transported over large distances, significantly influencing distant receptor concentrations. The realization of regional scale transport of pollutants, led to numerous air quality networks, models, and large scale field studies to relate the contributions from near as well as distant sources to receptor concentrations, i.e. to quantify the source receptor relationship. Many of the initial studies focused on sulfur oxides, and were design to attain better understandings of the physical/chemical processes governing regional scale transport. For example, in Europe, the OECD established the Long Range Transport of Air Pollutants (LRTAP) program in 1972 (1), and in the US, the Sulfate Regional Experiment (SURE) was conducted (2), along with numerous plume studies.Associated with these studies, were the development of models. The initial models tended to be simple, using aggregated and parameterized meteorology and rate coefficients to simulate the physical/chemical processes responsible for regional transport. These included trajectory models (3, 4), statistical models (5, 6), as well simple diffusion and box models (7,8). As the understanding of the atmospheric processes increased, these types of models were generalized to include processes such as non-linear chemistry and atmospheric diffusion (9, 10).During the 1980's, with the concern over acid rain, substantial effort was devoted to the development of elaborate Eulerian models, such as the Regional Acid Deposition Model (RADM) (11) and the Acid Deposition and Oxidant Model (ADOM) (12). These models attempt to simulate atmospheric processes, such as in cloud oxidation, with great detail. However, the data and computer resource needs have restricted ...