Abstract
A short-term steady state Gaussian-based air pollutant dispersion model has been developed and named HAWA. It is based on the U.S. Environmental Protection Agency (USEPA) Industrial Source Complex Short Term 3 (ISCST3) model. This model was developed to evaluate pollutant concentrations from elevated point sources (e.g. stacks) up to 10 sources in moderate terrain. HAWA generates text file and Matlab® file as output. Microsoft© Visual C++® 6.0 was used in writing the model in contrast to FORTRAN that was used to program ISCST3. The former was used to develop a user-friendlier model compared to other models that are difficult to use. Three configurations are modeled using HAWA. Stacks of different heights aligned along the x-axix, y-axis, in L vonfigurations produced different pollutant distribution trend, which illustrates the significant relation of stack height to pollutant dispersion of multiple stacks. Based on three stacks configuration, 50 m stack height for all 3 stacks will likely cause the highest ground level concentration of pollutants while 100 m stack for all three stacks will cause the lowest. Distnce of 500 m between same stack heights (aligned along the x-axis) is enough to not mix the pollutants coming from each stack, at least not at high concentration (>10 µg/m3). Closer distances warrant the stacks to have proper stack height (twice the height of a lower stack). The concentration of pollutants from a stack directly behind an upwind stack will add up to the pollutants emitted by the stack in front resulting in higher concentration downwind (aligned along the y-axis). It is advisable then to have a stack configuration where the either of the inline stacks is higher (2 times the height of the shorter stacks) than the other stack or both stack designed using the best stack height. All three stacks of same stack height (except very tall stacks) in-line will cause the highest ground level concentration, so this type of stack configuration is undesirable.
