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Gaussian dispersion of low-weight volatile fatty acids from a ground-level area source was assessed using STINK (a research-grade, Gaussian plume model from Australia) and AERMOD (an AMS/EPA regulatory model). The goal of this research was to determine if these models could effectively utilize a back-calculation methodology to reasonably assess the emission rate and near-source-dispersion of odorous compounds. VFAs were sampled at six receptors using thermal desorption tubes in one experiment and solid phase microextraction (SPME) fibers in a second experiment. Measured concentrations, when compared with those predicted by STINK and AERMOD, showed good agreement. However, better prediction by AERMOD, compared to STINK, was observed for the experiments involving SPME sampling. The use of AERMOD, combined with the back-calculation approach for the dispersion modeling of odorous constituents, appears promising.

The performance of AERMOD was also assessed using meteorological conditions averaged over various time intervals. It was assumed that the average conditions observed during 1, 5, 15 and 30 minute intervals prevailed for the entire 1-hr modeling period. This showed that selection of an appropriate averaging time for meteorological data is important for dispersion modeling when forced to make assumptions about constant meteorological conditions as in the case of Gaussian models like AERMOD.