Comparative Analysis of the Results from Frequently Applied Methodologies and Approaches for Dispersion Modeling

Abstract

Accurate air quality assessment through dispersion modeling is crucial for regulatory compliance and environmental management, particularly in complex industrial areas. In Bulgaria, the software package PLUME is frequently used, often employing an unofficial instruction from the Ministry of Environment and Water (MEW) to merge multiple emission sources into a single “Virtual Emission
Device” (VED) when their number exceeds ten. This study performs a critical comparative analysis of this approach. The annual average concentrations of NOx (nitrogen oxides) and PM10 (particulate matter) from sources in the industrial zone of Devnya, Bulgaria, were modeled using three distinct methods: PLUME with the MEW’s VED instruction; PLUME applying the  methodologically sound superposition principle; and the advanced regulatory model Breeze AERMOD as a benchmark.

The results reveal significant discrepancies. The VED approach was found to severely underestimate both the maximum concentration values and the spatial extent of pollution impacts. For PM10, the maximum annual concentration calculated using VEDs was 2.36 μg m-3, whereas the superposition method yielded a value of 13.09 μg m-3. Furthermore, the analysis shows that the PLUME model’s inherent limitations, such as its inability to process hourly meteorological data or account for terrain, lead to unrealistic “feather-like” pollutant distributions, in contrast to the more precise results from Breeze AERMOD.
The study concludes that the VED method is flawed, introduces substantial errors, and contradicts established dispersion principles. For accurate and reliable air quality assessments required for regulatory purposes such as Environmental Impact Assessments and Integrated Permits, the use of advanced models like Breeze AERMOD is essential.