Dispersion modeling is the process of using sophisticated mathematical computer models to estimate how pollutants are dispersed in the atmosphere. This modeling is often used in air permitting to estimate the potential impacts of a proposed facility on nearby air quality. Dispersion modeling is typically done to ensure a new or modified facility does not cause or contribute to a violation of the National Ambient Air Quality Standards (NAAQS) or other standards, to assess the potential health risks of air pollution, or to protect areas of particular environmental concern. The two most commonly used dispersion models are AERMOD and CALPUFF.
AERMOD is a dispersion model that is based on Gaussian plume dispersion and incorporates air stability, wind speed, and atmospheric turbulence information in its predictions. AERMOD is the preferred dispersion model for many regulatory applications and is typically used for short-range modeling (up to 50 kilometers from a facility). CALPUFF is a Lagrangian dispersion model that uses puff dispersion and incorporates information on atmospheric stability, wind speed, and atmospheric turbulence in its predictions. CALPUFF is typically used for longer-range modeling than AERMOD (beyond 50 kilometers from a facility).
More specialized modeling, like visibility modeling, can be done using other models. The PLUVUE II visibility model is based on the premise that atmospheric conditions (e.g., cloud cover, humidity, etc.) and air pollution can influence light scattering and absorption. The model then uses these estimations to predict the visibility conditions under given conditions. Visibility modeling can be a useful tool to protect some of the most important vistas, like national parks, from air-pollution-related visibility degradation.
Tipple Consulting can help you select and execute the appropriate model for your facility. Contact us for more.