Here are some links to open source, high-quality articles about dispersion modeling from the online Citizendium encyclopedia:

http://en.citizendium.org/wiki/Air_pollution_dispersion_modeling

http://en.citizendium.org
/wiki/Air_pollution_dispersion_terminology

http://en.citizendium.org/wiki/Fundamentals_of_Stack_Gas_Dispersion

http://en.citizendium.org
/wiki/Accidental_release_source_terms

Milt Beychok