From your question, I cannot give a definitive recommendation. There are several aspects to consider, when you select the appropriate dispersion model. Do you have point sources or do you want to model traffic emissions? Is a steady state model sufficient for your purpose?

Without having used the model myself, I'd say you could use AERMOD for an urban dispersion situation, maybe also CALPUFF.

ISCST is a plume model that does not take complex terrain into account. Please check the following link to get more insight into these models.

https://www.epa.gov/scram/air-quality-dispersion-modeling-preferred-and-recommended-models

I recommend AERMOD, I do not recommend it has been the best but I have used it a couple of times and it doing well

Hi Leila Khazini,

There is no a best model, but the most suitable for your purpose. There are several variables in the choice of a model that better fit to the region of study. USEPA recommends some models but you have to knowthe features of each model and the characteristcs of sources and the region. Is a complex terrain? Are there different types of sources? Do you want to include dry and wet removal processes? Chemical reactions must be considered? Aermod and Calpuff are models recommended by USEPA most cited in the literature. I suggest you read articles that have used both models, observing the description of terrain and of the sources, and then choose the most appropriated for your project.

HI

ADSM IS A Practical software FOR Air pollution modeling

You can see the link below

http://www.environment-lab.ir/environment-software/327-adms-software