What 3d engine should I choose?

Question

I'd like to do some air pollution simulation in three dimension. Some key features are:

1. large amount of data
2. better if it supports particle systems
3. better if it combines terrains and buildings and air. That is, there are interactions between them.
4. better if it can be run on web.

EDIT:

Language can be C++, C#, or python. Engines I know so far are like OpensSourceGraph, Ogre, Open Inventor, but I don't know the exact differences among them. Unity3D is a good choice for web 3D, but I'm not sure if it supports large amount of data. Besides, I have tried with OpenSim for a while, but it seems to not support particle systems and the data structure is not flexible enough.