How do you make a model on any type of pollution for a school science exibition?

Answer 1

You could make a model of a pond and the types of life that live in and near it, showing how man-made products and litter destroy water habitats.

You could build a model of a beaver's dam and show how plastic bottles and plastic bags harm the beaver's habitat.

Answer

You can either do the diminution of pollution from a source with distance, This is what happens with a smoke plume leaving a source and gradually getting less concentrated with distance. it can be represented with a 2D representation of a cone (or triangle ) of the areas covered by the plume as they leave the source with the pollution getting less dense as distance increases.

Alternately it can be represented as a bio-accumulation model where each level of predator concentrated the pollution from the species it eats.