- Explain how each of these variables: action, receptor and environment relate to environmental impact assessment and how they affect the concentration of a pollutant released by an action in the environment temporally or spatially: time, source, receptor, convection, dispersion, reaction.

For example: time time is the duration over which the impact assessment is modeled, and extends from 0 before the action (existing condition) to some time in the future after the action has occurred (impacted condition); time affects concentration for unsteady problems.