Downwind pollutant concentration from a point source follows a Gaussian plume model — particles spread laterally and vertically as they're carried by the wind, and ground concentration peaks at a certain downwind distance then falls off:
C(x,y,z) ∝ (Q / u) · exp(−y²/2σ_y²) · exp(−(z−H)²/2σ_z²)
σ_y, σ_z grow with downwind distance x (atmospheric turbulence spreading)
- Wind speed — advects the plume downwind faster and dilutes it more (concentration ∝ 1/u).
- Wind direction — deflects the whole plume left/right off the stack's downwind axis.
- Emission rate — source strength Q; more emitted particles per second means a denser, more visible plume.
- Scrubber toggle — models an exhaust-gas scrubber that removes ~70% of emissions before they leave the stack.
This Gaussian plume approach is the same model environmental engineers use (e.g. in EPA AERMOD-style tools) to predict ground-level pollutant concentrations downwind of factories and power plants and to site air-quality monitors.