About the Site
While Smog City 2 is an imaginary place, its pollutant emissions are similar to those in many large cities in the United States. The ozone and particle pollution levels in Smog City 2 are estimated by simulating the air quality over an imaginary city using a computer model. The model creates a box over the area to represent the atmosphere above Smog City 2. Air quality conditions in the box are simulated to account for both human influences and natural factors that affect ground-level concentrations of ozone and particle pollution.

Each simulation represents one day. In the morning, the air in the box is usually healthy. With each passing hour, pollutants from human activities (such as industry and cars and trucks) and from natural sources (like trees and plants) are emitted into Smog City 2's atmosphere. The model takes into account variations in human activity, such as morning and evening rush-hour traffic. Emissions are subjected to movement, mixing, and dilution, which are influenced by weather characteristics such as wind speed, sunlight, and temperature. The computer model accounts for these meteorological effects to determine the rate of chemical reactions that cause ozone and particle pollution levels to increase or decrease.

To develop relationships among weather, population, emissions levels, fuel sources, and air quality in Smog City 2, 18,900 model simulations were run. The model uses 86 chemical reactions and 43 chemical compounds (34 gases and 9 types of particles) to simulate the formation and removal of ozone and particle pollution in Smog City 2's atmosphere.

Relationships between ground-level ozone, emissions, and weather conditions are very complex. Smog City 2 is based on a simplified model of complex atmospheric processes. It illustrates general behavior of air pollution processes, and should not be used for quantitative purposes or in planning of control strategies.