Understanding Smog, Air Pollution, and Thermal Inversion
1. What is Smog? Smog is a portmanteau of “smoke” and “fog.” It describes air pollution in cities, resulting from specific weather conditions combined with pollutants.
2. What is Industrial Smog? Industrial smog was common in cities with heavy industry that burned large amounts of coal and heavy oil with high sulfur content. This created a mixture of sulfur dioxide, sulfuric acid droplets, and solid particles, resulting in a heavy, polluted fog harmful to health and infrastructure.
3. What is Photochemical Smog? Photochemical smog is a mixture of primary pollutants (NOx and volatile hydrocarbons) and secondary pollutants (ozone, peroxyacyl, hydroxyl radicals, etc.) formed by sunlight-driven reactions.
4. What are the Effects of Photochemical Smog? This mixture darkens the atmosphere, leaving a reddish-brown haze loaded with harmful ingredients for living organisms and materials.
5. Where Does This Contamination Occur? This type of pollution occurs in cities worldwide, especially in dry, warm, and sunny climates with many vehicles. Summer is the worst season.
6. What is a Gas? A gas is a substance that flows in its normal state and expands indefinitely to fill a container completely.
7. What are Vapors? Vapors are the gaseous state of a substance that is normally solid or liquid.
8. What are Aerosols, Dust, Smoke, and Metallic Smoke?
- Aerosols: Toxic chemical substances present in the atmosphere.
- Dust: Airborne solid particles from physical disintegration processes.
- Smoke: Airborne solid particles from incomplete combustion processes.
- Metallic Smoke: Airborne solid metal particulate generated in a condensation process from the gaseous state, based on sublimation or volatilization of the metal, accompanied by a chemical oxidation reaction.
9. What is Dew? Airborne liquid droplets generated by condensation from a gaseous state or disintegration of a spray liquid state (boiling, etc.). Droplet sizes range from 0.01 to 10 μm, some visible to the naked eye.
10. What is Fog? Airborne liquid droplets visible to the naked eye, caused by condensation of the gaseous state. Their size ranges between 2 and 60 μm.
11. What is Thermal Inversion? A natural phenomenon involving heat energy exchange between the Earth’s crust and atmospheric air layers. It prevents the dispersion of air pollutants, increasing adverse consequences when pollutants are present.
12. What Problem Does Inversion Bring? It prevents air currents because the colder, denser top layer acts like a lid, preventing pollutant dispersion.
13. How are Air Layers Stratified by Temperature? Normally, atmospheric layers have cooler air above and warmer air below, causing the warmer air to rise and cool.
14. What are the Main Causes of Thermal Inversion?
- Advection-radiation
- Subsidence phenomena
- Frontal systems
15. Explain Thermal Inversion by Thermal Gradient. The thermal gradient refers to the decrease of temperature with altitude. Because the heat source is radiation from the ground, the air is colder further from the source.
16. What is Subsidence Inversion? Occurs when an increase in gas volume implies expansion at the expense of internal energy consumption, resulting in a temperature decrease. Conversely, compression increases internal energy, resulting in warming, a phenomenon known as subsidence.