To start off this blog on air pollution, we must know what the atmosphere is made of. Our atmosphere is 78% Nitrogen, 21% Oxygen, and 0.9% Argon, and 0.1% CO2, Water vapor, etc. There are four major layers as well:
- Troposphere: Greenhouse effect occurrence where heat gets trapped on the surface
- Stratosphere: Ozone layer filtering UV radiation
- Mesosphere: Coldest layer
- Thermosphere: Separated into two layers (lower is ionosphere and upper is exosphere)
Air pollution is when chemicals are present in the atmosphere that is in amounts that cause harm to life forms and structures. There are two types of pollutants: primary and secondary. Primary pollutants are formed from natural events or human actions. Secondary pollutants are from reactions between primary pollutants and other substances like the sunlight.
Let’s dive into urban pollution first!
Photochemical smog is a type of secondary pollutant that is formed in reactions between primary pollutants and the sun. Some examples are HNO3, PANs, and Tropospheric Ozone.
Industrial Smog contains sulfuric components like SO2 and sulfuric acid in the form of soot. Sulfur along with oil and coal reacts with O2 to form SO2. As SO2 reacts with O2 it forms SO3 and then reacts with Water Vapor forming H2SO4 (sulfuric acid), an example of a secondary pollutant.
Suspended particulates are solid particles like droplets that are released through burning fossil fuels. Thermal inversions occur when cold air is trapped under warm air, trapping pollutants with the air at the surface. Normally warm air should be rising to cold air and then cooler air. But in an inversion warm air is trapped in between two cold sections in the atmosphere and therefore the cold air does not rise.
Acid Deposition is when secondary acid pollutants descent to the surface of the Earth creating a buildup of acidic soil. It is usually composed of rain, acid, particulates, and fog. This causes soil acidification that lowers soil quality, lake acidification which lowers the pH of aquatic environments, and also acidic harm to living beings. It is usually transported through wind currents.
Next, indoor air pollutants!
Indoor air pollution is a bigger threat than outdoor pollution and is a huge cause of many respiratory problems in people that spend most of their lives in buildings. Poor ventilation and high indoor pollutants in a building are called the sick-building syndrome.
Tobacco smoke, asbestos, radon, formaldehyde, etc are all examples of indoor air pollutants and they can enter through cracks in the building, decomposing material under the building, and poor ventilation.
Methods of preventing air pollution include reducing fossil fuel use, reducing deforestation, and switching to renewable resources.
Cleanup is more complicated, for all methods end up cleaning the air but produces hazardous waste in another form. Electrostatic precipitators use electrodes to clean gas separating particulates. Other technologies include Baghouse filters, cyclone separators, and wet scrubbers. Car exhaust is a huge emitter of air pollutants and inspections as well as control devices to reduce pollutants help as well with prevention.
Transportation is a big producer of pollutants. Biking, walking, or using public transportation all reduce pollutants.
One important government law called the Clean Air Act from 1970,77, and 90 have helped. Six major air pollutants have decreased by 30%+ levels.
Thank you and stay tuned for the next talk about water pollution!
Editor at StemTalksNC