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Understanding Air Pollution: Types, Sources, and Effects

Learn about primary and secondary air pollutants, their sources, and the detrimental environmental effects of air pollution on human health, plants, and animals. Explore how atmospheric stability and wind dispersion impact the transport of pollutants in the air.

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Understanding Air Pollution: Types, Sources, and Effects

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  1. Air Pollution 1 Omowumi Alabi Department of Geosciences University of Missouri-Kansas City Kansas City, MO

  2. Atmospheric Composition The primary components of air are nitrogen (N2), oxygen (O2) and water vapor (H2O). About 99 percent of dry air is nitrogen (78%) and oxygen (21%). The remaining percent includes trace quantities of substances such as carbon dioxide (CO2), methane (CH4), hydrogen (H2), argon (Ar) and helium (He).

  3. What is an Air Pollutant? A substance that is - not naturally found in the air - wrongly located or - in high enough concentrations such that it produces a detrimental environmental effect.

  4. Detrimental Environmental Effects The two basic physical forms of air pollution are • Gases • Particulate Matter These can affect -the health of humans (primarily the respiratory system) -the health of plants and animals -non-living materials

  5. Types of Pollutants Pollutants can also be classified as either primary pollutants or secondary pollutants. A primary pollutant is one that is emitted into the atmosphere directly from the source of the pollutant and retains the same chemical form i.e. the ash produced by the burning of solid waste. The effect of primary pollutants is most pronounced in the immediate vicinity of the source. A secondary pollutant is one that is formed by atmospheric reactions of precursor or primary emissions. Secondary pollutants are not emitted. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ozone. Secondary pollutants take time to form and may not affect the immediate vicinity of the pollutant source.

  6. Sources of Air Pollutants Asource of air pollution is any activity that causes pollutants to be emitted into the air. Human-generated sources of air pollution are categorized in two ways: mobile and stationary sources. Mobile sources of air pollution include most forms of transportation such as automobiles, trucks, and airplanes. Stationary sources of air pollution consist of non-moving sources such as power plants and industrial facilities

  7. Types & Sources of Air Pollutants

  8. Stationary Sources Air pollution from stationary sources is produced by two primary activities: - stationary combustion of fuel such as coal and oil at power generating facilities -the pollutant losses from industrial processes such as refineries and chemical manufacturing facilities.

  9. Transport & Dispersion of Air Pollutants On the local level, the primary factors affecting transport and dispersion of pollutants are wind and atmospheric stability.

  10. Wind • the natural horizontal motion of the atmosphere • caused by differences in pressure in the atmosphere. • air moves from high pressure areas to low pressure areas

  11. Effect of Wind on Dispersion of Pollutant • Wind speed can greatly affect the pollutant concentration in a local area. • The higher the wind speed, the lower the pollutant concentration. • Wind dilutes pollutants and rapidly disperses them throughout the immediate area.

  12. Atmospheric Stability • refers to the vertical motion of the atmosphere • Unstable atmospheric conditions result in a vertical mixing, thereby promoting dispersal of polluted air

  13. Unstable Atmosphere Promotes Dispersal of Polluted Air Typically, the air near the surface of the earth is warmer in the day time because of the absorption of the sun's energy. The warmer and lighter air from the surface then rises and mixes with the cooler and heavier air in the upper atmosphere causing unstable conditions in the atmosphere. This constant turnover also results in dispersal of polluted air.

  14. Stable Atmospheric Condition Discourages Dispersal of Polluted Air Stable atmospheric conditions usually occur when warm air is above cool air and the mixing depth is significantly restricted. This condition is called temperature (or thermal) inversion. An inversion can prevent the rise and dispersal of pollutants from the lower layers of the atmosphere and cause localized air pollution problem.

  15. Unstable Atmosphere • Temperature decreases with height • Vertical air motion is promoted • Horizontal air motion is promoted • Promotes dispersion • Stable Atmosphere • Temperature increases with height • Vertical air motion is restricted • Horizontal air motion is restricted • Discourages dispersion

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