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Lecture 21

11:375:101 Lecture Notes - Lecture 21: Indoor Air Quality, Mucus, Myocardial Infarction


Department
Environmental Sciences
Course Code
11:375:101
Professor
Craig Phelps
Lecture
21

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Air Pollution
Chapter 18: Air Pollution and Ozone Depletion
18-1: What is the Nature of the Atmosphere?
The two innermost layers of the atmosphere
Troposphere - supports life
Stratosphere - contains the protective ozone layer
The Atmosphere Consists of Several Layers
Atmosphere - thin blanket of gases surrounding the Earth
Density - number of gas molecules per unit of air volume
Density decreases as you move higher in the atmosphere
Air Movements in the Troposphere Play a Key Role in Earth’s Weather and
Climate
Troposphere
75-80% of Earth’s air mass
Closest to Earth’s surface
Composition of gases
78% nitrogen; 21% oxygen
Rising and falling air currents and greenhouse gases play a
major role in weather and climate
The Stratosphere Is Our Global Sunscreen
Stratosphere
Similar composition to the troposphere except that it contains:
Much less water
Ozone layer (O3)
Filters 95% of harmful UV radiation
Allows life to exist on land
18-2: What Are the Major Outdoor Pollution Problems?
Pollutants mix in the air to form smog
Primarily as a result of burning coal and photochemical smog
Caused by emissions from motor vehicles, industrial facilities, and power
plants
Air Pollution Comes from Natural and Human Sources
Air pollution - presence of chemicals in the atmosphere
Concentrations high enough to harm organisms, ecosystems,
human-made materials, and to alter climate
Natural sources
Dust blown by wind
Pollutants from wildfires and volcanoes
Volatiles organics released by plants
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Human Sources
Mostly in industrialized and/or urban areas
Stationary sources -power plants and industrial facilities
Mobile sources - motor vehicles
Some Pollutants in the Atmosphere COmbine to Form Other Pollutants
Primary pollutants
Emitted directly into the air
Secondary pollutants
From reactions of primary pollutants
What Are the Major Outdoor Air Pollutants?
Carbon Oxides
CO; CO2
Nitrogen oxides (NO) and Nitric Acid (HNO3)
Acid deposition; photochemical smog
Sulfur dioxide (SO2) and Sulfuric Acid (H2SO4)
Particulates
Suspended particulate matter
Ozone
Volatile organic compounds (VOCs)
Methane
Burning Coal Produces Industrial Smog
Chemical composition of industrial smog
Sulfur dioxide, sulfuric acid, and suspended solid particles
Formed from the burning of fossil fuels
Carbon monoxide, carbon dioxide,and soot result
Sublight Plus Cars Equals Photochemical Smog
Photochemical smog
VOCs + NOX + Heat + Sunlight yields:
Ground level O3 and other photochemical oxidants
Aldehydes
Other secondary pollutants
Several Factors Can Decrease or Increase Outdoor Air Pollution
Outdoor air pollution may be decreased by:
Settling of particles due to gravity
Rain and snow
Salty sea spray from the ocean
Winds
Chemical reactions
Outdoor air pollution may be increased by:
Urban buildings
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