1. Air pollutants consist of chemicals in the atmosphere that have harmful effects on
living organisms and inanimate objects.
B. Why Do We Care?
1. We inhale 20,000 liters of air each day
a. Causes 150,000 premature deaths in the world each year (53,000 in the United
States); aggravates other disease
b. Three categories of health impact:
·Acute: pollutants bring on life-threatening reactions within a period of
hours or days; causes headache, nausea, and eye and throat irritation;
aggravate preexisting respiratory conditions such as asthma and
·Chronic: pollutants cause gradual deterioration of health over many
years, and exposures are relatively low
·Carcinogenic: some pollutants are suspected or known human
carcinogens. Benzene, a common component of air pollution, is known
as human carcinogen
c. U.S. human health costs from outdoor air pollution range from $40 to $50
billion per year (CDC).
2. Damage to Plants
a.Agriculture: crop loss estimated to be about $5 billion per year
b. Forests: significant damage to Jeffrey and Ponderosa Pine along entire
Western slope of the Sierra Nevada; in San Bernadino Mountains, the rate of
tree growth has declined 75%
c. Plants have increased susceptibility to disease and insect pests
3. Materials: damage to buildings, bridges, statues, books
4. Aesthetics: We don't like how it looks. We try to live in places without pollution,
thus contributing to the problem by commuting
II. Outdoor Air Pollutants
A. Primary Pollutants: Sources
B. Secondary Pollutants: Formation
Fig. 22.2 This is a simplified model of atmospheric cleansing by the hydroxyl radical. The first step is the photochemical destruction of ozone. The second step produces hydroxyl that reacts rapidly with many pollutants.
Fig. 22.3 The threshold level for harmful effects diminishes with increasing exposure time. It differs for each pollutant.
Fig. 22.4A Industrial smog, or gray smog, occurs where coal is burned and the atmosphere is humid.
Fig. 22.4B Photochemical smog, or brown haze, occurs where sunlight acts on vehicle pollutants.
Fig. 22.6 (a) Normally, air temperatures are highest at ground level and decrease at higher elevations. (b) A temperature inversion is a situation in which a layer of warmer air overlies cooler air at ground level.
III. Major Air Pollutants
A. What are the Major Pollutants?
1. Suspended Particulate Matter
2. Volatile Organic Compounds
3. Carbon Monoxide
4. Nitrogen Oxides
5. Sulfur Oxides
6. Lead and Other Heavy Metals
7. Ozone and Other Photochemical Oxidants
8. Air Toxics and Radon
B. What is the History of the Major Pollutants? How Did We Get Here?
1. Gray Smog
2. Photochemical Smog
Fig. 22.12 This figure shows the prime sources of the major air pollutants.
Fig. 22.13 Fuel combustion refers to fuels burned for electrical power generation and for space heating. Note especially the different contributions by transportation and fuel combustion, the two major sources of air pollutants.
Fig. 22.14 Improvements in Carbon monoxide and VOC emissions reflect Clean Air Act successes. Nitrogen oxides have not improved because little attention has been paid to them.
Fig. 22.15A Nitrogen oxides alone do not cause ozone and other oxidants to reach damaging levels; reactions with them are cyclic.
Fig. 22.15B When VOCs are present, reactions lead to accumulation of damaging compounds; ozone is the most injurious.
IV. Acid Deposition
A. Define Acid Deposition
B. Who and What are Affected?
1. Aquatic Ecosystems
3. Humans and Human Artifacts
C. Acids and Bases
1. Sulfur Dioxide
2. Nitrogen Oxide
a. Sulfur: volcanoes, sea spray, microbial
b. Nitrogen oxides: lightning, forest fires, microbial
a.Sulfur: power plants, industry, fossil fuels
b.Nitrogen oxides: power plants, industrial fuel combustion, transportation
Fig. 22.16 Emissions of sulfur dioxide and nitrogen oxides react with the hydroxyl radicals and water vapor in the atmosphere to form their respective acids, which come back down either as dry acid deposition or, mixed with water, acid precipitation.
Fig. 22.17 Numbers on the pH scale below 7 are acidic, above 7 are basic.
Fig. 22.18 Acid deposition occurs over the eastern U.S. and Canada.
Fig. 22.19 This figure shows the locations of the 50 largest sulfur dioxide emitters, all of which are utility coal-burning power plants.
Fig. 22.20 Acids may be neutralized by certain nonbasic compounds called buffers.
A buffer such as limestone (calcium carbonate) reacts with hydrogen ions as shown. Hence, the pH remains close to neutral despite the additional acid.
G. Solutions: Reducing Emissions
1. Output Control (pollution control)
b. Coal washing (uses large amount of and pollutes water)
c. Fluidized bed combustion (produces a waste ash that must be disposed of)
2. Input Control (pollution prevention)
b. Switch fuel
c. Build less polluting power plants
d. Cleaner burning gasoline
Fig. 22.21 This figure shows the average car emissions from vehicles, in grams per vehicle mile traveled, from 1965 to (estimated) 2000. Note numbers of vehicles on the road in the United States for 1980 to 1995
V. Pollutants and Atmospheric Cleansing or "Is All Waste a Problem?"
A. Factors that Determine If You Have Air Pollution
1. Quantity of Pollutants Produced (reduced by pollution prevention) and released
(reduced by pollution control technologies) into Atmosphere
2. Volume of Space into which the Air Pollutants are Dispersed
a. Inversion layers
3. Rate of Removal of Pollutants from Atmosphere
a. Dilution and dispersal
·Pollutant transport to the Arctic
·Pollutant transport to remote lakes and streams (also can be caused
when anadromous fish return from the ocean
b. Reaction with Hydroxyl Radical
c. Reaction of Soil Microorganisms Pollutants that Precipitate from Atmosphere
B. When is a Pollutant a Pollutant
VI. Indoor Air Pollutants
A. Types: benzene, formaldehyde, radon, cigarette smoke
B. Sources: off gassing from furniture, rugs, and building materials, dry cleaning,