Page 124 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

88 part I The energy–atmosphere System
is caused by chemicals introduced into the atmosphere by humans. Since World War II, quantities of human-made chlorofluorocarbons (CFCs) have made their way into the stratosphere. The increased ultraviolet light at those alti- tudes breaks down these stable chemical compounds, thus freeing chlorine atoms. These atoms act as catalysts in re- actions that destroy ozone molecules.
chlorofluorocarbons (CFCs) (p. 74)
8. Why is stratospheric ozone so important? Describe the effects created by increases in ultraviolet light reaching the surface.
9. Summarize the ozone predicament, and describe treaties to protect the ozone layer.
10. EvaluateCrutzen,Rowland,andMolina’suseofthe scientific method in investigating stratospheric ozone depletion and the public reaction to their findings.
■ Distinguish between natural and anthropogenic pollut- ants in the lower atmosphere.
Within the troposphere, both natural and human-caused pollutants, defined as gases, particles, and other chemi- cals in amounts that are harmful to human health or cause environmental damage, are part of the atmosphere. Volca- noes, fires, and dust storms are sources of smoke and par- ticulates, also known as aerosols, consisting of suspended solids and liquid droplets such as pollens, dust, and soot from natural and human sources. We coevolved with natu- ral “pollution” and thus are adapted to it. But we are not adapted to cope with our own anthropogenic pollution. It constitutes a major health threat, particularly where people are concentrated in cities. Earth’s next atmosphere most accurately may be described as the anthropogenic at- mosphere (human-influenced atmosphere).
pollutants (p. 73)
aerosols (p. 73)
anthropogenic atmosphere (p. 76)
11. Describe two types of natural air pollution. What regions of Earth commonly experience this type of pollution?
12. What are pollutants? What is the relationship be- tween air pollution and urban areas?
■ Construct a simple diagram illustrating the pollution from photochemical reactions in motor vehicle exhaust, and describe the sources and effects of industrial smog.
Transportation is the major human-caused source for car- bon monoxide and nitrogen dioxide. Odourless, colour- less, and tasteless, carbon monoxide (CO) is produced by incomplete combustion (burning with limited oxygen) of
fuels or other carbon-containing substances; it is toxic be- cause it de-oxygenates human blood.
Photochemical smog results from the interaction of sunlight and the products of automobile exhaust, the sin- gle largest contributor of air pollution over urban areas in Canada and the United States. The nitrogen dioxide and volatile organic compounds (VOCs) from car exhaust, in the presence of ultraviolet light in sunlight, convert to the principal photochemical by-products—ozone, peroxyacetyl nitrates (PANs), and nitric acid. The volatile organic com- pounds (VOCs), including hydrocarbons from gasoline, surface coatings such as paint, and electric utility combus- tion, are important factors in ozone formation.
Ground-level ozone (O3) has negative effects on human health and kills or damages plants. Peroxyacetyl nitrates (PANs) have no known effect on human health but are particularly harmful to plants, including both agricultural crops and forests. Nitrogen dioxide (NO2) in- flames human respiratory systems, destroys lung tissue, and damages plants. Nitric oxides participate in reactions that produce nitric acid (HNO3) in the atmosphere, form- ing both wet and dry acidic deposition.
The distribution of human-produced industrial smog over North America, Europe, and Asia is related to coal- burning power plants. Such pollution contains sulfur di- oxide (SO2), which reacts in the atmosphere to produce sulfate aerosols, which in turn produce sulfuric acid (H2SO4) deposition. This deposition has detrimental effects on living systems when it settles on the landscape. Partic- ulate matter (PM) consists of dirt, dust, soot, and ash from industrial and natural sources.
Vertical temperature and atmospheric density dis- tribution in the troposphere can worsen pollution condi- tions. A temperature inversion occurs when the normal temperature decrease with altitude (normal lapse rate) reverses, and temperature begins to increase at some alti- tude. This can cause cold air and pollutants to be trapped near Earth’s surface, temporarily unable to mix with the air above the inversion layer.
carbon monoxide (CO) (p. 76) photochemical smog (p. 76)
volatile organic compounds (VOCs) (p. 76) nitrogen dioxide (NO2) (p. 77) peroxyacetyl nitrates (PANs) (p. 77) industrial smog (p. 80)
sulfur dioxide (SO2) (p. 80)
sulfate aerosols (p. 80)
particulate matter (PM) (p. 80) temperature inversion (p. 81)
13. What is the difference between industrial smog and photochemical smog?