air quality

air quality

Pollutants include materials that are naturally occurring but are added to the atmosphere so that they are there in larger quantities than normal. Pollutants may also be human-made compounds that have never before been found in the atmosphere. Pollutants dirty the air, change natural processes in the atmosphere, and harm living things.

photochemical smog

Photochemical smog, a different type of air pollution, first became a problem in Southern California after World War II. The abundance of cars and sunshine provided the perfect setting for a chemical reaction between some of the molecules in auto exhaust or oil refinery emissions and sunshine (Figure 1.2). Photochemical smog consists of more than 100 compounds, most importantly ozone. Smog over Los Angeles as viewed from the Hollywood Hills.


the clean air act

Terrible air pollution events in Pennsylvania and London, in which many people died, plus the recognition of the hazards of photochemical smog, led to the passage of the Clean Air Act in 1970 in the United States. The act now regulates 189 pollutants. The six most important pollutants regulated by the Act are ozone, particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and the heavy metal lead. Other important regulated pollutants include benzene, perchloroethylene, methylene chloride, dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds. What is the result of the Clean Air Act? In short, the air in the United States is much cleaner. Visibility is better and people are no longer incapacitated by industrial smog. However, despite the Act, industry, power plants, and vehicles put 160 million tons of pollutants into the air each year. Some of this smog is invisible and some contributes to the orange or blue haze that affects many cities.

problems with air quality

Air pollution started to be a problem when early people burned wood for heat and cooking fires in enclosed spaces such as caves and small tents or houses. But the problems became more widespread as fossil fuels such as coal began to be burned during the Industrial Revolution.


Air pollution started to be a problem when early people burned wood for heat and cooking fires in enclosed spaces such as caves and small tents or houses. But the problems became more widespread as fossil fuels such as coal began to be burned during the Industrial Revolution (Figure 1.1). The 2012 Olympic Games in London opening ceremony contained a reen- actment of the Industrial Revolution - complete with pollution streaming from smokestacks.


regional air quality

Air quality in a region is not just affected by the amount of pollutants released into the atmosphere in that location but by other geographical and atmospheric factors. Winds can move pollutants into or out of a region and a mountain range can trap pollutants on its leeward side. Inversions commonly trap pollutants within a cool air mass. If the inversion lasts long enough, pollution can reach dangerous levels. Pollutants remain over a region until they are transported out of the area by wind, diluted by air blown in from another region, transformed into other compounds, or carried to the ground when mixed with rain or snow. Table 1.1 lists the smoggiest cities in 2013: 7 of the 10 are in California. Why do you think California cities are among those with the worst air pollution? The state has the right conditions for collecting pollutants including mountain ranges that trap smoggy air, arid and sometimes windless conditions, agriculture, industry, and lots and lots of cars. Rank 1 2 3 4 5 6 7 8 9 10 City, State Los Angeles area, California Visalia-Porterville, California Bakersfield-Delano, California Fresno-Madera, California Hanford-Corcoran, California Sacramento area, California Houston area, Texas Dallas-Fort Worth, Texas Washington D.C. area El Centro, California

instructional diagrams

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all air pollutants are human-made materials.

a) true

-->  b) false

air pollution became more widespread as fossil fuels began to be burned for energy during the

a) american revolution

b) green revolution

-->  c) industrial revolution

d) russian revolution

air pollution is

a) released directly into the air.

b) the result of chemical reactions.

c) still occurring despite the implementation of the clean air act.

-->  d) all of these.

photochemical smog is common in southern california because of

-->  a) the abundance of cars and sunshine.

b) the high number of industries.

c) the intensive agriculture.

d) the dust that blows off the deserts in the east.

as of 2013, the clean air act regulates this many pollutants.

-->  a) 89

b) 189

c) 289

d) 389

as of 2013, most of the smoggiest cities in the united states were in california.

-->  a) true

b) false

passage of the clean air act of 1970 was a response to

a) air pollution events in which many people died.

b) awareness of the dangers of photochemical smog.

c) recognition that excess carbon dioxide was raising global temperatures.

-->  d) a & b

the six important pollutants that were regulated in the clean air act of 1970 are

a) carbon dioxide, methane, carbon monoxide, cfcs, water vapor and nitrous oxide

b) benzene, perchloroethylene, methylene chloride, dioxin, and asbestos.

-->  c) ozone, particulates, sulfur dioxide, nitrogen dioxide, carbon monoxide and lead.

d) cadmium, mercury, lead, chromium, sulfur and silver compounds.

parts of california are especially susceptible to trapping smog due to its

a) abundant mountain ranges

b) inversions

c) dry and wind-free conditions

-->  d) all of these

smog can build up on a winter day because inversions trap pollutants in a cool air mass.

-->  a) true

b) false

diagram questions

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