Chapter 12: Air

Section 1: What Causes Air Pollution Clean air consists mostly of nitrogen and oxygen gas as well as very small amounts of argon, carbon dioxide, and water vapor. When harmful substances build up in the air to unhealthy levels, the result is air pollution. Most air pollution is the result of human activity. Some does come from natural sources such as volcanic eruptions.

Primary and Secondary Pollutants A pollutant that is put directly into the air by human activity is called a primary pollutant. Soot from smoke is an example. Secondary pollutants form when primary pollutants react with other primary pollutants or with naturally occurring substances such as water vapor. Ground level ozone is an example. This happens when UV rays cause emissions from vehicles to react with oxygen in the atmosphere.

Sources of Primary Air Pollution Household products, power plants, and motor vehicles are sources of primary air pollutants such as carbon monoxide, nitrogen oxide, sulfur dioxide, and chemicals called volatile organic compounds (VOCs). Carbon monoxide is an important component in the exhaust from vehicles. Nitrogen oxides come from vehicles and coal burning power plants. Sulfur dioxide forms when coal and oil are burned. Power plants, refineries, and metal smelting are contributors as well. Most VOCs are from vehicles and gas station spillage

The History of Air Pollution The problem is not new :( 2,000 years ago, Seneca, a Roman philosopher, complained about the foul air in Rome. In 1273, King Edward I ordered the burning of sea coal illegal. Air quality is worse today because of industrial societies burn large amounts of fossil fuels. Most air pollution comes from motor vehicles and industry.

Motor Vehicle Emissions Almost 1/3 of our air pollution from gasoline burned by vehicles. In 1998 Americans drove over 2.6 trillion miles and 90% of that was passenger vehicles.

Controlling Vehicle Emissions The Clean Air Act, passed in 1970, gives the EPA the authority to regulate vehicle emissions in the U.S. The EPA called for the gradual elimination of lead in gasoline. As a result, lead pollution has been reduced by more than 90%. Catalytic converters, which are now required, clean exhaust gases of pollutants before the pollutants are able to escape the tailpipe. Cars today burn fuel 35% more efficiently and with 95% fewer emissions.

California Zero Emission Vehicle Program In California, vehicle emissions account for more than half of the ozone and particulate matter that pollutes the air. In 1990, the state's Air Resource Board established the Zero Emission Vehicle (ZEV) program. Battery powered vehicles are the only true ZEVs at the moment. There are two types of partial ZEVs. Hybrids which are powered by both battery and gasoline and methanol fuel cell cars (which are still developmental prototypes).

Industrial Air Pollution Many industries and power plants burn fossil fuels to produce energy. Burning fossil fuels releases sulfur dioxide and nitrogen oxides into the air. Power plants emit at least 2/3 of all sulfur dioxide and more than 1/3 of all nitrogen oxides that pollute the air. Dry cleaning also produces VOCs as do oil refineries, chemical manufacturing plants, furniture refinished, and automobile repair shops.

Regulating Air Pollution from Industry The Clean Air Act requires many industries to use scrubbers to remove some of the more harmful substances that would otherwise pollute the air. A scrubber is a machine that moves gases through a spray of water to dissolve many pollutants. Electrostatic precipitators are used in cement factories and coal burning power plants. Gas containing dust particles are blown through an electrically charged chamber causing the particles to stick together and the sides of the chamber. Clean gas is released and particle can be collected and removed. Electrostatic precipitators remove 22 million metric tons of ash every year.

Smog When air pollution hangs over urban areas and reduces visibility, it is called smog. Smog results from chemical reactions that involve sunlight, air, automobile exhaust, and ozone.

Temperature Inversions The circulation of air in the atmosphere usually keeps air pollution from reaching dangerous levels. During the day, the sun heats the surface of the Earth and air near the surface. Warm air rises through the cooler air above it carrying pollutants away from the ground. Sometimes pollution is trapped near the Earth's surface. Usually air temperature decreases with altitude, but sometimes a temperature inversion occurs. When this happens, the warmer air keeps the cooler air at the surface from moving upward trapping pollutants in the cooler air closer to the surface. Cities in valleys have a greater chance of this occurring.

Copy now, answer later :) Name five primary air pollutants, and give important sources for each. Name the two major sources of air pollution in urban areas. Describe the way in which smog forms. Define temperature inversion. Explain how temperature inversion traps pollutants near Earth's surface. Should automobile manufacturers be made to adhere to quotas of zero-emission vehicles set by states, even if the quota causes automakers to lose revenue?