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What Causes Air Pollution?

• Air pollution: the contamination of the atmosphere by wastes or natural particulates

• Most the result of human activities

• Natural: includes dust, pollen, spores, sulfur dioxide from volcanic eruptions.

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• Primary pollutant: put directly into the atmosphere by human or natural activity.

– Ex: soot from smoke.

• Secondary pollutant: forms in the atmosphere by chemical reactions with primary air pollutants, natural components in the air, or both.

– Ex: ground-level ozone.

– emission from cars react with the UV rays and then mix with the oxygen in the atmosphere.

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Sources of Primary Air Pollutants

• Vehicles, gas stations, household products

– human-made emissions of VOCs (volatile organic compounds )(VOCs).

• Power plants, refineries, and metal smelters

– sulfur dioxide emissions

• Vehicles and coal-burning power plants

– major sources of nitrogen oxide emissions, carbon monoxide

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• Fine particles enter the

– air from fuel burned by vehicles and coal-burning power plants.

• Course particles

– cement plants, mining operations, incinerators, wood-burning fireplaces, fields, and roads.

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The History of Air Pollution

• Not a new phenomenon. Whenever something burns, pollutants enter the air.

• The world’s air quality problem is much worse today because modern industrial societies burn large amounts of fossil fuels.

• Almost 1/3 of our air pollution comes from gasoline burned by vehicles.

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Controlling Vehicle Emissions

• The Clean Air Act, 1970 gives the Environmental Protection Agency (EPA) the authority to regulate vehicle emissions in the United States.

– gradual elimination of lead in gasoline

– catalytic converters, clean exhaust gases of pollutants

• 1990, the California Air Resources Board established the zero-emission vehicle (ZEV) program

– by 2016, 16% of vehicles sold in Ca. required to be ZEV

– ZEV programs in Maine, Massachusetts, New York, and Vermont.

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Industrial Air Pollution

• Power plants that produce electricity emit at least 2/3 of all sulfur dioxide and more than 1/3 of all nitrogen oxides

• Dry cleaning, oil refineries, chemical manufacturing plants, furniture refinishers, and automobile repair shops contribute to the VOCs in the air

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Regulating Air Pollution From Industry

• Clean Air Act requires many industries to use scrubbers or other pollution-control devices.

• Scrubber: machine that moves gases (Ex: NH3) by dissolving in spray of water

• Electrostatic precipitators: machines used in cement factories, coal-burning power plants to remove dust particles from smokestacks by causing them to stick together and to the sides of the chamber

– remove 20 million tons of ash yearly in US

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Smog

• Urban air pollution

– a mixture of smoke and fog from industrial pollutants, vehicles, and burning fuels

– results from reactions that involve sunlight, air, automobile exhaust, and ozone

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Temperature Inversions

• Circulation of air usually keeps air pollution from reaching dangerous levels.

• Sun heats the air near the Earth, warm air rises through the cooler air above, carries pollutants away from the ground

• Temperature inversion: warm air traps cooler air near Earth’s surface.

– pollution also trapped

– cities located in a valley have a greater chance of experiencing temperature inversions Ex: Los Angeles