AirSection 1 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.

AirSection 1 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.

AirSection 1 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

AirSection 1 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.

AirSection 1 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.

AirSection 1 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.

AirSection 1 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

AirSection 1 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: NH 3 ) 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

AirSection 1 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

AirSection 1 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