CHAPTER 12.1 ENVIRONMENTAL SCIENCE What Causes Air Pollution?

 In most places in the United States the air is fairly clean. In other parts of the world, like India and Bangladesh the air is so polluted it harms peoples health.  Clean air consists of mostly nitrogen and oxygen, with very small amounts of argon, carbon dioxide, and water vapor.  Air pollution is when harmful substances are at unhealthy levels in the air.  Most air pollution is caused by human activity. There are natural pollutants like when a volcano erupts, also dust, spores, and pollen in the air.

PRIMARY AND SECONDARY POLLUTANTS  A primary pollutant is pollution that is put in the air by human activity.  An examples is soot from smoke.  Secondary pollutants are when primary pollutants react with other primary pollutants or naturally occurring substances.  An example is ground-level ozone. This forms when uv rays cause automobile emissions to react with oxygen in the atmosphere.

SOURCES OF PRIMARY AIR POLLUTANTS  Many household products, power plants, and automobiles are sources of primary air pollution like carbon monoxide, nitrogen oxide, sulfur dioxide, and chemicals called volatile organic compounds.  Particulate matter can also pollute the air. There are 2 types of particulate matter – fine and coarse particles.  Fine particles enter the air from fuel burned by vehicles and coal-burning power plants.  Coarse particles are made from cement plants, mining operations, incinerators, wood-burning fireplaces, field, and roads.

THE HISTORY OF AIR POLLUTION  Air pollution is not a new idea – whenever you burn something pollutants enter the air.  The problem is the air-quality is much worse because of the amount of fossil fuels that are burned.

MOTOR VEHICLE EMISSIONS  1/3 of our air pollution comes from gasoline burned by vehicles.  The Clean Air Act passed in 1970 (revised in 1990). It gives the EPA (Environmental Protection Agency) the authority to regulate vehicle emissions.  The first thing it did was eliminate lead used in gasoline. This has reduce the amount of lead pollution 90%.  Also catalytic converters are used on vehicles to clean the exhaust coming from cars.

CALIFORNIA ZERO-EMISSION VEHICLE PROGRAM  To improve air quality in California the states Air Resources Board made the Zero Emission (ZEV) program in These vehicles have no tailpipe emissions, no emissions from gasoline, and no emission-control system.  Battery power electric vehicle are the only true ZEVs. There are 3 types of partial ZEVs: one is clean, fuel-efficient hybrid cars (powered by both batter and gasoline engines), another is a hydrogen- powered car that emits only water vapor. There are also hybrid cars that required being plugged in.

INDUSTRIAL AIR POLLUTION  Many industries and power plants burn fuel to produce energy. Mostly they burn fossil fuels. This release sulfur dioxide and nitrogen oxides into the air.  Other industries like dry cleaning produce VOCs.

REGULATING AIR POLLUTION FROM INDUSTRY  The Clean Air Act requires many industries to use scrubbers or other pollution-control devices.  Many cement factories and coal- burning power plants use electrostatic precipitators to remove dust particles from smoke stacks.

SMOG  Smog is when air pollution hangs over an area and reduces visibility.  This usually happens from a reaction between sunlight, air, automobile exhaust, and ozone.  Industries and vehicles are the main sources of smog.

TEMPERATURE INVERSIONS  Most of the time circulation of air in the atmosphere keeps air pollution from reaching dangerous levels.  Sometimes air pollution gets stuck near the Earth’s surface.  A temperature inversion is when air above is warmer than the air below. Usually air temperature decreases with altitude. This inversion traps air near Earth’s surface.  A city in a valley has a greater chance of experiencing an temperature inversion. This is why Los Angeles has a lot of smog. It gets trapped in that area.