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Air - PowerPoint PPT Presentation

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Air. Section #1: What Causes Air Pollution. when harmful substances build up in the air to unhealthy levels these harmful substances can be in the form of a solid, liquid, or gas most pollution is from human activities, but some comes from natural sources. Air Pollution.

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Section #1:

What Causes Air Pollution

air pollution
when harmful substances build up in the air to unhealthy levels

these harmful substances can be in the form of a solid, liquid, or gas

most pollution is from human activities, but some comes from natural sources

Air Pollution
natural sources of air pollution
volcanoes – spew clouds of particles (ash) & gases (sulfur dioxide)

dust (think about the dust kicked up from plowing a field)

pollen & spores (growing season)

salt from sea spray

Natural Sources of Air Pollution
primary pollutants
pollutant that is put directly into the air by a human activity

Example = soot from smoke (burning wood, industries, vehicles, etc.)

main sources of primary pollutants = electricity, industry, & transportation

Primary Pollutants
other primary air pollutants
carbon monoxide

nitrogen oxide

sulfur dioxide

chemicals called VOCs (volatile organic compounds)

particulate matter (PM)

Other Primary Air Pollutants
sources of air pollutants
vehicle exhaust emissions

coal-burning power plants


metal smelters

burning fuels

mining operations


wood-burning fireplaces

fields & roads

Sources of Air Pollutants
secondary pollutants
when a primary pollutant comes in contact with other primary pollutants or with naturally occurring substances (like H2O vapor) and a chemical reaction takes placeSecondary Pollutants
secondary pollutants1
an example of a secondary pollutant is ground level ozone that forms when car & truck emissions react with the UV rays of the sun & then mix with O2 in the atmosphereSecondary Pollutants
history of air pollution
not a new phenomenon – occurs whenever something is burned

there are records from 2000 years ago from a Roman philosopher complaining about the foul air in Rome

in 1273, England’s King Edward I ordered the hanging of a citizen for disobeying the “clean air act” when he illegally burned a very dirty kind of coal called sea-coal

History of Air Pollution
motor vehicle emissions
almost 1/3 of our air pollution comes from gasoline burned by vehicles

the EPA started regulating emissions in 1980

required the gradual elimination of lead from gasoline & the addition of catalytic converters to tailpipes to clean exhaust gases of pollutants

Motor Vehicle Emissions
a car s contribution of air pollution
car seats can be covered in a plastic that contains a VOC called vinyl chloride

steel smelters send 1000s of metric tons of SO2 into the atmosphere to produce the body & frame

VOCs escape into the atmosphere whenever you fill the tank with gasoline

A Car’s Contribution of Air Pollution
a car s contribution of air pollution1
exhaust is a major source of nitrogen oxides, carbon monoxide, & hydrocarbons

in some developing countries, exhaust can also contain poisonous substances

each car releases 4.5 metric tons of CO2 each year

A Car’s Contribution of Air Pollution
california zero emission program
established in 1990

vehicles that have no tailpipe emissions, no emissions from gasoline, & no emissions from control systems

by 2016, 16% of all vehicles (including SUVs, trucks, etc.) must be zero-emission vehicles

California - Zero Emission Program
zero emission vehicles
include electric cars & vehicles with advanced battery power

vehicles powered by hydrogen fuel

also includes partial zero-emission vehicles like hybrid-electric cars & cars with methanol fuel cells

programs have been adopted by Maine, Massachusetts, New York, & Vermont

Zero-Emission Vehicles
industrial air pollution
industries & power plants burn fossil fuels to get the energy they need

this releases huge quantities of SO2 & NO into the air

they also produce VOCs that form toxic fumes

Industrial Air Pollution
industries producing vocs
oil refineries

chemical manufacturing plants

furniture refinishers

automobile repair shops

dry cleaners

Industries Producing VOCs
regulating industrial pollution
Clean Air Act requires many industries to use scrubbers or other pollution-control devices

scrubbers remove some of the more harmful substances

electrostatic precipitators are machines used in cement factories & coal-burning power plants to remove dust particles from smokestacks

Regulating Industrial Pollution
The scrubber machine moves gases through a spray of water that dissolves many pollutants like ammonia
electrostatic precipitators
gas containing dust particles is blown through a chamber containing an electrical current

an electrical charge is transferred to the dust particles, causing them to stick to each other & the sides of the chamber

Electrostatic Precipitators
when air pollution hangs over urban areas & reduces visibility

results from chemical reactions that involve sunlight, air, automobile exhaust, & ozone

affected cities include, LA, Denver, & Phoenix

temperature inversions
air circulation usually keeps air pollution from reaching dangerous levels in the atmosphere

as the suns warms the earth and the warm air rises up, it carries pollutants away from the ground

sometimes though, pollution is trapped close to the surface with a temperature inversion

Temperature Inversions
temperature inversions1
during an inversion, the temperatures of the air above are warmer than the air below

this keeps the cooler air at the surface from moving upwards, thus trapping pollutants with the cooler air below

chances increase when a city is in a valley & surrounded by mountains

Temperature Inversions