1. Section #1: What Causes Air Pollution

2. 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

3. 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

4. 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

5. Sources of Primary Pollution in the U.S. per day

6. Other Primary Air Pollutants
carbon monoxide
nitrogen oxide
sulfur dioxide
chemicals called VOCs (volatile organic compounds)
particulate matter (PM)

7. Sources of Air Pollutants
vehicle exhaust emissions
coal-burning power plants
refineries
metal smelters
burning fuels
mining operations
incinerators
wood-burning fireplaces
fields & roads

8. VOCs from a Refinery

9. 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 place

10. Secondary Pollutants
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 atmosphere

11. 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

12. 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

13. Catalytic Converter

14. 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

15. A Car’s Contribution of Air Pollution
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

16. 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

17. 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

18. 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

19. Industries Producing VOCs
oil refineries
chemical manufacturing plants
furniture refinishers
automobile repair shops
dry cleaners

20. VOC Emissions from Dry Cleaning

21. 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

22. The scrubber machine moves gases through a spray of water that dissolves many pollutants like ammonia

23. 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

24. Smog 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

25. How Smog Forms over Major Cities

26. 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

27. Temperature Inversions
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

28. Major Sources of Groundwater Pollution