1. Air Pollution and Stratospheric Ozone Depletion
Chapter 15
Air Pollution and Stratospheric Ozone Depletion

2. Layers of the Atmosphere
The tropospheric layer is approximately 16 km above the earth
Earth’s climate occurs here.
The stratospheric ozone layer exists roughly kilometers above the Earth.
Ozone has the ability to absorb ultraviolet radiation and protect life on Earth.

3. During the 1950’s and 1960’s, most factories looked like this

5. Air Pollution
Air pollution- the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems.
Outdoor (ambient) air pollution = pollution outside
Has recently decreased due to government policy and improved technologies in developed countries
Developing countries and urban areas still have significant problems

6. Major Air Pollutants Sulfur Dioxide Nitrogen Oxides Carbon Oxides
Particulate Matter
Volatiles Organic Compounds
Ozone
Lead
Mercury

7. Criteria pollutants: CO and SO2
Carbon monoxide (CO) = colorless, odorless gas
Produced primarily by incomplete combustion of fuel
From vehicles and engines, industry, waste combustion, residential wood burning
Poses risk to humans and animals, even in small concentrations by blocking the ability for oxygen to bind with blood
Sulfur dioxide (SO2) = colorless gas with a strong odor
Coal emissions from electricity generation, industry
Can form acid precipitation

8. Criteria pollutants: NO2
Nitrogen dioxide (NO2) = a highly reactive, foul- smelling reddish brown gas
Nitrogen oxides (NOx) = formed when nitrogen and oxygen react at high temperatures in engines
Vehicles, industrial combustion, electrical utilities
Contribute to smog and acid precipitation

9. Criteria pollutants: tropospheric ozone
Tropospheric ozone (O3) = a colorless gas with a strong odor
Results from interactions of sunlight, heat, nitrogen oxides, and volatile carbon-containing chemicals
A secondary pollutant
A major component of smog
Participates in reactions that harm tissues and cause respiratory problems
The pollutant that most frequently exceeds EPA standards

10. Criteria pollutants: particulate matter and lead
Particulate matter = suspended solid or liquid particles
Primary pollutants: dust and soot
Secondary pollutants: sulfates and nitrates
Damages respiratory tissue when inhaled
From dust and combustion processes
Lead = in gasoline and industrial metal smelting
Bioaccumulates and damages the nervous system
Banned in gasoline in developed, but not in developing, countries

12. Other pollutants: mercury and VOCs
Mercury = trace metal
found in coal and oil
Toxic to nervous system
Volatile organic compounds = hydrocarbon compounds such as gasoline, ligher fluid, dry-cleaning fluids, oil-based paints and perfumes
play an important role formation of photochemical oxidants such as ozone
Natural VOCs not hazardous, like those given off by conifer trees

13. Other pollutants: carbon dioxide
Carbon dioxide = colorless, odorless gas
formed during combustion of most matter
Absorbed by plants during photosynthesis and released during respiration
Affects climate and alters ecosystems by increasing greenhouse gases

14. Areas in the U.S. fail air quality standards
Many Americans live in areas with unhealthy levels of criteria pollutants

15. Primary Pollutants
Primary pollutants- polluting compounds that come directly out of the smoke-stack, exhaust pipe, or natural emission source.
Examples: CO, CO2, SO2, NOx, and most suspended particulate matter.

16. Primary air pollutants come directly from factories and vehicles

17. Secondary Pollutants
Secondary pollutants- pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds.
Examples: ozone (O3), sulfate (SO42-) and nitrate (NO3-)

18. Secondary pollutants are created in the air from the reaction between other pollutants or water vapor.

20. Agencies monitor emissions
State and local agencies monitor, calculate, and report to the EPA the emissions of these pollutants:
Carbon monoxide, sulfur dioxide, particulate matter, lead, and all nitrogen oxides
Tropospheric ozone has no emissions to monitor
It is a secondary pollutant
Agencies monitor volatile organic compounds (VOCs) = carbon-containing chemicals
Used and emitted by engines and industrial processes
VOCs can react to produce ozone

21. U.S. air pollution
In 2008, the U.S. emitted 123 million tons of the six monitored pollutants
The average U.S. driver emits 6 metric tons of CO2/yr as well as other pollutants!

22. Natural Sources of Air Pollution
Volcanoes
Lightning
Forest fires
Dust storms
Plants (terpenes-fragrant smell of conifer trees and citrus fruits)

23. Anthropogenic Sources of Air Pollution
On-road vehicles
Power plants
Industrial processes
Waste disposal

25. Pollutants exert local and global effects
Residence time = the time a pollutant stays in the atmosphere
Pollutants with brief residence times exert localized impacts over short time periods
Particulate matter, automobile exhaust
Pollutants with long residence times exert regional or global impacts
Pollutants causing climate change or
ozone depletion

27. Photochemical (brown air) smog
Produced by a series of reactions
Formed in hot, sunny cities surrounded by mountains
Light-driven reactions of primary pollutants and atmospheric compounds
Morning traffic releases NO and VOCs
Irritates eyes, noses, and throats
Los Angeles smog kills 3,900/year and costs $28 billion/year
High levels of NO2 cause photochemical smog to form a brown haze over cities

28. Creation of industrial and photochemical smog
Industrial smog
Photochemical smog

29. Thermal Inversions
Thermal inversion = a layer of cool air occurs beneath warm air
Inversion layer = the band of air where temperature rises with altitude
Denser, cooler air at the bottom of the layer resists mixing
Inversions trap pollutants in cities surrounded by mountains

31. We can reduce smog
Regulations require new cars to have catalytic converters
Require cleaner industrial facilities
Close those that can’t improve
Financial incentives to replace aging vehicles
Restricting driving
Vehicle inspection programs (“smog checks”)
Reduce sulfur in diesel; remove lead in gasoline
Electronic pollution indicator boards raise awareness
But increased population and cars can wipe out advances

32. Acid Deposition
Acid deposition- occurs when nitrogen oxides and sulfur oxides are released into the atmosphere and combine with atmospheric oxygen and water. These form the secondary pollutants nitric acid and sulfuric acid.
These secondary pollutants further break down into nitrate and sulfate which cause the acid in acid deposition.

33. Acid Deposition

34. Effects of Acid Deposition
Lowering the pH of lake water
Decreasing species diversity of aquatic organisms
Nutrients leached from topsoil
Damages agricultural crops
Mobilizing metals that are found in soils and releasing these into surface waters
Damage to painted surfaces
Damaging statues, monuments, and buildings

35. pH of precipitation in the U.S.
The acid-neutralizing capacity of soil, rock, or water impacts the severity of acid rain’s effects
Many regions of acidification are downwind of major sources of pollution

36. We have begun to address acid deposition
Reducing acid deposition involves reducing the pollution that contributes to it
The Clear Air Act of 1990 established an emissions trading program for sulfur dioxide
Benefits outweighed costs 40:1
New technologies such as scrubbers have helped
Acid deposition is worse in the developing world
Especially in China, which burns coal in factories lacking pollution control equipment

37. The Montreal Protocol
Montreal Protocol = 196 nations agreed to cut CFC production in half by 1998
Follow-up agreements deepened cuts, advanced timetables, and addressed other ozone-depleting chemicals
Industry shifted to safer, inexpensive, and efficient alternatives
Challenges still face us
CFCs will remain in the stratosphere for a long time
Nations can ask for exemptions to the ban

38. The Montreal Protocol is a success
It is considered our biggest environmental success story
Research developed rapidly, along with technology
Policymakers included industry in helping solve the problem
Implementation of the plan allowed an adaptive management strategy
Strategies responded to new scientific data, technological advances, and economic figures
The Montreal Protocol can serve as a model for international environmental cooperation

39. Legislation addresses pollution
Air Pollution Control Act (1963) funded research and encouraged emissions standards
The Clean Air Act of 1970
Set standards for air quality, limits on emissions
Provided funds for pollution-control research
Allowed citizens to sue parties violating the standards
The Clean Air Act of 1990 strengthened regulations for auto emissions, toxic air pollutants, acidic deposition, stratospheric ozone depletion
Introduced emissions trading for sulfur dioxide

40. The EPA sets standards
The EPA sets nationwide standards for emissions and concentrations of toxic pollutants
States monitor air quality
They develop, implement, and enforce regulations
They submit plans to the EPA for approval
The EPA takes over enforcement if plans are inadequate
Criteria pollutants = pollutants that pose especially great threats to human health
Carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, lead

41. We have reduced air pollution
Total emissions of the six monitored pollutants have declined 60% since the Clean Air Act of 1970
Despite increased population, energy consumption, miles traveled, and gross domestic product

42. Ways to Prevent Air Pollution
Removing sulfur dioxide from coal by fluidized bed combustion
Catalytic converters on cars
Scrubbers on smoke stacks
Baghouse filters
Electrostatic precipitators

43. Baghouse filters

44. Electrostatic precipitators

45. Scrubbers

46. Synthetic chemicals deplete stratospheric ozone
Ozone layer = ozone in the lower stratosphere
Blocks incoming ultraviolet (UV-B and C) radiation
Protecting life from radiation’s damaging effects
Ozone-depleting substances = human-made chemicals that destroy ozone by splitting its molecules apart
Halocarbons = human-made compounds made from hydrocarbons with added chlorine, bromine, or fluorine
Chlorofluorocarbons (CFCs) = a halocarbon used as refrigerants, in fire extinguishers, in aerosol cans, etc.
Releases chlorine atoms that split ozone
Leading cause of ozone depletion

47. CFCs destroy ozone CFCs are inert (don’t react)
CFCs remain in the stratosphere for a century
UV radiation breaks CFCs into chlorine and carbon atoms
The chlorine atom splits ozone
Ozone hole = decreased ozone levels over Antarctica
One chlorine atom can destroy 100,000 ozone molecules

48. Formation and Breakdown of Ozone
First, UV-C radiation breaks the bonds holding together the oxygen molecule, leaving two free oxygen atoms: O2+ UV-C -> 2O
Sometimes the free oxygen atoms result in ozone: O2 + O -> O3
Ozone is broken down into O2 and free oxygen atoms when it absorbs both UV-C and UV-B ultraviolet light: O3 + UV-B or UV-C -> O2 + O

50. Depletion of the Ozone Layer
Global Ozone concentrations had decreased by more than 10%.
Depletion was greatest at the poles
Decreased stratospheric ozone has increased the amount of UV-B radiation that reaches the surface of Earth.

51. Indoor Air Pollutants
Wood, animal manure or coal used for cooking and heating in developing countries.
Asbestos-used once as insulation
Carbon Monoxide
Radon-gas found in crust
VOCs in home products
Molds and pollen

52. VOCs pollute indoor air
The most diverse group of indoor air pollutants
Released by everything from plastics and oils to perfumes and paints
Most VOCs are released in very small amounts
Unclear health implications due to low concentrations
Formaldehyde leaking from pressed wood and insulation irritates mucous membranes and induces skin allergies
Pesticides seep through floors and walls
Are brought in on shoe soles

53. Living organisms can pollute indoors
Dust mites and animal dander worsen asthma
Fungi, mold, mildew, airborne bacteria cause allergies, asthma, other respiratory ailments, and diseases
Building-related illness = a sickness produced by indoor pollution
Sick building syndrome = a sickness produced by indoor pollution with general and nonspecific symptoms
Reduced by using low-toxicity building materials and good ventilation

54. We can reduce indoor air pollution
In developed countries:
Use low-toxicity materials, limit use of plastics and treated wood, monitor air quality, keep rooms clean
Provide adequate ventilation
Limit exposure to known toxicants
Test homes and offices and use CO detectors
In developing countries:
Dry wood before burning
Cook outside
Use less-polluting fuels (natural gas)

55. Sources of indoor air pollution