Chapter 15 Air Pollution and Stratospheric Ozone Depletion

1. 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 16-50 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.