1. Chapter 17 Topics:  The Earth’s atmosphere  Weather, climate, and atmospheric conditions  Outdoor pollution  Stratospheric ozone depletion  Acidic deposition and consequences  Indoor air pollution

2. The atmosphere – its composition  Atmosphere = the thin layer of gases around Earth  A reservoir for nitrogen, carbon, and oxygen  Absorbs radiant energy and moderates climate  Transports and cycles water vapor  Major gases – 78% N 2 and 21% O 2  Minor gases  Permanent – Argon, Neon, Helium, Hydrogen, Xenon  Variable – water vapor, CO 2, CH 4, O 3, CFCs

3. The atmosphere has layers  The layers of the atmosphere are defined by vertical variations in its temperature  The variations occur because the atmosphere is heated at three places  The Earth’s surface  The Stratospheric ozone layer  The outer edge of the atmosphere

4. Our layer – the troposphere  Troposphere = layer closest to Earth (0 to 7 miles)  Heated by infrared energy given off by Earth’s surface Visible light is absorbed by Earth’s surface, warming it Earth’s “warm” surface gives off infrared light Certain gases in the troposphere absorb the infrared light  Temperature decreases with altitude  Contains most of the water vapor  Our weather occurs in this layer  Upper boundary is the tropopause – a real boundary

5. The overlying layers  Stratosphere = second layer (7 to 31 mi)  Heated by ultraviolet light absorbed in the ozone layer  Temperature increases with altitude  Mesosphere = third layer (31to 56 mi)  Heated by ultraviolet light absorbed in the ozone layer  Temperature decreases with altitude  Stratosphere = second layer (56+ mi)  Heated by high-energy light absorbed at the outer edges of the atmosphere  Temperature increases with altitude

6. Some atmospheric properties  Atmospheric pressure = the force per unit area produced by a column of air, atmospheric pressure decreases with altitude  Relative humidity = the amount of water vapor in the air as a percentage of the amount that could be in the air (at a given temperature)  Dew point – temperature at which the relative humidity is 100% (the air is “saturated”) – condensation occurs  As air cools, its relative humidity increases; as air warms, its relative humidity decreases

7. Uneven heating…  The surface of the Earth is unevenly heated because sunlight strikes the curved surface of the Earth at different angles  Tropical zone (30°N to 30°S)  Sunlight strikes the surface at high angles (60°-90° as measured from the horizon) – this is “direct” sunlight  Solar energy is more intense, it is concentrated in a smaller area – this zone is warmer than other zones

8. …of Earth’s surface…  Polar zone (60°N/S to 90°N/S)  Sunlight strikes the surface at low angles (0°-30° as measured from the horizon) – this is “indirect” sunlight  Solar energy is less intense, it is spread out over a larger area – this zone is colder than other zones  Temperate zone (30°N/S to 60°N/S)  Sunlight strikes the surface at different angles during different times of the year (due to axial tilt)  These zones receive more energy when their pole is tilted toward the sun – the sunlight angle is more direct

9. …causes seasons…  Earth’s seasons are caused by the tilt of Earth’s axis (NOT!! the distance between the Earth and the sun)  As Earth revolves around the sun, the tilt of its axis causes different regions to receive direct and/or indirect sunlight at different times of the year

10. …and movement of the air  The troposphere is heated from the bottom, by the (unevenly) heated surface of the Earth  This makes the troposphere density unstable and induces convective circulation  Warm, less dense air rises  Cool, denser air sinks

11. Global convection = global winds  If things were simple  But they’re not

12. Convection cells & global winds  Hadley Cell – air rises at 0°, travels north and south along the tropopause, and sinks at 30°N/S  At 30°N/S, air moves back toward the equator across Earth’s surface, becoming the Trade Winds  Ferrel Cell – air rises at 60°N/S, travels south and north along the tropopause, and sinks at 30°N/S  At 30°N/S, air moves back toward 60°N/S across Earth’s surface, becoming the Westerlies  Polar Cell – air rises at 60°N/S, travels north and south along the tropopause, and sinks at 90°N/S  At 90°N/S, air moves back toward 60°N/S across Earth’s surface, becoming the Polar Easterlies

13. Convection cells & global winds

14. Weather vs. climate  Weather and climate involve the physical properties of the troposphere – temperature, pressure, humidity, cloudiness, wind, etc.  Weather = specifies atmospheric conditions over short time periods and within small geographic areas  Climate = patterns of atmospheric conditions across large geographic regions over long periods of time (generally 30-year averages of weather conditions)  Mark Twain said, “Climate is what we expect; weather is what we get”

15. Air masses and fronts  Air Mass = a large body of air that take on the characteristics of the area over which it forms  Two main characteristics – temperature & humidity  Temperature – Tropical (warm, hot) or Polar (cool, cold)  Humidity – Maritime (moist) or Continental (dry)  Air masses move in response to the global winds  Fronts = the boundaries between air masses moving at different rates and in different directions

16. Weather changes along fronts  Cold front = when colder, drier air pushes into & displaces warmer, moister air  Warm front = when warmer, moister air pushes into & displaces colder, drier air

17. Pressure systems influence weather  High-pressure system = air that sinks because it is cool, spreading outward as it nears the ground  Sinking air means no clouds  Sunny conditions and fair weather  Low-pressure system = air that rises because it is warm, drawing air inward toward its center  Rising air means clouds (cooling and condensation)  Cloudy conditions and rainy weather

18. Thermal inversion  Sometimes (particularly in valleys) a layer of warm air becomes situated above cooler air – “inverting” the usual temperature change with altitude  As at the tropopause, rising air is blocked by the warm air layer (the rising air is cooler, denser)  If the rising air contains pollutants, these are trapped below the “thermal inversion”

19. Storms  Tropical cyclones = large, low pressure weather systems fed by the energy of tropical moisture  Called hurricanes in the western hemisphere and typhoons in the eastern hemisphere  Wind speeds greater than 72 mph; heavy rains can cause flooding, storm surges can inundate coastal areas  Tornadoes = a funnel-shaped zone of high winds  Form in severe thunderstorms due to very high, localized wind shear  Much smaller scale than tropical cyclones

20. Air pollution  The presence in the atmosphere of air pollutants, particulate matter [liquid and solid] and gases that can harm people, harm other organisms, or affect climate  The concepts of point-source and non-point-source pollution apply to air pollution  Air pollution sources are also evaluated and regulated as “mobile” and “stationary” sources

21. Aerosols  Aerosols = fine particulate matter (liquid and solid) suspended in the atmosphere  Reflect sunlight back to space  Cool Earth’s surface and therefore, the troposphere  Volcanic dust, sulfate particulates, soot, desert dust, clouds

22. Natural sources of air pollution  Volcanic eruptions can release large volumes of particulate matter, sulfur dioxide, and other gases  Forest fires release soot and gases  Dust from arid regions can be carried across oceans

23. Types of air pollutants  Primary pollutants = harmful materials emitted directly into the atmosphere (soot, sulfur dioxide)  Secondary pollutants = harmful materials that form when primary pollutants interact with each other or react with components of the atmosphere (smog)  Criteria pollutants = pollutants that pose especially great threats to human health: carbon monoxide, sulfur dioxide, nitrogen oxides, tropospheric ozone, particulate matter, lead

24. Criteria pollutants: CO and SO 2  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  Sulfur dioxide (SO 2 ) = colorless gas, strong odor  Coal emissions from electricity generation, industry  Can form acid precipitation

25. Nitrogen oxides and trop. ozone  Nitrogen oxides (NO x ) = formed when nitrogen and oxygen react at high temperatures in engines  Nitrogen dioxide (NO 2 ) = a highly reactive, foul-smelling reddish brown gas  Vehicles, industrial combustion, electrical utilities  Contribute to smog and acid precipitation  Tropospheric ozone (O 3 ) = a colorless gas with a strong odor (a secondary pollutant)  Results from interactions of sunlight, heat, nitrogen oxides, and volatile carbon-containing chemicals  Causes respiratory problems  The pollutant that most frequently exceeds EPA standards

26. Particulate matter and lead  Particulate matter (PM) = solid or liquid particles suspended in the atmosphere (aerosols)  Primary pollutants: dust and soot  Secondary pollutants: sulfates and nitrates  Damages respiratory tissue when inhaled  Lead = a heavy metal  From industrial metal smelting (formerly in gasoline)  Bioaccumulates and damages the nervous system

27.  Residence time = the time a pollutant stays in the atmosphere  Pollutants with brief residence times (PM, SO 2 ) exert localized impacts over short time periods  Pollutants with long residence times (CH 4, CFCs) exert regional or global impacts Local and global effects

28. Air pollution laws  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

29. The laws are effective  Emissions reduced and economy improved  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

31. Toxic air pollutants  Toxic air pollutants = substances that cause: cancer, reproductive defects, neurological, developmental, immune system, or respiratory problems  The EPA regulates 188 toxic air pollutants from metal smelting, sewage treatment, industry, etc.  Include heavy metals, VOCs, diesel emissions  Clean Air Act regulations helped reduce emissions by more than 35% since 1990

32. Air pollution in developing countries  Air pollution is getting worse in developing nations  Factories and power plants pollute more as governments emphasize economic growth, not pollution control  People burn traditional fuels (wood and charcoal) and more own cars

33.  China has the world’s worst air pollution  Asian (Atmospheric) Brown Cloud = a 2-mile-thick layer of pollution over southern Asia  Pollution was an issue during the Olympic in Beijing  The government is trying to decrease pollution  Shutting down heavily polluting factories  Installing pollution controls  Encouraging renewable and nuclear energy  Mandating cleaner burning fuels Air pollution in China

34. Rural air pollution  Feedlots, where cattle, hogs, or chickens are raised in dense concentrations  Significant amounts of dust, methane, hydrogen sulfide, and ammonia, and other objectionable odors  People living or working nearby have high rates of respiratory illness

35. Smog is our most common problem  Smog = a mixture of air pollutants in urban areas  Industrial (gray air) smog = from industries that burn coal or heavy oil; soot and sulfate particulates  Photochemical (brown air) smog = a sunlight-induced collection of secondary air pollutants derived from automobile exhaust (nitrogen oxides and VOCs)

36. Making smog

37. Reducing smog  New cars required to have catalytic converters  Financial incentives to replace aging vehicles  Annual vehicle inspection programs  Reduction of sulfur content in diesel fuel  Electronic pollution indicator boards raise awareness

38. Stratospheric ozone  Ozone layer = ozone in the lower stratosphere  Blocks incoming ultraviolet (UV) 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.

39. Ozone depletion  UV radiation frees a chlorine atom from the CFC  The chlorine atom splits the ozone molecule and then gives up the third oxygen  One chlorine atom can destroy 100,000 ozone molecules  CFCs remain in the stratosphere for a century

40. The Ozone hole  Ozone hole = decreased ozone levels over Antarctica  In addition to general depletion of stratospheric ozone, unique seasonal weather conditions over Antarctica cause further ozone depletion  Winter clouds and wind  Spring releases Cl  Summer eases winds  Diffusion “heals” hole

41. 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

42. A global environmental success  The Montreal Protocol is our biggest environmental success story  Research developed rapidly, along with technology  Policymakers asked industry to help solve the problem  Many chemical patents were about to expire  Implementation used an adaptive management strategy

43. Acid deposition  Acid deposition = the deposition of acid and acid- forming pollutants from the atmosphere onto Earth’s surface  Although common referred to as “acid rain”, over half of acid deposition is in the form of dry particles  Acid deposition originated with the burning fossil fuels, which release sulfur dioxide and nitrogen oxides into the atmosphere

44. Formation of acid rain

45. Impacts of acid rain  Affects surface water and kills fish  Leaches nutrients from topsoil and changes soil chemistry  The acid-neutralizing capacity of soil or water determines the severity of acid rain’s effects  Damages agricultural crops and forests  Erodes stone buildings and structures  Corrodes cars and exposed metal

46. Addressing 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  New technologies such as scrubbers have helped  Acid deposition continues to be a problem in the developing world, especially in China, which burns coal in factories lacking pollution control equipment

47. Scrubbers  Scrubbers = chemically convert or physically remove pollutants before they leave smokestacks

48. Indoor air pollution  Indoor air pollution = in workplaces, schools, and homes  Health effects are greater than from outdoor pollution  The average U.S. citizen spends 90% of the time indoors, exposed to synthetic materials that have not been comprehensively tested  Being environmentally prudent can make it worse  To reduce heat loss and improve efficiency, ventilation systems were sealed off  Windows do not open, trapping pollutants inside

49. Tobacco smoke and radon  The most dangerous indoor pollutants  Secondhand smoke from cigarettes is very dangerous  Contains over 4,000 chemical compounds  Causes eye, nose, and throat irritation  Smoking has declined in developed nations  Radon causes 21,000 deaths a year in the U.S.  A radioactive gas resulting from natural decay of rock, soil, or water that can seep into buildings  New homes are being built that are radon resistant

50. 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 and are brought in on shoe soles

51. Sources of indoor air pollution

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