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Lecture Outlines Chapter 17 Environment: The Science behind the Stories 4th Edition Withgott/Brennan

Lecture Outlines Chapter 17 Environment: The Science behind the Stories 4th Edition Withgott/Brennan. The Earth’s atmosphere Weather, climate, and atmospheric conditions Outdoor pollution and solutions Stratospheric ozone depletion Acidic deposition and consequences

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Lecture Outlines Chapter 17 Environment: The Science behind the Stories 4th Edition Withgott/Brennan

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  1. Lecture Outlines Chapter 17 Environment:The Science behind the Stories 4th Edition Withgott/Brennan

  2. The Earth’s atmosphere Weather, climate, and atmospheric conditions Outdoor pollution and solutions Stratospheric ozone depletion Acidic deposition and consequences Indoor air pollution and solutions This lecture will help you understand:

  3. Central Case: L.A. and its sister cities struggle for a breath of clean air • Vehicles caused smog in Los Angeles from 1970s to 1990s • Policies and technologies improved its air qualities • But its “sister cities” are not as clean • 3,600/month die in Tehran from air pollution • Old cars use cheap gas • Topography, immigration, etc.

  4. The atmosphere • Atmosphere = the thin layer of gases around Earth • Provides oxygen • Absorbs radiation and moderates climate • Transports and recycles water and nutrients • 78% N2, 21% O2 • Minute concentrations of permanent (remain at stable concentrations) gases • Variable gases = varying concentrations across time and place • Human activity is changing the amount of some gases • CO2, methane (CH4), ozone (O3)

  5. The atmosphere’s composition

  6. The first two layers of the atmosphere • Troposphere = bottommost layer (11 km [7 miles]) • Air for breathing, weather • The air gets colder with altitude • Tropopause = limits mixing between troposphere and the layer above it • Stratosphere = 11–50 km (7–31 mi) above sea level • Drier and less dense, with little vertical mixing • Becomes warmer with altitude • Contains UV radiation-blocking ozone, 17–30 km (10–19 mi) above sea level

  7. The two highest levels of the atmosphere • Mesosphere = 50–80 km (31–56 mi) above sea level • Extremely low air pressure • Temperatures decrease with altitude • Thermosphere = atmosphere’s top layer • Extends upward to 500 m (300 mi)

  8. The atmosphere’s four layers • Atmospheric layers have different • Temperatures • Densities • Composition

  9. Atmospheric properties • Atmospheric pressure = the force per unit area produced by a column of air • Relative humidity = the ratio of water vapor air contains to the amount it could contain at a given temperature • High humidity makes it feel hotter than it really is • Temperature = varies with location and time • Atmospheric pressure decreases with altitude

  10. Solar energy heats the atmosphere • The spatial relationship between the Earth and sun determines how much solar energy strikes the Earth • Microclimate = a localized pattern of weather conditions • Energy from the sun: • Heats and moves air • Creates seasons • Influences weather and climate • Solar radiation is highest near the equator

  11. Solar energy creates seasons • Because the Earth is tilted, each hemisphere tilts toward the sun for half the year • Results in a change of seasons • Equatorial regions are unaffected by this tilt, so days average 12 hours throughout the year

  12. Solar energy causes air to circulate • Air near Earth’s surface is warm and moist • Convective circulation = less dense, warmer air rises • Creating vertical currents • Rising air expands and cools • Cool air descends and becomes denser • Replacing rising warm air • Convection influences weather and climate

  13. The atmosphere drives weather and climate • Weather and climate involve the physical properties of the troposphere • Temperature, pressure, humidity, cloudiness, wind • 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 • Mark Twain said, “Climate is what we expect; weather is what we get”

  14. Front = the boundary between air masses that differ in temperature, moisture, and density Warm front =boundary where warm, moist air replaces colder, drier air Cold front = where colder, drier air displaces warmer, moister air Air masses produce weather Warm fronts produce light rain Cold fronts produce thunderstorms

  15. Air masses have different pressures • High-pressure system = air that descends because it is cool • It spreads outward as it nears the ground • Brings fair weather • Low-pressure system = warm air rises and draws air inward toward the center of low pressure • Rising air expands and cools • It brings clouds and precipitation

  16. Thermal (temperature) inversion • Air temperature decreases as altitude increases • Warm air rises, causing vertical mixing • 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

  17. Circulation systems produce climate patterns • Convective currents contribute to climatic patterns • Hadley cells =convective cells near the equator • Surface air warms, rises, and expands • Causing heavy rainfall near the equator • Giving rise to tropical rainforests • Currents heading north and south are dry • Giving rise to deserts at 30 degrees • Ferrel cells and polar cells = lift air and create precipitation at 60 degrees latitude north and south • Conditions at the poles are dry

  18. Global wind patterns • Atmospheric cells interact with Earth’s rotation to produce global wind patterns • As Earth rotates, equatorial regions spin faster • Coriolis effect =the apparent north-south deflection of air currents of the convective cells • Results in curving global wind patterns called the doldrums, trade winds, and westerlies

  19. Climate patterns and moisture distribution

  20. Global wind patterns • Doldrums = a region near the equator with few winds • Trade winds = between the equator and 30 degrees • Blow from east to west • Weaken periodically, leading to El Niño conditions • Westerlies = from 30 to 60 degrees latitude • Blow from west to east • People used these winds to sail across the ocean • Wind and convective circulation in ocean water maintain ocean currents • And can create violent storms

  21. Storms pose hazards • Atmospheric conditions can produce dangerous storms • Hurricanes = form when winds rush into areas of low pressure • Warm, moist air over the topical oceans rises • Typhoons (cyclones) = winds turn counterclockwise in the Northern Hemisphere • Drawing up huge amounts of water vapor • Which falls as heavy rains • Tornadoes = form when warm air meets cold air • Quickly rising warm air forms a powerful convective current (spinning funnel)

  22. Hurricanes and tornadoes • Understanding how the atmosphere works helps us to: • Predict violent storms and protect people • Comprehend how pollution affects climate, ecosystems, and human health

  23. Outdoor air pollution • Air pollutants = gases and particulate material added to the atmosphere • Can affect climate or harm people or other organisms • Air pollution = the release of pollutants • 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

  24. Natural sources pollute: volcanoes • Release particulate matter, sulfur dioxide, and other gases • Can remain for months or years • Aerosols = fine droplets of sulfur dioxide, water, oxygen • Reflect sunlight back to space • Cool the atmosphere and surface Volcanoes are one source of natural air pollution, as shown by the Mount Saint Helens eruption in 1980

  25. Natural sources pollute: fires • Fires pollute the atmosphere with soot and gases • Over 60 million ha (150 million acres) of forests and grasslands burn per year • Human influence makes fires worse • Fuel buildup from fire suppression, development in fire-prone areas, “slash-and-burn” agriculture • Climate change will increase drought and fires In 1997, unprecedented forest fires sickened 20 million and caused a plane to crash

  26. Natural sources pollute: dust storms • Wind over arid land sends huge amounts of dust aloft • Even across oceans • Businesses, schools, and governments close • Unsustainable farming and grazing promote: • Erosion • Desertification

  27. We create outdoor air pollution • Air pollution comes from mobile or stationary sources • Point sources = specific spots where large quantities of pollutants are discharged (power plants and factories) • Non-point sources = more diffuse, consisting of many small sources (automobiles) • Primary pollutants = directly harmful and can react to form harmful substances (soot and carbon monoxide) • Secondary pollutants = form when primary pollutants interact or react with components of the atmosphere • Tropospheric ozone and sulfuric acid

  28. 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

  29. 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

  30. 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

  31. 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 • Sulfur dioxide (SO2) = colorless gas with a strong odor • Coal emissions from electricity generation, industry • Can form acid precipitation

  32. 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

  33. 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

  34. Criteria pollutants: particulate matter andlead • 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

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

  36. 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

  37. 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!

  38. 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

  39. We reduced emissions and improved theeconomy • Technology and federal policies • Cleaner-burning engines and catalytic converters • Permit-trading programs and clean coal technologies reduce SO2 emissions • Scrubbers = chemically convert or physically remove pollutants before they leave smokestacks • Phaseout of leaded gasoline

  40. Toxic substances pose health risks • 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, urban hazards • Clean Air Act regulations helped reduce emissions by more than 35% since 1990

  41. U.S. health risks vary geographically Non-cancerous respiratory ailments Nationwide cancer risks

  42. Industrializing nations suffer increasing pollution • Outdoor pollution is getting worse in developing nations • Factories and power plants pollute • Governments emphasize economic growth, not pollution control • People burn traditional fuels (wood and charcoal) • And more own cars • China has the world’s worst air pollution • Coal burning, more cars, power plants, factories • Causing over 300,000 premature deaths/year

  43. Pollution in developing nations is high Smog in Beijing surrounds an Olympic stadium More people own cars

  44. Air pollution in China • The government is trying to decrease pollution • Shutting down heavily polluting factories and mines • Phasing out some subsidies for polluting industries • Installing pollution controls in factories • Encouraging renewable and nuclear energy • Mandating cleaner burning fuels • Air is improving in Beijing but not in other places • Asian (Atmospheric) Brown Cloud = a 2-mile-thick layer of pollution over southern Asia • Decreased plant productivity, increased flooding, etc.

  45. Air quality is a rural issue, too • Airborne pesticides from farms • Industrial pollutants from cities, factories, and power plants • Feedlots, where cattle, hogs, or chickens are raised in dense concentrations • Voluminous amounts of dust, methane, hydrogen sulfide, and ammonia • Also create objectionable odors • People living or working nearby have high rates of respiratory illness

  46. Smog: our most common air quality problem • Smog = an unhealthy mixture of air pollutants over urban areas • Sulfur in burned coal combines with oxygen to form sulfuric acid • Industrial (gray air) smog = industries burn coal or oil • Regulations in developed countries reduced smog • Coal-burning industrializing countries face health risks • Coal and lax pollution control Smog in Donora killed 21 people and sickened 6,000

  47. 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 NO2cause photochemical smog to form a brown haze over cities

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

  49. 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

  50. Synthetic chemicals deplete 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. • Releases chlorine atoms that split ozone

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