Chapter 13: Atmospheric Science and Air Pollution PDF

Third Canadian Edition 13 Atmospheric Science and Air Pollution PowerPoint® Slides prepared by Stephen Turnbull 13-1 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Upon successfully completing this chapter, you will be ab...

Third Canadian Edition 13 Atmospheric Science and Air Pollution PowerPoint® Slides prepared by Stephen Turnbull 13-1 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Upon successfully completing this chapter, you will be able to Describe the composition, structure, and major processes of Earth’s atmosphere Outline the scope of outdoor air pollution, successes and issues with addressing it, and potential solutions Explain stratospheric ozone depletion. Identify steps taken in addressing ozone depletion and key reasons for the degree of success achieved. Discuss broadly the scope and nature of indoor air pollution. 13-2 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Central CASE: “Apocalypse” in Beijing (and many other industrializing regions) Beijing and other industrializing regions experience significant air quality concerns Emissions regulations still catching up with industrial & economic expansion - E.g. coal fired power plants, more cars Also, natural wind blown dust worsened by agricultural practices in neighboring areas Wood burning stoves 13-3 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  The Atmosphere and Weather 13-4 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada The atmosphere and weather Atmosphere: the thin layer of gases that surrounds Earth Absorbs radiation and moderates climate (links to climate change Ch 14) Transports and recycles water and nutrients 78% nitrogen gas, 21% oxygen gas, 1% other gases Its four layers differ in temperature, density and composition (next slide) Which of the variable gasses at right have we significantly affected the levels of through human activities? 13-5 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada The atmosphere is layered Troposphere: bottommost layer Air for breathing (air is denser then in higher layers) Temperature declines with altitude (warmest at Earth’s surface (WHY?) Weather (and vertical mixing of air) Tropopause is like a cap that limits mixing between troposphere and the layer above it 13-6 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada The atmosphere is layered Stratosphere: 11-50 km (7-31 mi) above sea level Drier and less dense, Colder in its lower regions Little vertical mixing (implications for pollutants that enter?) Contains UV radiation- blocking ozone, 17-30 km (10-19 mi) above sea level 13-7 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada 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) (Why does it get warmer with greater elevation?) 13-8 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Atmospheric properties include temperature, pressure, and humidity Atmospheric pressure, density, relative humidity and temperature contribute to causing air movement in the troposphere. Atmospheric pressure: force per unit area produced by a column of air (relates directly to density at right) Relative humidity: a measure of the amount of water vapor a given volume of air contains (based on a ratio) 13-9 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Solar energy heats the atmosphere, creates seasons, and causes air to circulate The spatial relationship between the Earth and sun determines the amount of solar energy striking the Earth (and temperature). Energy from the sun Heats and moves air Influences weather & climate 70% is adsorbed by the atmosphere and Earth’s surface [see GHGs & climate change Ch 14], the remainder reflected back to space Solar radiation is highest near the equator (figure at right). 13-10 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Land & water adsorb solar energy, reradiate heat, water evaporates Convective circulation: less dense, warmer air rises and creates vertical currents Rising air expands and cools Cool air descends and becomes denser, replacing warm air Influences both weather and climate Where do you think there would be the most convective rising? 13-11 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Large-scale circulation systems produce global climate patterns Hadley cells: a pair of convective air currents near the equator where surface air warms, rises, and expands (resulting in, & links to deserts?) Ferrel cells and polar cells: convective cells that lift air and create precipitation at higher latitudes north and south Hadley, ferrel & polar cells interact with Earth’s rotation to produce global wind patterns (at left). Coriolis effect definition is out of scope (in Ch 14 we cover the impact of climate change on weather patterns). 13-12 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Air masses interact to produce weather (I’ve omitted warm and cold fronts: out-of-scope) In normal conditions air temperature decreases as altitude increases, and there is vertical mixing, BUT, in some circumstances we get a Thermal inversion: a layer of cool air occurs beneath a layer of warmer air The lower cool air being heavier, resists rising and mixing In urban settings this lower trapped air may contain pollutants, smog Happens often in mountain valleys – (Los Angeles, Okanagan) 13-13 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Urban heat island effect: buildings, cars, pavement etc. adsorb & concentrate heat. What role does “albedo” play in this effect? 13-14 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Solar energy heats the atmosphere, helps create seasons, and causes air to circulate (cont’d) Weather: atmospheric conditions over short time periods and within a small geographic areas Climate: The pattern of atmospheric conditions found across large geographical regions over long periods of time. Microclimate: Variations in weather and climate that occur on an extremely local scale, such as from one side of a hill to the other due to being sheltered from wind or direct sunlight Photo R. Friberg 13-15 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Outdoor Air Pollution 13-16 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada 14-16 Outdoor air pollution Air pollutants: gases & particulate material added to the atmosphere Can affect climate (HOW?) or harm people Outdoor (ambient) air pollution: pollution outside. Has recently decreased due to government policy and improved technologies in developed countries. Developing countries & urban areas still have significant problems Natural Dust storms: blown westward across the Atlantic Ocean by trade sources winds every year (from Africa to the Americas) can Unsustainable farming and pollute grazing, erosion, desertification 13-17 Volcanoes, Burning vegetation Copyright © 2017 Pearson Canada Inc. (forests) © 2010 Pearson Education Canada  We create various sources and types of outdoor air pollution Point Sources: specific spots where large quantities of pollutants are discharged (power plants and factories) Nonpoint Sources: more diffuse, consisting of many small sources (automobiles) 13-18 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Primary Pollutants: directly harmful and can react to form harmful substances (soot and carbon dioxide) Secondary Pollutants: form when primary pollutants interact or react with constituents or components of the atmosphere (tropospheric ozone and sulfuric acid). 13-19 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Environmental legislation commonly identifies harmful airborne substances Canadian Environmental Protection Act: four categories: Criteria air contaminants (first to be regulated): pollutants judged to pose especially great threats to human health, produced by processes including burning of fossil fuels, e.g. Sulphur dioxide, nitrous oxides. Persistent organic pollutants: Can last in the environment for a long time, can enter food supply, bioaccumulate in body tissues. Examples include industrial chemicals PCBs, DDT Heavy metals: poisonous even in low concentrations, accumulate in body tissues. Examples: mercury and lead Toxic air pollutants: broad category of “other” pollutants, e.g. cause cancer, neurological problems. Overlap with other types (lead, mercury), but include additional examples such as asbestos, CFCs. Arise from smelting, sewage treatment, industrial processes). 13-20 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Government agencies share responsibility for air pollution Federal Ministry of Environment & Climate Change Enters into international agreements (e.g. Montreal Protocol, Kyoto Protocol) Enters into transboundary agreements with the U.S. (e.g. Canada- United States Air Quality Agreement) Provincial/territorial Managed through each environment ministry Municipal Only Montreal and Greater Vancouver directly regulate sources of air pollution (example regulations?) Most municipalities raise public awareness 13-21 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Monitoring shows that many forms of air pollution have decreased Cleaner-burning vehicles, catalytic converters decrease carbon monoxide Permit-trading programs & clean coal technologies reduce SO2 emissions Scrubbers (technologies chemically convert or physically remove pollutants before they leave the smokestacks) Phaseout of leaded gasoline 13-22 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada 14-22 Smog is the most common, widespread air quality problem Smog: unhealthy mixtures of air pollutants that often form over urban areas. Industrial (gray air) smog comes from industries that burn coal or oil. Coal-burning regions face significant health risks Photochemical smog comes from light-driven reactions of primary pollutants and normal atmospheric compounds Morning traffic exhaust releases pollutants Sunlight then promotes the production of ozone and other constituents (this is where we don’t want ozone) 13-23 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Acid deposition is a transboundary problem Acidic deposition: the deposition of acid, or acid-forming pollutants, from the atmosphere onto Earth’s surface Acid rain: precipitation of acid Originates from burning fossil fuels release sulfur dioxide and nitrogen oxides react with water to form sulfuric and nitric acids 13-24 https://www.safewater.org/fact-sheets-1/2017/1/23/acid-rain-fact-sheet Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Acid deposition (con’t) Acidic deposition can have wide-ranging, cumulative detrimental effects on ecosystems and on our built environment: Acids leach nutrients from the topsoil Alters soil chemistry harming plants Has devastated forests in proximity to deposition Mobilizes toxic metal ions Run-off into surface waters Erodes and corrodes built 13-25 structures Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Acid deposition (con’t) Early 1970s (recall our first chapter – era of increasing environmental awareness) action began taking place: 1972 Inco “superstack” Why were stacks & superstacks only partly successful? (what’s the main issue?) https://commons.wikimedia.org/wiki/File:Inco_Superst ack.JPG 13-26 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Technology such as scrubbers has reduced SO2 emissions by 90%. But nitrate emissions & acidic nitrate precipitation remain high. Why the greater success with reducing SO2 vs nitrate emissions? (e.g. where do they each come from?) 13-27 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Stratospheric Ozone Depletion 13-28 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Stratospheric ozone depletion Ozone (O3) is a respiratory irritant in the troposphere, but in the lower stratosphere performs a crucial role for life on the planet: Blocks incoming damaging ultraviolet radiation Chlorofluorocarbon s (CFCs): chemicals that attack ozone. Lots were produced in early 1970s for use in refrigerators, etc. Caused the Ozone hole: ozone levels over Antarctica declined by 40-60%: causes skin cancer, harms crops, ocean productivity 13-29 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  The Montreal Protocol was successful in addressing ozone depletion It was helpful that research at the time confirmed a clear link (cause and effect) between CFCs and ozone loss 1987: Montreal Protocol: 197 nations agreed to cut CFC production in half Follow-up monitoring indicated a need to cut CFCs even more, and subsequent agreements deepened cuts, advanced timetables and addressed other ozone-depleting chemicals Production and use of ozone-depleting chemicals has decreased 95% The ozone layer is beginning to recover: But challenges still face us CFCs will remain in the stratosphere for a long time Nations can ask for exemptions (e.g. the USA uses methyl bromide to control pests on strawberries) Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada The Montreal Protocol (cont’d) Several factors contributed to the success of the Montreal Protocol: Cause and effect clearly established (the science) There was clear photographic visual evidence people could relate to Policymakers included industry in helping solve the problem (i.e. there was cooperation) Less expensive alternative chemicals were available (so changing over didn’t wasn’t terribly costly) Adaptive management was used: changes to the agreements were made after monitoring showed that more reductions were required. Why was this effort successful and to date climate change efforts have not been? (we’ll talk more about this in Chapter 14) 13-31 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada There are still many questions to be resolved about ozone depletion Will ozone depletion spread from the polar regions to encompass mid-latitude regions? Human health impacts? Other potential impacts (e.g., on ecosystems)? Are the substitute chemicals that are being proposed actually less damaging to the stratospheric ozone layer? It will take a while before the CFCs we already put into the atmosphere are able to dissipate. Why would the precautionary principle and adaptive management be important to consider in light of the above 13-32 concerns?) Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Stratospheric ozone depletion Keep in mind the distinction between the issue of the ozone hole versus climate change: these are separate issues. While also recognizing that: Ozone has different roles and benefit vs concern in the stratosphere verses troposphere (what's the distinction?). Ppt 27 CFCs while being the main contributor to ozone depletion also play a role in global warming: how so? 13-33 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Indoor Air Pollution 13-34 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada 14-34  Indoor air pollution Indoor air contains higher concentrations of pollutants than outdoor air, 11,000 people die per day from indoor air pollution The average person in North America is indoors at least 90% of the time Exposed to synthetic materials (insecticides, cleaning fluids, plastics, and chemically treated wood) 1973-74: ventilation systems were sealed off and windows put in that did not open, trapping pollutants inside (has this improved 13-35 with newer homes?) Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Indoor air pollution in the developing world arises from fuelwood burning Burning wood, charcoal, dung, crop wastes for cooking and eating Kills 1.6 million people each year Causes pneumonia, bronchitis, allergies, cataracts, asthma, heart disease, cancer and premature death 13-36 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  Tobacco smoke and radon are the most dangerous indoor pollutants in the industrialized world Secondhand smoke from cigarettes is especially dangerous After cigarette smoke, radon gas is the second- leading cause of lung cancer in the developed world - Colourless, odourless gas that can seep into buildings 13-37 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada  We can reduce indoor air pollution In developed countries: - Use low-toxicity material - Monitor air quality - Keep rooms clean - Limit exposure to chemicals In developing countries: - Dry wood before burning - Cook outside - Use less-polluting fuels (natural gas) 13-38 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Concluding thoughts There has been some success in addressing outdoor air pollution, more so in developed countries, but more progress is needed. Avoiding unhealthy pollutants in developing world will pose a challenge as less-wealthy nations industrialize Improvement is required in reducing acidic deposition, photochemical smog The sometimes-long duration of contaminants in the atmosphere, e.g. CFCs, means that we still don’t know the full scope of impacts, and the precautionary principle should be paramount. Indoor air pollution is a potentially serious health threat. 13-39 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada Interpreting Graphs and Data What does this graph show about the mesosphere and its properties? a) It contains the most ozone b) It is a very thin layer c) Temperature decreases with increasing altitude d) Temperature increases with increasing altitude 13-40 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada QUESTION: Review The major component of Earth’s atmosphere is … a) Nitrogen gas b) Oxygen gas c) Argon gas d) Water vapor 13-41 Copyright © 2017 Pearson Canada Inc. © 2010 Pearson Education Canada