Chapter 13. Atmospheric Science, Air Quality, and Pollution Control. Lecture Presentations prepared by Reggie Cobb Nash Community College

Transcription

1 Chapter 13 Atmospheric Science, Air Quality, and Pollution Control Lecture Presentations prepared by Reggie Cobb Nash Community College

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

3 Central Case Study: Clearing the Air in L.A. and in Mexico City Vehicles caused smog in Los Angeles from 1970s to 1990s Policies and technologies improved its air qualities Still has the nation s worst smog Mexico City is very polluted Traffic generates most pollution Topography, population increases make things worse

4 Central Case Study: Clearing the Air in L.A. and in Mexico City Mexico City began fighting back City leaders shut down oil refineries and pushed factories and power plants to switch to natural gas Lead was removed from gasoline Catalytic converters were added to vehicles New lines were added to subway system Fuel-efficient buses replaced old buses Bicycle sharing program for short-distance commuters All of these efforts are paying off Most pollutants have been slashed by 75%

5 The atmosphere Atmosphere The thin layer of gases around Earth Provides oxygen Absorbs radiation and moderates climate Transports and recycles water and nutrients 78% N 2, 21% O 2 Over history, the atmosphere has changed Human activity is now changing the amount of some gases CO 2, methane (CH 4 ), ozone (O 3 )

6 The atmosphere is layered Earth s four atmospheric layers have different: Temperatures, densities, composition Troposphere Bottommost layer (11 km [7 miles]) Responsible for Earth s weather The air gets colder with altitude Tropopause The boundary that limits mixing between the troposphere and stratosphere

7 The atmosphere is layered (cont d) Stratosphere km (7 31 mi) above sea level Drier and less dense, with little vertical mixing Gets warmer with altitude Ozone layer Blocks UV radiation Mesosphere Low air pressure Gets colder with altitude Thermosphere Top layer

8 The sun influences weather and climate An enormous amount of energy from the sun hits Earth 70% is absorbed by water, evaporating the water Air near Earth s surface is warm and moist Convective circulation Less dense, warmer air rises Creates vertical currents Rising air expands and cools Cool air descends and becomes denser Replaces rising warm air Convection influences weather and climate

9 The sun influences weather and climate (cont d) Weather and climate involve physical properties of the troposphere Temperature, pressure, humidity, cloudiness, wind Weather Atmospheric conditions within small geographic areas, over short time periods (hours, days) 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

10 Inversions affect air quality Thermal inversion A layer of cool air forms beneath warm air Inversion layer The band of air where temperature rises with altitude Dense, cool air at the bottom of the layer resists mixing Inversions trap pollutants in cities surrounded by mountains

11 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

12 Global wind patterns Atmospheric cells interact with Earth s rotation to produce global wind patterns As Earth rotates, equatorial regions spin faster Some areas of the planet s surface move more quickly than other areas Coriolis effect: the apparent north south deflection of air currents of the convective cells Results in curving global wind patterns Global wind patterns helped sailing ships travel the oceans

13 Large-scale convective cells create global patterns of moisture and wind

14 Outdoor air quality Air pollutants Gases and particulate material added to atmosphere Can affect climate or harm people or other organisms Air pollution The release of pollutants Outdoor (ambient) air pollution Has recently decreased owing to government policy and improved technologies in developed countries Developing countries and urban areas still have significant problems Greenhouse gas emissions may be our worst problem

15 Some pollution is from natural sources Humans make impacts worse Farming, grazing cause erosion, desertification Fire suppression leads to worse fires Fires generate soot and gases Winds send huge amounts of dust aloft Even across oceans Volcanoes release particulate matter, sulfur dioxide

16 We create outdoor air pollution Humans generate many types of air pollution Point sources Specific spots where large quantities of pollutants are discharged (e.g., power plants) Non-point sources More diffuse, consisting of many small, widely spread sources (e.g., automobiles) Primary pollutants Directly harmful or can react to form harmful substances (e.g., soot and carbon monoxide) Secondary pollutants Form when primary pollutants react with constituents of the atmosphere

17 We create outdoor air pollution (cont d) 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 Greenhouse gases Ozone destroyers

18 The Clean Air Act addresses pollution The Clean Air Act (1963, amended in 1970, 1990) Funds research for pollution control Sets standards for air quality, limits on emissions Allows citizens to sue parties violating the standards Introduced a cap-and-trade program for sulfur dioxide The EPA sets standards for emissions and pollutants States monitor air quality Develop, implement, and enforce regulations Submit plans to the EPA for approval The EPA takes over enforcement if plans are inadequate

19 Agencies monitor emissions State and local agencies monitor and report to the EPA emissions of six major pollutants Carbon monoxide, sulfur dioxide, nitrogen oxides, volatile organic compounds, particulate matter, lead Carbon monoxide (CO) Colorless, odorless gas Produced primarily by incomplete combustion of fuel From vehicles and engines, industry, waste combustion, residential wood burning Prevents blood hemoglobin from binding with oxygen

20 Agencies monitor emissions (cont d) Sulfur dioxide (SO 2 ) Colorless gas with a strong odor Coal emissions from electricity generation, industry Can form acid deposition Nitrogen oxides (NO x ) Formed when nitrogen and oxygen react at high temperatures in engines Vehicles, electrical utilities, industrial combustion Volatile organic compounds (VOCs) Carbon-containing chemicals emitted by vehicles and a wide range of solvents Can react to produce a number of secondary pollutants, as occurs in urban smog

21 Agencies monitor emissions (cont d) Particulate matter Suspended solid or liquid particles Damages respiratory tissue when inhaled Primary pollutants: dust and soot Secondary pollutants: sulfates and nitrates From dust and combustion processes Lead In gasoline and industrial metal smelting Bioaccumulates and damages the nervous system Banned in gasoline in developed countries, but not in developing countries

22 We have reduced U.S. air pollution Total emissions of the six monitored pollutants have declined 72% since the Clean Air Act of 1970 Despite increased population, energy consumption, miles traveled, and gross domestic product

23 We have reduced pollutant emissions Federal policies and technology Cleaner-burning engines and catalytic converters Reduced SO 2 emissions Permit trading programs and clean coal technologies Scrubbers Chemically convert or physically remove pollutants before they leave smokestacks

24 We have reduced pollutant emissions (cont d) Catalytic converters Engine exhaust reacts with metals that convert hydrocarbons into carbon dioxide, water vapor, and nitrogen

25 Air quality has improved Criteria pollutants Especially great threats to humans Carbon monoxide, sulfur dioxide, particulate matter, lead, and all nitrogen dioxides and tropospheric ozone EPA compiles data for these pollutants into a list called the Air Quality Index (AQI) Nitrogen dioxide (NO 2 ) Foul-smelling red-brown gas Contributes to smog and acid deposition

26 Air quality has improved (cont d) Tropospheric ozone (O 3 ): a colorless gas A secondary pollutant created from sunlight, heat, nitrogen oxides, volatile carbon-containing chemicals A major component of photochemical smog Participates in reactions that harm tissues and cause respiratory problems The pollutant that most frequently exceeds EPA standards Scientists, policymakers, industrial leaders, and everyday citizens have modified their actions to help reduce criteria pollutants

27 Air quality has improved (cont d) The reduction in outdoor air pollution since 1970 is one of our greatest accomplishments

28 Air pollution is getting worse in industrializing nations Outdoor pollution is getting worse in developing nations Polluting factories and power plants, increasing numbers of cars Nations emphasize economic growth, not pollution control People burn traditional fuels (wood and charcoal) China has the world s worst air pollution Coal burning, more cars, power plants, factories Causes over 300,000 premature deaths/year China is reducing pollution (closing factories, using cleaner fuels, raising efficiency standards, etc.)

29 Pollution in developing nations is high Air quality is poor in cities of today s developing nations

30 The Science Behind the Story Measuring the Health Impacts of Mexico City s Air Pollution Many studies confirm that Mexico City residents show poorer lung function than people from less polluted areas Respiratory problems and emergency room visits become more numerous when pollution is severe

31 The Science Behind the Story (cont d) Measuring the Health Impacts of Mexico City s Air Pollution Studies have also linked increased death rates with pollution intensity Infant mortality was significantly higher after strong pollution episodes

32 Smog poses health risks Smog An unhealthy mixture of air pollutants over urban areas Industrial smog Burning coal or oil releases CO 2, CO, soot, mercury, sulfur Sulfuric acid is formed Regulations in developed countries reduced smog Coal-burning industrializing countries face health risks due to lax pollution control

33 Smog poses health risks (cont d) Industrial smog results from fossil fuel combustion

34 Smog poses health risks (cont d) Photochemical smog Forms when sunlight drives a chemical reaction between primary pollutants and atmospheric compounds Ozone, NO 2, and many other compounds are formed Appears as a brownish haze Formed in hot, sunny cities surrounded by mountains Morning traffic releases NO and VOCs Irritates eyes, noses, and throats

35 Smog poses health risks (cont d) Photochemical smog results when pollutants from automobile exhaust react amid exposure to light

36 We can take steps to reduce smog Pollution control technology Vehicle inspection programs Financial incentives to replace aging vehicles Restricting driving Cleaner-burning fuels Cleaner industrial facilities Close those that can t improve Pollution indicator boards

37 Weighing the Issues Your Region s Air Quality What outdoor pollution challenges exist in your region? Explore one of the EPA websites that lets you browse information on the air you breathe How does your region s air quality compare to the rest of the nation? What factors influence the quality of your region s air? Propose three steps for reducing air pollution in your region. What benefits might your region enjoy after taking such steps?

38 Ozone depletion Ozone in the lower stratosphere absorbs the sun s ultraviolet (UV) radiation UV radiation can damage tissues and DNA Ozone-depleting substances Human-made chemicals that destroy ozone Halocarbons Human-made compounds made from hydrocarbons with added chlorine, bromine, or fluorine

39 Synthetic chemicals deplete the stratospheric ozone Chlorofluorocarbons (CFCs) Halocarbons used as refrigerants, in fire extinguishers, in aerosol cans, etc. They stay in the stratosphere for a century Sunlight releases chlorine atoms that split ozone Ozone hole Decreased ozone levels over Antarctica

40 We addressed ozone depletion with the Montreal Protocol Montreal Protocol (1987) 196 nations agreed to cut CFC production in half by 1998 Later agreements deepened cuts, advanced timetables, and addressed other ozone-depleting chemicals Industry shifted to safer alternative chemicals We stopped the Antarctic ozone hole from getting worse Challenges still face us CFCs will remain in the stratosphere for decades It can serve as a model for international environmental cooperation

41 The ozone layer has stopped growing Phasing out ozone-depleting substances in 1987 worked the Antarctic ozone hole stopped growing

42 Frequently Asked Question Is the ozone hole related to global warming?

43 Addressing acid deposition Acid deposition is another transboundary issue Acid deposition The deposition of acid, or acid-forming, pollutants from the air onto Earth s surface From automobiles, electric utilities, industrial facilities Acid rain Precipitation containing acid Includes rain, snow, sleet, hail Atmospheric deposition The wet or dry deposition of pollutants (mercury, nitrates, organochlorines, etc.)

44 Burning fossil fuels produces acid rain Burning fossil fuels releases sulfur dioxide and nitrogen oxides These compounds react with water, oxygen, and oxidants to form sulfuric and nitric acids

45 Acid deposition has many impacts Leaches nutrients from topsoil Changes soil chemistry Converts toxic metal ions (aluminum, zinc, etc.) into soluble forms that pollute water Affects surface water and kills fish Damages crops Erodes stone buildings, corrodes cars, erases writing on tombstones

46 Acid deposition has many impacts (cont d) Impacts of acid deposition in northeastern U.S. forests

47 We are addressing acid deposition The Clear Air Act (1990) established an emissions trading program for sulfur dioxide Benefits outweighed costs 40:1 New technologies such as scrubbers have helped Policies and regulations have lowered U.S. emissions of sulfur and nitrogen oxides 67% since 1989

48 We are addressing acid deposition (cont d) Precipitation has become less acidic as air quality has improved under the Clean Air Act

49 Indoor air pollution in the developing world Indoor air pollution In workplaces, schools, and homes Causes greater health effects than outdoor pollution The poor in developing nations burn wood, charcoal, dung, and crop wastes In buildings with little to no ventilation

50 Indoor air pollution in the developed world The most dangerous indoor pollutants in developed nations are cigarette smoke and radon Cigarette smoke Causes eye, nose, and throat irritation Lung cancer kills 160,000 people per year in the U.S. Radon A radioactive gas resulting from natural decay of rock, soil, or water that can seep into buildings Kills 21,000 people per year in the U.S. New homes are being built to be radon resistant

51 Many substances pollute indoor air VOCs The most diverse group of indoor air pollutants Released by everything from plastics and oils to perfumes and paints; new car smell Some are released in large amounts when new Others are released each time they are used Health implications are unclear because concentrations are low Formaldehyde leaking from pressed wood and insulation irritates mucous membranes and induces skin allergies Sick-building syndrome A sickness produced by indoor pollution in which the specific cause is not identified

52 Homes contain many indoor pollutants

53 Weighing the Issues How safe is your indoor environment? Name some potential indoor air quality hazards in your home, work, or school environment Are these spaces well ventilated? What could you do to improve the safety of the indoor spaces you use?

54 We can enhance indoor air quality Keys to alleviating indoor air pollution include: Using low-toxicity materials Monitoring air quality Keeping rooms clean Providing adequate ventilation People in developed nations can: Limit use of plastics and treated wood Limit exposure to toxic substances (pesticides, etc.) Test homes and offices for radon and mold Use CO detectors Keep rooms and air ducts clean and free of mildew and other biological pollutants

55 Conclusion Indoor air pollution is a potentially serious health threat But we can minimize our risk Outdoor air pollution has been addressed by: Government legislation, regulations, and technology Reduction in outdoor air pollution represents some of the greatest strides in environmental protection But there is still room for improvement, especially in developing countries