CLIMATE AND AIR POLLUTION

1. 1 CHAPTER 6 CLIMATE AND AIR POLLUTION

2. 2 Outline: Atmosphere and Climate Climate Change El Nino Human Causes Climate and Pollution Kinds of Pollution Sources Transport Effects of Air Pollution Air Pollution Control

3. 3 ATMOSPHERE AND CLIMATE Weather - A description of short-term physical conditions of the atmosphere. Climate - A description of the long-term weather pattern in a particular area. Weather and climate are primary determinants of biomes and ecosystem distribution.

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5. 5 Climate

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8. 8 Table 9.1 09_01.jpg09_01.jpg

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10. 10 Troposphere Troposphere Ranges in depth from 18 km over the equator to 5 km over the poles. Air circulates in convection currents. Air temperature drops rapidly with increasing altitude. Contains 75% of total air mass. Tropopause - Transition boundary limits mixing between the troposphere and upper zones.

11. 11 A Layered Envelope Stratosphere Extends from troposphere to about 50 km. Similar composition to Troposphere, but much more dilute. Temperature increases with altitude. Fraction of water vapor is 1000x less and ozone is 1000x more than in the troposphere. Relatively calm

12. 12 A Layered Envelope Mesosphere Middle Layer. Minimum temperature is about - 80o C. Thermosphere Ionized gases and high temperatures. Ionosphere - Lower Thermosphere Aurora borealis (northern lights)

13. 13 Air: Climate and Pollution Chapter 9

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15. 15 Atmospheric Temperature Changes

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17. 17 Energy and the Greenhouse Effect Solar Radiation Solar energy not evenly distributed over the globe. Of solar energy reaching outer atmosphere: 25% reflected 25% absorbed 50% reaches earth’s surface

18. 18 Solar Radiation Visible light passes through atmosphere undiminished. Ultraviolet light is absorbed by ozone in the stratosphere. Infrared radiation is absorbed by carbon dioxide and water in the troposphere. Albedo - Reflectivity Fresh clean snow 90% Dark soil 3% Net average of earth 30%

19. 19 Solar Radiation

20. 20 Solar Radiation Most solar energy reaching the earth is visible light. Energy reemitted by the earth is mainly infrared radiation (heat energy). Longer wavelengths are absorbed in the lower atmosphere, trapping heat close to the earth’s surface. Greenhouse Effect Increasing atmospheric CO2 due to human activities appears to be causing global warming.

21. 21 Convection and Atmospheric Pressure Water vapor contains a large amount of energy stored as latent heat. Evaporation converts solar energy into latent heat stored in evaporated water. Uneven heating produces pressure differences that cause wind, rain, and storms (weather). Vertical convection cells circulate air masses between warm and cooler latitudes.

22. 22 Why Does It Rain ? Releasing latent heat causes air to rise, cool, and lose more water vapor. Rising, expanding air creates an area of relatively high pressure at the top of the convection column. Air flows out of high-pressure zone towards areas of low-pressure, where cool, dry air is subsiding.

23. 23 Why Does It Rain ? Subsiding air is compressed as it approaches the earth’s surface where it piles up and creates an area of high pressure at the surface. Air flows out of this region back towards low pressure, closing the cycle. If condensation nuclei are present, or if temperatures are low enough, condensation will lead to precipitation.

24. 24 Convection Currents

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26. 26 Air Circulation

27. 27 Coriolis Effect and Jet Streams Surface flows do not move straight North and South, but are deflected due to Coriolis Effect. Major zones of subsidence occur at about 30o north and south latitude. Where dry, subsiding air falls on continents, it creates broad, subtropical desert regions. Winds directly under regions of subsiding air are often light and variable. Horse latitudes

28. 28 Convection Cells and Prevailing Winds

29. 29 Jet Streams

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31. 31 Seasonal Winds Monsoon - Seasonal reversal of wind patterns caused by differential heating and cooling rates of oceans and continents. Most prevalent in tropical countries where large land area is cut off from continental air masses by mountain ranges and surrounded by a large volume of water.

32. 32 Monsoon

33. 33 CLIMATE CHANGE Periodic weather cycles detected. Solar magnetic cycles Milankovitch Cycles - Periodic shifts in earth’s orbit and tilt. Change distribution and intensity of sunlight reaching the earth. Ice cores show drastic changes may have occurred over short periods of time (decades).

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36. 36 El Nino Southern Oscillation Large pool of warm surface water in Pacific Ocean moves back and forth between Indonesia and South America. Most years, the pool is held in western Pacific by steady equatorial trade winds. Every three-five years the Indonesian low collapses and the mass of warm surface water surges back east.

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40. 40 El Nino Southern Oscillation During an El Nino year, the northern jet stream pulls moist air from the Pacific over the U.S. Intense storms and heavy rains. During intervening La Nina years, hot, dry weather is often present.

41. 41 El Nino Southern Oscillation

42. 42 Short-Term Climate Changes: ENSO

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45. 45 Human-Caused Global Climate Change IPCC (2001) released report stating “recent changes in the world’s climate have had discernable impacts on physical and biological systems.” Concluded human activities must be at least partially responsible.

46. 46 Greenhouse Effect

47. 47 Rain Shadow Effect

48. 48 Table 9.3 09_03.jpg09_03.jpg

49. 49 Greenhouse Gases Carbon Dioxide - Fossil-fuel burning. Atmospheric levels increasing steadily. Methane - Ruminants, Coal-mines Absorbs more infrared than CO2. Chlorofluorocarbons (CFC’s) - Refrigerants Declined in recent years Nitrous Oxide - Burning organic material Sulfur Hexafluoride - Electrical insulation

50. 50 Aerosol Effects Aerosols have a tendency to reflect sunlight and cool surface air temperatures. Short-lived, thus effects are temporary. Mt. Pinatubo erupted in 1991 and ejected enough ash and sulfate particles to cool global climate about 1o C for nearly a year.

51. 51 Current Evidence of Climate Change Precipitation increased 1% in last century. Artic sea ice thinning. Alpine glaciers retreating. Coral reefs bleaching.

52. 52 Winners and Losers Residents of extreme northern areas would enjoy warmer temperatures and longer growing-seasons. Plant growth patterns may be altered. One-third of population living in areas likely flooded by rising seas. More evaporation may cause severe storms. Infectious disease likely to spread faster.

53. 53 International Climate Negotiations Kyoto Protocol (1997) 160 nations agreed to roll back carbon dioxide, methane, and nitrous oxide emissions about 5% below 1990 levels by 2012. Sets different limits for different countries, depending on prior output. Developing countries exempted.

54. 54 Controlling Greenhouse Emissions Switch to renewable energy sources. Capture and Store CO2. Trees and farmland Inject into underground strata or deep ocean.

55. 55 CLIMATE AND AIR POLLUTION Major Kinds of Pollutants Photochemical oxidants (compounds formed with solar energy). Fugitive emissions - Do not go through smokestack. Conventional Pollutants - Group of seven major pollutants that contribute the largest volume of air-quality degradation. Ambient Air

56. 56 Conventional Pollutants US Clean Air Act designated seven major (conventional or criteria) pollutants for which maximum ambient air levels are mandated. Sulfur Dioxide Carbon Monoxide Particulates Hydrocarbons Nitrogen Oxides Photochemical Oxidants Lead

57. 57 Major Pollutants Unconventional Pollutants Compounds produced in less volume than conventional pollutants, but are especially toxic or hazardous. Aesthetic Degradation Reduce quality of life.

58. 58 Lead and Other Toxic Elements Toxic metals and halogens are chemical elements that are toxic when concentrated and released in the environment. Metals Lead, mercury, arsenic, nickel, beryllium, cadmium, thallium, uranium, cesium, and plutonium. Halogens Fluorine, chlorine, bromine, and iodine.

59. 59 Indoor Air Pollution EPA found indoor concentrations of toxic air pollutants are often higher than outdoor. People generally spend more time indoors. Smoking is the most important air pollutant in the US. 430,000 die annually from a disease related to smoking. Associated costs are estimated at $100 billion annually.

60. 60 Indoor Air Pollution Less Developed Countries also suffer from indoor air pollution. Organic fuels make up majority of household energy. Often burned in smoky, poorly ventilated heating and cooking fires.

61. 61 CLIMATE PROCESSES AND AIR POLLUTION Long-Range Transport Fine aerosols can be carried great distances by the wind. Sensitive monitoring equipment increasingly reveals industrial contaminants in places usually considered the cleanest in the world. Contaminants trapped by winds at the north pole, concentrate and eventually precipitate out, entering the food chain.

62. 62 Long-Range Transport

63. 63 Stratospheric Ozone Discovered stratospheric ozone levels were dropping rapidly during September and October. Occurring since at least 1960. At ground-level, ozone is a pollutant, but in the stratosphere it screens UV radiation. A 1% decrease in ozone results in a 2% increase in UV rays reaching the earth.

64. 64 Stratospheric Ozone Circumpolar vortex isolates Antarctic air and allows stratospheric temperatures to drop and create ice crystals at high altitudes. Absorb ozone and chlorine molecules. When sun returns in the spring, energy liberates the chlorine allowing the depletion process to proceed rapidly. CFC’s believed to be main culprit. Persist for decades.

65. 65 CFC Production

66. 66 Urban Climates Temperature Inversions Cool, dense air trapped below a warmer, lighter air mass. Pollutants cannot disperse and thus increase in concentration. Heat Islands Temperature in cites warmer than surrounding areas. Dust Domes Tall buildings create updrafts.

67. 67 EFFECTS OF AIR POLLUTION Human Health EPA estimates each year 50,000 people die prematurely from illnesses related to air pollution. Likelihood of suffering ill health is related to intensity and duration of exposure. Inhalation is the most common route, but absorption through the skin and consumption via food can also occur.

68. 68 Plant Pathology Chemical pollutants can directly damage plants, or can cause indirect damage by disrupting normal growth and development patterns. Certain environmental factors have synergistic effects in which the injury caused by the combination is more than the sum of the individual exposures. Pollutant levels too low to cause visible effects may still be damaging.

69. 69 Acid Deposition Acid Precipitation - Deposition of wet, acidic solutions or dry, acidic particles from the air. pH scale ranges from 0-14. 7 = Neutral; <7 = Acidic; >7 = Basic Unpolluted rain generally has pH of 5.6. Carbonic acid from atmospheric CO2. In industrialized areas, anthropogenic acids in the air often outweigh natural sources of acid.

70. 70 Acid Deposition

71. 71 Acid Deposition Aquatic Effects Thin, acidic soils and oligotrophic lakes of southern Norway and Sweden have been severely affected by acid deposition. Generally, reproduction is the most sensitive stage in fish life cycles.

72. 72 Acid Deposition Forest Damage Air pollution and depositions of atmospheric acids are believed to be important causes of forest destruction in many areas. Buildings and Monuments Limestone and marble are destroyed by air pollution at an alarming rate. Corroding steel in reinforced concrete weakens buildings, roads, and bridges.

73. 73 AIR POLLUTION CONTROL Reducing Pollution Most effective strategy for controlling pollution is to minimize polluting activities. Particulate Removal - Remove particles physically by trapping them in a porous mesh which allows air to pass through but holds back solids. Electrostatic Precipitators

74. 74 Reducing Pollution Sulfur Removal Fuel Switching Switch from soft coal with a high sulfur content to low sulfur coal. Change to another fuel (natural gas). Limestone Injection Can reduce sulfur emissions by 90% by mixing crushed limestone with coal before it is fed into a boiler.

75. 75 Reducing Pollution Nitrogen Oxide Control Best method is to prevent creation. Staged Burners Selective Catalysts Hydrocarbon Control Use closed systems to prevent escape of fugitive emissions.

76. 76 CLEAN AIR LEGISLATION Clean Air Act (1963) - First national air pollution control. Clean Air Act (1970) rewrote original Act. Identified critical pollutants. Established ambient air quality standards. Primary Standards - Human health Secondary Standards - Materials, environment, aesthetic and comfort.

77. 77 Clean Air Act Revision (1990) - Included provision for: Acid Rain Urban Smog Toxic Air Pollutants Ozone Protection Marketing Pollution Rights Fugitive emissions of volatile organics Ambient ozone, soot, and dust. NOx emissions

78. 78 CURRENT AND FUTURE CONDITIONS In the United States, air quality has improved dramatically in the last decade in terms of major large-volume pollutants. Cities where pollution is largely from traffic still have serious air quality problems. Major metropolitan areas of many developing countries are growing at explosive rates, and environmental quality is very poor.

79. 79 Summary: Atmosphere and Climate Climate Change El Nino Human Causes Climate and Pollution Kinds of Pollution Sources Transport Effects of Air Pollution Air Pollution Control

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