Air: Climate and Pollution

1. Air: Climate and Pollution Chapter 9

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. 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. • The atmosphere has 4 distinct zones of contrasting temperature due to difference in absorption of solar energy:

4. Troposphere • Troposphere:layer of air immediately immediately adjacent to the Earth’s surface. • 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. • .

5. A Layered Envelope • Stratosphere • Extends from troposphere to about 50 km. • Similar composition to Troposphere, but much more dilute. • Temperature increases with altitude. • Almost no water vapor and 10 times more of ozone (O3) than in the troposphere. • Relatively calm

6. Stratosphere contd. • This ozone layer absorbs UV radiation which makes the stratosphere warmer towards the top. • Since UV normally damages living tissues, absorption of UV by stratosphere protects life on Earth. • The ozone layer over Antartica is depleting which will results in filtration of UV to the earth and causes skin cancer, mutations, crop failure etc.

7. A Layered Envelope • Above the Stratosphere , the temperature decreases creating the Mesosphere, the middle layer runs upto 85 km. Minimum temperature is about - 80o C • Thermosphere,the heated layer, begins at about 85 km, runs for 600 km a layer of highly Ionized gases and high temperatures. • Ionosphere – is the lower part of lower thermosphere which has high energy radiation which causes highly charged particles to glow called Aurora borealis (northern lights) & A.australis (southern light) • .

8. Atmospheric Temperature Changes

9. 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

10. 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 – surfaces that have high reflectivity • Fresh clean snow 90% • Dark soil 3% • Net average of earth 30%

11. Solar Radiation

12. Solar Radiation • Most solar energy reaching the earth is visible light. • Energy re-emitted 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 (atmosphere is considered as a green house, transmit sunlight but traps heat inside). • Increasing atmospheric CO2 due to human activities appears to be causing global warming and the Greenhouse effect.

13. 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. • When water vapor condenses, this latent heat is released. • The redistribution of heat and water around the globe is essential to life on earth.

14. Why Does It Rain ? • Water vapor condenses,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 . • Air flows out of high-pressure zone towards areas of low-pressure.

15. 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 (tiny particles of smoke, dust,spores, volcanic ash etc.)are present, or if temperatures are low enough, condensation will lead to precipitation.

16. Why it Rains? Contd. • Anytime when air is rising ,clouds, snow or rain might form. • Cooling occurs because of changes in pressure. • Air cools as it rises (as pressure increases) and if the air is moist it is likely to rain. • When air is sinking it warms up as it approaches the surface (increasing pressure).Available moisture evaporates. • Rainfall rarely occur in areas of high moisture ( refer pg 199).

17. CLIMATE CHANGE • Periodic weather cycles detected (periodic weather changes).Reasons: • Solar magnetic cycles (changes in the sunlight intensity). • Milankovitch Cycles studied by a Serbian scientist and he observed a Periodic shifts in earth’s orbit and its axis of rotation. • The above changes results in change in distribution and intensity of sunlight reaching the earth.

18. El Nino • La Nina, El Nino or the Southern oscillation: • A pool of warm surface water most of the years is held by the equatorial trade wind between Indonesia and the South America and moves this current westwards towards Indonesia. • Every 3-5 years the low-pressure system breaks in Indonesia. • This giant pool of warm water moves backward and forward between Indonesia and S America, this effect is called EL Nino.

19. 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 pressure system collapses and the mass of warm surface water surges back east.

20. El Nino Southern Oscillation • During an El Nino year, the northern jet stream (normally over Canada) pulls moist air from the Pacific over the U.S.This is accompanied by intense storms and heavy rains (from California across the midwest States). • The counterpart to El Nino is La Nina when the eastern tropical Pacific cools down. • During intervening La Nina years, hot, dry weather is often present (California to midwest) • Together these cycles are called El Nino Southern Oscillation (ENSO)

21. El Nino Southern Oscillation

22. Human-Caused Global Climate Change • IPCC (Intergovernmental Panel on Climate Change (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. • Noted that the earth’s surface temperature has risen by about 0.6 0C(1.1 0F) and IPCC concluded that human is partially to be blamed( Green house gases-CO2, methane,nitrous oxide).

23. Aerosol Effects • Burning fossil fuels, forests and grasslands and other human activities releases 30 billions of CO2 per year. • Aerosols counteract Greenhouse effect. • Aerosols( sulphate and soot) produced by same activities ) 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.

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

25. International Climate Negotiations • Kyoto Protocol (1997) signed in Japan as a follow up of the earth’s summit(1992) in Rio de Janeiro • 160 nations agreed to roll back carbon dioxide, methane, and nitrous oxide emissions about 5% below 1990 levels by 2012. • Also included 3 other green house gases to be reduced: hydrofluorocarbon (CFC), perfluorocarbon and sulphur hexafluoride. • The protocol sets different limits for different countries, depending on their output before 1990,however poorer countries like China and India were exempeted from their emission limit to allow thse countries to develop. • They also argued that wealthier countries created this mess and they should sort out this problem.

26. Controlling Greenhouse Emissions • Switch to renewable energy sources such as solar, wind, biomass etc. • CO2 is lives longer in the atmosphere than Methane and other greenhouse gases. • Capture and Store CO2: • Increase plantations of trees and farmland • Inject CO2 into underground strata or deep ocean (Read pg 208 for details).

27. Climate & Air Pollution • According to EPA (Env. Protection Agency), US releases 147 million metric tons of air pollution(excluding CO2) per year and world wide emission of these pollutants is 2 billion metric tons per year. • Major Kinds of Pollutants: Primary and secondary pollutants. • Primary pollutants are released in a hamrful way e.g Factorysmoke and secondary pollutants become hazardous after reactions in the air.

28. CLIMATE AND AIR POLLUTION • Photochemical oxidants (compounds formed with solar energy) e.g atmospheric acids are probably the most important secondary pollutants. • Fugitive emissions - Do not go through smokestack e.g dust from soil erosions, rock crushing, building constructions. • Conventional Pollutants - Group of seven major pollutants that contribute the largest volume of air-quality degradation (sulphur dioxide, carbon monoxide, particulates,volatile organic compounds,nitrogen oxide,ozone,and lead).

29. Conventional Pollutants • US Clean Air Act designated seven major (conventional or criteria) pollutants for which maximum ambient (Air around us) air levels are mandated. EPA sets allowable limits for concentrations of these pollutants: • Sulfur Dioxide • Carbon Monoxide • Particulates • Hydrocarbons • Nitrogen Oxides • Photochemical Oxidants • Lead

30. Major Pollutants • Unconventional Pollutants • Compounds produced in less volume than conventional pollutants, but are especially toxic or hazardous (e.gAsbestos,benzene, mercury etc.) • Aesthetic Degradation • Reduce quality of life (e.g noise,odors,dust particles etc.)-

31. 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.

32. 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.

33. Stratospheric Ozone • Pollution and chemical reactions has led to a phenomenon known as ozone “hole”. • The ozone hole is thinning of the ozone layer of the stratosphere. • Chlorofluorocarbon (CFCs) and other gases are the principal agent for ozone depletion. • Ozone(O3) aborbs UV rays which harms plants and animal tissues. • A 1% loss of ozone could result in a million extra human skins cancers per year.

34. 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.

35. Effects of Air Polution • Consequences of breathing dirty air leads to increased probability of heart attack,lung diseases and cancers. • 250 000 people in US suffer from pollution related bronchitis per year • Conditions are much worse in developing countries. • City dwellers are more prone to pollutant related diseases than countryside dwellers.

36. Acid Deposition Acid Precipitation/Acid rain: - 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. • Rain water react with CO2 in the air and carbonic acid is formed. • Rainfall acidity thus falls to pH 4.3.

37. AIR POLLUTION CONTROL • Reducing Pollution • Most effective strategy for controlling pollution is to minimize polluting activities. • Best effective strategy is to conserve energy: reducing electricity consumption,insulating homes and offices,better public transport to reduce air pollution. • Alternative energy source: wind & solar. • Technological advances

38. Air Pollution Control contd. Particulate Removal – Filtering Air Emission : Remove particles physically by trapping them in a porous mesh which allows air to pass through but holds back solids. Removal of sulfur, Nitrogen oxides ,hydrocarbon and others by advance technology.

39. Reducing Pollution • Sulfur Removal • Fuel Switching • Switch from soft coal with a high sulfur content to low sulfur coal. • Limestone Injection • Can reduce sulfur emissions by 90% by mixing crushed limestone with coal before it is fed into a boiler.

40. CLEAN AIR LEGISLATION • Clean Air Act (1963) - First national air legislation pollution control. • Clean Air Act (1970) rewrote original Act. • Identified critical pollutants. • Established ambient air quality standards mainly: Primary Standards – to protect human health Secondary Standards –to protect materials, environment, and comfort.

41. Clean Air Act • Since 1970 the Clean Air Act has been modified & amended: Revision in1990 and have addressed principal problems : • Acid Rain • Urban Smog • Toxic Air Pollutants • Ozone Protection • Marketing Pollution Rights • Fugitive emissions of volatile organics • Ambient ozone, soot, and dust. • NOx emissions (Nitrogen oxides)

42. CURRENT AND FUTURE CONDITIONS Read while you relax • 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.