GSC 1620 Chapter 18

1. GSC 1620 Chapter 18 Air Pollution

2. Air Pollution The quality of the air we breathe is both a personal health and a major economic issue Every industrialized country has to grapple with this issue and it appears that some countries with rapidly expanding economies (e.g., China) are making the same pollution mistakes as the United States did earlier As you’ll see, air pollution is often an international issue since the air pollution generated in one country can be transported to another by the prevailing winds

3. Air Pollution • As I stressed last week, don’t forget that elements and compounds (natural and synthetic) participate in geochemical cycles of varying complexities and timescales • Remember: quantitative assessment of the nature and interaction of these cycles is very difficult – we understand very few cycles well • Refresh my memory: what three factors primarily determine the potential of a substance to pollute a reservoir?

4. Air Pollution • The atmosphere is a very fluid medium with regional and global-scale circulation patterns • Therefore, are atmospheric pollutants likely to be transported away from their source area? What implications could this have for international relations? • See slides illustrating carbon cycle, atmospheric composition and residence times, and major sources of U.S. air pollution

5. Simplified Global Carbon Cycle

7. Major U.S. air pollution sources 2011

8. Air Pollution Statistics/Costs • Air pollution generates direct and indirect damage and costs • E.G., In the U.S., estimated annual air pollution damage costs exceed $16 billion, including $500 million per year crop and livestock damage • Worldwide: air pollution likely lowers forest-product harvests by about $40 billion annually • Health: one study suggested that reduction of air pollution levels by 50% in major urban areas would save $2 billion annually in health care costs

9. Air Pollution Statistics/Costs • Particulate air pollution has been linked to at least 60,000 annual U.S. deaths and a host of other ailments including: asthma, emphysema, bronchitis, heart disease and some cancers • Air quality in the U.S. has actually improved from the mid 1900s but air pollution is still a big concern

10. Major Air Pollution Issues • Given our time constraints, we’ll investigate the major air pollution issues and learn that we need to consider the quality of our indoor air as well • Issues we’ll address: acid rain; particulates; ground-level ozone (photochemical smog) and stratospheric ozone depletion; airborne lead; indoor air carbon monoxide and indoor air radon pollution

11. Acid Rain • Remember all rainfall is acidic to some degree; the pH of normal rainfall is 5.6 • The pH scale is a logarithmic scale like the Richter Magnitude scale – Remind me, what is meant by a logarithmic scale? • See slide illustrating the pH scale; the lower the pH the more acidic the solution

12. increasingly acidic 7 = neutral increasingly basic

13. Acid Rain • One human source: sulfur dioxide gas released from coal-fired electrical power plants • The sulfur dioxide gas reacts with atmospheric oxygen to form sulfur trioxide gas • The sulfur trioxide gas reacts with atmospheric water vapor to form sulfuric acid which subsequently falls as acid rain

14. Acid Rain • Another human source: nitrogen oxide gases released by transportation modes • The nitrogen oxides react with water vapor in the atmosphere and form nitric acid which subsequently falls as acid rain • The pH of some acidic rainfall = 3.6; compare this for me to normal rainfall (pH = 5.6)

15. Acid Rain • A study released in 2001contends that acid rain caused a very serious problem in the U.S. Northeast, Midwest and Southeast

16. Acid Rain Effects

17. Acid Rain • These researchers contend that 41 percent of the lakes in the Adirondack Mountains (New York) and 15 percent of the lakes in New England have become acidified – about 24 percent of the 1469 lakes in the Adirondacks have become too acidified to support life (pH ~ < 4.2) • They also contend the acidic rain is damaging certain tree species (sugar maple, red spruce) by direct contact or by leaching nutrients from the underlying soil

18. Acid Rain • However, improvements in fossil fuel combustion technologies, spurred by the 1990 Clean Air Act Amendments, have resulted in less sulfurous and nitrogen gas emissions (see animation) Change in sulfate ion deposition across the US, 1985 - 2008

19. Acid Rain • However, the research of the last 25 years illustrates that perhaps 30% or more of acidified waterways were naturally acidified; this complicates the determination of whether an acidified waterway is the result solely of human activities • Regardless, the reduction in sulfurous and nitrogen gas emissions has reduced the severity of the acid rain problem (see slide)

20. Acid Rain Trends 2010

21. Acid Rain Updates • In 2011 the US EPA finalized the Cross State Air Pollution Rule which aims at reducing sulfur oxide (another 70%) and nitric oxide (another 50%) by 2014 • Hundreds of ponds and lakes in the Adirondacks, previously devoid of life, are being restocked with fish and other species – so far the fish are surviving

22. Acid Rain • Over the years, this issue has strained international relations between the U.S. and Canada: the Canadian government contends the bulk of their acidified waterways in the provinces of Ontario and Quebec are the result of U.S. air pollutants (sulfur dioxide, nitrogen oxides) drifting into Canada – they have limited sources of these gas emissions compared to the perceived damage • How do you think this issue should be addressed?

24. Acid Rain • Besides the environmental damage, don’t forget that acid rain hastens corrosion of most metals and dissolution of certain (e.g., limestone) building materials (see slide)

25. Dissolution of limestone and marble by acidic rain

26. Acid Rain • Acid rain problems are accentuated when the affected area is underlain by granitic bedrock (like most of Ontario and Quebec) and acid soils; there’s little chance for neutralizing reactions • If the affected area is underlain by limestone or similar rocks and alkaline soils the effects of the acid rain can be somewhat neutralized • What’s the main ingredient in many antacids (e.g., TUMS)?

27. Acid Rain Response • Stricter air quality laws mandating lower emissions by polluters • Waterway liming – lime, ground limestone, dropped into waterways from low-flying airplanes to reduce the water acidity • Viability of this process? (“An ounce of prevention is worth a pound of cure.”)

28. Particulate Pollution • Anthropogenic (human-produced) particulate pollution (e.g., diesel engine exhaust, road construction dust) probably < 10% of natural particulate pollution (e.g., loess – natural rock dust) • Nature of the problem depends on the reactivity of the particulates, their concentration and residence time; e.g., fine rock and mineral dust may be carcinogenic; some particulates are chemically toxic

29. Particulate Pollution • It was previously thought that aerosols and particulates had short atmospheric residence times – however, we are now concerned about < 2.5 and < 10 micron particulates • Related note: the U.S. Centers for Disease Control and Prevention stated in 2012 that an estimated 25 million Americans have asthma • Is there a microscopic particulate particle air pollution cause? Perhaps even a connection to the wear of radial tires? • Fortunately, overall human sources of particulate pollution in the U.S. are decreasing (see slide)

30. U.S. Particulate Emissions

31. Particulate Pollution • Another interesting connection: much atmospheric soot drifts in the upper atmosphere and settles onto Arctic ice • The darkened ice absorbs sunlight more effectively, encouraging more rapid ice melting – another aspect of global climate change to consider!

32. Ground-level Ozone • Ozone (O3) – a pale blue gas that near the Earth’s surface is a component of photochemical (light induced) smog • E.G., NOx (nitrogen oxides) gases are released from vehicle exhaust; sunlight energy breaks the bond between the N and O atoms in the NOx compound • Then O + O2  O3 • Why should we care? LA smog

33. Ground-level Ozone • Ground-level ozone is a serious lung pollutant; moderate-term (days – weeks) exposure to atmospheric levels > 160 ppb (parts per billion) could cause permanent lung tissue damage (scarring) • How does this issue relate to the “ozone-action” days we hear announced by the media? • How could this and other near-surface pollutants be affected by weather (e.g., thermal inversions) and topography?

34. Weather/Topography Complications • Normally air temperature decreases with altitude in the lower atmosphere • Thermal inversion – air temperature increases with increasing altitude in lower atmosphere; a warmer, less dense overlying air mass can trap pollutants in the colder, more dense underlying air (see slides) • Note also how the topography (e.g., mountains) can restrict air circulation and encourage pollutant concentration

35. Normal Thermal Inversion

36. Examples of How Topography Facilitates Thermal Inversion

37. Stratospheric Ozone • Stratosphere – volume of Earth’s atmosphere that extends from ~ 10 – 15 km altitude to an altitude of ~ 50 km; it contains about 90% of the atmosphere’s naturally occurring ozone • How does stratospheric ozone benefit life on Earth?

38. Stratospheric Ozone Stratosphere – volume of Earth’s atmosphere that extends from ~ 10 – 15 km altitude to an altitude of ~ 50 km; it contains about 90% of the atmosphere’s naturally occurring ozone How does stratospheric ozone benefit life on Earth?

39. Stratospheric Ozone • Studies show there are natural reactions which create and destroy ozone; e.g., O3 + UV (Ultraviolet light)  O + O2 ; O + O2  O3; O2 + UV  O + O; O3 + O  2 O2 • The previous reactions typically maintain an average stratospheric ozone concentration of ~ 10 ppm or 300 DU (Dobson Units) • Remember: there is no discrete “ozone layer” (see slide)

41. Stratospheric Ozone • Satellite and ground-based measurements suggest worldwide average stratospheric ozone levels have declined about 6-9% over the last few decades (see slides) • Make sure you really understand what is meant by the term “ozone hole” (concentrations < 220 Dobson Units) • Why should we care about declining stratospheric ozone levels?

43. South Pole

45. Antarctic Ozone 2010: ~21 2010: 118 Source: NASA

46. Ozone Depletion Over Northern Hemisphere Source: Data from NASA, Goddard Space Flight Center.

47. Stratospheric Ozone • Ramifications of stratospheric ozone reduction? • 1) Increase in skin cancers • 2) Increase in eye disorders • 3) Decrease in immune response • 4) Decrease in plant productivity • 5) Possible enhancement of Greenhouse Effect due to less plant productivity • 6) Increase in ground-level ozone concentrations

48. Stratospheric Ozone • Possible anthropogenic (human) cause of stratospheric ozone depletion? • Major culprit: Chlorofluorocarbons (CFCs – also known as freons – primarily used as a refrigerant gas, created in the 1930s) • Lab experiments suggest the components of CFCs (especially chlorine), once they ascend into the stratosphere and react with UV light, initiate ozone-depleting reactions that occur faster than the natural replenishment reactions (see slides)

49. CFCs in Ozone Destruction Source: Images courtesy NASA.

50. Stratospheric Ozone • Outcomes of research? International agreements (Montreal Protocol and its amendments) signed by more than 100 nations terminated CFC production at end of 1996; the use of some freons still being “phased out” • Concern: a batch of CFCs may take 10 years to ascend into the stratosphere and remain active in the stratosphere for 75-100 years! • Therefore, can we forget this issue?