1. NATS 101 Lecture 23 Air Pollution Meteorology

2. AMS Glossary of Meteorology
air pollution—The presence of substances in the atmosphere, particularly those that do not occur naturally.
These substances are generally contaminants that substantially alter or degrade the quality of the atmosphere.
The term is often used to identify undesirable substances produced by human activity, that is, anthropogenic air pollution.
Air pollution usually designates the collection of substances that adversely affects human health, animals, and plants; deteriorates structures; interferes with commerce; or interferes with the enjoyment of life.

3. Major Air Pollution Episodes of Historic Significance
Some of the worst events in the last two centuries occurred in London
Key ingredients: calm winds, fog, smoke particles from coal burning
deaths
deaths
,000 deaths (Dec 5 - 9)
Last event led to the Parliament passing a Clean Air Act in 1956

5. Major U.S. Air Pollution Episodes of Historic Significance
U.S. air quality degraded shortly after the beginning of the industrial revolution
Coal burning in Central and Midwest U.S.
1939 St. Louis Smog Nov 28
1948 Donora, PA in the Monongahela River Valley
20 deaths, 1000’s took ill in 5 days Oct 27
Prompted Air Pollution Control Act of 1955
Ignored automobiles

6. Major U.S. Air Pollution Episodes of Historic Significance
1960s - NYC had several severe smog episodes
1950s onward – LA had many smog alerts from an increase in industry and motor vehicle use
Led to passage of the Clean Air Act of 1970 (updated 1977 and 1990)
Empowered Federal Government to set emission standards that each state had to meet

7. U.S. Air Pollution Examples
Smog in San Gabriel Valley, (Photo: EPA.)
1963 photo of a severe smog episode in New York City. (Photo: AP/Wide World Photo, EPA Journal Jan/Feb 1990.)

8. Air Pollution in Grand Canyon
Even remote areas are affected by pollution
Canyon on a clear day
Canyon on a smog day
Nice link to Lyndon Valley State College that has useful material for a NATS-type course

9. Primary Pollutants Injected directly into atmosphere
Carbon Monoxide (CO)
odorless, colorless, poisonous gas
byproduct of burning fossil fuels
body acts as if CO is O2 in blood, can result in death
Nitrogen Oxides (NOx, NO)
NO - nitric oxide
emitted directly by autos, industry

10. Primary Pollutants Sulfur Oxides (SOx)
SO2 - sulfur dioxide
produced largely through coal burning
responsible for acid rain problem
Volatile Organic Compounds (VOCs)
highly reactive organic compounds
released through incomplete combustion and industrial sources
Particulate Matter (dust, ash, smoke, salt)
10 um particles (PM10) stay lodged in your lungs
2.5 um particles (PM2.5) can enter blood stream

11. Secondary Pollutants Form in atmosphere from chemical-photochemical reactions that involve primary pollutants
Sulfuric Acid H2SO4
major cause of acid rain
Nitrogen Dioxide NO2
brownish hue
L.A. Sky Colors Dec 2000
Mark Z. Jacobson

12. Secondary Pollutants Ozone O3
colorless gas
has an acrid, sweet smell
oxidizing agent
Primary and secondary pollutants are found in the two types of smog:
London-type smog
LA-type photochemical smog (LA AQMD)
SMOG = SMOKE + FOG

13. Human Response to One Hour Pollutant Exposure (Turco, p194)
Concentration
Part per million by mass
Symptom CO
10-30 ppmm
Time distortion (typical urban level)
100 ppmm
Throbbing headache (freeway background, 100 ppmm)
300 ppmm
Vomiting, collapse (tobacco smoke, 400 ppmm)
600 ppmm
Death
CO sticks to hemoglobin, forming carboxyhemoglobin (COHb), which reduces the capacity of hemoglobin to carry O2 to cells

14. Physiology of Exposure to CO
COHb level is 5%-15% for cig puffers!

15. Human Response to One Hour Pollutant Exposure (Turco, p194)
Concentration
Parts per million by mass
Symptom
NO2
ppmm
Respiratory impact (long term exposure promotes disease)
ppmm
Breathing difficulty
ppmm
Acute asthma
150 ppmm
Death (may be delayed)

16. Human Response to One Hour Pollutant Exposure (Turco, p194)
Concentration
Parts per million by mass
Symptom O3
0.02 ppmm
Odor threshold (sweet)
0.1 ppmm
Nose and throat irritation in sensitive people
0.3 ppmm
General nose and throat irritation
1.0 ppmm
Airway resistance, headaches (long term lead to premature aging of lung tissue)

17. Human Response to One Hour Pollutant Exposure (Turco, p194)
Concentration
Parts per million by mass
Symptom
SO2
0.3 ppmm
Taste threshold (acidic)
0.5 ppmm
Odor threshold (acrid)
1.5 ppmm
Bronchiolar constriction Respiratory infection

19. Table 12-2, p.328

20. Beijing Air Pollution
Record Pollution Levels AQI > Hazardous AFP Photo
Where’s Beijing? NASA MODIS Visible
Beijing smog during 2008 summer olympics

21. Pollution Knows No Boundaries
FIGURE 12.4 A thick haze about200 km wide and about 600 km long covers a portion of the East China Sea on March 4, The haze is probably a mixture of industrial air pollution, dust, and smoke.
April 2001 China Dust Transport Across Pacific
Fig. 12-4, p.322

22. U.S. Pollutant Trends
Most pollutants decreased after the 1970 Clean Air Act
Lead
Particulates
SO2
VOC’s CO
NO2 is Leveling Off
FIGURE 12.9 Emission estimates of six pollutants in the United States from1940–1995. (Data courtesy of United States Environmental Protection Agency.)
Fig. 12-9, p.328

23. AQI > 150 for CO, SO2, NO2, O3 and PM
FIGURE The number of unhealthful days(by county) across the United States for any one of the five pollutants(CO, SO2, NO2, O3, and particulate matter) during1990. (Data courtesy of United States Environmental Protection Agency.)
AQI > 150 for CO, SO2, NO2, O3 and PM
Fig , p.329

25. 90% total pollutants
10% total pollutants
Table 12-1, p.320

26. Percentage of Primary Pollutants
FIGURE 12.2 (a) Estimates of emissions of the primary air pollutants in the United States on a per weight basis
Fig. 12-2a, p.320

27. Percentage of Primary Sources
FIGURE 12.2 (b) the primary sources for the pollutants. (Data courtesy of United States Environmental Protection Agency.)
Fig. 12-2b, p.320

28. Air Pollution Weather Strong low-level inversion
Subsidence inversion that diurnal heating does not break or weaken significantly
Weak surface winds
Persistent surface anticyclone
Sunny weather for photochemical smog
Hot weather to accelerate O3 production

29. FIGURE The inversion layer prevents pollutants from escaping into the air above it. If the inversion lowers, the mixing depth decreases and the pollutants are concentrated within a smaller volume.
Fig , p.333

30. Top of Mixing Layer Fig. 12-13, p.333
FIGURE A thick layer of polluted air is trapped in the valley. The top of the polluted air marks the base of a subsidence inversion and the top of the mixing layer.
Fig , p.333

31. Valleys Trap Pollutants
L.A. is in a basin surrounded by mountains that trap pollutants and usually has onshore flow that creates frequent inversions.
Pollutants can only escape through narrow canyons
FIGURE At night, cold air and pollutants drain downhill and settle in low-lying valleys.
Fig , p.334

32. Leading Edge of Sea Breeze and “Smog Front” over Inland SoCal
FIGURE The leading edge of cool, marine air carries pollutants into Riverside, California.
Fig , p.333

33. Air Pollution Dispersion
Air pollution dispersion is often studied with simple models, termed Box Models.  How is a box defined for the LA basin?
Box Model Boundaries for the LA Basin
Ventilation factor is a simple way of relating concentrations of pollutants to parameters that modulate the dispersion of pollutants in a local environments.
An increase in either the mixing height or the wind speed increases the effective volume in which pollutants are allowed to mix.
The larger the volume, the lower the pollution concentration.
How does a box model work?

34. Ventilation Factor (VF)
Mixing Height
Length = Wind Speed  Time
Volume ~ Length  Height
VF = Mixing Height  Wind Speed

35. Acid Rain and Deposition
Sulfur dioxide (SO2) and oxides of nitrogen (NOx) within clouds (including fog) form acidic particles when they react with water:
SO2 + H2O  H2SO4 (sulfuric acid)
NOx + H2O  HNO3 (nitric acid)
Acid Rain is worse downstream of the point sources of pollution
Acid Rain affects Trees, Lakes, Structures
Acid Deposition is a world-wide problem

36. pH is logarithmic scale
pH is logarithmic scale. An one unit change denotes a factor of 10 difference.
FIGURE The pH scale ranges from 0 to 14, with a value of 7considered neutral. Values greater than 7 are alkaline and below 7 are acidic. The scale is logarithmic, which means that rain with pH 3 is 10 times more acidic than rain with pH 4 and 100 times more acidic than rain with pH 5.
Fig , p.338

37. pH = 5.6 for pristine rain

38. Acidified Forest in Czechoslovakia
FIGURE The effects of acid fog in the Great Smoky Mountains of Tennessee.
Fig , p.339

39. Impact on Aquatic Organisms

40. Sandstone Figure in Germany
Herr Schmidt-Thomsen
Herr Schmidt-Thomsen
1908
1968

41. Summary Air Pollutants – Long History
Primary: CO, NOx, SOx, VOC, PM
Secondary: H2SO4, NO2, O3
Global Problem - Knows No Boundaries!
Serious Health Consequences
US Air Improving - Clean Air Act
But It is Degrading in Emerging Economies
Air Pollution Weather and Air Dispersion
Acid Rain

42. NATS 101 Lecture Ozone Depletion

43. Supplemental References for Today’s Lecture
Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN )
Moran, J. M., and M. D. Morgan, 1997: Meteorology, The Atmosphere and the Science of Weather, 5th Ed. 530 pp. Prentice Hall (ISBN )

44. Review: Ultraviolet (UV) Absorption
Visible
Review: Ultraviolet (UV) Absorption IR
O2 and O3 absorb UV (shorter than 0.3 m)
Therefore, reductions in the level of O3 would increase the amount of UV radiation that penetrates to the surface
Ahrens, p 36

45. Hazards of Increased UV
Increase number of cases of skin cancers
Increase in eye cataracts and sun burning
Suppression of human immune system
Damage to crops and animals
Reduction in ocean phytoplankton

46. Natural Balance of Ozone
Disassociation of O2 absorbs UV < 0.2 m
O2 + UV  O + O
O3 forms when O2 and O molecules collide
O2 + O  O3
Disassociation of O3 absorbs m UV
O3 + UV  O2 + O
Balance exists between O3 creation-destruction
CFC’s disrupts balance
Danielson et al, Fig 2.28

47. Sources of CFC’s CFC’s make up many important products Refrigerants
Insulation Materials
Aerosol Propellants
Cleaning Solvents

48. Commonly Used CFC’s
Name Formula Primary Use Residence Time
(50% decrease)
CFC-11 CCl3F Propellant ~55 years
CFC-12 CCl2F2 Refrigerant ~100 years
CFC-113 C2Cl3F3 Cleaning Solvent ~65 years
It would take years for CFC levels to start falling if all production ended today due to leakage of CFC’s from old appliances, etc.

49. Chronology of Ozone Depletion
1881 Discovery of ozone layer in stratosphere
1928 Synthesis of CFC’s for use as a refrigerant
1950s Rapid increase in use of CFC’s
1974 Description of ozone loss chemical reactions
1979 Ban of CFC use in most aerosol cans in U.S.
1980s Growth of CFC use worldwide
1985 Discovery of Antarctic ozone hole
1987 Adoption of Montreal Protocol calling for a 50% reduction in use of CFC’s by 1998

50. Chronology of Ozone Depletion
1989 Confirmation of ozone declines in mid-latitudes of Northern Hemisphere and in the Arctic
1990 Montreal Protocol amended to require a complete phase out of all ozone depleting chemicals by 2000
1990 U.S. requirement for recycling of CFC’s
1992 Discovery of high levels of ClO over middle and high latitudes of Northern Hemisphere
1992 Further amendment of Montreal Protocol calling for an accelerated phase out by ozone depleting chemicals
2100 Time needed for ozone layer to heal completely?

51. How O3 is Measured: Dobson Unit
Ozone can be measured by the depth of ozone if all ozone in a column of atmosphere is brought to sea-level temperature and pressure.
One Dobson unit corresponds to a 0.01 mm depth at sea-level temperature and pressure
The ozone layer is very thin in Dobson units.
There are only a few millimeters (few hundred Dobsons) of total ozone in a column of air.

52. Mean Monthly Total Ozone
Huge decrease in O3 over Antarctica during the period

53. Williams, The Weather Book
Setting the Stage
Conditions over Antarctica promote ozone loss.
Circumpolar vortex keeps air over Antarctica from mixing with warmer air from middle latitudes.
Temperatures drop to below oC in stratosphere.
Chemical reactions unique to extreme cold occur in air isolated inside vortex.
Williams, The Weather Book

54. Williams, The Weather Book
How Ozone is Destroyed
June: Winter begins.
Polar vortex strengthens and temperatures begin to fall.
July-August: The temperatures fall to below -85oC.
Ice clouds form from water vapor and nitric acid.
Chemical reactions that can occur on ice crystals, but not in air, free chlorine atoms from the CFC.
Williams, The Weather Book

55. How Ozone is Destroyed
Sept: As sunlight returns in early Spring, stratospheric temperatures begin to rise.
Clouds then evaporate, releasing chlorine atoms into air that were ice locked.
Free chlorine atoms begin destroying ozone.
Oct: Lowest levels of ozone are detected in early spring.
Nov: Vortex weakens and breaks down, allowing ozone poor air to spread.
Danielson et al, Fig 2.29

56. Chemistry of the Ozone Hole
Chlorine atoms can be freed from CFC’s by UV reaction
CCl3F + UV  CCl2F + Cl
CCl2F2 + UV  CClF2 + Cl
C2Cl3F3 + UV  C2Cl2F3 + Cl
Once a chlorine atom is freed, it can destroy thousands of ozone molecules before being removed from the air
Cl + O3  O2 + ClO
ClO + O  O2 + Cl
CFC-11
Moran and Morgan, Fig 2.19

57. Annual Cycle of Ozone over SP

58. Mean Monthly Total Ozone
NASA web site
Decrease in O3 over N.H. during the period 1979 to 1993.

59. Ozone Hole Statistics Largest ozone hole ever observed: 24 Sept 2006.
Daily max ozone hole area (2009): 24 million km2 on 17 September.
Daily min ozone value area (2009): 94 DU on 26 September.
Largest ozone hole ever observed: 24 Sept 2006.

60. Key Points: Ozone Hole
Chlorofluorocarbons (CFCs) disrupt the natural balance of O3 in S.H. stratosphere
CFCs responsible for the ozone hole over SP!
Responsible for lesser reductions worldwide.
Special conditions exist in stratosphere over Antarctica that promote ozone destruction:
Air trapped inside circumpolar vortex
Cold temperatures fall to below -85oC

61. Key Points: Ozone Hole CFCs stay in atmosphere for ~100 years
One freed chlorine atom destroys thousands of O3 molecules before leaving stratosphere
Montreal Protocol mandated total phase out of ozone depleting substances by 2000.
Even with a complete phase out, O3 levels
Would not increase for another years
Would not completely recover for ~100 years