NATS 101 Lecture 23 Air Pollution Meteorology

AMS Glossary of Meteorology air pollution—The presence of substances in the atmosphere, particularly those that do not occur naturally. atmosphere 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. anthropogenic 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.

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 – deaths Last event led to the Parliament passing a Clean Air Act in 1956 Other notable events over western Europe Meuse Valley –Key ingredients – calm winds, strong inversion close to ground, fog, smoke from factories –Pollution trapped in lowest m of a narrow valley –600 very ill, 60 deaths

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

Major Air Pollution Episodes of Historic Significance Other notable events over western Europe Meuse Valley, Belgium –Key ingredients: calm winds, strong inversion close to ground, fog, smoke from factories –Pollution trapped in lowest m of a narrow valley –600 very ill, 60 deaths

Major U.S. Air Pollution Episodes of Historic Significance U.S. air quality degraded with the beginning of the industrial revolution Coal burning in Central and Midwest U.S. –1939 St. Louis Smog Nov St. Louis Smog –1948 Donora, PA in the Monongahela River Valley1948 Donora –20 died, 1000’s ill in 5 days Oct 27 Prompted Air Pollution Control Act of 1955 –Ignored automobiles 1960s - NYC had several severe smog episodes 1950s onward – LA had many smog alerts from increase in industry and motor vehicle use Led to passage of the Clean Air Act of 1970 (updated 1977 and 1990) –Empowered Feds to set emission standards that each state had to meet

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 St. Louis Smog –1948 Donora, PA in the Monongahela River Valley1948 Donora, PA –20 deaths, 1000’s took ill in 5 days Oct 27 Prompted Air Pollution Control Act of 1955 –Ignored automobiles

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

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

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

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

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

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

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)LA AQMD SMOG = SMOKE + FOG

Human Response to One Hour Pollutant Exposure (Turco, p194) Pollutant Concentration Part per million by mass Symptom CO10-30 ppmmTime distortion (typical urban level) 100 ppmm Throbbing headache (freeway background, 100 ppmm) 300 ppmm Vomiting, collapse (tobacco smoke, 400 ppmm) 600 ppmmDeath CO sticks to hemoglobin, forming carboxyhemoglobin (COHb), which reduces the capacity of hemoglobin to carry O2 to cells

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

Human Response to One Hour Pollutant Exposure (Turco, p194) Pollutant Concentration Parts per million by mass Symptom NO ppmm Respiratory impact (long term exposure promotes disease) ppmmBreathing difficulty ppmmAcute asthma 150 ppmmDeath (may be delayed)

Human Response to One Hour Pollutant Exposure (Turco, p194) Pollutant Concentration Parts per million by mass Symptom O30.02 ppmmOdor threshold (sweet) 0.1 ppmm Nose and throat irritation in sensitive people 0.3 ppmmGeneral nose and throat irritation 1.0 ppmm Airway resistance, headaches (long term lead to premature aging of lung tissue)

Human Response to One Hour Pollutant Exposure (Turco, p194) Pollutant Concentration Parts per million by mass Symptom SO20.3 ppmmTaste threshold (acidic) 0.5 ppmmOdor threshold (acrid) 1.5 ppmm Bronchiolar constriction Respiratory infection

Table 12-2, p.328

SMOG and Haze over China January 10,

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

Fig. 12-4, p.322 Pollution Knows No Boundaries April 2001 China Dust Transport Across Pacific

U.S. Pollutant Trends Most pollutants decreased after the 1970 Clean Air Act Lead Particulates SO 2 VOC’s CO NO 2 is Leveling Off Fig. 12-9, p.328

Fig , p.329 AQI > 150 for CO, SO2, NO2, O3 and PM

Table 12-1, p % total pollutants 10% total pollutants

Fig. 12-2a, p.320 Percentage of Primary Pollutants

Fig. 12-2b, p.320 Percentage of Primary Sources

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

Fig , p.333

Fig , p.333 Top of Mixing Layer

Fig , p.334 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

Fig , p.333 Leading Edge of Sea Breeze and “Smog Front” over Inland SoCal

Ozone Production VOCs create Reactive Organic Gases (ROGs). ROGs react to form radicals. Alkylperoxy radical (RO2*) oxidizes NO to form NO2 faster than NO reacts with O3. Thus O3 is not destroyed to produce NO2. Each time a NO2 molecule is formed, it quickly results in the production of O3).

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?

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

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

Fig , p.338 pH is logarithmic scale. An one unit change denotes a factor of 10 difference.

pH = 5.6 for pristine rain

Fig , p.339 Acidified Forest in Czechoslovakia

Impact on Aquatic Organisms

Sandstone Figure in Germany Herr Schmidt-Thomsen

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

NATS 101 Lecture Ozone Depletion

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, 5 th Ed. 530 pp. Prentice Hall. (ISBN )

Review: Ultraviolet (UV) Absorption O 2 and O 3 absorb UV (shorter than 0.3  m) Therefore, reductions in the level of O 3 would increase the amount of UV radiation that penetrates to the surface IR Ahrens, p 36 UV Visible

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

Natural Balance of Ozone Danielson et al, Fig 2.28 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

Ozone Production-Destruction Moran and Morgan, Fig 2.18 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

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

Commonly Used CFC’s NameFormulaPrimary Use Residence Time (50% decrease) CFC-11CCl 3 FPropellant~55 years CFC-12CCl 2 F 2 Refrigerant~100 years CFC-113C 2 Cl 3 F 3 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.

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

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

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.

Mean Monthly Total Ozone Huge decrease in O 3 over Antarctica during the period

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 -85 o C in stratosphere. Chemical reactions unique to extreme cold occur in air isolated inside vortex. 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 -85 o C. 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

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

Chemistry of the Ozone Hole Chlorine atoms can be freed from CFC’s by UV reaction CCl 3 F + UV  CCl 2 F + Cl CCl 2 F 2 + UV  CClF 2 + Cl C 2 Cl 3 F 3 + UV  C 2 Cl 2 F 3 + Cl Once a chlorine atom is freed, it can destroy thousands of ozone molecules before being removed from the air Cl + O 3  O 2 + ClO ClO + O  O 2 + Cl Moran and Morgan, Fig 2.19 CFC-11

Annual Cycle of Ozone over SP

Mean Monthly Total Ozone Decrease in O 3 over N.H. during the period 1979 to NASA web site

Ozone Hole Statistics Daily max ozone hole area (2009): 24 million km 2 on 17 September. Daily min ozone value area (2009): 94 DU on 26 September. Largest ozone hole ever observed: 24 Sept 2006.

Key Points: Ozone Hole Chlorofluorocarbons (CFCs) disrupt the natural balance of O 3 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 -85 o C

Key Points: Ozone Hole CFCs stay in atmosphere for ~100 years One freed chlorine atom destroys thousands of O 3 molecules before leaving stratosphere Montreal Protocol mandated total phase out of ozone depleting substances by Even with a complete phase out, O 3 levels Would not increase for another years Would not completely recover for ~100 years