| 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. | ||
| 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. | ||
| 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 | ||
| 1873 - 700 deaths | ||
| 1911- 1150 deaths | ||
| 1952 - 12,000 deaths (Dec 5 - 9) | ||
| Last event led to the Parliament passing a Clean Air Act in 1956 | ||
| Slide 4 |
| 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, 1000Õs 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 |
| Air Pollution in Grand Canyon |
| Even remote areas are affected by pollution | |
| Canyon on a clear day | |
| Canyon on a smog day |
| 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 | ||
| 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 | ||
| Human Response to One Hour Pollutant Exposure (Turco, p194) |
| Physiology of Exposure to CO |
| Human Response to One Hour Pollutant Exposure (Turco, p194) |
| Human Response to One Hour Pollutant Exposure (Turco, p194) |
| Human Response to One Hour Pollutant Exposure (Turco, p194) |
| Slide 18 |
| Slide 19 |
| Beijing Air Pollution |
| Slide 21 |
| U.S. Pollutant Trends 1940-1995 |
| Most pollutants decreased after the 1970 Clean Air Act | ||
| Lead | ||
| Particulates | ||
| SO2 | ||
| VOCÕs | ||
| CO | ||
| NO2 is Leveling Off | ||
| Slide 23 |
| Slide 24 |
| Slide 25 |
| Slide 26 |
| Slide 27 |
| 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 |
| Slide 29 |
| Slide 30 |
| Slide 31 |
| Slide 32 |
| 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) |
| 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 Þ H2SO4 (sulfuric acid) | |
| NOx + H2O Þ 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 |
| Slide 36 |
| Slide 37 |
| Slide 38 |
| Impact on Aquatic Organisms |
| Sandstone Figure in Germany |
| 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 TodayÕs Lecture |
| Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN 0-697-21711-6) | |
| Moran, J. M., and M. D. Morgan, 1997: Meteorology, The Atmosphere and the Science of Weather, 5th Ed. 530 pp. Prentice Hall. (ISBN 0-13-266701-0) |
| Review: Ultraviolet (UV) Absorption |
| O2 and O3 absorb UV (shorter than 0.3 mm) | |
| Therefore, reductions in the level of O3 would increase the amount of UV radiation that penetrates to the surface |
| 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 |
| Disassociation of O2 absorbs UV < 0.2 mm | |
| O2 + UV ¨ O + O | |
| O3 forms when O2 and O molecules collide | |
| O2 + O ¨ O3 | |
| Disassociation of O3 absorbs 0.2-0.3 mm UV | |
| O3 + UV ¨ O2 + O | |
| Balance exists between O3 creation-destruction | |
| CFCÕs disrupts balance |
| Sources of CFCÕs |
| CFCÕs make up many important products | |
| Refrigerants | |
| Insulation Materials | |
| Aerosol Propellants | |
| Cleaning Solvents | |
| Commonly Used CFCÕs |
| 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 10-20 years for CFC levels to start falling if all production ended today due to leakage of CFCÕs from old appliances, etc. |
| Chronology of Ozone Depletion |
| 1881 Discovery of ozone layer in stratosphere | |
| 1928 Synthesis of CFCÕs for use as a refrigerant | |
| 1950s Rapid increase in use of CFCÕs | |
| 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 CFCÕs by 1998 |
| 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 CFCÕs | |
| 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? |
| 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 |
| 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 -85oC in stratosphere. | |
| Chemical reactions unique to extreme cold occur in air isolated inside vortex. |
| 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. |
| 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. |
| Chemistry of the Ozone Hole |
| Chlorine atoms can be freed from CFCÕs 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 |
| Annual Cycle of Ozone over SP |
| Mean Monthly Total Ozone |
| Ozone Hole Statistics |
| 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 |
| 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 10-20 years | |
| Would not completely recover for ~100 years |