1 / 51

ATMOSPHERIC POLLUTION

ATMOSPHERIC POLLUTION. Chapter 21. Donora – Pennsylvania, Oct 26,1948. Air-pollution essentials. Constituents of the atmosphere. N2 78.08% O2 20.95% Ar 0.93% CO2 0.03% Water vapor 0 – 4%

kasia
Download Presentation

ATMOSPHERIC POLLUTION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ATMOSPHERIC POLLUTION Chapter 21

  2. Donora – Pennsylvania, Oct 26,1948

  3. Air-pollution essentials

  4. Constituents of the atmosphere N2 78.08% O2 20.95% Ar 0.93% CO2 0.03% Water vapor 0 – 4% 40 trace gases (O3, He, H, NOx, SO2, Ne) Aerosol, dust, C particles, pollen, sea salts, microorganisms

  5. Air pollutants • Substances in the atmosphere that have harmful effects. Depends on: • Amount of pollutant • Amount of space • Mechanism that removes the pollutant from air

  6. Atmospheric cleansing • Three natural occurring cleansers: • Hydroxyl radical (OH) • Sea salts • Microorganisms

  7. Atmospheric cleansing: hydroxyl radical (OH)

  8. Appearance of smog • Industrial smog: • Acombination of smoke and fog • An irritating grayish mixture of soot, sulfurous compounds and water vapor

  9. Appearance of smog • Photochemical smog • Brownish irritating haze • Produced when several pollutants from automobile exhausts react with sunlight

  10. Temperature Inversions

  11. Impact of Smog • Long term temperature inversions can produce a build up of pollutants to dangerous levels • Smog causes headaches, nausea, eye and throat irritationand aggravate preexisting respiratory conditions • Air pollution affects trees and plants • Accelerates metal corrosion and the deterioration of rubber, fabrics and other materials.

  12. Major air pollutants and their sources

  13. Types of air pollutants • Primary pollutants • Combustion of coal, gasoline, other liquid fuels and refuse • CH4 + 2O2 CO2 + 2 H2O • Evaporation and strong winds • Secondary pollutants

  14. 578

  15. U.S. emissions of five primary air pollutants (2001)

  16. Clean Air Act impacts

  17. How ozone and other photochemical oxidants form? In the absence of VOCs • NO2  NO +O • O + O2  O3 • NO + O3  NO2 + O2

  18. How ozone and other photochemical oxidants form? With VOCs • NO2  NO +O • O + O2  O3 • NO + VOCs  PANs • VOCs + O  Aldehydes, ketones Accumulation of ozone, VOCs, aldehydes and ketones

  19. Acid deposition • Acid precipitation • Any precipitation that is more acidic than usual • Acid deposition • Combination of precipitation and dry particle fallout

  20. Acids and bases • pH: concentration of hydrogen ions • Acid: any chemical that releases hydrogen ions when dissolved in water • HCl, H2SO4, HNO3, H2CO3 • Base: any chemical that releases hydroxide ions • NaOH, Ca(OH)2, KOH, NH4OH

  21. Extent and potency of acid precipitation • Rainfall  pH 5,6 • CO2 + H2O  H2CO3 • Acid precipitation  pH 5,5 or less • SO2 + OH-  H2SO4 • NOx + OH-  HNO3

  22. Natural vs anthropogenic sources Anthropogenic sources • Industry • Transportation • Fossil fuel and Coal burning electric utility plants Natural sources • Sulfur dioxides • Volcanoes • Sea spray • Microbial processes • Nitrogen oxides • Lighting • Burning biomass • Microbial processes

  23. Impacts of air pollutants Health and Environment

  24. Effects on human health • Chronic effects: • Long term exposure to SO2  bronchitis • Inhalation of ozone  inflammation / fibrosis of lungs • CO2  reduced capacity of the blood to carry oxygen • CO  heart disease • NOx  impairs lung function/ affects the immune system • Particulate matter  respiratory and cardiovascular pathologies. • Allergens and other compounds in polluted air  Asthma • Lead  mental retardation, high blood pressure (banned on 1996)

  25. Effects on human health • Acute effects • In severe cases air pollution may cause death • Air pollution may increase pre-existing symptoms.

  26. Effects on human health • Carcinogenic effects • One major source of carcinogens is diesel exhausts. • Soot • Benzene • Found in motor fuels, manufacture of detergents, explosives and pharmaceuticals, tobacco smoke • Causes leukemia and other blood disorders and damage to the immune system.

  27. Effects on the environment • Crop damage • Forest damage

  28. Effects on the environment • Materials and aesthetics • Visibility

  29. Effects on the environment • Acid deposition in aquatic ecosystems • Higher organisms die off • Leach aluminum and various heavy metals from the soil

  30. Buffering capacity of aquatic ecosystems • Buffer: a substance that, when present in a solution, has a large capacity to absorb hydrogen ions and thus maintain the pH at a relatively constant value.

  31. Bringing air pollution under control

  32. Clean air act (1970) • Law administered by the EPA • Foundation of U.S. air pollution control efforts • Calls for • identifying the most widely spread pollutants • Setting ambient standards • Establishing control methods and timetables to meet standards.

  33. National Ambient Air Quality Standards (NAAQS) • Standards for primary pollutants known as criteria pollutants • Primary standard is based on the presumed highest level that can be tolerated by humans without noticeable ill effects minus a 10% to 50% margin of safety • Short term standards are set to protect against acute effects • Long term standards are set to protect against chronic effects.

  34. National ambient air quality standards for criteria pollutants

  35. National Emission Standards for Hazardous Air Pollutants (NESHAPs) • Issued for eight toxic substances • Arsenic • Asbestos • Benzene • Beryllium • Coke-oven emissions • Mercury • Radionuclides • Vinyl chloride • The clean air act of 1990 extended this section naming 188 toxic air pollutants for the agency to track and regulate.

  36. Control strategies • Command and control • Industry was given regulations to achieve a set of limits on each pollutant • A local government agency would be in control • Difficult to implement • Total air pollutants were reduced by 48%

  37. Control strategies • Reducing particulates • The CAA mandated a phase-out of open burning of refuse and required that particulates from industrial stacks be reduced to “no visible emissions” • To reduce PM industries were required to install filters, electrostatic precipitators and other devices. • In 1997 the EPA added a new ambient air quality standard for particulates (PM2.5) • 1990 Clean Air Act Amendments (CAAA)  target specific pollutants under the control of a State Implementation Plan (SIP). Polluters obtain a permit that identifies the type of pollutant released, quantities and steps taken to reduce pollution. Permit fees provide funds for States to use in their air-pollution control activities. • Under the CAAA, states that fail to attain the required levels must submit attainment plants based on reasonably available control technology (RACT) measures

  38. Limiting pollutants from motor vehicles • CAA mandated a 90% reduction of emissions by 1975 • A new car emits today 75% less pollution that pre-1970 cars

  39. How are pollutants limited in motor vehicles? • Reduction in the size of passenger vehicles • Pollution control devices • Catalytic converter

  40. CAAA changes for motor vehicles • New cars sold in 1994 and thereafter were required to emit 30% less VOCs and 60% less NOx that cars sold in 1990 • Starting in 1992 in regions with continuing carbon monoxide problems, oxygen was to be added to gasoline • Initiate inspection and maintenance programs in metropolitan areas

  41. Managing ozone • The best way to reduce ozone levels is to reduce the emissions of VOCs • Motor Vehicles (50%) • Point sources: industries (30%) • Area sources: dry cleaners, print shops, household products (20%) • VOC emissions have declined 35% • A reduction of NOx levels should remove the ozone further.

  42. Controlling toxic chemicals in the air • Under the CAAA, 188 toxic pollutants were identified • EPA was in charge to identify sources and develop maximum achievable control technology (MACT) standards. • Options for substituting nontoxic chemicals • Giving industry some flexibility to achieve goals • Giving the state and local authorities the responsibility of control • Requiring cleaner burning fuels in urban areas

  43. Coping with acid deposition • Political developments • States where coal-burning power plants produced most of their electrical power blocked attempts to pass a legislation to take action on acid deposition • Other states, the scientific community and Canada’s diplomacy put pressure toward a resolution.

  44. Coping with acid deposition • Political developments • As a result the Title IV of the CAAA was passed • Mandates a reduction in both sulfur dioxide and nitrogen oxide levels • Provides emission allowances regulated by the EPA

  45. Coping with acid deposition • Accomplishments of Title IV • Many utilities are switching to low sulfur coal • Many utilities are adding scrubbers (liquid filters) • Many utilities are trading their emission allowances

  46. Unresolved issues

  47. Cost vs benefit • Measures taken to reduce air pollution carry an economic cost • The Office of Management and Budget (OMB) found that the yearly benefits of environmental regulations ranged from $121 to $193 billion, while the costs ranged from $37 to $43 billion • New source review • CAA requires all power plants and other polluting industrial facilities built after 1970 to incorporate “best available” pollution control technology. • Political and economical disagreements arose.

  48. Clear skies act • Addresses three major pollutants simultaneously: SO2, NOx and mercury • Applies a cap and trade strategy: • Cut SO2 emissions to a cap of 3 million tons • NO x emissions to a cap of 1.7 million tons • Mercury to a cap of 15 tons • Proposes to achieve goals by 2018

  49. Getting around • Half of the major air pollutants come from vehicles • Raising CAFE standards would help to address: • Dependence on imported oil • Health issues from smog and particulates • Carbon dioxide emissions and global climate change • Auto industry, fossil fuel industry and politicians continue to resist raising CAFÉ mileage requirements • Options considered to reduce automobile emissions include • Emission free vehicles: powered by electricity • Hybrid cars • Partial zero-emission vehicle: uses super clean gasoline • Mass transit ridership

More Related