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The Atmosphere and Atmospheric Pollution. Atmospheric Components. Chemical Components (elements) Nitrogen gas (N 2 ) makes up about 78% of the atmosphere Oxygen gas (O 2 ) makes up about 21% Other gases (Ar, He, etc.) <1%. Atmospheric Components. Most abundant compounds:

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atmospheric components
Atmospheric Components
  • Chemical Components (elements)
    • Nitrogen gas (N2) makes up about 78% of the atmosphere
    • Oxygen gas (O2) makes up about 21%
    • Other gases (Ar, He, etc.) <1%
atmospheric components1
Atmospheric Components
  • Most abundant compounds:
    • Carbon dioxide (CO2)
    • Water vapor varies greatly
      • Evaporation ()
      • Transpiration by plants ()
      • Precipitation, condensation ()
atmospheric components2
Atmospheric Components
  • Other components
    • Ozone (O3) - UV filter in upper stratosphere; bad in troposphere
    • Dust - from volcanoes, sandstorms, fires, etc. (pretty sunsets!)
atmospheric layers
Atmospheric Layers


  • Closest to the Earth’s surface
  • All weather changes take place here
  • Most of CO2 and H2O vapor here
  • Height varies from about 20 km at equator to about 8 km at poles - Why?
  • Temperature decreases with height
atmospheric layers1
Atmospheric Layers


  • Contains almost all the ozone (O3) in the atmosphere 3O2 +UV 2O3
  • Temperature rises with altitude
  • Gases released from volcanic eruptions stay here for years
  • Tops of thunderclouds can penetrate
outdoor air pollution1
Outdoor Air Pollution

The presence of atmospheric chemicals at concentrations high enough to harm organisms, ecosystem, or human-made materials

Come from natural sources: dust, wildfires, VOCs (plants)

Come from human sources: near industrialized/urban areas

outdoor air pollution2
Outdoor Air Pollution

Is air pollution a recent development?

outdoor air pollution3
Outdoor Air Pollution

Primary Pollutants:

  • emitted directly into the air

Secondary Pollutants:

  • Products of chemical rxns of 1⁰ pollutants
  • Good news?
  • Bad news?
  • What is the biggest pollution threat to poor?
outdoor air pollution4
Outdoor Air Pollution

Point source: specific spots where large quantities of pollutants are discharged (power plants and factories)

Nonpoint source: more diffuse, consisting of many small sources (automobiles)

outdoor air pollution5
Outdoor Air Pollution

Carbon Oxides:

CO and CO2

  • CO a result of incomplete combustion
  • CO from vehicle exhaust, tobacco smoke, forest fires, inefficient stoves, furnaces
  • Chronic exposure to CO: heart attacks, lung diseases
  • Acute exposure to CO: headache, nausea, drowsiness, death
outdoor air pollution6
Outdoor Air Pollution

Carbon Oxides:

CO and CO2

  • CO2 in the atm: 93% a result of carbon cycle, rest is from human activity
  • Considerable evidence: human-introduced CO2 is changing the climate
outdoor air pollution7
Outdoor Air Pollution

Nitrogen oxides (NOx):

Nitric oxide (NO)

  • Formed from high-temp engines, coal plants, lightning, bacteria (N-cycle)

2NO + O2 → 2NO2 (brownish gas; photochemical smog)

2NO2 + H2O → 2HNO3 (acid deposition)

  • Eye, nose, throat irritant, aggravate lung ailments
outdoor air pollution8
Outdoor Air Pollution

Sulfur oxides (SOx):

Sulfur dioxide (SO2)

  • One-third comes from S cycle
  • Rest from coal-burning plants, oil refining, smelting
  • Converted to aerosols of H2SO4 – more on this later
outdoor air pollution9
Outdoor Air Pollution


Solid particles and liquid droplets small enough to remain suspended

  • ~62% from natural sources
  • Human input: coal, cars, plowed fields, road construction, tobacco smoke
  • Fine (< 10μ) and ultrafine (<2.5μ) particles most damaging
outdoor air pollution10
Outdoor Air Pollution


  • Aggravate asthma, bronchitis
  • Shorten life

Toxic particles (Pb, Cd, PCBs)

  • Cause mutations, reproductive problems, cancer
  • According to EPA: 60-70,000 deaths
outdoor air pollution11
Outdoor Air Pollution


  • Part of smog
  • Causes coughing, breathing problems, aggravates heart and lung disease
  • Reduce resistance to colds, etc.
  • Irritant; damages plants, fabrics, tires, paints
  • Good O3 v. bad O3
outdoor air pollution12
Outdoor Air Pollution

Volatile Organic Componds (VOCs)

  • Organic cpds that exist as gas
  • Most are hydrocarbons
  • Methane is one example
  • Others: benzene, trichloroethylene, vinyl chloride are industrial solvents
  • Benzene →→ leukemia, blood disorders, immune damage, et al.
outdoor air pollution13
Outdoor Air Pollution

Industrial Smog

  • Main components: SO2, H2SO4, other particulates
  • Most of carbon in coal, oil → CO, CO2, soot
  • Ammonium sulfate also produced
  • Not as problematic in developed countries
outdoor air pollution14
Outdoor Air Pollution

Photochemical Smog

  • Activated by light
  • A mixture of 1⁰ and 2⁰ pollutants
  • Reactants: VOCs + NOx + sunlight
  • Products: O3, aldehydes, oxidants, HNO3, peroxyacyl nitrates (PANs)
  • Hotter days: more ozone
  • Natural smog: Smokey Mountains (terpenes)
outdoor air pollution15
Outdoor Air Pollution

Factors Affecting: natural reduction

  • Settling
  • Precipitation
  • Ocean spray wash-out
  • Winds
  • Chemical reactions
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Outdoor Air Pollution

Factors Affecting: increase

  • Urban buildings slow winds
  • Hills/mountains
  • High temperatures (↑ rxn rates)
  • VOCs from oak, poplar trees, kudzu
  • Grasshopper effect – transport by global winds
  • Temperature inversion
outdoor air pollution control
Outdoor Air Pollution Control

Prevention, Technology, Innovation

  • Fluidized bed combustion: coal burned w/ CaCO3, produces CaSO4, which is used to make sheetrock
  • Controlling T and O2 can reduce NOx
  • Catalytic converters also reduce NOx (also led to removal of Pb from gasoline)
  • Control of particulates: baghouse filters, electrostatic precipitators, scrubbers
outdoor air pollution control1
Outdoor Air Pollution Control

Prevention, Technology, Innovation

  • Municipal restrictions developed, including restrictions on dry-cleaners, gas stations, even bakeries (oh, no!), car use restrictions, carpool lanes
  • Clean Air Act amendments → reduced sulfur emissions; buying and selling of allowances that allowed release of certain amount of S
acid deposition1
Acid Deposition

Industry Smokestacks

  • Reduce local air pollution
  • Increase regional pollution as SOx and NOx are carried downwind
  • Sulfuric and nitric acids are formed
acid deposition2
Acid Deposition

Acid Deposition

  • Remain in atmosphere 2 – 14 days
  • Fall as wet deposition (rain, snow) or dry deposition (crystals)
  • Some regional soils can buffer
  • Worst acid deposition - Asia
acid deposition3
Acid Deposition


  • Respiratory disease
  • Damages human-made structures
  • Leach toxic chemicals from soils/rock
  • Aquatic systems (ΔpH, release Al3+)
  • Forest, crop damage
acid deposition4
Acid Deposition


  • Reduce coal use/use low-sulfur coal
  • Increase natural gas, renewable energy
  • Remove SOx and NOx from smokestacks
  • Tax emissions
  • Cleanup: lime to lakes, phosphate fertilizer
indoor air pollution1
Indoor Air Pollution

Common Pollutants

  • Pesticides, lead (brought in on shoes)
  • Organic solvents
  • Dust mites, droppings
  • Molds and mildews
  • Formaldehyde & other VOCs
  • Radon
indoor air pollution2
Indoor Air Pollution

Alarming Facts (more harmful than outdoor)

  • Levels are generally higher in homes and cars (5x, 18x, respectively)
  • In developed countries, people spend more time inside
  • EPA: 18 indoor pollutants on carcinogen list
indoor air pollution3
Indoor Air Pollution

Sick Building Syndrome

  • Due in part to increased insulation
  • Indoor levels of VOCs and other materials increase
  • Synthetic materials (glues, etc)
  • Ventilation, chemical contamination, air intake, biological contamination
health effects1
Health Effects

Natural Defense

  • Simple columnar epithelium contains cilia and produce mucus
  • This line of defense gets broken down
  • Particulates embed in alveoli
  • Emphysema is irreversible; alveoli damaged, lose surface area
legislation addresses pollution
Legislation addresses pollution
  • Congress passed a series of laws starting in 1955
  • The Clean Air Act of 1970
    • Sets standards for air quality, limits on emissions
    • Provides funds for pollution-control research
    • Allows citizens to sue parties violating the standards
  • The Clean Air Act of 1990
    • Strengthens standards for auto emissions, toxic air pollutants, acidic deposition, stratospheric ozone depletion
    • Introduced emissions trading

Ambient Air Quality Standards

  • Standards for 6 criteria pollutants – CO, NOx, SO2, O3, Pb, & particulates
  • Standards for 188 hazardous chemicals
  • Public record: Toxic Release Inventory