PBIO 100 Lecture Notes

I. THE ATMOSPHERE

• A. The atmosphere is a thin layer of gasses that envelope the earth (picture). It is composed of gasses held close to the Earth by gravity and the thermal movement of air molecules

  B. The major gasses in the atmosphere are nitrogen (78%), oxygen (21%), argon (0.9%), and carbon dioxide (0.03%). The atmosphere also contain trace amounts of numerous other elements and compounds

  C. The atmosphere is divided into several layers:

               200 km
               100   Thermosphere
                80                  
                70   Mesosphere
                50
                30   Stratosphere
                10   Troposphere
                 0

• • 1. Thermosphere - layer greater than 90 km
    • a. the hottest layer of the atmosphere (can reach 1300-1800 degrees Celsius); heat from absorption of solar radiation by oxygen molecules

    2. Mesosphere - layer about 70-80 km

    • a. atmosphere reaches coldest temperatures (about -90 degrees Celsius)

    3. Stratosphere - layer about 20-50 km

    • a. where commercial jets fly
      b. has a steady wind (but no turbulence or other weather)
      c. temperature increases with altitude because ozone gas absorbs ultraviolet radiation creating heat

    4. Troposphere - layer closest to Earth's surface; extends up to about 8-18 km (depending on location)

    • a. weather occurs in the troposphere; area that gets smog pollution
      b. contains abut 75% of the total mass of the atmosphere
      c. maximum air temperatures of this layer occur near the surface (air temperature drops with increasing height at a rate of 6.5 degrees Celsius per 1000 meters

II. FOSSIL FUELS

• A. Types of fossil fuels

• • 1. Coal (solid organic material) - formed from Carboniferous Period (300-350 million years ago) when most of the land was low and swampy; trees (horsetails, ferns, club mosses, gymnosperms) died but were covered over before they were decomposed - little oxygen for decomposition; over time, heat and pressure ---> peat and later ---> coal
    2. Oil and natural gas (liquid and gaseous organic material) - Actual process is not well understood, but organisms that contributed to oil and natural gas were probably planktonic
     

  B. Environmental effects of burning fossil fuels - the release into the atmosphere of particulates including:

  • •  

    1. sulfur dioxide - from burning fossil fuels, mostly coal in power plants
    2. carbon monoxide - about 90% in the atmosphere is from natural sources, and 10% comes mainly from fires, automobiles, and other sources of incomplete burning of organic compounds
    3. nitrogen oxides - from automobiles and power plants that burn fossil fuels
    4. hydrocarbons - about 80% from natural sources, and 20% primarily from automobiles

III. ENVIRONMENTAL CONSEQUENCES OF BURNING FOSSIL FUELS

• A. Acid rain 
  • 1. cause
    • a. acid rain is the acidic depositions that occur near or downwind of areas where there are major emissions of sulfur dioxide and nitrogen oxides (see figures one and two from W.H. Freeman Publishing)
      b. in the atmosphere they are transformed by reactions with oxygen and water to form sulfuric and nitric acids
      c. they fall from the atmosphere in the rain
      d. review these 1995 national maps of acid rain from the National Atmospheric Deposition Program/National Trends Network:
      • 1) total precipitation
        2) pH measurements (below 7 acid, 7 neutral, above 7 alkaline)
        3) sulfate ion deposition
        4) nitrate ion deposition

    2. effects

    • a. the acid rain changes the pH of the soil and water to damage plants (in Europe, see SO2 concentrations resulting in forest damage) and aquatic organisms
      b. in humans, acid rain can cause or aggravate lung disorders
      c. it also damages many building materials, including steel paint, plastics, cement, masonry, limestone, sandstone, and marble
      d. additionally it damages automobile coatings

  B. Global climate change  - probably the most pressing environmental problem today
   

  

  1. causes

  • a. greenhouse effect: carbon dioxide and other greenhouse gases (nitrogen oxides, ozone, CFCs, and methane) released into the atmosphere from human activities trap the infrared wavelengths of radiant energy so that the heat is not dispersed into space
    b. works like insulation
    • 1) review short wave and long wave radiation (long wave = infrared = heat) - example - park your car in the summer sun with windows rolled up; your car ends up like a oven, the glass traps the heat inside

    c. carbon dioxide

    • 1) carbon dioxide is a trace gas (less than 1%) in our atmosphere
      2) natural biological source is respiration; natural sink (what removes the gas) is photosynthesis
      3) until 150-200 years ago carbon dioxide in = carbon dioxide out
      4) Why is carbon dioxide increasing?
      • a) burning fossil fuels
        b) deforestation - has been estimated that 25-30% of carbon dioxide being added to the atmosphere is due to deforestation; from burning the forests and removing the carbon sinks

      5) see this figure from W.H. Freeman Publishing 

  2. effects

  • a. 2030 - doubling of CO₂ projected (since beginning of Industrial Revolution) resulting in surface air temperature changes (see chart)
    b. 3-8 degree F temperature increase in the next 100 years
              1) 1997 warmest year of the century
              2) 1997-98 warmest winter on record
              3) 1998 - each month January through May has set a new all-time record
              high global temperature
              4) 1998 warmest year of the millennium
    c. rise in sea level = flooding of coastal areas and islands; loss of land (1 foot rise will cause 10 mile loss in Florida) - warmer water expands, ice melts
    d. increase in severity and frequency of storms in coastal areas
    e. expanding deserts in interior of continents (U.S. grain belt) and a loss of water resources
    f. loss of species diversity
    • 1) many species are already under stress from other causes; this will push them over the brink
      2) will trees be able to migrate fast enough to keep pace with the change in climate? - climate change too rapid

    g. changes in agriculture due to environmental change (see the CIESIN link)
    h. humans living along coastal areas (Bangladesh and Egypt) or in drought areas will become environmental refuges; where will they go?
    i. there may also be an increase in human diseases with the spread of the tropics and tropical diseases and the effects of increased temperature on the human body

  3. solutions

  • a. developed nations must cut back on emissions (20% of population consumes 80% of world's resources)
    b. develop alternative, non-polluting energy sources (solar and solar hydrogen, wind) - only nuclear can presently supply large amounts of energy
    c. plant trees (plants use CO₂)
    d. develop energy-efficient products and conserve energy; example- fluorescent light bulbs - use energy conservation measures
    e. develop mass transit and reduce automobile use
    f. involve developing nations in global climate change efforts
    • 1) during 1990s, 96% of population growth will occur in developing nations
      2) as developing countries become industrialized, they will emit large quantities of greenhouse gases

IV. THE OZONE PROBLEM

• A. Ozone (O₃) - a form of oxygen

• • 1. It is naturally created in the Stratosphere when ultraviolet radiation breaks down the oxygen molecule (O₂) into two individual oxygen atoms. Each of these atoms combines with an O2 molecule to form ozone
     

  B.  Essential in one part (stratosphere) and a pollutant in another part of the atmosphere (troposphere)
   

  • 1. Ozone shield - the stratosphere (layer above the troposphere) is the location of ozone shield
    • a. ozone in stratosphere forms naturally- oxygen reacts with incoming ultraviolet (UV) radiation (from sun) to form ozone - pollution is breaking down faster than replenished
      b. stratospheric ozone blocks much of the UV from penetrating to Earth's surface - reflects it out; approximately 99% of all ultraviolet solar radiation is absorbed or screened out in the ozone layer
      c. ozone depletion in the stratosphere (see TOMS image)
      • 1) cause
        • a) ozone is broken down by human-made pollutants. Primary cause chlorofluorocarbons (CFCs) - used as propellants in aerosol cans, as coolants in a.c. and refrigerators, as foam for insulation and packaging, as sterilizers for hospitals
          b) also caused by halons (in many fire extinguishers), methyl chloroform (used to degrease metals), and carbon tetrachloride (used to manufacture pesticides and dyes)
          c) all contain chlorine

        2) effect

        • a) 1 atom of chlorine can destroy 100,000 ozone molecules
          b) initially observed over South Pole and later over North pole; ozone is also thinning everywhere else including North America
          • i. compare world maps from Toms Ozone Image Data
               world ozone map - 1979
               world ozone map - 1991

          c) tropospheric ozone doesn't replenish stratospheric ozone
          d) decrease in stratospheric ozone results in an increase in surface UV levels

        3) effects of high levels of UV

  • • • • a) humans - higher incidence of skin cancer and cataracts; also weakened immune system (see UV Index, Minutes to get a Sunburn, Health effects of overexposure to the sun, Health effects from increased exposure to UV-B radiation)
          b) plants- substantial crop damage, UV destroys chlorophyll
          c) concern - UV may damage plankton that forms the base of the food chain in Antarctica
          • i. if this occurs, the whole food chain might collapse- fish, seals, whales, penguins, and other birds
            ii. 1992 - evidence published that productivity in Antarctica is down

  2. Smog - ozone in troposphere formed by human activities

  • a. cause
    • 1) photochemical smog is caused by the reaction between solar radiation and the pollutants hydrocarbons and nitrogen dioxides emitted primarily from automobile use (see Los Angeles picture)
      2) also caused by large fires

    b. effects

    • 1) plants - at low concentrations can reduce plant growth rates and at higher concentrations can kill plant tissues and entire plants
      2) animals - the effects on animals involves reduced visibility and health problems (eye irritations and aggravate respiratory illnesses)
      3) Climate - Involved in global climate change (tropospheric ozone is a greenhouse gas)

Other Sites of Interest

Acid Rain
The effects of acid rain on forests
Acid rain program - EPA
Global Warming
Global change data 
Greenhouse effect
Ozone
The ozone hole, a multimedia tour
The science of ozone depletion - EPA
The Ozone Layer
Graphing stratospheric ozone
Smog
The air that we breathe
Global map
Global mapping datasets
 
 

Last revised: 6 April 1999 - Browning