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Human Impact on the Biosphere Chapter 50. Pollutants are substances with which ecosystems have no prior evolutionary experience and therefore cannot deal with them. Carbon oxides CO, CO 2 Sulfur oxides SO 2 , SO 3 Nitrogen oxides NO, NO 2 , N 2 O

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Human Impact on the Biosphere Chapter 50

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Pollutantsare substances with which ecosystems have no prior evolutionary experience and therefore cannot deal with them
  • Carbon oxides CO, CO2
  • Sulfur oxides SO2, SO3
  • Nitrogen oxides NO, NO2, N2O
  • Volatile organic CH4, CFC’s, compounds
  • Photochemical oxidants Ozone, H2O2
  • Suspended particles Dust, soot, lead, pesticides

Each day 700,000 metric tons of pollutants are dumped into the atmosphere in the US alone



cooler air

cool air

Thermal Inversions are when weather conditions trap a layer of cool, dense air under a layer of warm air. Thermal inversions can trap pollutants close to the ground

cooler air

cool air

Normal air circulation pattern

warm air

cool air

warm inversion air

Air pollutants trapped under a thermal inversion layer

cool air


cooler air

cool air


  • Industrial smog - is gray air found in industrial cities that burn fossil fuel (usually in cities that are cold and wet)
  • Photochemical smog- is brown air found in large cities in warm climates, the key culprit is nitric oxide.

Acid Rain

  • Burning coal & metal smelting produces sulfur dioxides
  • Burning fossil fuels, vehicles and fertilizers result in nitrogen oxides
  • Tiny particles of these oxides can fall to the earth in 2 forms:
      • - Dry acid deposition
      • - Acid Rain

Average acidities of precipitation in the United States in 1998

Major coal-burning power and industrial plants














Ultrafine particles reach alveoli in lungs and contribute to respiratory disorders. High concentrations can cause lung cancer.

Ultrafine particles

Fine particles

Large particles

metallurgical dust, fumes

photochemical smog

tobacco smoke

carbon black


sea salt

oil smoke

paint pigments

cement dust

fly ash

insecticide dust

coal dust

milled flour







Average particle diameter (µm)


Ozone Thinning -

Why is the loss of the Ozone Scary?

  • Ozone protect us from UV radiation!
  • Ozone in the lower stratosphere absorbs most of the UV radiation from the sun.
    • - the thinning of the ozone layer has produced a seasonal ozone “hole” over Antartica
    • - in response, skin cancer has increased, cataracts may increase, and phytoplankton may be affected
  • Chlorofluorocarbons (CFC) seem to be the cause - one chlorine atom can convert 10,000 ozone molecules to oxygen.

Ozone Thinning -

Top 1979,

Middle 1991

Bottom 1996.

Lowest ozone values are in magenta and purple.

ice clouds

ozone thinning


CFC’s in Air

Free Cl

Light rays


+ ClO

Ozone Thinning
  • Antarctica
  • CFC’s
  • Refrigerators and air conditioning solvents
  • Plastic foams

Each Cl can convert 10,000 O3 to O2


Where to put Solid Wastes? Where to produce food?

In NATURAL ecosystems, one organism’s waste serves as resources for others.

  • Paper products and non-returnable bottles and cans are perhaps our biggest problem.
    • - each week 500,000 trees end up as Sunday newspapers in US
    • - if every reader recycled just 1 out of 10 papers, we could save 25 million trees a year
    • - recycling paper could reduce air born pollutants released by paper manufacturing by 95% and requires 30 to 50% less energy than making new paper
  • We face a challenge to move from a “throw-away” society to one of conservation and re-use. Land fills leak and threaten groundwater.
  • What if we burn wastes instead? - greater amount of air pollution

Where to put Solid Wastes? Where to produce food?

Converting Marginal Lands for Agriculture

- Almost 21% of land is used for Agriculture; another 28% is available but may not be worth the cost

- the green revolution has increased crop yields but uses many times more energy and mineral resources

- a growing human population is moving into marginal lands to meet our increasing needs



tropical forest




arid lands


arid lands




ice, snow, deserts, mountains


At one time tropical forest cloaked regions that were collectively 2X the size of Europe and home of 50-90% of all land dwelling species.

In  4 decades humans have destroyed more than half of the forests and most of the species.

Each year another 34 million acres is logged over = to leveling 34 city blocks every minute.


Deforestation- the removal of all trees from large tracts of land for logging agriculture and grazing.

In Shifting cultivation (slash-and-burn agriculture) trees are cut, the land used for a few growing seasons and then abandoned as fertility plummets.



  • Forest are watersheds; they control erosion, flooding, & sediment buildup in rivers and lakes.
  • Deforestation can
    • - reduce fertility
    • - change rainfall patterns
    • - increase temperatures
    • - increase carbon dioxide (CO2)
  • Clearing large tracts of tropical forest may have global repercussions, such as altering:
    • - rates of evaporation
    • - rates of transpiration
    • - runoff of nutrients and rainfall
    • - photosynthetic activity rates.

Why are we destroying our forests?

  • Increase demand for lumber, fuel and other forest products as well as for cropland and grazing land
  • When vegetation cover gets stripped away, the exposed soil becomes vulnerable to leaching of nutrients and erosion
  • In logged area, annual precipitation declines and rain swiftly drains from the exposed nutrient poor soil.
    • -desert like conditions might prevail

Desertification is the conversion of grasslands and croplands to desert-like conditions

  • Desertification, also applies when agricultural productivity drops by 10% or more.
  • At least 200,000 sq. kilometers are being converted annually
    • - overgrazing of livestock on marginal lands is the main cause of large scale desertification
    • - prolong droughts accelerate the process

A Global Water Crisis

  • Most of the earth’s water is too salty for human consumption or for agriculture.
  • Desalination (removal of salt from sea water) processes are available and can be used when absolutely necessary.
  • However, desalinization is not cost effective in most locales and it uses valuable fuel reserves to provide the energy for the desalination equipment, also produces mounds of salt.
  • Consequences of heavy irrigation -
    • - large scale agriculture account for nearly 2/3 of the human population’s use of fresh water (“piped in water” - high in mineral salts)
    • - salt buildup (salinization) of the soil and waterlogging can results
    • - withdrawl of underground water causes water tables to drop

A Global Water Crisis

  • Water Pollution - amplifies the problem of water scarcity
  • Causes ?
    • - radioactive materials
    • - human wastes
    • - insecticides
    • - herbicides
    • - chemicals
    • - heat
the coming water wars
The Coming Water Wars
  • Water, not oil, may become the most important fluid of the 21st century. National, regional and global policies for water usage and water rights have yet to be developed.
    • In the past decade, 33 nations have engaged in conflicts over reductions in water flow, pollution, and silt buildup
    • By restricting water flow, countries upstream may attempt to influence political behavior in countries downstream.
  • By building dams and irrigation systems at the headwaters of the Tigris and Euphrates rivers, Turkey could stop the water flow in Syria and Iraq for as long as eight months “to regulate their political behavior”.

Fossil Fuels are limited resources, extraction costs are increasing and atmospheric levels of carbon, nitrogen and sulfur oxides are also increasing.

a question of energy inputs
A Question of Energy Inputs
  • Increases in human population and extravagant life-styles has increased energy consumption.
  • Extraction and use of abundant reserves of oil shale and coal are not “environmentally attractive” - environmental cost
    • Valdez tanker ~11 million gallons of oil spilled near the Alaskan coastline
    • Coal burning is primary source of air pollution contributing to acid rain and greenhouse effect.
    • Extensive strip mining of coal reduces the land available for agriculture, grazing, and wildlife; restoration difficult

Developed Countries

Developing Countries

Hydropower, geothermal, solar 7%

Nuclear power 5%

Hydropower, geothermal, solar 6%

Biomass 3%

Nuclear power 1%

Natural gas 25%

Biomass 35%

Natural gas 7%

Coal 25%

Coal 25%

Oil 26%

Oil 37%

a question of energy inputs26
A Question of Energy Inputs
  • Nuclear Energy
    • - with nuclear energy, the net energy produced is low and the cost is high compared with coal-burning plants
    • - meltdowns may release large amounts of radioactivity to the environment
    • - nuclear waste is so radioactive that it must be isolated for 10,000 years.

April 26, 1986 — Chernobyl in Ukraine

Nuclear fuel burned for 10 days right through a 6-foot thick steel and gravel barrier

Distribution of radioactive fallout within 2 weeks of the meltdown - Reached Europe

Made crops & live stock unfit for consumption


April 27

April 30

May 2

May 6


After soviet union's breakup, some underpaid workers of a Russian nuclear power plant have been selling fuel elements on the black market.

The buyers?

Developing nations that want to produce nuclear weapons - possibly deliver them to the hand of terrorist organization

alternative energy sources
Alternative Energy Sources
  • (1) Solar-Hydrogen Energy
    • Solar-hydrogen energy is an attractive technology b/c it depends on a renewable energy source … The SUN!
    • Photovoltaric cells produce an electric current that splits water into oxygen and hydrogen gas (H2) which can be used directly as fuel or to produce electricity
alternative energy sources32
Alternative Energy Sources
  • (2) Wind Energy
    • - where wind travels faster than 7.5 meters per sec, wind turbines are cost-effective producers of energy
    • - b/c winds do not blow on a regular schedule, wind turbines cannot be the exclusive source of energy
alternative energy sources33
Alternative Energy Sources
  • (3) Fusion Power
    • - temperatures like those on the sun cause atomic nuclei to fuse and release energy
    • fusion power on earth is possible but many obstacles make the technology a distant possibility
    • Researchers confine a heated gas of two isotopes of hydrogen in magnetic fields, then bombard it with lasers. The fuel (hydrogen) implodes and energy is released.

“ If we make the transition to an energy-efficient solar-hydrogen age, we can say good-bye to smog, oil spills, acid rain, and nuclear energy, and perhaps to global warming. The reason is simple. As Hydrogen burns in air, it reacts with oxygen gas to produce water vapor – not a bad thing to have coming out of tailpipes, chimneys, and smokestacks.”

-G. Tyler Miller, Jr. (Environmental Scientist)