Greenhouse Effect

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Greenhouse Effect
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Greenhouse Gases

• Naturally occurring greenhouse gases include
• Water vapor
• carbon dioxide (CO2)
• Methane (CH4)
• Nitrous oxide
• Ozone

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(CO2)

• released to the atmosphere when solid waste,
  fossil fuels (oil, natural gas, and coal), and
  wood and wood products are burned.

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Methane (CH4)

• Methane (CH4) remains in the atmosphere for
  approximately 9-15 years.
• Methane is over 20 times more effective in
  trapping heat in the atmosphere than carbon
  dioxide (CO2) over a 100-year period
• Emitted from a variety of natural and
  human-influenced sources.
• Methane is also a primary constituent of natural
  gas and an important energy source.

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Methane Human-influenced sources

• include landfills
• natural gas and petroleum systems
• agricultural activities
• coal mining
• stationary and mobile combustion
• wastewater treatment
• certain industrial process emissions
• also result from the decomposition of organic
  wastes in municipal solid waste landfills, and
  the raising of livestock.

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Nitrous oxide

• emitted during agricultural and industrial
  activities, as well as during combustion of solid
  waste and fossil fuels.

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Nitrous oxide (N2O)

• Largest source of emissions from agricultural
  activities.
• Nitrogen fertilizers on agricultural soils 74
• Small amount from agriculture is from handling
  animal waste.
• Small amount is from burning crop residues
• Over the past few years, the US has slightly
  lowered it emissions of N2O.

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N2O - 2nd source

• Second-largest source is from energy consumption
• Mobile source combustion from cars, buses,
  motorcycles, trucks,
• Stationary sources combustion for commercial,
  residential, industrial, and electric power
  sector
• Energy consumption 21 of emissions, of that
  78 of those emissions are from mobile combustion.

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Non Natural gases

• hydrofluorocarbons (HFCs)
• perfluorocarbons (PFCs)
• sulfur hexafluoride (SF6) - which are generated
  in a variety of industrial processes.

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How much is produced

• In the United States, approximately 6.6 tons
  (almost 15,000 pounds carbon equivalent) are
  emitted per person every year.
• About 82, are from burning fossil fuels to
  generate electricity and power our cars.

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Emissions
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Emissions per sector
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The Other Greenhouse Gases

• Account for about 2 of gas emissions
• HFCs are on the rise
• PFCs and SF6 emissions are on the decline.

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Hydrofluorocarbons - HFCs

• Increase of emissions is result of their use as
  replacements for ozone-depleting substances,
  mainly Chlorofluorocarbons (CFCs)
• HFCs are compounds containing hydrogen, fluorine,
  and carbon.
• HFCs do not destroy stratospheric ozone, but are
  a powerful greenhouse gas.

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• HFCs are used in
• solvents
• domestic and commercial refrigerants
• firefighting agents
• propellants for pharmaceutical and industrial
  aerosols
• foam-blowing agents
• blends for air conditioning refrigerants.

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Tetraflouroethane HFC-134a

• Largest share of all HFC emissions
• HFC-134a is the largest share of any one gas for
  all HFC, PFC, and SF6 emissions combined
• HFC-134a is the transportation industries
  replacement for CFCs in air conditioners for
  cars, trucks, trains, and buses
• Like because it is nonflammable, low toxicity,
  thermal and chemical stability
• Also used in refrigeration, freezing, a
  propellant for aerosols, and a blowing agent for
  extruded polystyrene foam.

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• How HFC-134a is emitted
• Leakage in commercial chillers, and automotive
  air conditioners
• Leakage occurs usually during servicing
• Short term uses aerosols

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Perfluorocarbons - PFCs

• Compound of carbon and fluorine
• PFCs are a byproduct of aluminum smelting
• PFCs emissions on the decline
• Improvements in the aluminum industry
• Decrease in aluminum production
• Atmospheric lifetime up to 50,000 years,
  essentially permanent.

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Sulfur Hexafluoride - SF6

• SF6 is used in electrical applications
• An excellent dielectric gas for high-voltage
  applications
• Chemically inert
• Gaseous at low temps
• Nonflammable
• Nontoxic and noncorrosive
• Acts as an insulator and arc for circuit breakers
• SF6 is also a byproduct of magnesium metal
  casting
• Used to replace toxic and corrosive materials
• Used as a cover gas to prevent excessive
  oxidation if molten magnesium in the presence of
  air.

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• How it is emitted
• Leakage through seals on older equipment
• Emissions occur during equipment installation,
  servicing, and disposal
• SF6 is the most potent of greenhouse gases

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OZONE O3

• A gas that occurs both in the Earth's upper
  atmosphere and at ground level.
• "good" or "bad" depending on its location in the
  atmosphere

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BAD 03

• troposphere, the air closest to the Earth's
  surface, ground-level or "bad" ozone is a
  pollutant that is a significant health risk,
• Asthma
• It also damages crops, trees and other
  vegetation

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Causes

• One main ingredient of urban smog
• Motor vehicle exhaust
• industrial emissions
• gasoline vapors
• chemical solvents
• natural sources emit oxides of nitrogen (NOx) and
  volatile organic compounds (VOC)
• Sunlight and hot weather cause ground-level ozone
  to form in harmful concentrations in the air. 

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Concerns

• Triggers a variety of health problems even at
  very low levels
• May cause permanent lung damage after long-term
  exposure
• Damages plants and ecosystems
• Peak ozone levels typically occur during hot, dry
  summertime conditions. 
• Southern and Southwestern states may have an
  ozone season that lasts nearly the entire year.
• Wind can carry O3 hundreds of miles from their
  origins, causing air pollution over wide regions

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Impact on humans

• can irritate lung airways and cause inflammation
  much like a sunburn
• Symptoms include wheezing, coughing, pain when
  taking a deep breath, and breathing difficulties
  during exercise or outdoor activities
• People with respiratory problems are most
  vulnerable,
• Healthy people can be affected when ozone levels
  are high.
• Repeated exposure to ozone pollution for several
  months may cause permanent lung damage. 
• Even at very low levels, ground-level ozone
  triggers a variety of health problems
• aggravated asthma,
• reduced lung capacity,
• and increased susceptibility to respiratory
  illnesses like pneumonia and bronchitis.

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Impact on plants

• Ground-level ozone interferes with the ability of
  plants to produce and store food
• Ozone damages the leaves of trees
• Ozone reduces crop and forest yields
• Ozone makes them more susceptible to disease,
  insects, other pollutants, and harsh weather

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Efforts to Reduce Ground-level Ozone

• reducing NOx emissions from power plants and
  industrial combustion sources
• introducing low-emission cars and trucks
• using "cleaner" gasoline
• improving vehicle inspection programs
• Monitor air qualities
• Ozone action days

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Good O3

• stratosphere extends upward from about 6 to 30
  miles
• protects life on Earth from the sun's harmful
  ultraviolet (UV) rays
• Ozone depletion means more UV from the sun gets
  to the ground, leading to more cases of skin
  cancer, cataracts, and other health problems

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Depleted

• Being damaged or "depleted" by man-made chemicals
  
• chlorofluorocarbons (CFCs).
• hydrochlorofluorocarbons (HCFCs)
• Halons
• methyl bromide
• carbon tetrachloride
• methyl chloroform.

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Bad chemicals from where?

• These substances were formerly used and sometimes
  still are used
• Coolants
• foaming agents
• fire extinguishers
• Pesticides
• Aerosol propellants

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What is Being Done?

• Montreal Protocol -1987 - a treaty called to
  phase out the production and use of
  ozone-depleting substances
• Releases into the air of refrigerants used in car
  and home air conditioning units and appliances
  are also prohibited
• Kyoto Protocol 1999 addition to Montreal
  protocol

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Acid Rain

• What is Acid Rain?
• acid that falls from the atmosphere
• Two types wet and dry deposition
• Wet acidic rain, fog, and snow
• Dry acidic gases and particles

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• What causes acid rain?
• sulfur dioxide (SO2) and nitrogen oxides (NOx)
  are the primary causes of acid rain
• In the US, About 2/3 of all SO2 and 1/4 of all
  NOx comes from electric power generation that
  relies on burning fossil fuels like coal
• occurs when these gases react in the atmosphere
  with water, oxygen, and other chemicals to form
  various acidic compounds. Sunlight increases the
  rate of most of these reactions. The result is a
  mild solution of sulfuric acid and nitric acid.

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• How do we measure acid rain?
• Using the pH scale
• Pure water has a pH of 7.0.
• Normal rain is slightly acidic because carbon
  dioxide dissolves into it, so it has a pH of
  about 5.5.
• As of the year 2000, the most acidic rain falling
  in the US has a pH of about 4.3.

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• Who measures acid rain?
• The EPA supports two networks
• The National Atmospheric Deposition Program
  measures wet deposition
• The Clean Air Status and Trends Network (CASTNET)
  measures dry deposition

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• What are the effects of acid rain?
• damage to forests and soils
• fish and other living things
• Materials
• human health
• visibility reduction - reduces how far and how
  clearly we can see through the air

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• How to reduce Acid Rain?
• Educate
• Clean up smokestacks and exhaust pipes
• Use alternative power sources
• Reduce emissions
• Conserve energy