Revision:Environmental Chemistry - D (Higher)

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D.1 Primary Air Pollution

D.1.1 Source of Pollutants

• CO (carbon monoxide): natural-forest fires :anthropogenic-transportation industry (automobile exhaust), incomplete combustion of fossil fuels: eg.

.

• NO_x (nitrogen oxides): natural-forest fires :anthro.-stationary combustion sources (factories and power plants), transportation:

,

,

• SO_x (sulfur oxides): nat-volcanoes :anthro.-stationary combustion sources, industry, found in metal ores, coal:

,

,

• Particulates:nat-forest fires, volcanoes, windstorms, pollen, sea salts :anthro- industry (smoke, cement, ash), domestic-heating

• HC (hydrocarbons): nat-living and decaying plants :anthro.-transportation: (you can just invent your own equation)

D.1.2 Health Effects of P.A.P.

• CO:acute exposure- headaches, dizziness, decreased physical performance :chronic expo-stress on cardiovascular system, heart attack

• NO_x: acute-lung irritation :chronic-bronchitis (persistent inflammation of bronchial tubes)

• SO_x: acute-inflammation of respiratory tract, asthma :chronic-emphysema (breakdown of alveoli in lungs), bronchitis

• Particulates:irritation of respiratory system, cancer

• HC:Unknown (according to the sources I looked up, but they're old!)

D.1.3 Control and Prevention of P.A.P.

Catalytic converters- devices attached to a vehicle's exhaust system to convert CO and HC into water and carbon dioxide. (CO, HC) Scrubbers- pollutant-laden air is passed through a mixture of water and lime, trapping particulates and sulfur oxide gases Filters- cloth bags through which smoke is passed to stop particulates from flowing into the air (and more, see syllabus for details on which pollutants can be controlled by which methods)

D.2 Ozone Depletion

D.2.1 Evidence for O.D.

• A thin layer of ozone gas (O₃) encircles the earth and prevents about 99% of the ultraviolet light (UV) from the sun from reaching the earth.

• Measurements made by British scientists at Halley Bay, Antarctica demonstrated the thinning of the ozone layer.

• Satellite measurements of the ozone layer over Antarctica revealed that there was a hole in the layer, the size of the United States. The ozone layer over Antarctica was depleted by more than 50% in 20 years (1965-1985)

• A similar hole was discovered above the Arctic, but smaller in size.

• Other data from satellites showed that the ozone layer was depleted even over non-polar regions (about 3%)

D.2.2 Formation and Depletion of Ozone: (the natural process)

• UV light strikes O₃ molecules, which split apart. The products reunite, giving off heat and reforming ozone. The ozone layer continues renewing itself while converting UV light into heat (infrared radiation).

Balanced equations

O₃ is ozone.

(heat)

D.2.3 Pollutants and Their Sources

• CFC's:Propellants-spray cans: de-o, insecticides, paint, aerosols :Coolants-refrigerators, air conditioners, freezers :Styrofoam

• NOx:High-altitude jets: supersonic transport (SST), commercial jets :Detonation of nuclear weapons, fertilizers, volcanoes (minor)

As Catalysts for O.D.:

• CFC's:react with stratospheric ozone. When CFC's are broken down, chlorine free radicals are produced These can react with more than 100,00 molecules of ozone. Thus depleting the ozone layer.

• NO_x:nitric oxides react with ozone to form oxygen gas (O₂), thus interfering with the natural process of formation of ozone.

D.2.4 Environmental Effects of O.D.

• Ozone depletion increases the amount of UV light that strikes the earth's surface. An excess of this type of light causes damage to living organisms, including:
  • Eyes:cataracts- blurred vision or blindness
  • Skin: severe burns/cancer
  • Immune system: weaker immune response->more susceptible to diseases
  • Crops: interference with photosynthesis->lower crop yields
  • Marine ecosystem: plankton near surface die-> disrupts food chain

CFC Alternatives

HCFC's and HFC's are used in place of CFC's because they are largely destroyed in the lower region of the atmosphere.

• HCFC's:composed of hydrogen, chlorine, fluorine and carbon :contain chlorine, but most is destroyed in the lower atmosphere before reaching the stratospheric ozone layer (20 times less destructive than CFC's)

• HFC's:do not contain chlorine or bromine and therefore have no potential to depleting the ozone layer

D.3 Global Warming

D.3.1 Evidence for G.W.

• (a bit of history) the level of carbon dioxide in the Earth's atmosphere had remained relatively stable until about 100 years ago. This was the time that the human race began burning fossil fuels at a high level (its all our grandparents' and great-grandparents' fault!). In just over a century, industrial civilization has added 360 billion tons of carbon dioxide to our atmosphere. Carbon dioxide is very difficult to get rid of- the natural processes are very slow and we aren't intelligent enough to have invented our own way of doing it.

• there is a correlation between the rise in CO₂ levels and the rise in temperature over the years.

(Much more will be needed about evidence for global warming than what is here)

D.3.2 Main Gases involved

The gases that trap the heat near the Earth's surface and radiate it back:

• CH₄ -H₂O (water vapor) -CO₂ and chlorofluorocarbons (CFC's) and nitrous oxide. (you don't need to know these two, but knowing them won't harm you)

Their Sources

• CH₄: Paddy fields- it is produced by the bacterial decomposition of vegetation under water that occurs in flooded rice fields. :Cattle- "ruminants" (because they "ruminate") i.e. cows, etc. have four stomachs (it's incredible how much they eat!) In the complicated process of digesting the grass (which I don't think will interest you very much) the food is fermented, producing a large quantity of methane gas as a by-product which the cow expels. (I don't advise you to stay too much near a cow that is "ruminating" -you might have an unpleasant surprise!!! hold your noses!-oh, and never light a match near a cow either!)

• H₂O: I mean, water vapor is always present in the atmosphere...the water cycle...(you know what I mean, don't you?!?!?)

• CO₂: It is produced naturally by the decomposition of organic materials, growing plants, and weathering of rocks. (while they are burning millions of trees in the tropical rain forest, not only are they suffocating us, and killing many species of animals, but they are also contributing to G.W.!!!!!)

It is produced by the burning of fossil fuels- coal, oil and natural gas. (because, as you may or may not know- remember, I called you ignorant- fossil fuels are essentially stored carbon, left over from the bodies of plants and animals that died millions of years ago and were trapped underground-- isn't that amazing?!?!) i.e. use of furnaces and coal fires, aircrafts and cars, industrial plants, etc.

D.3.3 Influence of Gases on G.W.

The greenhouse theory proposes that the greenhouse gases are increasing in the atmosphere to such an extent that less reradiated energy is able to escape from the atmosphere. The greater quantities of greenhouse gases absorb this long-wave radiation, effectively trapping it. The energy is then reradiated into the lower atmosphere. The gases may be said to be acting like a blanket, absorbing more and more radiation in the atmosphere. In theory, this could lead to a progressive increase in temperatures and eventually to climatic change.

• CH₄: this gas is present in the atmosphere only in very small quantities, but it absorbs radiation more effectively than CO₂.

• CO₂: naturally occurring CO₂ allows sunlight to pass through the atmosphere and heat the Earth, but also absorbs infrared radiation escaping from the Earth's surface and radiates it back to earth. This process helps maintain Earth's temperature.

The increase of CO₂ concentration in the air slows down the escape of heat -> G.W.

• Like almost anything in the world, little carbon dioxide is good; too much may be devastating

Effects of G.W.

• Oceans will absorb more heat energy, making hurricanes and typhoons more common

• There will be a change in ocean current patterns: ->the world's weather patterns will be altered significantly- flooding in some areas/droughts in others
  • areas like USA and Canada will become warmer and drier and the agricultural plains might become too dry to support dry-land farming.

• Melting of polar ice caps and glaciers: -> this would raise the sea level, flooding up to 20% of the world's land mass. (bye-bye Florida and especially Holland, which is already half-inside the sea-they just retrieved it by building canals!)

• The construction of climate models is difficult because of feedback processes: -> the Earth warms -> more water evaporates -> more clouds form -> clouds reduce the amount of heat reaching Earth -> the warming trend will slow down

OR -> polar ice caps melt -> ice reflects back sunlight instead of absorbing -> when ice decreases, warming speeds up

D.3.4 Influence of Particulates (that's a big word) on Temperature

• Particulates consist of smoke, ash, soot, dust, lead, and other particles from burning fuel.

• They come from industrial processes and motor vehicles that burn fossil fuel, burning wood, and dust from construction and agriculture. (see D.1 and D.8 for further details)

• can form clouds that reduce visibility and cause a variety of respiratory problems. Particulates have also been linked with cancer. They also corrode metals, erode buildings and sculptures, and soil fabrics.

• they can lower the temperature by reflecting sunlight

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