control of air pollution
Control of Air Pollution
adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane University
Control
of Air Pollution
Smog
Air
Inversion
Global
Warming
Greenhouse
Gases
Acid
Rain
Sources
Control of Air Pollution
Automobiles- Catlytic converter converts carbon monoxide, nitrous oxides and hydrocarbons into carbon dioxide, nitrogen and water.
- Recirculating exhaust gas along with a catlytic converter greatly reduces emissions.
-
Main problem is the sulfur dioxide
it produces upon burning. Solutions:
- Burn only low sulfur coal.
- Wash coal to remove pyrite.
- Convert coal to gas (called Gasification)
- Fluidized Bed Combustion (or Limestone Injection): Mix coal with limestone, to form calcium sulfides or sulfates, which are prevent sulfur from forming sulfur dioxide.
- Scrubbing - slurries of lime or limestone.
Smog
- Smoke plus Fog (U.K.) (Grey smog).
- Photochemical Smog - brown air. (U.S.A.) Results from exhausts from cars, buses and trucks.
- Nitrogen Oxide + Oxgen + Hydrocarbons + Sunlight -- > Ozone
- 6ppm ozone is deadly - We need ozone in stratosphere; at lower altitudes, however, it can kill.
- Sulfurous Fog- gray air.
-
Dominantly from burning coal with a
significant pyrite content. The fogs of London in the past were
actually
sulfuous fog. This type of smog is no longer common in London as a
result
of environmental regulations on burning coal.
Air Inversion
-
In valleys or on the lee side of mountains,
air inversion may occur. A warmer air mass moves above cooler air,
trapping
the cooler, denser air underneath and increasing the severity of air
pollution.
Los Angeles is a good example of this, where warm desert air from the
east
comes over the mountains to the east of Los Angeles and lies over the
cooler
Pacific Ocean air. The cooler air is trapped because it cannot rise
through
the less dense warm air above it, and the pollution in the cold air
accumulates.
A similar situation arises in mountain
valleys where warm air overlies the colder air which accumulates in the
valleys.
Also, cities tend to form featuers known as heat islands or dust domes, which tend to collect warm air filled with pollutants, and help spread it out over nearby suburbs.
There are several gases which cause the greenhouse effect, and whose concentrations determine the amount of heat retained by the earth. Primary among these are water vapor, carbon-dioxide and methane. The chart below shows how the concentration of CO2 in the atmosphere has changed in the last 40 years:
- The increase in CO2 is anthropogenic (related to human activities). It is mostly due to the burning of fossil fuels and deforestation.
| Gases contributing to Anthropogenic Greenhouse Effect | ||
| Gas | Rate of
Increase (% per year) |
Relative Contribution(%) |
| CO2 | 0.5 | 60 |
| CH4 | 1 | 15 |
| N2O | 0.2 | 5 |
| O3 | 0.5 | 8 |
| CFC-11 | 4 | 4 |
| CFC-12 | 4 | 8 |
- Global Warming has been studied extensively, and currently, a large percentage of the scientific community have reached a consensus on various issues related to global warming. They are listed below:
| Scientific Consensus on Global Warming | |
| Statement | Consensus |
| Fundamental Physics | 90+% |
| Added greenhouse gases add heat | 90+% |
| Added gases are anthropogenic | 90+% |
| Reduction of uncertainty will require a decade | 90+% |
| Full recovery will require many centuries | 90+% |
| Large stratospheric cooling | 90+% |
| Precipitation will increase | 90% |
| Reduction of sea ice | 90% |
| Warming in arctic | 90% |
| Rise in sea level | 90% |
| Local details of global change | ? |
| Tropical storms increase | ? |
| Details of next 25 years | ? |
- Burning Fossil Fuels
- Deforestation
- Coal Mines
- Termites
- Wetlands
- Rice Paddies
- Cattle
- Subpolar Soil and Wetlands (Methane Hydrate)
- Main source of acid rain is sulfur dioxide and nitrogen oxides in the atmosphere.
Power plants are a major source for sulfur dioxide and as well nitrogen oxide.
Automobiles, trucks and buses are major contributors of nitrogen oxides in urban and suburban environments.
Effects of Acid Rain
- If the bedrock consists of limestone, effect is not so severe. The limestone helps to neutralize the acid.
- If bedrock is granitic, there is no buffer. Results severe.
- Acid solutions free nutrients as well as toxic metals from the soil. As a result, nutrients are lost from the soils and the plants may take on toxic elements.
- In lakes, acidity keeps the nutrients in solution. Nutrient are then lost with the outflow of water. Algae cannot grow as a result, and so there is no food for aquatic animals present in the lake.
- Fish may be poisoned by heavy metals in solution, and are very intolerant of high acidity.
- High acidity kills trees.
- Tree ring studies have shown that concentrations of calcium (which is an essential nutrient for trees) have been decreasing steadily in areas of increased acid rain.
- The Environmental Protection Agency acid rain page: http://www.epa.gov/docs/acidrain/
- A good general guide to acid rain and acid rain resoures online: http://qlink.queensu.ca/~4lrm4/
- A somewhat more technical page on acid rain: http://www.igc.org/acidrain/
- Clean Air Act: http://gurukul.ucc.american.edu/TED/CLEAN.HTM
- A collection of Links on Air Pollution: http://www.deb.uminho.pt/fontes/enviroinfo/air.htm
- NASA Climate News page: http://www.climatenews.com/
- The Union of Concerned Scientists have a global warming page: http://www.ucsusa.org/warming/index.html
- The Sierra Club page: http://www.toowarm.org/home.html
- The Environmental Protection Agency site on Global Warming: http://www.epa.gov/globalwarming/
- This is a page arguing against global warming: http://www.webaxs.net/~noel/gwarming.htm
- This page details the myths and misarguments by both sides of the global warming debate: http://members.aol.com/jimn469897/warming.htm A Collection of sites that NASA put together about global warming: http://gcmd.gsfc.nasa.gov/faq/globwarm.html
Air Pollution
Global Warming