Group+4+Ozone+Depletion


 * Hi we are informing you about ozone depletion here is some infomation to get started on:**

> [|www.nsc.org/ehc/glossar1.htm] > [|www.nrdc.org/reference/glossary/o.asp] > [|antron.dupont.com/content/resources/green_glossary/ant06_04_15.shtml] > [|www.greenhouse.gov.au/ago/annual-report/2003-04/glossary.html] > [|www.thegreenguide.org/definitions.php] > [|www.knowledgebank.irri.org/glossary/Glossary/O.htm] > [|en.wikipedia.org/wiki/Ozone_depletion] > > > Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of [|ozone] in [|Earth's] [|stratosphere] since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly referred to as the ozone hole. > The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is [|catalytic] destruction of ozone by atomic chlorine and bromine.[|[1]] The main source of these [|halogen] atoms in the stratosphere is [|photodissociation] > of [|chlorofluorocarbon] (CFC) compounds, commonly called [|freons], and of bromofluorocarbon compounds known as [|halons]. These compounds are transported into the stratosphere after being emitted at the surface. Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased. > CFCs, halons and other contributory substances are commonly referred to as ozone-depleting substances (ODS). Since the ozone layer > prevents most harmful UVB wavelengths (270–315 nm) of [|ultraviolet light] (UV light) from passing through the [|Earth's atmosphere], observed and projected decreases in ozone have generated worldwide concern leading to adoption of the [|Montreal Protocol] banning the production of CFCs and halons as well as related ozone depleting chemicals such as [|carbon tetrachloride] and [|trichloroethane] (also known as methyl chloroform). It is suspected that a variety of biological consequences such as increases in [|skin cancer], damage to plants, and reduction of [|plankton] populations in the ocean's [|photic zone] may result from the increased UV exposure due to ozone depletion. > Scientists and many others are concerned about Antarctica's annual ozone hole because ozone blocks harmful ultraviolet energy from reaching the Earth. > But, when ozone is near the ground it's considered "bad" because it's harmful. It's air pollution. (Related: [|Good and bad ozone]) > All ozone molecules consist of three oxygen atoms, while the molecules of ordinary oxygen - the stuff in the air that all animals need - are made of two oxygen atoms. Good ozone refers to ozone high in the atmosphere where it blocks potentially harmful ultraviolet energy. > Bad ozone refers to ozone near the ground - it's a product of pollution - that can make our eyes water and is dangerous for people with certain kinds of illnesses. > One of the three British scientists who discovered the Antarctic ozone hole says similar damage is likely soon in the Arctic. > The scientist, Jonathan Shanklin, says the Earth's ozone layer is cooling, which makes its recovery more difficult. > The cooling is the result partly of ozone loss itself, and also of a little-noticed effect of global warming. > And although ozone-depleting gases are no longer increasing in the atmosphere, the damage is being maintained by a feedback mechanism. > The ozone layer protects all living creatures against harmful ultra-violet radiation from the Sun, which in humans can damage the eyes and the immune system and also cause skin cancer. > Cooling atmosphere
 * __defonition of ozone depleation__**
 * Destruction of the stratospheric ozone layer which shields the earth from ultraviolet radiation harmful to life. This destruction of ozone is caused by the breakdown of certain chlorine and/or-bromine containing compounds (chlorofluorocarbons or halons), which break down when they reach the stratosphere and then catalytically destroy ozone molecules.
 * the reduction of the protective layer of ozone in the upper atmosphere by chemical pollution.
 * Destruction of the earth's ozone layer, which can be caused by the photolytic breakdown of certain chlorine- and/or bromine-containing compounds (eg, chlorofluorocarbons),which catalytically decompose ozone molecules.
 * The reduction of ozone (O 3 ) in the upper atmosphere as a result of human-produced chemicals, such as CFCs. Ozone depletion is especially severe over Antarctica in September to November each year, causing the ozone ‘hole’. However, at all latitudes away from the equator, the layer of ozone that protects us from the Sun’s harmful radiation is thinner that it was in the late 1970s. ...
 * Thinning of the protective layer of the upper atmosphere, known as the ozone layer, by chlorofluorocarbons (CFCs) and other human-created ozone-depleting chemicals (ODCs). The ozone layer is a strong-smelling, slightly bluish gas layer in the stratosphere, 10 to 25 miles above the earth, that shields us from the burning ultraviolet rays of the sun, and traps reflected solar heat around the earth, keeping the earth warm.
 * Reduction of the ozone layer in the atmosphere. Influenced by aerosols and other gaseous pollutants.
 * Ozone depletion refers to the phenomenon of reductions in the amount of ozone in the stratosphere. There was a reduction of approximately 5% detected from 1979 to 1990. ...
 * Ozone is very rare in our atmosphere, averaging about three molecules of ozone for every 10 million air molecules. In spite of this small amount, ozone plays a vital role in the atmosphere. In the information below, we present "the basics" about this important component of the Earth's atmosphere.
 * How can I reduce my contribution to ground-level ozone?**
 * Avoid idling your motor vehicle excessively.
 * Conserve energy and recycle.
 * Do not refuel your vehicle or lawn mower on Ozone Action Days. If you must refuel, do so after dark — remember that sunlight assists ozone-forming reactions.
 * Keep your vehicle well tuned.
 * Limit driving; carpool, walk, ride a bicycle, and combine trips.
 * Start charcoal with an electric lighter or a newspaper-fueled “chimney” instead of lighter fluid.
 * Use public transportation.

The gap in the blanket of gas that keeps out dangerous rays from the sun seems to have stopped getting bigger, say experts monitoring it. The huge hole, as big as North America, was discovered over Antarctica in 1986, and is thought to have been caused by polluting chemicals called CFCs. Once the hole was found, CFCs were banned, and it's now hoped the hole could close altogether within 60 years
 * The hole in the ozone layer is starting to recover, according to scientists.**