Name : lara abubaker البحث العلمي Time : 8-9 Doctor : Isam al ashqar Ozone layer

1. Name : laraabubaker البحث العلمي Time : 8-9 Doctor : Isam al ashqar Ozone layer

2. Introduction • Atmosphere of Earth • Ultraviolet (UV) • Ozone • Ozone layer • refrences

4. Introductin • The ozone layer is a deep layer in the stratosphere, encircling the Earth, that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun. The ozone layer is mainly found in the lower portion of the stratosphere from 15 to 30 km. The concentrationof ozone molecules is 10 parts ozone per 1 million parts air. The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson.

5. introduction The ozone layer absorbs 97–99% of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms on Earth The ozone layer became more widely appreciated by the public when it was realized that certain chemicals mankind manufactures, called chloroflurocarbons, find their way up into the stratosphere where, through a complex series of chemical reactions, they destroy some of the ozone

6. Maurice Fabrys • Maurice Paul AugusteCharleFabrys was born on June 1867, in Marsellie, France. • He died on the 11th of Decemeber 1945. • He was the first peron to discover the Ozone Layer in 1913 with his partner, Henri Buisson. • In 1904, he was appointed Professor of Physics at the University of Marsellie, where he spent 26 years.

7. Henri Buisson Henri Buisson was born in Paris on the 15th of July 1873 and died on the 6th of January 1944. Henri was a very personal man so many information about himself has been kept a secret and public are not to know

8. Atmosphere of Earth • The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

9. Atmosphere of Earth • The common name given to the atmospheric gases used in breathing and photosynthesis is air. air contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%

11. Layers of the atmosphere

12. Exosphere • The exosphere is the highest layer of the atmosphere. It extends from the top of the thermosphere up to 480 km • This is the upper limit of our atmosphere. In this region of the atmosphere, hydrogen and helium are the prime components and are only present at extremely low densities. This is the area where many satellites orbit the Earth.

13. Thermosphere The thermosphere is the outer layer of the atmosphere, separated from the mesosphere by the mesopause. It extends from the top of the mesosphere to 480 km. Within the thermosphere temperatures rise continually to well beyond 1000 degrees C. The few molecules that are present in the thermosphere receive extraordinary amounts of energy from the Sun, causing the layer to warm to such high temperatures. Although the measured temperature is very hot, the thermosphere would actually feel very cold to us because the total energy of only a few air molecules residing there would not be enough to transfer any appreciable heat to our skin.. The International Space Station orbits in this layer, between 320 and 380 km.

14. Mesosphere The mesosphere is the region above the stratosphere and below the thermosphere. It extends from the top of the stratosphere to the range of 80 km . Temperatures in the mesosphere drop with increasing altitude to about -100 degrees Celsius (C). The mesosphere is the coldest of the atmospheric layers. In fact it is colder then Antarctica's lowest recorded temperature. It is cold enough to freeze water vapor into ice clouds. The mesosphere is also the layer in which a lot of meteors burn up while entering the Earth's atmosphere. From the Earth they are seen as shooting stars.

15. Stratosphere • The second lowest layer of Earth's atmosphere, it lies above the troposphere and is separated from it by the tropopause. It extends from the top of the troposphere to about 50 km. • The stratosphere contains the ozone layer, the part of the Earth's atmosphere which contains relatively high concentrations of ozone. and it contains up to 24% of the mass of the atmosphere. The stratosphere defines a layer in which temperatures rises with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet (UV) radiation from the Sun by the ozone layer. Consequently, the stratosphere is almost completely free of clouds or other forms of weather.

16. Troposphere • The lowest layer of Earth's atmosphere. It extends from Earth's surface up to 11 km. • The troposphere is bounded above by the tropopause, a boundary marked by stable temperatures. Although variations do occur, temperature usually declines with increasing altitude in the troposphere. • The troposphere is denser than the layers of the atmosphere above it (because of the weight compressing it), and it contains up to 75% of the mass of the atmosphere. Fifty percent of the total mass of the atmosphere is located in the lower 5.6 km of the troposphere. It is primarily composed of nitrogen (78%) and oxygen (21%) with only small concentrations of other trace gases. Nearly all atmospheric water vapor or moisture is found in the troposphere. The troposphere is the layer where most of the world's weather takes place.

17. Temperature curve

18. Ultraviolet (UV) • Ultraviolet (UV) radiation is part of the electromagnetic spectrum emitted by the sun. • with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range between 400 nm and 10 nm, corresponding to photon energies from 3 eV to 124 eV. It is so-named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. These frequencies are invisible to humans, but near UV is visible to a number of insects and birds.

19. Discovery • The discovery of UV radiation was associated with the observation that silver salts darkened when exposed to sunlight. • In 1801, the German physicist Johann Wilhelm Ritter made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum darkened silver chloride-soaked paper more quickly than violet light itself • . He called them "oxidizing rays" to emphasize chemical reactivity and to distinguish them from "heat rays," discovered the previous year at the other end of the visible spectrum. • The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century. The terms chemical and heat rays were eventually dropped in favour of ultraviolet and infrared radiation, respectively

20. silver salts darkened when exposed to sunlight

21. There are three subtypes of UV : UVA : (320-400 nm wavelength) . UVA ratiation penetrates deeper into the skin and is the major contributor to skin aging and wrinkles. It also contributes to the development of skin cancer (along with UVB). UVA is sometimes divided into two subtypes: long UVA ( 350-400 nm wavelength), and short UVA ( 320-350 nm wavelength). UVB : (280-320 nm wavelength). UVB causes sunburn but has a relatively modest effect on skin wrinkles because most of it is absorbed in the epidermis (the outer skin layer) and does not reach the dermis where wrinkles form. It also contributes to the development of skin cancer (along with UVA). UVC : (100-280 nm wavelength). UVC is the harshest type of UV radiation. Luckily, UVC is almost completely absorbed by the ozone layer and does not reach the Earth's surface. As long as we haven't destroyed the ozone layer, we don't have to worry about the UVC.

23. Ozone Absorption in the UV Band • UV-C • Nearly all UV-C is absorbed in the upper atmosphere • UV-B • 90% of UV-B is absorbed by the atmosphere, mostly by O3 • UV-A • Not strongly absorbed by the atmosphere

24. Harmful effects on the skin • Skin changes induced by ultraviolet radiation may be divided into acute and chronic: • Acute changes: sunburn, suntan, freckles (small, brown spots), moles,photodermatoses (diseases associated with oversensitivity to light) • Chronic changes: lentigos (small, brown spots similar to freckles but with more distinct contours), seborrhoeic warts (convex skin lesions), skin photoageing, preneoplastic and neoplastic changes as a resultof DNA damage and affect on the efficiency of the immune system Ptthbytha for Alokolh cells in the skin or destroyed. Types of skin cancer : • squamous cell carcinoma • In situ squamous cell carcinoma • Melanoma

25. Absorption of ozone in the skin

27. Camera UV private imagine the devastation that hit result of exposure to the sun

28. Harmful effects on the Eye High intensities of UVB light are hazardous to the eyes, and may lead to cataracts, pterygium,andpinguecula formation. UV light is absorbed by molecules known as chromophores, which are present in the eye cells and tissues. Chromophores absorb light energy from the various wavelengths at different rates. If too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged

29. Ultraviolet radiation's influence on DNA UV radiation has a great impact on DNA. UVA stimulate the appearance of free radicals, which may then damage cell DNA. Whereas the main mechanism of UVB activity consists in direct damage of cell DNA, which leads to its mutation. A healthy organism has a number of specific reparative mechanisms enabling, to some degree, regeneration of damaged DNA. One of them is a spontaneous death of a cell (apoptosis) with damaged genetic material. It is a positive mechanism which prevents the spread of mutated DNA, which could lead to the development of neoplasm.However, if the skin is often exposed to the sun, DNA mutations cumulate in cells over the years. They may be transformed into neoplastic cells.

30. Ultraviolet radiation's influence on DNA

31. Prevention • To prevent the danger of the harmful rays of the sun as follows:1 - Planning for outdoor activities in the period before ten in the morning and after the fourth afternoon.2 - Wear protective clothing, blankets and underwear and T-shirts with long sleeves.3 - wear sunglasses.4 - Wearing broad-brimmed hats on the head to save face and neck

32. What is ozone? Ozone is a natural gas composed of three atoms of oxygen. It chemical symbol is O3. It is blue in color and has a strong odor. Slightly soluble in water. It is diamagneticand will resist formation of a magnetic field. Environmental scientists have classified O3 into two: Good Ozone and Bad Ozone.

33. Good Ozone • Good Ozone Good ozone(also called Stratospheric Ozone) occurs naturally in the upper Stratosphere. The stratosphere is the layer of space 6 to 30 miles above the earth's surface. Even though Ozone is only a small part of the gases in this layer, it plays a vital role because it shields us from the sun's harmful UV rays. It is called Good Ozone, for obvious reasons—because it protects humans, life and animals on earth.

34. Where does good Ozone come from? The air is full of gases reacting with each other, even though our eyes do not see. When UV light strikes (Oxygen) O2 molecules, they are split into two individual O atoms — O and O. When one of the O atoms combine with O2 molecule, ozone (O3) is created.

35. Bad Ozone • Bad Ozone Bad Ozone is also known asTropospheric Ozone, or ground level ozone. This gas is found in the troposphere, the layer that forms the immediate atmosphere. Bad Ozone does not exist naturally. Human actions cause chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC).

36. Where does bad ozone come from? Each time there is a reaction of chemicals such as those found in cars, power plants and factory emissions, in the presence of sunlight (UV light), Bad Ozone is created.Bad ozone contaminates (dirties) the air and contributes to what we typically experience as "smog" or haze. Note that this kind of smog is different from the deadly London winter type that killed 4000 people. Smog from bad ozone is usually in the summer, caused by the action of sunlight on a mixture of hydrocarbons and oxides of nitrogen. It is known as Photochemical or Summer Smog.

37. The Ozone Layer • The ozone layer is a layer in Earth's atmosphere that absorbs most of the Sun's UV radiation. It contains relatively high concentrations of ozone (O3), although it is still very small with regard to ordinary oxygen, and is less than ten parts per million, the average ozone concentration in Earth's atmosphere being only about 0.6 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere from approximately 20 to 30 kilometres (12 to 19 mi) above Earth, though the thickness varies seasonally and geographically

38. The ozone layer • The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958 Dobson established a worldwide network of ozone monitoring stations, which continue to operate to this day. The "Dobson unit", a convenient measure of the columnar density of ozone overhead, is named in his honor. • The ozone layer absorbs 97–99% of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms on Earth

39. The Dobson spectrophotometer The Dobson spectrophotometer, also known as Dobsonmeter or Dobson spectrometer, is the earliest instrument used to measure atmospheric ozone. It was invented in 1924 by Gordon Dobson. Dobson spectrophotometers can be used to measure both total column ozone and profiles of ozone in the atmosphere. The Dobson Spectrometer measures the total ozone by measuring the relative intensity of the dangerous UVB radiation that reaches the Earth and comparing it to that of UVA radiation at ground level. If all of the ozone were removed from the atmosphere, the amount of UVB radiation would equal the amount of UVA radiation on the ground. As ozone does exist in the atmosphere, the Dobson Spectrometer can use the ratio between UVA and UVB radiation on the ground to determine how much ozone is present in the upper atmosphere to absorb the UVC radiation.

40. Ozone-oxygen cycle in the ozone layer • Ozone in the Earth's stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (O2), splitting them into individual oxygen atoms (atomic oxygen); the atomic oxygen then combines with unbroken O2 to create ozone, O3. The ozone molecule is also unstable (although, in the stratosphere, long-lived) and when ultraviolet light hits ozone it splits into a molecule of O2 and an atom of atomic oxygen, a continuing process called the ozone-oxygen cycle, thus creating an ozone layer in the stratosphere.

41. Ozone-oxygen cycle in the ozone layer

42. Chemistry • 1. an oxygen molecule is split (photolyzed) by higher frequency UV light (top end of UV-B, UV-C and above) into two oxygen atoms • O2 + UV → 2O • 2. Each oxygen atom then quickly combines with an oxygen molecule to form an ozone molecule: • O + O2 → O3

43. The Ozone Depletion • Ozone layer depletion, is simply the reduction of the amount of ozone in the stratosphere. Unlike pollution, which has many types and causes, Ozone depletion has been pinned down to one major human activity.

44. The Ozone Depletion • Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 5% per decade in the total volume of ozone in Earth's stratosphere (the ozone layer), and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon is referred to as the ozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone depletion events.

45. The Ozone Depletion • Measurements that have been pointed out by satellites that the amount of ozone in the atmosphere has decreased by 5 % in 1978 from what it was in 1971. Discovered the ozone hole over the South Pole in 1985 as the shortfall reached 50%, and Jouret shows in August and September of each year over Antarctica , then take to widen in the autumn months , then shrinks and disappears in the month of November . It happens hole inside the polar vortex is a large block of the air isolated relatively over Antarctica during the polar winter and spring , and with the hole appears seasonally but it is getting worse every time shows where its predecessor, and as a result the breadth Antarctic it portends dangers will be exposed to southern Argentina .

47. Causes of ozone depletion • 1. CFC compounds : an organic material enters the installed chlorine , fluorine and carbon. And up the amount of global production of these gases annually about 1,400 million tons , of which 970 thousand kg of ozone - destructive type . America comes on top of the countries that consume CFCs where it produces 350 million tons annually and statistics indicate that the amount of CFCs 11 and 12 ( and are cheaper, but they are the most harmful substances ) have tripled times the amount accumulated between 1970-1980 . And next to no vehicles helium gases that cause ozone depletion, CFC compounds are used in the processing of the basics of houses and containers used to fight fires in pesticides and containers used in hairdressing , deodorants and other cosmetics .

48. Chlorofluorocarbons • (CFC) CFC’s are created and used in refrigerators and air conditioners. These are not harmful to humans and have been a benefit to us. Once released into the atmosphere, chlorofluorocarbons are bombarded and destroyed by ultraviolet rays. In the process chlorine is released to destroy the ozone molecules. • 1 - The UV-destroying chlorofluorocarbons (CFCs), which leads to the release of active chlorine atom2 - active chlorine atoms interact with a molecule of ozone gas3 - result from the interaction of chlorine atom with ozone molecule = molecule of oxygen and chlorine monoxide4 - interact with the active oxygen atom of chlorine monoxide where off active chlorine atom to destroy the ozone molecule new and so are the session

50. Ozone depletion diagram that shows the process by which ozone (O3) is depleted in the stratosphere