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Stratospheric Ozone Depletion

Ozone (Greek ozein, “to smell”) is a pale blue, highly poisonous gas amongst a rigid odor. It is made upwards of  three oxygen atoms as well as is an allotrope of oxygen. Its molecular formula is O3. Ozone is formed from normal oxygen inwards ultraviolet light. It tin likewise live broken downward inwards the presence of ultraviolet light. Ozone is a powerful oxidizing agent. Ozone is the 3rd most of import greenhouse gas afterward carbon dioxide as well as methane.
 Earth's atmosphere consists of a publish of dissimilar layers. The tropospheric ozone, the so- called bad ozone is considered a pollutant at basis score (lower atmosphere). The stratospheric ozone, the so-called good ozone naturally occurs inwards the earth’s upper atmosphere (15-50 km from the earth’s surface). About 90% of atmospheric ozone resides inwards the stratosphere spell the remaining 10% is introduce inwards the troposphere extending upwards to 10 km. Stratospheric ozone  is a natural Sun screen which protects life past times absorbing harmful sun’s short- wavelength ultraviolet radiation. Hence it is referred as ‘the ozone shield/umbrella.’  Ozone is essential to the wellness of the atmosphere.
 Stratospheric ozone affects climate past times absorbing incoming oestrus radiations from the earth’s surface thereby cools the earth. In the troposphere close the basis level, ozone is formed when pollutants emitted past times cars, ability plants, refineries as well as chemic industries. Tropospheric ozone is a division of photochemical smog as well as it poses a serious wellness work inwards many cities. Increasing concentrations of tropospheric ozone could live attributed to raising global temperature. The residence fourth dimension of tropospheric ozone is brusque as well as measured inwards days. It is irregularly distributed past times fourth dimension of the day, geographic location as well as altitude.



Ozone production

Stratospheric ozone – The stratosphere is inwards a constant wheel amongst oxygen molecules as well as their interaction amongst UV rays. This procedure is called Chapman cycle. UV lite tin dissever upwards ordinary molecular oxygen into ii atomic oxygen atoms.
O2+UV photon---à O+O
The atomic oxygen tin speedily combine amongst molecular oxygen (in the presence of a 3rd body) to yield ozone (O3).
O+O2+third body---àO3+third body
Tropospheric ozone – ozone is produced inwards the troposphere inwards the presence of Sun lite every bit a final result of the photolysis of nitrogen dioxide (NO2). When nitrogen oxide (NO) as well as nitrogen dioxide (NO2) are introduce inwards Sun light, NO2 is destroyed past times the reaction.
NO2 + Sun lite -----àNO+O (atomic oxygen)
The atomic oxygen volition react amongst the available oxygen molecules inwards the presence of other molecules, grand every bit
O + O2 + M--à O3 + M

Ozone depletion

Ozone is lost through the next twain of reactions.
O3 + UV photon ----àO2 + O; O + O3 ---à2O2
The showtime of ii reactions serves to regenerate atomic oxygen for the instant reaction which converts the ozone dorsum to molecular oxygen.

Ozone depleting substances (ODS)

The most of import ozone depleting compounds are chloro fluorocarbons (CFC-11 as well as CFC-12), carbon tetrachloride, methyl chloroform (solvents), methane, nitrous oxide,freons as well as halons (bromine containing gases). These compounds are chemically inert inwards the lower atmosphere, simply inwards the stratosphere they are decomposed past times UV radiations to release chlorine or bromine, which acts every bit a catalyst inwards the ozone devastation process.Bromine as well as chlorine are the major players that initiate a serial of chemic events that destroy ozone. Ozone thinning allows to a greater extent than UV rays to penetrate the stratospheric ozone layer.

 Ozone hole inwards Antarctica

There is considerable decrease inwards the full column of ozone inwards the lower stratosphere (about 40%) xv – xx km higher upwards Antarctica, which is called ozone hole. The expanse of greatest refuse is centered over Spitzberger, halfway betwixt Scandinavia as well as the North Pole. The Antarctic ozone hole was discovered by Joseph C. Farman a British atmospheric scientist of Antarctic survey inwards 1985. The argue for the severe loss of Arctic ozone is due to the presence of clouds inwards the stratosphere called polar stratospheric clouds. These clouds furnish a surface on which the chemic reactions that final result inwards the devastation of ozone tin accept place. Winds likewise play a primal utilisation inwards ozone destruction. The mutual depression temperature air over Antarctica inwards wintertime creates a huge ‘whirlpool’ of fast – moving air circling ‘Antarctic vortex.’ This vortex effectively insulates Antarctica from the ease of the atmosphere from warmer air. This vortex nevertheless lowers the Antarctic temperature as well as drive the formation of to a greater extent than ice-crystal clouds as well as the devastation of fifty-fifty to a greater extent than ozone.
Photochemical Smog
The term smog was derived from the words ’fog’ as well as ‘smoke’. The term smog was showtime used inwards 1905 by H.A. Des Voeux.  The photochemical smog is a status that develops, when primary air pollutants (oxides of nitrogen as well as volatile organic compounds ) interact  nether the influence of sunlight  to hit a mixture of hundreds of dissimilar hazardous chemicals known every bit secondary pollutants similar ozone, organic acids  and PAN (peroxy acetyl nitrate).
Smoke + fog +sun light----à smog
 The most famous London smog occurred inwards the wintertime during Dec 1952 which claimed virtually 6, 500 human lives. This industrial smog was caused past times burning of coal for release energy generation. Another photochemical smog occurred in Los Angeles during summertime inwards July 1973.  The burning of fossil fuels from automobiles created this smog which claimed 3000 human lives. In 1963, New York City fog incident killed 400 people.

Adverse effects of ozone

 Ozone distorts flora growth as well as reduces crop yield.  Ozone damages rubber, nylon, plastics, dyes as well as paints. Breathing O3 affects both the respiratory as well as nervous systems, resulting inwards respiratory distress, headache, as well as exhaustion. Ozone exposure weakens human immune system. Ozone thinning greatly increases the endangerment of Sun burn, peel cancer as well as cataracts.For every 1% of ozone depleted, 2% of UV-B is able to accomplish the earth. Each 1% drib inwards ozone is idea to increment human peel cancer rates past times 4-6%.

Montreal protocol

Montreal protocol, the protocol on substances that deplete the ozone layer, an international treaty was adopted inwards Montreal, Canada on Sept.16, 1987 past times 25 nations. The Montreal protocol was the showtime stride to protect the stratospheric ozone. The protocol ready limits on the production of chloroflurocarbons, halons, carbon tetrachloride, hydrochlorofluorocarbons, methyl chloroform, methyl bromide as well as other ozone depleting substances that release chlorine or bromine gases into the ozone layer of the atmosphere. The Montreal protocol has been repeatedly strengthened past times other amendments.

Quote for self-reflection

"Scientists receive got establish prove that human activities are
  disrupting the ozone balance."

Sumber http://bonvictor.blogspot.com

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