Science of Ozone in the StratosphereSlide 2
Levels of stratospheric ozone have been dropping NASA - http://toms.gsfc.nasa.govSlide 3
Decreasing Levels of stratospheric ozone is unsafe There has been an expansion in the quantity of instances of skin disease and waterfalls Evidence of harm to plant and marine life Note: tropospheric ozone is hurtful, stratospheric ozone is gainful.Slide 4
Increase in yearly bright radiation : The % expansion from 1980 to 1997 in UV radiation (bringing about the skin to turn red) is figured utilizing watched add up to ozone values from the TOMS satellite instruments and expecting clear sky conditions. Environment in the European Union when the new century rolled over, European Environment Agency, Chapter 3.2. Ozone-exhausting substancesSlide 5
O Structure of Ozone, O 3Slide 6
Where is ozone found in the air ? NASA Goddard Space Flight Center Note, higher fixation in stratosphere, contrasted and troposphereSlide 7
Role of Ozone in the Stratosphere Solar Flux Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling - JPL Publication97-4Slide 8
Role of Ozone in the Stratosphere Solar Flux Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling - JPL Publication97-4Slide 9
Role of Ozone in the Stratosphere Absorption Spectrum of OzoneSlide 10
Role of Ozone in the Stratosphere "The Ozone Depletion Phenomenon", Beyond Discovery, National Academy of SciencesSlide 11
Role of Ozone in the Stratosphere UV A (~400 to 350 nm) not consumed by earth\'s climate UV B (~ 350 to 270 nm) incompletely consumed by earth\'s air UV C (~270 to 150 nm) totally consumed by earth\'s environmentSlide 12
How is ozone shaped in the stratosphere? Chapman component - Sidney Champman, 1930 O 2 + h n ( l < 242 nm) - > O + O k 1 ~ 5 x 10 - 11 s - 1 2[O + O 2 + M-> O 3 + M] k 2 ~ 5.6 x 10 - 34 cm 6 mol - 2 s - 1 O 3 + h n - > O + O 2 k 3 ~ 9.5 x 10 - 4 s - 1 O + O 3 - > 2 O 2 k 4 ~ 1 x 10 - 15 cm 3 mol - 1 s - 1 Note: k 1 and k 3 rely on upon power of light; above qualities are for late morningSlide 13
"Ozone: What is it and why do we think about it?", NASA Facts, Goddard Space Flight CenterSlide 14
This instrument, which depicts how daylight changes over the different types of oxygen starting with one then onto the next, clarifies why the most elevated substance of ozone happen in the layer in the vicinity of 15 and 50 km - the ozone layerSlide 15
Kinetics of Chapman Mechanism Rate of development of O and O 3 d[O]/dt = 2k 1 [O 2 ] - k 2 [O][O 2 ][M] + k 3 [O 3 ] - k 4 [O][O 3 ] d[O 3 ]/dt = k 2 [O][O 2 ][M] - k 3 [O 3 ]-k 4 [O][O 3 ] Steady-State Approximation d[O]/dt = d[O 3 ]/dt= 0Slide 16
Kinetics of Chapman Mechanism Can re-compose [O 3 ] as: Since the rate constants and convergence of species are known, can demonstrated that: Hence,Slide 17
Kinetics of Chapman Mechanism [O 3 ] relies on upon rate of response 2 and the force of light 2[O + O 2 + M-> O 3 + M] k 2 O 3 + h n - > O + O 2 k 3 Reaction 2 is moderate (termolecular); makes ozone "defenseless" to ozone-exhausting responsesSlide 18
Later estimations indicated calculable deviations from Chapman\'s hypothesis. Computations of ozone fixation in view of the Chapman component were impressively higher than watched ones. Must be other concoction responses adding to the decrease of the ozone content.Slide 19
Competing Reactions Marcel Nicolet: HO x cycle H, OH and HO 2 species shaped by response of energized O molecules with H-containing environmental species like H 2 O and CH 4 O 3 + h n ( l < 310 nm)- > O + O 2 O + H 2 O - > OH + OH O + CH 4 - > CH 3 + OH H 2 O + h n - > H + OHSlide 20
Reactions of HO x species with O 3 OH + O 3 - > HO 2 + O 2 HO 2 + O - > OH + O 2 Net Reaction O + O 3 - > 2O 2 "Ozone Depletion"Slide 21
Competing Reactions Paul Crutzen: NO x Cycle NOx species are created amid the response of O particles with N 2 O (delivered in the dirt by microorganisms) O + N 2 O - > 2 NOSlide 22
Reactions of NO x species with O 3 NO + O 3 - > NO 2 + O 2 NO 2 + O - > NO + O 2 Paul Crutzen, ~ 1970 Net Reaction O + O 3 - > 2O 2 "Ozone Depletion"Slide 23
The primary "man-made" risk to the ozone layer was noted by Harold Johnston (1971): supersonic airplanes These flying machine would be equipped for discharging nitrogen oxides ideal amidst the ozone layer at elevations of 20 km. This was additionally the begin of concentrated research into the science of the environment.Slide 24
Competing Reactions Mario Molina, Sherwood Rowland (1974): ClO x cycle ClO x species are created from chlorofluorocarbons (CFC\'s) and methyl chloride CFC\'s are falsely delivered; methyl chloride is a normally occuring concoction. Cases of CFC\'s : Freons (CFCl 3 , CF 2 Cl 2 ) CCl 2 F 2 + h n - > CF 2 Cl + Cl CCl 2 F 2 + O - > CF 2 Cl + ClOSlide 25
Reactions of ClO x species with O 3 Cl + O 3 - > ClO + O 2 ClO + O - > Cl + O 2 Net Reaction O + O 3 - > 2O 2 "Ozone Depletion" 1974 - Mario Molina, Sherwood RowlandSlide 26
Paul Crutzen, Mario Molina, Sherwood Rowland 1995 Nobel Prize in Chemistry - for their work in environmental science, especially concerning the development and deterioration of ozone " http://www.nobel.se/science/laureates/1995/press.htmlSlide 27
Consequences of Competing Reactions Catalytic Reactions Cl + O 3 - > ClO + O 2 impetus moderate ClO + O - > Cl + O 2 impetus middle of the road - bring down initiation vitality E a for Chapman system = 17.1 kJ/mol E a for ClO x response = 2.1 kJ/molSlide 28
Consequences of Competing Reactions Effect of contending response on rate of ozone arrangement Depleting responses are NOT autonomous of each other; all happen at the same time NET LOSS OF OZONESlide 29
Sources of ozone exhausting atoms in the stratosphere Naturally occuring species (H 2 O, N 2 O, CH 4 ) Artificial, "man-made" species CFC\'s (CCl 3 F,CCl 2 F 2 , and so on.) CCl 4 , CHCl 3 HBFC (CHFBr 2 ,CHF 2 Br) CH 3 Br NO from supersonic flying machines The manufactured mixes have the most serious impactSlide 30
What is the "Ozone Hole"? Initially saw in 1985 by the British Antarctic Survey - "acknowledgment" of ozone draining responses Every spring, a colossal "opening" in climatic levels of ozone is seen over the Antarctic. July - Sept 2001 NASA Goddard Space Flight CenterSlide 31
Variation of Partial Pressure of Ozone over the Antarctic for 3 months in 1997 http://www.epa.gov/ozone/science/gap/size.htmlSlide 32
Comparison of Ozone Levels over the Antarctic http://www.epa.gov/ozone/science/opening/size.htmlSlide 33
Why does the Ozone Hole shape over the Antarctic and why in spring? The Antarctic Vortex Polar Stratospheric Clouds Concentrations of Active ChlorineSlide 34
The Antarctic Vortex In the winter, the air around the S. Shaft cools and circles west making a "vortex" Cold air containing ozone exhausting species is caught in the vortex Heat from outside is "close off", drawing out the length of low stratospheric temperatures.Slide 35
Polar Stratospheric Clouds Low stratospheric temperatures result in "ice mists" called Polar Stratospheric Clouds (Crutzen, et. al) The surface of the ice mists fill in as response destinations for heterogeneous gas-surface responses ClO + NO 2 + M - > ClONO 2 + M (gas stage) ClONO 2 + HCl - > HNO 3 + Cl 2 (ice surface) ClONO 2 + H 2 O - > HNO 3 + HOCl (ice surface) Cl 2 and HOCl are "Cl stores"Slide 36
Heterogenous responses similar responses in the gas stage have much higher actuation energies. High E an and low temperatures result in moderate rates. (NASA\'s Goddard Space Flight Center Atmospheric Chemistry and Dynamics Branch )Slide 37
Concentrations of Active Chlorine The Cl 2 and HOCl framed photodissociate to yield responsive Cl iotas Cl 2 + h n - > Cl + Cl HOCl + h n - > Cl + OH Cl + O 3 - > ClO + O 2 OZONE DEPLETIONSlide 38
"Fixings" for the arrangement of the Ozone Hole The Antarctic vortex traps CFC\'s The low polar temperatures brings about ice particles on which gas-strong responses can happen effectively The onset of spring compares to higher light powers and consequently photolysis of Cl containing species (Cl 2 , HOCl)Slide 39
Arctic Ozone Hole Unlike the Antarctic where it is chilly every winter, the winter in the Arctic stratosphere is profoundly factor, NASA satellite and airborne perceptions demonstrate that noteworthy Arctic ozone misfortune happens just after exceptionally cool winters.Slide 40
What is being done to diminish ozone consumption? Montreal Protocol (1987) and resulting arrangements boycott overall utilization of ozone exhausting substances http://www.nobel.se/science/laureates/1995/press.html Given consistence with the denials, the ozone layer ought to bit by bit start to mend. It will take no less than 100 years before it has completely recuperated.Slide 42
2001 OZONE HOLE ABOUT THE SAME SIZE AS PAST THREE YEARS - "This is predictable with human-created chlorine aggravates that decimate ozone achieving their pinnacle focuses in the climate, leveling off, and now starting a moderate decay" http://www.gsfc.nasa.gov/topstory/20011016ozonelayer.htmlSlide 43
References NASA Goddard Space Flight Center (www.gsfc.nasa.gov/) EPA (www.epa.gov) Center for Atmospheric Science, Cambridge University (www.atm.ch.cam.ac.uk/visit/index.html) British Antarctic Survey http://www.antarctica.ac.uk/Chemical Kinetics and Dynamics,Ch 15, J. Steinfeld, J. Francisco, W. Hase
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