Stratospheric Ozone Reduction

Stratospheric Ozone Reduction - 3/22/11 Stratospheric...

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Unformatted text preview: 3/22/11 Stratospheric Ozone Reduc7on GEOG 371 March 15th, 2011 Outline/Reminders •  Today: Ozone •  17th/22nd: Climate Change •  24th: Exam # 2 – will cover chapters 6,7,9, 10, 11 •  New homework dates and assignments on blackboard 1 3/22/11 Historical Mo7va7on •  hRp://www.dailymo7on.com/video/xTxdx_discovering ­the ­hole ­in ­the ­ozone ­layer_tech The story of the snowflakes •  Published in 2000 2 3/22/11 Ozone Structure Ozone Lifecycle O2+hν  O +O (λ<240nm) O3+hν  O +O2 O+ O2 +M O3+M 3 3/22/11 Ozone Column Abundance in 2000 Versus La7tude and Month La7tude (degrees) 90 0  ­90 Jan 50 Jun 100 150 200 250 300 350 Ozone column abundance (DU) Dec 400 450 Figure 11.2 4 3/22/11 5 3/22/11 The Chapman Cycle Photolysis Rate Dependence 6 3/22/11 Chapman Cycle Doesn’t Explain Everything •  Cataly7c destruc7on by NOx and HOx •  Both have natural produc7on cycles in the stratosphere •  CO and CH4 also produce ozone, but at a slow rate in the stratosphere. Ozone Variability 7 3/22/11 500 450 400 350 300 250 200 150 100 Ozone (Dobson units) Ozone (Dobson units) Ozone Changes in Polar Regions 500 October zonal average 1979 450 2000 350 300 250 1999 -60 1979 1999 400 2000 -90 March zonal average 200 -30 0 30 60 Latitude (degrees) 90 -90 -60 -30 0 30 60 Latitude (degrees) 90 Ozone Hole Size Changes •  hRp://ozonewatch.gsfc.nasa.gov/index.html 8 3/22/11 UV ­B Trends A 1% reduc7on in ozone results in roughly a 2% increase in UV ­B Observed UV ­B changes 1970 ­1998 7% higher in NH midla7tudes during winter/spring 4% higher in NH midla7tudes during summer/autumn 6% higher in SH midla7tudes all year 130% higher in Antarc7ca during SH spring 22% higher in Arc7c during NH spring “It’s absolutely stupid that we live without an ozone layer. We have men, we’ve got rockets, we’ve got saran wrap – FIX IT!!!” – Lewis Black 9 3/22/11 History of CFCs •  1928 – in an aRempt to make air condi7oning and refrigera7on safer  Freon (CFC ­12) •  Inexpensive, non ­toxic nonflammable, nonexploseive, insoluble and chemically unreac7ve (under tropospheric condi7ons) •  Eventually incorporated into spray can’s, foam produc7on, military aircraq and other industrial prac7ces Chlorine Compounds Mixing ra7o Chemical (pptv) Life7me (yr) Chlorofluorocarbons CFCl3 (CFC ­11) (1932) 270 45 CF2Cl2 (CFC ­12) (1928) 550 100 CFCl2CF2Cl (CFC ­113) (1934) 70 85 Hydrochlorofluorocarbons (HCFCs) CF2ClH (HCFC ­22) (1943) 130 11.8 Other chlorinated compounds CCl4 (Carbon tetrachloride) 100 35 CH3CCl3 (Methyl chloroform) 90 4.8 CH3Cl (Methyl chloride)* 610 1.3 HCl (Hydrochloric acid)* 10 ­1000 <1 Table 11.2 10 3/22/11 Bromine and Fluorine Compounds Chemical Bromocarbons ­Halons CF3Br (H ­1301) CF2ClBr (H ­1211) Other bromocarbons CH3Br (Methyl bromide) Fluorine compounds CH2FCF3 (HFC ­134a) C2F6 (Perfluoroethane) SF6 (Sulfur hexafluoride) Mixing ra7o Chemical (pptv) Life7me (yr) 2 2 65 11 12 0.7 4 4 3.7 13.6 10,000 3200 Table 11.2 11 3/22/11 CFC sales (1000 metric tonnes/year) Reported Sales of CFC ­11 and 12 in 1976 and 1998 700 Tota l Propellant Blowing agent 600 500 Refrigerant Other 400 CFC-11 300 CFC-12 200 100 0 1976 1998 1976 1998 Year Figure 11.11, AFEAS (2000) 12 3/22/11 Summary of Ozone Hole Forma7on Southern ­Hemisphere winter (June ­Sept.) without sunlight over Antarc7ca  ­ ­> cold Polar vortex (jet stream) encircles Antarc7ca, confining air, cooling it further When temperatures drop below 195 K in the stratosphere, polar stratospheric clouds (PSCs) form On the surface of these clouds, “inac7ve” chlorine reservoirs, HCl(g) and ClONO2(g), react to form Cl2(g), HOCl(g), ClNO2(g) When sun rises in spring, sunlight breaks down new molecules into “ac7ve” chlorine, which destroys ozone  ­ ­> ozone hole As air warm, PSCs melt, vortex breaks down, outside air brought in. Ozone hole re ­fills by November UV Effects on the Skin Sunburn (erythema) Skin reddening, blisters Photoaging (accelerated aging of skin) Loss of skin elas7city, wrinkles, altered pigmenta7on, decrease in collagen Basal ­cell carcinoma (BCC) (79%) Tumor develops in basal cells, deep in skin Grows through skin and scabs Doesn’t spread; removable by surgery, radia7on, rarely fatal Squamous ­cell carcinoma (SCC) (19%) Tumor develops in squamous cells, outside of skin Appears as red mark Spreads but removable by surgery, radia7on, rarely fatal Cutaneous melanoma (CM) (2%) Dark ­pigmented malignant tumor arising in melanocyte cell Spread quickly; fatal in 1/3 of cases CM as common as SCC in Northern Europe Skin cancer rates increase from Equator to poles Rela7vely high cancer rates in Australia/New Zealand Life7me exposure to UV not necessary to obtain skin cancer 13 3/22/11 UV Effects on the Eye Snowblindness Inflamma7on or reddening of the eyeball Cataract Loss in transparency of the lens Blindness unless lens removed Ocular melanoma Cancer of iris and related 7ssues Other UV Effects Immune system effects Reduces ability to fight disease and tumors Effects on microorganisms (e.g., phytoplankton), animals, plants Effects on global carbon and nitrogen cycles Damage to phytoplankton reduces CO2(g) uptake UV ­B enhances photodegrada7on of plants, increasing CO2(g) UV ­B affects rate of nitrogen fixa7on by cyanobacteria Effects on tropospheric ozone Enhanced UV ­B increases tropospheric ozone Enhanced absorbing aerosols reduce UV ­B, reducing ozone 14 3/22/11 Some last thoughts hRp://svs.gsfc.nasa.gov/vis/a000000/a003500/a003586/index.html 15 ...
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This note was uploaded on 06/16/2011 for the course GEOG 371 taught by Professor Hiscox during the Spring '11 term at South Carolina.

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