ozone depletion
DESCRIPTION
environmental science 10. Our powerpoint presentation about ozone depletion, its effects and its causes. It contains some videos and gif at thte end from an external source.TRANSCRIPT
Ozone Depletion
Atas, Bryan B.
Bondoc, Christian Earvin D.
Hubag, Patrick Paulo Amor C.
INTRODUCTIONINTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
• The main point, ladies and gentlemen, is that OZONE DEPLETION exists!!!
• This serves as an introduction to the terms needed in the following chapters
INTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
• A form of oxygen gas
• Composed of three atoms of oxygen (O3)
• Colorless
• Has a harsh odor
• It has the ability to absorb most UV radiation
Ozone
Ozone’s ability to absorb Ozone
INTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
Ozone Layer
• greatest concentration of ozone occurs at altitudes 19 - 30km above the Earth's surface
• Ozone layer is IN the stratosphere
• Concentration of O3 in ozone layer is roughly 10 parts per million
The stratosphere and the
ozone layer
INTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
• The thinning of the ozone layer
• It can happen naturally but human intervention is the main reason for ozone depletion
• Is brought about by ODC’s or Ozone Depleting Chemicals
Ozone Depletion
M
O
N
I
T
O
R
I
N
G
• Dobson Unit measures the total amount of ozone in an overhead column of the atmosphere
• … measured by how thick the layer of ozone would be if it were compressed into one layer at 0 oC and with a pressure of 1 atm above it
• 0.01 mm = 1 D.U.
Monitoring Ozone
Ozone depletion is scientific and not Ozone depletion is scientific and not just an environmentalists’ hoaxjust an environmentalists’ hoax
It is monitored by satellites It is monitored by satellites
Ozone Hole
• Technically….
• regions where stratospheric ozone depletion is so severe that levels fall below
200 Dobson Units (D.U.)
Antarctic ozone hole
2006 record breaker hole ….. 11.4 M sq. miles
2007 average
INTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
• A form of electromagnetic energy
• Three categories of UV radiation: – UV-A, between 320 and 400 nm – UV-B, between 280 and 320 nm – UV-C, between 200 and 280 nm
Ultra violet rays
INTRODUCTION
Ozone
Ozone layer
Ozone depletion
Ultraviolet rays
• UV-A has the least energy– 98.7% of the ultraviolet radiation that reaches the
Earth's surface is UVA
• UVB – higher energy, breaks down O3
– Has the ability to destroy DNA linkages
• UVC – very easily absorbed by oxygen and ozone– Highest energy
Ultra violet rays
CAUSES
ODC
Mechanism
CFC’s
Sources
• Mechanism of Ozone layer destruction
• Chemicals that deplete the ozone layer
CAUSES
CAUSES
ODC’s
CFC’s
Mechanism
Sources
• ODC – Ozone Depleting Chemicals
• ODS – Ozone Depleting Substances
ODC
CFC
• A group of compounds known as Chlorofluorocarbons
•It is The main source of ozone depletion
• Very stable• Insoluble in water (rain)
• As a result: it can travel from the lower atmosphere up until it reaches the ozone layer
CFC
others
ODC
CFC
Five main CFC’s
• CFC-11 (trichlorofluoromethane - CFCl3)
• CFC-12 (dichloro-difluoromethane- CF2Cl2)
• CFC-113 (trichloro-trifluoroethane- C2F3Cl3)
• CFC-114 (dichloro-tetrfluoroethane- C2F4Cl2)
• CFC-115 (chloropentafluoroethane- C2F5Cl)
others
ODC
Other ODC
• Halons or bromofluorocarbons are Bromine containing compounds that function the same way as CFC’s but are 10-100 times more reactive
• HCFC’s are the alternative to CFC but are still ODS but with a smaller lifespan– They are also greenhouse gases
CFC
others
ODC
• 82% of stratospheric chlorine came from ODC
• with 51% being carried there by CFC-11 and CFC-12.
CFC
others
ODC
Source: World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project - Report No. 44, Geneva, 1998.
CFC
others
ODC
Source: Scientific Assessment of Ozone Depletion: 2002
List of ODS according to Scientific Assessment of Ozone Depletion: 2002
Table of ods part IICFC
others
ODC
Source: Scientific Assessment of Ozone Depletion: 2002
Want some more?
Sources of ODS
• CFCs are widely used as coolants in refrigeration and air conditioners
• …used as solvents in cleaners (for electronic boards)
• …used as a blowing agents in the production of foam (i.e., frire extinguishers)
• …used as propellants in aerosols. • Some ODS are used as pesticides and
fumigants
In depth ODC uses and their alternatives
Bottom line is: many man made technologies depend on the use of ODC
Natural sources of Cl
• Major volcanic eruptions can inject Cl into the stratosphere mostly in the form of HCl
• …but volcanic aerosols are quickly dissolved
– Example: Mt. Pinatubo eruption of 1991which released 30 Megatons of debris
Amount of aerosols in the stratosphere
CAUSES
ODC
CFC’s
Mechanism
sources
Mechanism
• CF2Cl2 ---------> Cl + CF2Cl
• As CFC reaches the stratosphere, they are broken down by light and this process releases Cl
Light energy
CAUSES
ODC
CFC’s
Mechanism
sources
• Cl + O3 ClO + O2
• ClO + O Cl + O2
O3 is converted to O2
therefore, less O3 is available to block the UV rays
• Most of the chlorine comes from man made emissions such as CFC’s
Mechanism
Mechanism
Cl + O3 O2 +ClO
ClO +O O2 + Cl
Take note that the ozone depleting process is a cycle as Cl can react again for as much as 100,000 times
Mechanism
BrO + ClO -> BrCl + O2 BrCl + hv -> Br + Cl Br + O3 -> BrO + O2 Cl + O3 -> ClO + O2 -----------------------
Net: 2 O3 -> 3 O2
Bromine are 10 to 100 times more destructive than Cl
Take note that: decreasing Cl also decreases Br’s destructiveness
Effects of Ozone Depletion
• This is the reason why
WE SHOULD CARE
Effects of Ozone Depletion
• Damage to marine life - Smith et.al _Science_1992 found a 6-12% drop in phytoplankton productivity once their ship entered the area of the spring-time ozone hole
• When over 200 agricultural plants were tested, more than half showed sensitivity to UV-B light.
• Marine wild life and ecosystem – plankton are sensitive to UV
• radiation affects orientation mechanisms and motility in phytoplankton, thus: reduced survival rates for these organisms
• decreased reproductive capacity and impaired larval development
Effects of Ozone Depletion
• Genetic damage - DNA absorbs UV-B light and the absorbed energy can break bonds in the DNA
• Skin cancers – effect of genetic damage– 90% of the skin carcinomas are attributed to
UV-B exposure • [R.P.Wayne, Chemistry of the Atmospheres 2nd
ed. Oxford 1991]
• Strong UV radiation from the Sun can cause inflammation of the cornea, the outer coating of the eyeball, leading to photokeratosis or "snow blindness“
• … permanent damage to the cornea
• …dimming of the eye's lens and increased risk for cataracts
• …eye cancer, conjunctivitis and pterygium
• 1% decrease in stratospheric ozone may result in 100,000 to 150,000 additional cases of blindness due to eye cataracts worldwide.
• Material damages - Increased UV-B radiation can accelerate the deterioration of plastics, wood, paper, cotton and wool (Manins et. al., 2001).
• Air pollution - as more UV reaches the lower troposphere, more high-energy EM waves will decompose oxygen and produce Ozone... Resulting to photochemical smog
» By the way, Ozone is poisonous
Sources
U.S. Environmental Protection Agency
NASA
Wikipedia
http://www.ace.mmu.ac.uk
http://www.ozone.gi.alaska.edu
Apologies to many others who have been forgotten
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