Ozone Depletion

transcript

Ozone Depletion

Atas, Bryan B.

Bondoc, Christian Earvin D.

Hubag, Patrick Paulo Amor C.

INTRODUCTIONINTRODUCTION

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 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’s ability to absorb Ozone

INTRODUCTION

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 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

• 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 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 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

Mechanism

CFC’s

Sources

• Mechanism of Ozone layer destruction

• Chemicals that deplete the ozone layer

CAUSES

ODC’s

CFC’s

Mechanism

Sources

• ODC – Ozone Depleting Chemicals

• ODS – Ozone Depleting Substances

• 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

others

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

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

others

• 82% of stratospheric chlorine came from ODC

• with 51% being carried there by CFC-11 and CFC-12.

others

Source: World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project - Report No. 44, Geneva, 1998.

others

Source: Scientific Assessment of Ozone Depletion: 2002

List of ODS according to Scientific Assessment of Ozone Depletion: 2002

Table of ods part IICFC

others

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

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

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

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

• 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

• 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

Wikipedia

http://www.ace.mmu.ac.uk

http://www.ozone.gi.alaska.edu

Apologies to many others who have been forgotten

The End

Trends

What was….is and will be…

Ozone Depletion

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