Ppt 2

April 8, 2023 IST,JNTUH, Hyderabad 1

Global CFC production

Ozone hole in Southern hemisphere October 1979 &

• Monthly means of total ozone in the Southern Hemisphere observed with TOMS

• Images for October of 1979 (left) and 1998 (right).

Ozone hole: size by month

Ozone hole measurements over the Antarctic region

1980-98

Ozone concentration at the center of ozone hole

Ozone hole over continents: comparison

Image of the ozone hole over the South pole: July

10 2003

Image of the ozone hole over the North pole: July

10 2003

Ozone status: full day global image, July 9th 2003

Dynamic Equilibriumcreation of ozone

breakdown of ozone

Anthropogenic Ozone Depletioncreation of ozone

breakdown of ozone

Effects of UV rays on Aquatic Ecosystems

Ozone depletion causes increases in UV rays’s effects on aquatic ecosystems by:

1. decreasing the abundance of phytoplankton – affects the food stock for fishes and the absorption of CO2

2. decreasing the diversity of aquatic organisms – reduces food stock and also destroys several fish and amphibians.

Effects of UV rays on Terrestrial Ecosystems

• Damage to plant cell DNA molecules - makes plants more susceptible to pathogens and pests

• Reductions in photosynthetic capacity in the plant - results in slower growth and smaller leaves

• Causes mutations in mammalian cells and destroys membranes

Harmful effects of UV rays on people

• Skin cancer

• Premature aging (photoaging) of the skin (different from normal chronological aging)

• Cataracts and eye disorders (corneal sunburn and blindness)

• Immune system damage

Correlation between Ozone depletion and skin

diseases

The Ultraviolet Exposure Index

INDEX VALUES EXPOSURE

0 – 2 = Minimal 3 - 4 = Low

5 - 6 = Moderate 7 - 9 = High

10 + = Very High

Factors affecting UV exposure

• Clouds cover - partly cloudy days do little to reduce UV exposure but rainy or substantially overcast days reduce UV exposures

• The time of day – peak exposure time is 12:00 noon - 1:00 p.m. UV intensity is reduced by about half at three hours before and three hours after the peak exposure time.

Factors affecting UV exposure..2

• The time of year - more UV is received in the late spring and early summer and much less is received in the late fall and early winter.

• Life style – determines a person’s risk to UV exposure. Skiing, sunbathing, or swimming can lead to extremely high exposures. Use of tanning parlors also increase risk.

Ozone Layer Depletion: Historical Perspective

• The ozone 'hole', it is really not a hole but rather a thinning of the ozone layer in the stratosphere. We will use the term 'hole' in reference to the seasonal thinning of the ozone layer.

• The appearance of a hole in the earth's ozone layer over Antarctica, first detected in 1976.

• 1974: Rowland & Molina theorize CFCs destroy stratospheric ozone molecules

• 1975: U of M / Harvard papers predict that CFCs deplete Earth’s ozone layer

• 1985: Ozone holes found over Antarctic • 1988: Ozone layer thinning over North Pole • 1993: Thinning over mid-latitudes of the Northern Hemisphere • 1997: Low values of total ozone occur in Arctic as well as Antarctic

Antarctic Ozone Hole Progression

CH4 itself is an important greenhouse gas, and links climate with air pollution via its influence on tropospheric ozone

CONTINENT 1 OCEAN CONTINENT 2

Ozone Layer Depleting Chemicals

• chlorofluorocarbons (CFCs)carbon tetrachloride (CCl4)methyl chloroform (CH3CCl3)hydrochloric acid (HCl)methyl chloride (CH3Cl)methyl bromide(CH3Br)

International Response to Ozone Layer Depletion

• 1985: United Nations Environment Program (UNEP)• 1987: The Montreal Protocol• 1992: Copenhagen Amendments• 1998: The Montreal Protocol is affecting stratospheric

chemical composition. • 1999-2000: Stratospheric ozone layer recovery will be a

slow process and extend into the next century.Scientific Assessment of Ozone Depletion: 1994 and 1998 (World Meteorological Organization).

Ozone Layer Depleting Chemicals: CFCs

• CFCs are inert, nonreactive, nontoxic, nonflammable.

• Human-made CFCs used in:- refrigeration- air conditioning- foam blowing- cleaning electronic components- solvents

Biological Effects of Ultraviolet Radiation

• Sunburn,Premature Aging & PreCancer

• Cancer of Skin-Basal and Squamous Cell Carcinoma-Melanoma

• Cataracts

• Photosensitivity

• Immune system changes

Human Immune System can be suppressed by ultraviolet radiation• suppression of immune system

• increased incidence of infection

• promotion of cancer growth

Good & Bad Effects of Sunlight

Modern Impacts to Ozone (2)

Methyl Bromide

• What is it?

• Challenges to Montreal Protocol

Methyl Bromide

Uses of Methyl Bromide

60 million lbs /yr in US

• Agricultural (75%)– Strawberries

• Stored products (11%)

• Flame retardants (6%)

• Pest management (6%)– Termite removal

• Chemical production (2%)

Schedule for Elimination

1991: Designated Class I ozone depleter in Montreal Protocol

1997: Agreed to following schedule

Developed Countries—elimination by 2005

Developing Countries—elimination by 2015

Requests for “Critical Use Exemptions”

US Strawberry Industry

• US supplies 80% of plants from nurseries or strawberries to world market

• Average consumption:

4 lb/person/yr

Benefits of Methyl Bromide

• Worker safety – Non-toxic

– Reduces need for toxic pesticides

• Economical• Easy-to-Use • Effective

Alternatives

• Fumigants applied through drip irrigation

• Harnessing “good microbes”

• Composting for weed suppression

• Soil solarization• Crop rotation

Effectiveness

• Other fumigants do not work

• Worker health issue• Lower yields • Loss of nurseries

– Even organic farms get plant stocks from nurseries that rely on methyl bromide

CFCs vs MEBr

Why did one industry eventually support ban while another is struggling and begging for exemptions?

Methyl Bromide CFCs-no viable alternatives -DuPont developed HFCs

Another potential threat?

Hydrogen Fuel Cells

Production of Hydrogen

• Anticipate that 10% of all hydrogen manufactured will leak into the atmosphere during production, storage and transport.

• Current loss is higher

• Estimate: 60 million tons / year

• Roughly doubles current input (all sources)

Hydrogen chemistry

• Hydrogen is light—rises rapidly to stratosphere

• Reacts with oxygen to form water

• A “wetter” atmosphere would cool the lower stratosphere, especially around Poles

• Increase in water vapor is catalyst for ozone depletion by freeing Cl free radicals

Spatial and Temporal Patterns

• Poles have greater ozone loss than other regions:– Colder– More vapor formation– Also: polar vortex

• Particularly severe in polar spring (October)• Increased hydrogen would enhance this

phenomenon

Ozone Layer Impacts

• 7-8% depletion around Poles anticipated

• Depends upon if and how quickly hydrogen economy introduced

• If >50 years, may not be critical issue

• Possible work to lessen H leakage

Current Status of Ozone Hole

Extent of ozone depletion:

1981— 900,000 sq mi

2001—17,100,000 sq mi

Location of Ozone Losses

Ozone loss extends beyond Antarctica and Arctic Polar regions

Ozone loss over US currently 5% below normal rates

Current Rate of Ozone Depletion

• Decrease in rate of ozone depletion (since 1997)• Slowing of buildup of harmful Cl- from CFCs• Ozone hole is still growing, but…

Models anticipate restoration of “normal” balance of ozone in stratosphere by 2050

Impacts of Ozone Depletion

Human Health • Skin cancer• Melanoma• Cataracts• Immune system function• Increased incidence,

severity and duration of infectious diseases

• Reduced efficacy of vaccinations

Ecological Health• Pathogen locally up &

down• Biodiversity locally up &

down• Aquatic organisms

adversely impacted• Decreased biomass

productivity • Polar systems especially

vulnerable

Impacts of Ozone Depletion

Economic• Plastics

– designed with stabilizers to withstand UV radiation of certain intensity

– replacement of key medical equipment and supplies, decreased lifespan of plastics

• Manufacturing practices• Agriculture• Consumer costs and burdens

Breakdown of Sources

Sterilization 3%

Aerosols5%

Refrigeration and Air

Conditioning30%

Other P roducts 12%

Solvent Cleaning P roducts

36%Foam P roducts14%

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