Ozone!

I. Ozone Basics

A. Ozone is O3

B. Found in the stratosphere in concentrations of about 400 ppb (parts per billion).

C. Three types of UV light come from the sun – The highest energy and shortest wavelength UVC, lower energy and longer wavelength UVB, and longest wavelength and lowest energy UVA

D. When UVC light hits the O2 molecules in the stratosphere, it breaks them apart into 2 O atoms.

E. These lone oxygen atoms are very reactive, and quickly combine with another O2 molecule to form O3.

1)O2 UVC O + O

2)O2 + O O3 and voila! Ozone!

F. All of the UVC’s energy is used splitting O2 molecules, and negligible UVC reaches the earth’s surface.

G. When UVB hits ozone molecules, it does not have enough energy to split anything up, and the ozone absorbs the UVB energy. Some UVB still gets through to earth.

H. All UVA light passes through the ozone layer and gets to earth.

I. Ozone is the only known gas to absorb UVB! If there are less molecules of ozone in the atmosphere, more UVB reaches earth.

II. A Little Science Mystery

A. In 1974, Rowland and Molina discovered something shocking (very shocking to the $28 billion dollar CFC industry)

1) CFCs are persistent chemicals in the atmosphere

2) CFCs migrate to the stratosphere (11 to 20 yrs) via convection, random drift, and atmospheric turbulence

II. A Little Science Mystery

3) In the stratosphere, CFCs break down by UV light and release their highly reactive halogen atoms (Cl, F, sometimes Br) which attack and break down ozone. Ozone is destroyed faster than it can reform.

4) CFCs last from 65 to 385 years in the atmosphere, each molecule can convert HUNDREDS of ozone molecules back to diatomic oxygen.

II. A Little Science Mystery

B. The CFC industry, led by DuPont, worked hard to discredit the scientists, but over the next 14 years, they expanded their research, and by 1988 DuPont and others agreed to stop producing CFCs.

C. In 1995, Roland and Molina received the Chem Nobel Prize.

II. A Little Science Mystery

D. Chlorofluorocarbon reaction:1)CFCl3 + UV Cl + CFCl2

2)Cl + O3 ClO + O2

3)ClO + O Cl + O2

Steps 2 and 3 just get repeated over and over again!

II. A Little Science Mystery

E. Two main classes of compounds1) CFCs and Halocarbons/HalonsA) CFCs used for coolant in refrigerators, ect. Aerosol or propellant, foam blowing for

Styrofoam, solvents and cleanersB) Halocarbons/Halons used for fire retardant,

soil pesticides, solvents, and more foam blowing for insulation

Fig. 18-26 p. 473Fig. 18-26 p. 473

III. The Ozone HolesA. Ozone hole = ozone levels over Antarctica

had declined by 40-60% – Depletion also in the Arctic and globally

B. Primarily happened during November and December. Special isolated air masses at the poles allow for enhanced reactions – CFCs get “stuck” in this “polar vortex.”

C. Additionally special high-altitude polar clouds provide reaction surfaces at just the right altitude for ozone destruction. When seasonal thinning ends each year, this air mass travels over Australia and New Zealand, raising UV- B levels between 10 and 20%.

III. The Ozone Holes

D. Montreal Protocol (1987) = 180 nations agreed to cut CFC production in half1) Follow-up agreements (Copenhagen 1992)

deepened cuts, advanced timetables and addresses other ozone-depleting chemicals

2) Today, production and use of ozone-depleting chemicals has decreased 95%

3) The ozone layer is beginning to recover

III. The Ozone Holes

E. Challenges still face us1) CFCs will remain in the stratosphere for a

long time2) Nations can ask for exemptions to the ban

The Montreal Protocol is a success

F. Considered the biggest environmental success story1) Policymakers included industry in helping solve the

problem2) Implementation of the plan allowed an adaptive

management strategy that changed strategies in response to new scientific data, technological advances, and economic figures

G. The Montreal Protocol can serve as a model for international environmental cooperation

IV. UVB caused problems

A) Human Problems1) UVB strong enough to mutate DNA in living

cells – SKIN CANCER2) General unpleasant sunburn3) Cataract eye damage4) Immune system suppression

IV. UVB caused problems

B. Ecosystem problems1)Kills polar phytoplankton, which are the

primary producers in marine polar ecosystems (HUGE PROBLEM)

2)Disrupts food chains3)Direct damage to fish and amphibians4)Causes decreased plant productivity (including

food crops – yikes!)

V. Tropospheric Ozone Pollution

A. Ozone formed in the troposphere is bad.(Sooo good, Tooo bad). Formed during

photochemical reactions on sunny days with major air pollutants (nitrogen oxide, hydrocarbons, ect). It is a secondary pollutant formed when primary pollutants react in the sun.

B. Tropospheric ozone is a major pollutant for humans. It causes the following:

1)Aggravated lung conditions (asthma, emphysema, ect.)

2)Lung and throat pain/burning3)Coughing4)Impaired lung development in youth5)Mucous membrane irritant

C. Tropospheric ozone damages cell walls in lungs and airways, causing swelling and cellular fluid leaks into lungs, lungs decrease in elasticity and scar tissue forms. This scar tissue and swelling promotes increased susceptibility to infection.

D. At low doses of ozone, plants have bleaching and spotting of their leaves, and reduced production. This stresses the plants and leads to diseases. At high doses, plant tissue is killed outright.

E. Ozone is the air pollutant standard that is most frequently violated in urban areas.