Earth’s Atmosphere and the Ozone Layer

Earth’s Early Atmosphere

The Atmosphere “Blanket” of gases surrounding the Earth Absorbs energy from the sun Recycles water & other chemicals Protects from high-energy radiation Protects and supports life Atmospheric Composition (What it’s made of) 78% Nitrogen 21% Oxygen <1% Argon 0.038% Carbon Dioxide Trace (Minute) Amounts: Helium, Neon, Methane, Hydrogen, Ozone, Water Vapor

Exosphere 640-64,000km “Leaking” into space Satellites Thermosphere 80-640km High temps Absorbs UV radiation Space shuttles/satellites Aurora Borealis Mesosphere 50-80km Cold layer, Temp decreases w altitude meteors burn up here Very thin air Stratosphere 15-50km Ozone Layer Aircraft sometimes Temperature increases w altitude Troposphere 0-15km Weather 75% of Earth’s atmosphere Temp/Pressure decrease w altitude, Air Craft 99% of Earth’s water vapor Ionosphere

3 oxygen molecules bonded together. What is Ozone? Ozone = 3 oxygen molecules bonded together.

The Ozone Layer is in the Stratosphere

Ozone is a “double-edged sword” At the earth’s surface - can be dangerous. It is corrosive and harmful to breathe in. And considered a form of air pollution. In the lower stratosphere - it protects from the sun’s harmful UV rays. Without ozone - too dangerous to walk outside without having to wear a special suit. 

Ozone in the troposphere Ozone is a naturally occurring gas found in the troposphere and other parts of the atmosphere. It is found in low concentrations at ground-level. Two major sources: NITROGEN OXIDES: RELEASED BY PLANTS AND SOIL OZONE FROM THE STRATOSPHERE: MIGRATES DOWN TO EARTH’S SURFACE NO + NO2 O3 and O O + O2 Ozone forms naturally in the troposphere when Nitrogen Dioxide is split by sunlight. The freed oxygen bonds with O2 molecules to make ozone. These reactions BALANCE each other.

Additional OZONE in the TROPOSPHERE is considered pollution. It’s produced when nitrogen oxides (NOx) and volatile organic compounds (VOC) interact with sunlight.  The amount of ozone present in the troposphere varies from day to day and from place to place

VOCs : Volatile Organic Compounds NOx: Nitrous Oxides natural sources vs man-made sources animal manure intentional burning of crops Chemical processes in soil automobiles Lightning sewage treatment Forest fires burning fossil fuels VOCs : Volatile Organic Compounds produced by a variety of sources fossil fuel refining and combustion thousands of industrial chemical products. Plants/bacteria processes in soil

Breathing in ground-level ozone can be harmful to your health. Who is most at risk? People with asthma or other lung diseases Older adults People of all ages who exercise or work hard outside Babies and children

Air Quality Index (AQI) number used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become

** Ozone is good up high, But bad Nearby**

What is Ozone (O3) in the stratosphere? 3 Oxygen Atoms bonded together Performs critical function to life on Earth Filters/Shields UV radiation from the sun Absorbs UVA and UVB radiation Can be found in the troposphere and stratosphere HOW IS IT MADE?? Oxygen (O2) absorbs UVC wavelengths. Ozone (O3) absorbs UVA and UVB wavelengths

Humans need a small amount of UV Radiation to maintain health. UV radiation activates vitamin D in the human body. VITAMIN D: assists intestines in absorbing minerals. (Ex: Calcium and Phosphorous) Which play a crucial role in: Skeletal development Immune function Blood cell formation used to successfully treat a number of diseases (Rickets, Psoriasis, Eczema, and Jaundice) 5 to 15 minutes of sun exposure (hands, face and arms) 2-3 times a week during summer is enough to keep your vitamin D levels high

3 Types of UV Wavelengths: UVC – shortest wavelength UVA – longest wavelength UVB- middle wavelength We cannot see or feel UV radiation UVA goes deep into the skin. It can cause long-term damage like wrinkles, blotchiness, sagging and skin cancer.  UVB Effects top layer of skin. Can cause sunburn, skin damage and skin cancer. Changes the shape of DNA molecules  UVA and UVB wavelengths cause 65% to 90% of melanoma of the skin (accounts for ¾ of all skin cancer deaths)

Ozone Formation and Depletion

Ozone Depletion: How Does it Happen??? O3 molecules interact with CFC’s and Halons They DESTROY molecular bonds of O3 ONE Chlorine molecule can eliminate 100,000 O3 molecules Halons are even more potent O3 destroyers than CFCs Chloroflurocarbons (Chlorine, Flourine, Carbon) Man-made Commercial & Consumer Applications: refrigeration, air conditioning, foam production, aerosol propellants, and circuit board cleaning. Halons: Synthetic (man-made) Chemicals used to extinguish fires Stable Long-lived Remain chemically active in the atmosphere for decades

Effects from volcanoes are short lived. Volcanoes RELEASE Hydrogen Chloride (HCl) They account for 3% of Chlorine in the stratosphere HIGH Amounts of Hydrogen chloride (HCl) can deplete Ozone At least two factors reduce the impact of HCl... Chlorine appears to be released during low-levels of volcanic activity. Limiting it to the troposphere, where it is most likely to be washed out by rain Hydrogen chloride may also condense in the rising volcanic plume, again to be scrubbed out by rain or ice Effects from volcanoes are short lived. Volcanic particles settle out of the atmosphere in 2-3 years

Death of phytoplankton Disrupts food chain Reduces photosynthesizers Humans: Increased incidences of skin cancer Premature aging of the skin Sunburns Increased incidences of cataracts Weakened immune response Ozone Depletion Leads to Increased UV Radiation Effects of Ozone Depletion on Plants and Animals Plants: Interferes with photosynthesis Reduced disease resistance Reduced crop yields Interferes with DNA Marine Life: Death of phytoplankton Disrupts food chain Reduces photosynthesizers

considered by many the most successful environmental global action. Montreal Protocol (1987): Mid 1980s, concerns grew over what appeared to be a ‘hole’ in the ozone layer over Antarctica in spring smaller hole over the Northern Hemisphere Scientists determined it was caused by humans due to man-made chemicals (CFCs) Signed by 197 Countries 1st treaty in the history of the United Nations to achieve universal ratification. considered by many the most successful environmental global action. US signed in 1987 In 1995, the UN named September 16 - International Day for the Protection of the Ozone Layer.

THE GOAL: Reducing/stopping the production of CFCs. Provided a double benefit: stopping ozone depletion slowing the growth of greenhouse gases. ISSUES: Many substitutes for ozone depleting substances are ozone safe, BUT many are powerful greenhouse gases. They have the potential for offsetting climate gains currently achieved by the Montreal Protocol.

HFC – Hydrofluorocarbons: The alternative to CFCs synthetic organic compounds  composed of hydrogen, fluorine, and carbon. used as alternatives to ozone depleting substances **They became widely used as refrigerants (late 1980’s) due to the Montreal Protocol.  NOW THERE’S A NEW PROBLEM: HFCs are potent greenhouse gases. Atmospheric observations show that the volume of HFCs in the atmosphere is increasing rapidly, about 10-15% per year.

The Ozone is on the ROAD to RECOVERY

Ozone Monitoring VS Local Remote Require air to be drawn directly into an instrument Remote Detection occurs far away from the measurement instrument VS Measure key air quality components and aerosol characteristics. Distinguish between aerosol types, such as smoke, dust, and sulfates. Measure cloud pressure and coverage, which provide data to derive tropospheric ozone. Map global distribution and trends in UV-B radiation.

SAGE III Stratospheric Aerosol and Gas Experiments Will be mounted on the ISS (International Space Station) It will measure: Aerosols Water Vapor Ozone Other Atmospheric Gases Clouds Pressure Temperature The first prototype was launched in 1979, critical to discovery of Earth’s ozone hole & creation of Montreal Protocol https://www.youtube.com/watch?v=VVyNQXWxH24&t=3s