Ozone Gas (O3) & the Ozone Layer
- Sylvia Rose
- 2 days ago
- 3 min read
Ozone manifests as pale blue gas. The ozone layer, a concentrated region in the stratosphere, protects Earth from damage by UV rays. Ground level or tropospheric ozone is a major pollutant.
About Ozone
Ozone (O3) is a molecule made up of three oxygen atoms, one more than oxygen (O2). This slight difference gives ozone its unique properties.
A pale blue gas, it has a distinct, pungent odor. Ozone is the smell after a lightning storm. Lightning generates nitrogen oxides (LNOx) which contribute to higher tropospheric ozone.
In the stratosphere, 10-50 km above Earth's surface, ozone builds up to create a protective layer. The ozone layer absorbs 97-99% of the sun's ultraviolet (UV) radiation.
While stratospheric ozone is essential for life, tropospheric ozone is a pollutant. It's formed by reaction of sunlight with volatile organic compounds (VOCs) like vehicle emissions and nitrogen oxides (NOx).
Concentration of ozone in this layer is thicker over the poles in winter, and thinner in the tropics. Seasonal changes and weather patterns can cause ozone levels to vary regionally.
Atmospheric ozone absorbs infrared radiation emitted by the Earth's surface. This traps heat in the troposphere.
Formation of Ozone
Ozone forms naturally in the atmosphere by photodissociation. When ultraviolet light from the sun strikes oxygen (O2) molecules, it splits them into individual oxygen atoms (O).
These highly reactive single oxygen atoms collide with other oxygen molecules. A single free oxygen atom combines with an oxygen molecule to form ozone (O3).
Human activities causing release of chlorofluorocarbons (CFCs) disrupt the balance. Thinning of the ozone layer, noted in the 1980s, creates an "ozone hole" over Antarctica. Consumer aerosol products are widely banned.
Importance of the Ozone Layer
The ozone layer absorbs most of the sun's ultraviolet radiation, such as UVA, UVB and UVC rays. These powerful types of UV radiation can have devastating effects on living organisms.
Ultraviolet A (UVA) has the longest wavelength of the UV spectrum. While UVB radiation affects the epidermis, UVA goes deeper into the dermis. It degrades collagen and elastin causing skin to age and wrinkle prematurely.
It's also a factor in sunburn, which is caused primarily by UVB rays. UVBs are shorter in wavelength than UVA rays and are primary factors in sunburns and skin cancer.
UVC radiation is the shortest wavelength in the ultraviolet spectrum, with wavelengths between 100 and 280 nanometers. It's also known as short-wave or germicidal UV.
UVC radiation is largely absorbed by the Earth's atmosphere, especially the ozone layer. Humans are exposed to UVC mainly through artificial sources like UV lamps or lasers.
UVC is extremely harmful. Because it disrupts microbial DNA it's used for disinfection and sterilization.
Effects of UVs
DNA Damage: UV radiation damages DNA, causing mutations and increasing risk of skin cancer, cataracts and other health problems.
Plant Damage: UV radiation inhibits plant growth, reduces yields of crops like wheat and soybeans, and undermines delicate ecosystems.
Marine Life Disruption: UV radiation can be deadly to phytoplankton, the the base of the marine food web, causing ecosystem upheaval.
Immune System Suppression: Exposure to high levels of UV radiation weaken the human immune system.
Facts About Ozone & Ozone Layer
The Montreal Protocol: After discovery of the ozone hole, nations sign the Montreal Protocol in 1987, pledging to phase out the production and consumption of ozone-depleting substances like CFCs. It's considered one of the most successful environmental treaties in history.
Measuring Ozone: Scientists use numerous methods to measure ozone levels, including ground-based instruments, balloons and satellites.
Ozone Therapy: Some alternative practitioners use ozone to treat medical conditions through blood transfusions.
Ozone Day: On September 16, the United Nations celebrates International Ozone Day to raise awareness about the importance of the ozone layer.
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