Stratospheric Ozone Depletion - AP Environmental Science

Polar vortex. Circular wind patterns isolate polar air, creating conditions for severe depletion.

It catalyzes the breakdown of $O_3$. One chlorine atom can destroy thousands of ozone molecules through catalytic cycles.

$O_2 + UV \rightarrow 2O$; $O + O_2 \rightarrow O_3$. UV splits oxygen molecules, then atomic oxygen combines with $O_2$ forming ozone.

Stratosphere. This layer contains about 90% of Earth's ozone, located 10-50 km above Earth's surface.

Chlorine. HCFCs contain some chlorine but much less than CFCs, reducing ozone impact.

Hydrofluorocarbons (HFCs). These contain no chlorine or bromine, so they don't harm the ozone layer.

Sunlight availability. UV radiation drives chemical reactions, so depletion peaks during polar spring.

Measures total ozone column. This unit quantifies the total amount of ozone in a vertical atmospheric column.

Release CFCs as refrigerants. Old refrigerators contain CFC coolants that escape when units are improperly disposed.

Volcanic eruptions. Volcanic emissions can release chlorine and bromine compounds into the stratosphere.

Hydrochlorofluorocarbons (HCFCs). These transitional chemicals have shorter lifespans and contain less chlorine than CFCs.

UV light breaks them down, releasing chlorine. Photolysis by UV radiation breaks C-Cl bonds, freeing reactive chlorine atoms.

Chlorofluorocarbon. These synthetic compounds contain carbon, fluorine, and chlorine atoms.

High GWP. CFCs trap thousands of times more heat than carbon dioxide per molecule.

Damages DNA. UV-B breaks chemical bonds in DNA, causing mutations and cellular damage.

Up to 100 years. CFCs have extremely long atmospheric lifetimes, causing persistent ozone depletion.

Increased UV radiation. Less ozone means more harmful UV-B radiation reaches Earth's surface.

Dobson Unit (DU). Named after ozone researcher Gordon Dobson, measures atmospheric ozone thickness.

London Amendment. This 1990 amendment strengthened CFC phase-out timelines and added new substances.

UV-B radiation. This wavelength range (280-315 nm) increases most when ozone levels drop.

Use of aerosol sprays. Aerosols historically contained CFCs as propellants, releasing them into the atmosphere.

Ultraviolet (UV) radiation. Ozone molecules absorb UV-B and UV-C radiation, protecting life on Earth.

They provide surfaces for chlorine activation. Ice crystals convert stable chlorine compounds into reactive forms that destroy ozone.

Increased UV exposure causes cataracts. Higher UV-B levels damage eye lenses, leading to clouding and vision problems.

Mid-21st century. Recovery depends on continued compliance with international ozone protection agreements.

Montreal Protocol. This 1987 agreement successfully phased out production of ozone-depleting chemicals worldwide.

They provide energy to release chlorine. High-energy UV photons break carbon-chlorine bonds, releasing reactive chlorine.

Reduces greenhouse gases. CFCs are potent greenhouse gases, so eliminating them helps climate protection.

Chlorine monoxide (ClO). This radical forms when chlorine reacts with ozone, continuing destructive cycles.