The Ozone Crisis

Outline

Introduction

Main body

Recovery

Concluison

Works cited

Introduction

Ozone is slightly soluble in water, has a molecular weight of 48.000, has a specific gravity of 1.658, and a boiling point of -112 degrees Celcius. As a gas ozone has a light blue color. As a liquid, it is deep blue in color and very explosive. Ozone is a strong oxidizer as it wants to give one of its oxygens to just about any other molecule or atom which will even lightly accept it. Ozone was first named in 1840 by C.F. Schonbein from the Greek verb, ozein, "to smell."

The scenario for rapid ozone depletion over the poles begins with the formation of the polar vortex in wintertime and the decrease in stratospheric temperatures. The rotation of air about the pole in the vortex prevents the usual mixing of air between the polar region and midlatitudes. Polar stratospheric clouds form at the lower temperatures (< - 78 Degree Celsius) soaking up water vapor and nitric acid, the reservoir species for nitrogen oxides. The particles that make up these clouds also provide sites for the conversion of the inert chlorine reservoir species, hydrogen chloride and chlorine nitrate, into chlorine compounds that are easily broken down into chlorine atoms by the weak ultraviolet light of the polar spring. If the stratospheric temperature drops below - 85 Degree Celsius, enough water can be absorbed by the particles for them to fall into the troposphere, taking the water and nitric acid with them.

Main body

The chlorine is activated by sunlight, reacting with ozone to form chlorine monoxide. Chlorine monoxide, now the dominant chlorine species, either reacts with itself to form a linked pair of chlorine monoxide molecules which can then be split back into chlorine atoms and molecular oxygen by sunlight, or reacts with bromine monoxide, its bromine analog, to regenerate chlorine and bromine atoms that again attack ozone. The catalytic cycles involving chlorine and bromine are thus formed. With most of the chlorine as chlorine monoxide, and with all the nitrogen oxides removed from the isolated air-mass inside the polar vortex, ozone can be depleted quite rapidly until the vortex breaks down and air from midlatitudes containing nitrogen oxides is mixed into the polar air, quenching the runaway chlorine chemistry.

A conclusive test of the link between chlorine and bromine and ozone depletion is the comparison between the observed ozone loss and the loss predicted by photochemical computer simulations that include the observed abundances of chlorine monoxide and bromine monoxide. Using the data from the Airbome Antarctica Ozone Experiment, the calculated losses explain, to within the limits of experimental uncertainty, all the observed ozone loss.

Of immediate concern is what happens when the Antarctic polar vortex breaks apart in late spring (late October-November) when the vortex air, now devoid of ozone, mixes with air from midlatitudes. Does the loss of ozone accumulate year-round in the Southern Hemisphere? Model simulations of the vortex breakup show that the mixing of the ozone-poor vortex air with air from midlatitudes ...