the depth stays the same. Ozone concentrations do vary naturally because of sunspots, the.
change in seasons, and latitude. Scientists have established records over several decades.
that map the normal levels of ozone. With each reduction comes a recovery. Recently,.
however, records show that the ozone shield is being depleted well beyond the normal.
changes dues to natural processes.
Scientists have determined the ozone is being depleted. The main reason for this.
is chlorofluorocarbons (CFCs). Fifty years ago, CFCs were thought of as miracle.
substances because they were stable, nonflammable, low in toxicity, and cheaply.
produced. They have been used in refrigerants, solvents, foam blowing agent, and in.
other small applications. Other chlorine-containing chemicals are methyl chloroform, a.
solvent, and carbon tetrachloride, and industrially used chemical. Halons, very effective.
fire extinguishing agents, and methyl bromide, an effective soil and produce fumigator,.
both contain bromide. All of these chemicals have atmospheric lifetimes long enough to.
allow them to be transported by winds into the stratosphere. There they break down and.
release the chlorine and bromine that are in side them and by doing so, damage the ozone.
layer.
Not until 1973 was chlorine found to be a catalytic agent in ozone destruction.
Catalytic destruction of ozone removes the odd oxygen species [atomic oxygen (O) and.
ozone (O3)] while leaving chlorine unaffected. This process was known to be potentially.
damaging to the ozone layer, but conclusive evidence of stratospheric ozone loss was not.
discovered until 1984. Announcement of polar ozone depletion over Antarctica in March.
1985 prompted scientific initiatives to discover the Ozone Depletion Processes, along.
with calls to freeze or diminish production of chlorinated fluorocarbons. A complex.
scenario of atmospheric dynamics, solar radiation, and chemical reactions was found to.
explain the anomalously low levels of ozone during the polar springtime.