qualitative+effects+of+ozone+depletion+and+photochemical+smog


 * //Qualitative effects of ozone depletion and photochemical smog// **


 * Videos**

Human contribution to the ozone hole/climate change || media type="custom" key="24157448" CFCs and ozone depletion || media type="custom" key="24157592" Evidence for the ozone hole ||
 * media type="custom" key="24155580"

Photochemical smog ||
 * media type="custom" key="24179150"


 * Common misconceptions:**
 * CFCs are heavier than air, so they can't reach the ozone layer.
 * Volcanoes are causing ozone layer completion.
 * Ozone layer depletion only occurs in Antarctica.
 * Natural sources of tropospheric chlorine are four to five times larger than man-made ones, and these affect the ozone hole
 * Smog is a single chemical substance.
 * 'Good' ozone is different than 'bad' ozone.

> Drifting around inside the polar vortex are reservoir molecules that have bonded with chlorine atoms and in so doing prevented them—so far—from attacking ozone. When polar stratospheric clouds form above Antarctica, chlorine reservoir molecules bind to the icy particles that make up the clouds. Once this happens, complex chemical reactions begin to take place that result in molecules of chlorine gas being released from the reservoirs. All through the long, dark winter, especially during July and August, the chemical reactions taking place on the surfaces of the polar stratospheric cloud particles continue, and more and more chlorine gas builds up inside the vortex. This is when ozone depletion is triggered. In late August, the sun begins to rise, is. As the first rays of spring sunlight strike the stratosphere high over the frozen continent, conditions change very rapidly. The UV rays coming from the sun strike the chlorine molecules inside the vortex. The molecules break apart, releasing billions of chlorine atoms that begin an attack on ozone molecules. The result is massive ozone destruction. Before long, so much ozone is destroyed inside the vortex that an ozone hole is formed.
 * Interesting facts:**
 * 'Holes' in the ozone layer allow more 'heat rays' to reach the earth, causing global warming.
 * Increase of carbon dioxide in the atmosphere causes ozone depletion.
 * The sun 'burns' holes in the ozone layer.
 * Atmospheric gases are not sorted by weight; the forces of wind can fully mix the gases in the atmosphere. The CFCs are evenly distributed throughout the turbosphere and reach the upper atmosphere.
 * Although volcanic eruptions are powerful events that can inject hydrogen chloride into the atmosphere, the vast majority of eruptions are too weak to reach the stratosphere.
 * Ozone layer depletion has been measured everywhere outside of the tropics, not just Antarctica. However, the biggest depletion is above Antarctica. In winter, the stratosphere above the Antarctic continent gets colder than anywhere else on Earth. Antarctica is also one of the windiest places on Earth. In May and June, strong winds in the stratosphere begin to blow clockwise around the continent. These stratospheric winds gradually form an enormous ring of moving air, called the Antarctic polar vortex.
 * It is //stratospheric// chlorine that affects ozone depletion, //tropospheric// chlorine is irrelevant. Chlorine from ocean spray is soluble and thus is washed by rainfall before it reaches the stratosphere. CFCs, in contrast, are insoluble and long-lived, allowing them to reach the stratosphere. In the lower atmosphere, there is much more chlorine from CFCs and related haloalkanes than there is in HCl from salt spray, and in the stratosphere halocarbons are dominant. Only methyl chloride, which is one of these halocarbons, has a mainly natural source and it is responsible for about 20 percent of the chlorine in the stratosphere; the remaining 80% comes from man made sources.
 * It's estimated that is all the ozone in the stratosphere was brought down to sea level was evenly spread across the world, it would only be about 3mm thick!
 * Carbon monoxide emissions from car engines can be reduced by tuning the engine regularly and using catalytic converters, which oxidise the carbon monoxide to carbon dioxide.
 * Smog is a mixture of chemicals.
 * Ozone always has the chemical composition of three oxygen atoms bound together, O3. So in one sense ozone is ozone. However, we know that ozone in the stratosphere absorbs UV radiation from the sun and so protects humans from its harmful effects. We refer to this as “good” ozone. On the other hand, ozone that occurs near the surface of the earth can damage the human respiratory system, and so we called this ozone “bad” ozone. But remember, ozone is ozone.


 * Resources:**
 * Ozone Layer from National Geographic Education.
 * Smog from National Geographic Education.
 * Formation of photochemical smog from yTeach.