ATMOFERIC CONTAMINATION - NATURAL SCIENCE FOR STUDENTS OF 5 GRADE.

The frenetic industrial activity that takes place in the countries of the so-called First World, and in those in the process of developing in the Third World, provokes a whole series of substances that, emitted into the atmosphere, change the composition of the air "purely" " These substances include, for example, oxides of sulfur and nitrogen, hydrocarbons, CO2, lead, asbestos, radioactive substances, etc. Each substance, on the other hand, can cause a certain effect, among them the most known for alarming are the ozone hole, the greenhouse effect and acid rain.

Ozone is a gas present in the upper layers of the atmosphere, in the stratosphere, responsible for curbing ultraviolet radiation from the sun. If they reach the biosphere without going through the ozone filter, the consequences would be very serious for life : among them, increased skin cancer, eye diseases, damage to the immune system, altered crops, decreased marine production due to alteration in the photosynthesis of plankton, etc. The main cause is the accumulation of pollutants with high chlorine content, called chlorofluorocarbons (CFC), which, when they react with ozone, destroy it. CFCs are present in refrigeration liquids, aerosols, circuit cleaning liquids, insulating materials, etc., so their widespread use makes an easy solution to the problem difficult.

The greenhouse effect is caused by gases that let in short-wave solar radiation but absorb the long-wave radiation reflected by the earth's surface, radiation that appears in the form of heat. It is as if these gases create a bell of glass around the surface, a bell in which, when the Sun strikes, everything inside it warms up, hence the name of the effect.

The main gases involved in the effect are three: carbon dioxide, methane and nitrogen oxide. These gases are found naturally in the atmosphere, but their concentration increases considerably due to the burning of fossil fuels and trees in the case of CO2, to considerable agricultural and livestock activity in the case of nitrogen oxide. The increase of the temperature by the greenhouse effect can bring more problems than advantages, among them, the fusion of water retained in the polar ice caps with the possible episodes of floods. Be that as it may, it is clear that the solution to this problem is to look for alternative energy to fossil fuels and avoid the abusive felling of trees, whose presence would help, on the other hand, to reduce the effect of using CO2 in respiration.

Acid rain is an evil of development, that is, it is an environmental problem that mainly affects the industrialized countries. The cause is simple, its origin is found in nitric and sulfuric acids from industrial pollutants modified in the atmosphere and transported by currents until they are deposited on Earth. Acid rain affects especially the long, where the biological diversity decreases markedly by acidifying the environment, and in the forests, where they cause a fall of the leaves of the trees due to the difficulty in obtaining nutrients by acidifying the substrate. As in the case of the greenhouse effect, the solution is to look for less polluting energy alternatives.

Nuclear energy emerged as a hope for clean, inexpensive and inexhaustible energy, but it was not considered to do with radioactive waste (waste with a half-life of the order of thousands of years) and how to build 100% safe reactors. The construction costs of highly safe reactors, but not completely, dismantled the concept of cheap energy, and the problem of what to do with tons of waste converted this energy, nowadays, into uncomfortable. The failures in its mechanism and the dispersion in the atmosphere of radioactive contaminants.