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موضوع عن تلوث الهواء بالانجليزي قصير

موضوع عن تلوث الهواء بالانجليزي قصير




موضوع عن تلوث الهواء بالانجليزي قصير
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Air pollution ... not just in the air


Be in a traffic jam, forced to breathe the exhaust of hundreds of vehicles, we observe the black smoke spewed by factory chimneys or the horizon disappears hidden by the smog of a hot day summer, the air pollution jumps our eyes ... and lungs. But it can be much more insidious.

Air pollution knows no boundaries. She travels briskly beyond countries, continents and seas. Pollutants such as fine particles can travel thousands of kilometers1. Thus, up to 50% of the human activity mercury deposited each year in North America would come from other continents, in particular coal-fired plants from China and India2. The airborne deposit is now the primary source of mercury in Canada's lakes, soil and vegetation3.

Of course, pollution can reach us by the air we breathe, but also by the contact on our skin. Polluted air can contaminate everything with which it comes in contact: fruits and vegetables as well as water and soil and, indirectly, food products (plants, animals, fish) that will have fed on it.

Finally, it should be known that pollutants in the air in minute quantities can be concentrated as they move up the food chain. For example, if there is mercury in the air, it can settle on water and be absorbed by small fish. As larger fish eat smaller fish, the concentration of mercury increases as this persistent pollutant accumulates in living organisms. Finally, when eating fish contaminated with mercury, we may actually be victims of air pollution!

ABC of air pollutants

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Air pollutants that are harmful to health are in the form of gases and respirable particles.

Four gases are the main contributors to pollution4,5:

ozone (O3)
nitrogen dioxide (NO2)
sulfur dioxide (SO2)
carbon monoxide (CO)
Added to these are other chemical pollutants such as heavy metals and volatile organic compounds (VOCs) that include harmful products such as benzene and polycyclic aromatic hydrocarbons (PAHs).

Respirable particles (also called fine or ultrafine particles) refer to a heterogeneous mixture of solid and liquid particles suspended in the air. They are classified in two categories according to their size rather than their composition. The smaller they are, the more they can be toxic because they penetrate deeper into the respiratory system and can even reach the cardiovascular system. They are commonly called PM, the abbreviation of the English term particulate matter.

PM10 (less than 10 micrometers in diameter). Note that a human hair is 50 to 150 micrometers in diameter.
PM2.5 (less than 2.5 micrometers) the most toxic.
According to the experts, it is relatively difficult to know which pollutant in particular may be responsible for a specific health problem6. Most of the time, pollutants, regardless of their origin, are in the form of a cocktail composed of many elements that act synergistically. Thus, epidemiological studies often focus on the different adverse effects of "combined" pollution. The intensity of this pollution is generally estimated by evaluating the concentration of one or two of the main pollutants, which then serve as markers, rather than systematically measuring each element.

Pollutants: where are they?

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Surface Ozone or Ozone Layer?

Surface ozone is a toxic pollutant. It should not be confused with the famous ozone layer that protects us from the sun's rays. Ground-level ozone is formed when nitrogen oxides and volatile organic compounds from vehicles and industries are transformed by solar radiation and heat. Ozone, with respirable particles, is one of the main components of smog that has a harmful effect on health.

The vast majority of pollutants, gases or particulates come from the use of fossil fuels (oil, natural gas and coal), which alone account for about 80% of global energy needs. These fuels are mainly used for transportation, industry, heating and in thermal power generation plants. Most of them are concentrated in urban areas7,8. It should also be noted that in several large cities, wood burning is a very important source of air pollution.

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2016