مواضيع بالعربية و الانجليزية topics مواضيع بالعربية و الانجليزية topics
random

آخر المواضيع

random
recent
جاري التحميل ...
recent

موضوع عن التلوث بالانجليزي the pollution

موضوع عن التلوث بالانجليزي the pollution



موضوع عن التلوث بالانجليزي the pollution

-----
-----
Main regulated pollutants:

O3 (Ozone)

Ozone is a secondary pollutant formed in the lower atmosphere from a mixture of gaseous precursors composed of nitrogen oxides and volatile organic compounds. These pollutants required to produce ozone are mainly emitted by human activities. and also by vegetation. Solar radiation controls the intensity of ozone production.

High surface concentrations therefore occur in the summer period when sunshine is important and when the weather conditions are not very dispersive and promote accumulation. Generally it is during a weather situation under anticyclonic influence that episodes of pollution with ozone are observed. The episode will be even more important if the anticyclonic situation persists.

Ozone has a lifespan of a few days in the lower layers of the atmosphere, so it can be transported far from its production area: this pollution is usually observed more intensively in peri-urban areas and rural downwind of agglomerations.

Ozone from the lower atmosphere affects ecosystems and human health. It therefore has a toxic effect which is to oppose the role of stratospheric ozone whose significant concentrations are located at more than 10 km altitude and which filters a harmful part of the ultraviolet rays of solar radiation. Ozone is an aggressive gas that penetrates deep into the lungs and can react to cellular components and affect respiratory capacity. These effects are accentuated by the presence of other pollutants such as oxides of sulfur and nitrogen, or during physical exertion and prolonged exposure. Ozone has a detrimental effect on vegetation (crop yield, for example) and on some materials.

The chemical production of an ozone molecule (O3) is always the result of a reaction between a molecule of oxygen (O2) and an oxygen atom (O). It is the photodissociation of nitrogen dioxide (NO2) that produces the required oxygen atom (O), provided that the nitric oxide (NO) reacts with a hydroperoxyl (HO2) radical rather than with O3, which would have a zero balance. In low-pollution areas, HO2 is derived from the oxidation of carbon monoxide (CO) and methane (CH4) present in the natural atmosphere. But in polluted areas, the production of ozone is favored, because the oxidation of volatile organic compounds (VOCs) is faster than that of CO or CH4. In highly polluted zones, and under certain conditions of insolation, the high concentrations of NOx, can lead to nocturnal destruction of ozone (titration effect).

NOx (Nitrogen oxides)

The family of nitrogen oxides groups mainly nitrogen dioxide (NO2) and nitric oxide (NO). NOx is mainly emitted during high temperature combustion; whether by oxidation of the nitrogen present in the fuel or by fixing the nitrogen present in the air at very high temperature. Combustion generally emits NO, part of which is oxidized to NO2 directly in the combustion chamber, and another part continues its oxidation in the atmosphere. NOx are precursors of ozone, as well as some strong acids, responsible for acid rain events.
Among the main emitting sectors of NOx, the road sector is predominant (56% of national emissions in 2011), followed by manufacturing (14% in 2011) and agriculture / forestry (10% in 2011). Large combustion plants and the residential / tertiary sector are also major contributors.

VOCs (Volatile Organic Compounds)

VOCs are gases composed of at least one carbon atom, combined with one or more of the following: hydrogen, halogen, oxygen, sulfur, phosphorus, silicon or nitrogen. There is often methane (CH4), which is the most common VOC in the atmosphere but is not directly harmful to health or the environment but is, on the other hand, a greenhouse gas. The rest of the VOCs are commonly referred to as NMVOCs (Non-Methane Volatile Organic Compounds). VOCs are precursors of ozone and fine particles (secondary organic aerosols).
Anthropogenic NMVOCs are emitted during combustion phenomena but also by the evaporation of solvents (contained in paints for example), fuels, etc. There is a very large number of VOCs that can be either directly emitted or produced in the atmosphere.
The main sectors emitting VOCs are the residential sector (38% of emissions in 2011) due to the use of solvents for domestic use or in the building industry, the manufacturing industry (paints), then the transportation, the transformation of the energy then agriculture / forestry.

التعليقات



إذا أعجبك محتوى مدونتنا نتمنى البقاء على تواصل دائم ، فقط قم بإدخال بريدك الإلكتروني للإشتراك في بريد المدونة السريع ليصلك جديد المدونة أولاً بأول ، كما يمكنك إرسال رساله بالضغط على الزر المجاور ...

إتصل بنا

جميع الحقوق محفوظة

مواضيع بالعربية و الانجليزية topics

2016