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what are they and main types

The atmospheric pollution It is defined as the introduction into the atmosphere of energy or substances that produce a harmful action such as air pollutants. It can be about the atmosphere itself, or about biological resources and ecosystems. That they suppose a deterioration of the material goods. Or that could threaten or disturb the established agreements or other legitimate uses of the environment.

Components of air pollution

It can be said that air pollution is made up of three basic components:

  • The cause. Sources of emission of pollutants.
  • The atmosphere. In it, the transport, diffusion and chemical transformation of pollutants takes place.
  • The effects. On the receiving environment (man, animals, vegetation, materials, etc.).

Depending on the effects that a substance produces on its receptors, it will be considered polluting or not.

Thus, pollutants are those substances, chemical, biological or radiological, which may give rise to risk or damage to people or property in certain circumstances.

In the atmosphere, the necessary physical and chemical transformations of pollutants take place. And, in turn, it acts as a means of transport and dispersal. Dispersion is the natural tendency of pollutants. To cover the entire volume of the medium that contains them. Consequently, they tend to spread and disperse through the air as a result of the wind.

Emission of gases is defined as the production of gaseous products in any industrial, natural or domestic process, which is dispersed through the atmosphere. By varying the characteristics of the air prior to its effect.

Classification of air pollutants

According to their origin, pollutants can be classified into:

  • Natural: caused by forest fires, volcanic eruptions, storms, etc.
  • Anthropic: man-made.

According to their nature, pollutants can be classified as:

  • Chemical: Organic substances (molecular structure based on carbon atoms) and inorganic (they do not contain or contain few carbon atoms, such as halogens, acids, metals, etc.).
  • Biological: Forms of life (bacteria, viruses, protozoa, etc.) that can cause damage to the environment and health.
  • Radiological: Radiation, noise and vibrations or heat.

According to their origin and chemical reactivity, pollutants can be classified into:

  • Primary. They are those that are emitted into the atmosphere directly. From the different emission sources. And they can have a natural or anthropic origin. The most common primary pollutants are:
    • Carbon monoxide and dioxide.
    • Sulfur oxides. Hydrocarbons.
    • Volatile organic compounds (VOC).
    • Aerosols and particulate matter. Radioactive substances.
  • Secondary. They are those that are formed as a consequence of the reactions and transformations experienced by primary pollutants in the atmosphere. In most cases, the by-products of these processes have the worst effects on human health and the quality of the environment. Depending on the effects of secondary pollutants, the consequences on the atmosphere can be:
    • Photochemical contamination (photochemical smog).
    • Acid rain (acidification of the environment).

Nitrogen oxides (NOx)

The term is used nitrogen oxides (NOx) to name mainly the sum of NO and NO2. Also to a lesser extent, other oxides of this element (including N 2O3, N2O4, NO3, N2O and N2O5). They play a preponderant role in the formation of tropospheric ozone when they react with volatile organic compounds in the presence of sufficient solar radiation.

The most important sources of NOx emission they are transportation, thermal power plants, fuel combustion. Such as natural gas, incinerators, cement plants and glass factories. Both NO2 and NO appear in the atmosphere. Naturally during volcanic eruptions or storms, its normal concentration being 800-900 μg / m3.

  • Nitrogen Monoxide (NO) it is a colorless gas. Which is generated by the reaction between N2 and O2 in the air during combustion processes at high temperatures. As well as by the oxidation of nitrogen that is part of fuels.
  • Nitrogen dioxide (NO2), It is formed from the oxidation of NO, it is a reddish-brown gas, irritating, toxic at high concentrations and very reactive. In high concentrations it can irritate the alveoli and increase the risk of lung infections. NO has detrimental effects on health. But these effects are appreciably less than those of an equivalent amount of NO2.

Carbon monoxide (CO)

E l carbon monoxide (CO) it appears as a by-product of the combustion of organic compounds. Generally hydrocarbons, in incomplete conditions. That is, with a shortage of oxygen. It is a colorless, odorless and poisonous gas.

It is one of the main polluting gases that are emitted by the exhaust pipes of vehicles. Its highest concentration occurs in urban areas. Due to the transit. Other important sources are industrial combustion processes in boilers and combustion processes.

The emission of CO constitutes a pollution problem of air indoor and outdoor type.

In terms of accidental deaths due to suffocation, the high concentrations and, therefore, the exposures that are generated inside houses and in closed spaces are much more critical.

Carbon dioxide (CO2)

CO2 is a colorless gas, tasteless and odorless, it is naturally present in the atmosphere and is non-toxic.

It is present in the atmosphere. Due to its lack of toxicity, it should not be considered a contaminant. But it is considered a primary pollutant. Because it is emitted into the atmosphere by anthropogenic combustion processes. What has caused an exponential increase in their concentrations in recent centuries.

Really, what makes it polluting is its contribution to the global warming for him greenhouse effect. The fact that their concentration is increasing due to the burning of fossil fuels and the destruction of their sinks (oceans and biomass).

Sulfur oxides (SOx)

Sulfur dioxide (SO2) is a primary pollutant. That is emitted fundamentally by the combustion of fossil fuels. They contain sulfur (mainly coal and heavy fractions of oil).

In addition to oil refineries, cement plants, transportation, mainly diesel vehicles. And during the processing of minerals that contain sulfur (as in the extraction of copper, lead, zinc and nickel).


They are substances that contain hydrogen and carbon. Hydrocarbons that contain few carbon atoms son gases at ordinary temperatures. These are the most important from the point of view of air pollution. Since they favor the formation of photochemical reactions.

The presence in the atmosphere of hydrocarbons light is not usual. Since they are not natural components of the air. These come mainly from the incomplete combustion of the gas. Although the evaporation of petroleum derivatives in large deposits is also a source.

One of the most common hydrocarbons in large cities is the olefins, whose origin is the cracking or fragmentation of long hydrocarbon chains due to the effect of heat, and which play a very important role in the creation and development of oxidative smog.

As hydrocarbons contain more carbons and fewer hydrogens, you start talking about hollines, which generate visibility problems.

The oxidation of some hydrocarbons in the atmosphere can give rise to formaldehydes and acroleins, which in high concentrations cause eye irritation problems.

Heavy metals

The heavy metals they are chemical elements. Which are generally present in the atmosphere in very low concentrations. Its origin comes from anthropic sources in its great majority.

One of the most serious consequences of the presence of heavy metals in the environment is that they are not gradients. Neither chemically nor biologically, by nature. What causes its persistence in it and its bioaccumulation. This persistence leads to the biological amplification of metals in the trophic chains.

As a consequence of this process, the concentrations of metals in the upper members of the chain can reach values ​​much higher than those found in the atmosphere.

Mineral substances

The iron oxides and silicates.

Iron oxides they are generated mainly in the steel industry.

The burning process of the carbon present in the original mineral inevitably involves the reaction of oxygen with a part of the iron. Forming ferrous oxide (FeO) and, above all, ferric oxide (Fe2O3). That are scattered around the furnaces.

The two main sources of silicate emissions are the cement factories and quarries. Around cement factories, white powder is deposited. But the field of action is broader due to the displacement of small particles carried with the wind.

Aerosols and particulate matter

The term aerosol or particulate matter it is used generically. To refer to a mixture of solid and liquid particles found in the air. They can be formed by condensation or photochemical reactions of gaseous pollutants. For the most part, secondary particles are formed from hydrocarbons, nitrogen oxides, and sulfur oxides.

The American Environmental Protection Agency (US EPA) divides particulate matter into:

  • Primary particles: particles that enter the atmosphere as a direct emission from different sources. They include filterable particles and condensable particles.
    • Filterable particles: particles that are emitted directly into the atmosphere. In solid or liquid state. They can be retained in a filter of defined characteristics, established as standard.
    • Condensable particles: matter that is emitted in a gaseous state. But it immediately changes to a liquid or solid state once it is in the atmosphere.
  • Secondary particles: are formed in the atmosphere. As a consequence of chemical reactions and their subsequent condensation / liquefaction. They are formed at some distance from the emitting source normally.

Radioactive substances

Radioactivity It is a natural physical phenomenon by which some bodies emit radiation that has the property of producing fluorescence or ionizing gases.

The reason for understanding these substances as pollutants is that they emit ionizing radiation that can cause harmful effects when they interact with living beings.

The penetration capacity of the radiation in matter it depends on the different types of radiation. From alpha radiation, which can be stopped with a sheet of paper. Until neutron bombardment, which can only be isolated by a thick layer of concrete.

High exposure to radioactive substances can cause genetic mutations.


The smell it is a sensory reaction of certain cells located in the nasal cavity. That, from a certain perception value, can cause annoyance.

The smell can have several origins depending on the source that generates it. Therefore, the way to treat the associated complaints must be approached in a different way.

Finally, it must be taken into consideration that the impact on the environment varies. It has specific characteristics according to the …

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