Air contamination


Contents:
What is air contamination?
Sources of air contamination
Effects of air contamination
Preventing pollution of air



What is air contamination?

Air pollution are all substances (gases, liquids, solids), which exist in the atmospheric air, but they are not the its natural ingredients. Air pollution also comprise substances that are its natural ingredients, but are occurring in greatly increased quantities.

Air pollution has been divided into four groups:

1. Gases and vapors of chemical compounds, e.g. carbon oxides (CO, CO2), sulfur oxides (SO2, SO3), and nitrogen oxides (NOx), fluorine (2), ozone (O3), radon (Rn), ammonia (NH3), hydrocarbons and their chlorinated derivatives, phenols
2. Fine liquid droplets, e.g. droplets of bases, acids, solvents
3. Fine solids, such as ashes, particulates, heavy metals, carbon blacks, solid organic compounds, asbestos, pesticides
4. The microorganisms, in quantity or of type that is not typical for natural air composition; macro-organisms (e.g. fungi) with the products of their metabolism.

Air pollution also comprises acoustic pollution - noise. It is related mainly to the big cities, where its intensity is 65 - 75 dB.



Sources of air contamination

Sources of air pollution can be divided by origin into two groups: natural and anthropogenic.
By the time of rapid industrial development of virtually all air pollutants are of natural origin. They were formed as a result of:
- volcanic eruptions,
- fires of forrests, grasslands, savannahs and steppes,
- release of gases through swampy areas,
- the evaporation of salty water of the seas and oceans,
- erosion of rocks and soil,
- sandstorms in the deserts,
- the production of pollen by green plants,
- fall of cosmic dust.

However, roughly from the mid-eighteenth century (industrial revolution) the share of anthropogenic pollution (caused by human activity) has increased significantly.

Table below presents amounts of all emission of main air pollution in Poland (1998).

Pollution Emission in thousands tons
Sulphur dioxide (SO2) 2368
Nitrogen dioxide (NO2) 1154
Carbon dioxide (CO2) 373200
Not-methane volatile organic compounds 1089
Ammonia (NH4) 364
Dust 1250

Source: GUS (1998)

Most of air pollutants is produced by fuel/energy industry (over 50%), metallurgical industry (approx. 20%) and the chemical industry.
The greatest amount of air pollutants is created by the combustion of fossil fuels (coal, lignite, petroleum, natural gas, etc.). The result is the emission into the atmosphere of enormous amounts of exhaust gases (carbon oxides (CO, CO2), sulfur oxides (SO2, SO3), nitrogen oxides (NOx) and others) as well as dust, ashes, carbon black.
Air pollution is a side effect of many industrial processes. Harmful chemicals are released into the atmosphere by the branches of chemical industry. Refineries and petrochemical plants emit certain by-products of crude oil into the atmosphere. Steel mills, mines and cement plants produce large amounts of dust and other small solids air pollutants. The mining industry is also linked to emissions of methane - a gas which is the main component of natural gas. On pollution of the atmosphere affects even the agri-food industry. Along with the production of certain products (e.g. fish meal, starch) odors are emitted - substances with a very unpleasant smell.
Transport takes a significant part in air pollution, especially wheel transport. It was calculated that in North America along with car exhaust gases, a third of the total carbon dioxide emissions into the atmosphere.
Air transport contributes to contaminating the lower layers of the stratosphere, which adversely affects the state of the ozone, and may be one of the causes of ozone hole . Also, water transport should not be omitted, which in addition to air, it pollutes also water.
The status of air is also adversely affected by the storage and disposal of sewage and waste. Decomposition of organic substances by microorganisms leads to emissions of methane (a greenhouse gas) and gases being odoriferous substances, which are burdensome to the environment.
The last source of air pollution are households. They emit gases into the atmosphere as a result of the combustion of coal used for heating of residential buildings.




Effects of air contamination

Air pollution adversely affect the entire natural environment. It destroys the natural resources: both animate and inanimate.

As I mentioned before, the food industry, large cattle and pig farms, as well as chemical, petrochemical, and cellulose industry pollute the air with odors and other unpleasant smells. Fragrant substances are burdensome for animals and humans. Very often these substances are aromatic hydrocarbons (compounds of carbon and hydrogen of the ring structure). These chemical compounds are especially harmful to the human body, because of carcinogenic properties. The increased sulfur dioxide concentration in the ambient air in humans causes irritation of mucous membranes. This can cause coughing, swelling of the mucous membranes and bronchial muscle contraction.
Lead is one of the most toxic substances emitted to the atmosphere. Its harmfulness consists in stopping the production of enzymes that are necessary for the synthesis of hemoglobin. In addition, lead can damage the central and peripheral nervous system and interfere with the liver, heart and kidneys. Into the organism gets mainly ingestion and inhalation. Also, lead negatively affects the plant. Conifers are most sensitive to lead. It weakens mostly their growth and development.
Also dust pollution can impair the human health. Prolonged inhalation of inorganic dust leads to pneumoconiosis - chronic respiratory disease. Air pollution can also cause reproductive disorders and allergies.
The presence of infrared absorbing gases in the air such as carbon dioxide, methane, nitrous oxide, chlorofluorocarbons (CFCs), and water vapor is the cause of the greenhouse effect. Moreover, CFCs that are present in the atmosphere, are the main causes for the reduction of the ozone layer and the ozone hole. The consequences of these serious environmental problems have been described in separate sub-pages of this website.
Some of the gases emitted from industry (SO2, CO2, NOx, H2S, HCl) in chemical terms are anhydrides of inorganic acids. In the reaction with water molecules contained in the atmosphere they constitute weak inorganic acids. As a result, the formation of acid precipitation occurs. In the presence of water, weak inorganic acids undergo electrolytic dissociation (disintegrate into positive hydrogen cations and negative anions) and react with metal, causing an increase of the oxidation state. The visible effect of these reactions is the destruction of structural metal beginning of the surface and progressing into the depth i.e. corrosion. Acid anhydrides are transported over long distances (up to 500 km). Thus, they act even in very remote locations from industrial centers. In the form of acid rain they cause acidification of surface waters and soil. This has a negative impact on flora and fauna. It was established that already at pH equal to 5.4 reproduction of all fish species stops. Acidification of soil can cause changes of silicates and release of aluminum that is toxic to organisms. In acidic soils faster eluting of nutrients occurs. It is not difficult to predict the effects of acidification. Many organisms that have a narrow range of ecological tolerance to changes in pH of environment will disappear from the surface of the Earth. In the forests only some species of conifer would remain, that are resistant against slightly acidic soil environment.
Sulfur dioxide has a negative effect on plants. Even at a concentration of 10-500 m3 it causes destruction of the leaves of many species of plants. The most vulnerable are: wheat, barley, oats, tobacco, alfalfa, spinach and Scots pine. These are mainly crops. Forests are particularly vulnerable to air pollution. They are sensitive to fluoride compounds, sulfur, nitrogen, chlorine, zinc, lead, copper and hydrocarbons. It is calculated that the harmfulness of fluorine on plants is approx. 100 times greater than the harmful effects of sulfur dioxide.
Increasing the level of air pollution by industrial fuel - energy, mining, refining, petrochemical, etc. will therefore be reflected in other sectors of the economy. Reduction of quantities of crops, as well as reduction of the quality and quantity of trees and animals, will therefore result in suffering of agriculture, forestry, hunting and fishing.
Excessive air pollution is present now over more than 20% of the Polish area, mainly in the vicinity of industrial districts and large urban centers.

A classic example of destruction of the environment as a result of air pollution can be observed in the Jizera Mountains in the western part of the Sudetenland. As a result of transgenic gases, forests growing on mountain slopes have become enormously damaged. Currently, it depends only on us whether such phenomena will appear again in other parts of our country. To avoid increasing area of regions of ecological disasters, we must protect the atmospheric air.



Preventing pollution of air

Issues related to the protection of air in the Act of 31 January 1980 on environmental protection and management. This law defines the rules for the protection and rational development of the environment, to ensure favorable living conditions to the current and future generations.
Certainly, a complete stop of emission of harmful substances will never be possible. To protect our air, we should should take measures to reduce emissions of atmospheric pollutants.
All factories, steel mills and other industrial centers having the chimney exhaust gas routing shall apply filters. In order to reduce odor emissions, refineries should be provided with equipment for deodorizing gases, best if placed right next to the emitters. The decrease in emissions will also occur with the improvement of encapsulation of production (i.e. production completely isolated from the environment).
Transport is a major cause of air pollution. To reduce the emission of harmful components of exhaust gases, catalysts, which affect the rate of combustion of gasoline, should be installed in the cars. In order to reduce the emission of lead, we should use unleaded petrol, which is completely devoid of tetraethyl lead. To protect the environment from excessive carbon monoxide pollution we should also eliminate from the traffic often seen cars with a very bad technical condition because they do not completely burn fuel. Almost every person can influence the reduction of the level of vehicle exhaust emissions through the use of public transport and non-polluting vehicles, such as bicycles.
The process of desulfurization of coal is a very effective way to reduce emissions of sulfur dioxide SO2 . One way to desulfurization of coal is to carry out a chemical reaction between sulfur compounds and Fe3O4:
Fe3O4 + 3H2S + H2 -> 3FeS + 4H2O
The obtained iron sulfide (II) is then combusted, resulting in a sulfur dioxide:
4FeS + 7O2 -> 2Fe2O3 + 4SO2
The resulting sulfur dioxide is reduced with the carbon to chemically pure sulfur:
C + SO2 -> CO2 + S

The above method of desulfurization of coal is very effective, but unfortunately also expensive.
Significant amounts of gases that pollute air are also emitted by the combustion of fuels for heating of residential buildings. In that case, filters for cleaning of gases discharged through the chimneys should be used. You can also use insulating materials to protect buildings against excessive heat loss, making it possible to limit the burning of coal, and thus reduce CO2 and CO emissions. You should also consider the use for heating fuels that do not cause release of such large amounts of dust, such as coal. I mean the oil and natural gas.
In order to reduce greenhouse gases generated by the decomposition of organic substances contained in landfills, it is necessary to develop new methods of waste disposal.
In urban air it can be protected through proper placement of new of new industrial plants. In big cities also insulating green belts play an important role. In addition to absorbing certain amount of air pollution, they reduce noise (green belt with a width of 50 m reduces the noise level by 20 dB).
Today, air pollution is no longer just a local problem, unfortunately. It is an international problem. Therefore, international agreements are signed for the reduction of emissions of harmful gases and dust. On 13 November 1979 in 35 countries (including Poland) signed the Convention on Transboundary Air Pollution. It is aimed at reducing the quantity and range of spread of air pollution.
Certainly, comforting phenomenon is the fact that dust emissions in the years from 1989 to 1993 decreased from 2.4 million tonnes to 1.5 million tonnes per year. This may be evidence of concern about the state of the atmospheric air.