Air pollution is defined as the presence of dangerous chemicals or compounds in the air (including those of biological origin) at levels that are injurious to one’s health. In a broader sense, air pollution refers to the presence of chemicals or substances in the air that are not normally present and that degrade the quality of the air or have a negative impact on people’s quality of life (such as the damaging of the ozone layer or causing global warming).

TYPES OF POLLUTANTS

Nitrogen dioxide -Nitrogen dioxide is a gas that contributes significantly to urban air pollution.

Ozone -Ozone is a gas made up of three oxygen atoms. It absorbs damaging Ultraviolet rays in the upper layers of the Earth’s atmosphere.

Sulphur dioxide -Sulphur dioxide is a colourless gas with a suffocating, unpleasant odour. It’s created when sulphur-containing fuels like coal and oil are burned. This covers the transportation sector, energy generation, and heating.

Carbon Monoxide- Carbon monoxide is a colourless, odourless, and tasteless dangerous gas created by the incomplete combustion of carbonaceous fuels like wood, petrol, charcoal, natural gas, and kerosene.  Carbon monoxide diffuses through the lungs and into the blood circulation, making oxygen binding difficult for the body’s cells.

Air Pollution Control devices

Particulate Control

Particulate matter is removed from flue gases using specialised technology. Since particulate matter is big enough to be trapped in this manner, much of this separation is done by physical means rather than chemical separation processes.

Electrostatic Precipitators-

An electrostatic precipitator is a type of filter that removes soot and ash from exhaust gases before they escape the smokestacks by using static electricity. By employing static electricity in the precipitators, unburned carbon particles in smoke are drawn out of the smoke, allowing clean, hot air to leave the smokestacks.

Cyclone Separators-

A cyclone separator is a separation device that removes particulate particles from flue gases using the concept of inertia. Dirty flue gas enters a chamber containing a tornado-like vortex in these separators. Gas particles travel up the cylinder due to the difference in inertia between them and bigger particulate matter, whilst larger particles strike the inside wall and fall down. The particulate matter is separated from the flue gas, leaving clean flue gas.

Fabric Filters-

One very easy approach for removing dust from flue gases is to use fabric filters. They can also remove acidic gases from certain gases if they use basic chemicals. This approach simply involves placing a piece of cloth in such a way that flue gases must pass through it before leaving the smokestacks. Dust particles are caught in the fabric when the gas flows through.

Gas Control

Separating harmful gases from flue gas usually requires more intensive chemical separation procedures. This extraction is necessary, however, because many acidic gases in flue gas contribute to acid rain. The following are some of the most common methods for extracting gases.

Scrubbers-

Scrubbers are a sort of equipment for removing dangerous pollutants from industrial exhaust gases before they are discharged into the environment. These pollutants are usually gaseous, and flue gas desulfurization refers to the use of scrubbers to remove Sulfur dioxide specifically. 

Carbon Capture-

To prevent carbon dioxide from entering the atmosphere, it may potentially be caught and stored underground, in forests, and in the seas. The method of trapping carbon dioxide and storing it underground, in geologic layers, is known as carbon capture and storage. This procedure is rarely employed, although it is frequently discussed as a means to reduce greenhouse gas emissions, which contribute to climate change.

Impact of Air Pollution on Plants

Oxidants-

The primary pollutant in the oxidant smog complex is ozone. Ozone effects often occur as flecking, bronzing, or bleaching of the leaf tissues on the top surface of damaged leaves. Although yield declines are most often associated with obvious leaf damage, crop loss can occur even when there are no visible signs of pollution stress. 

Sulfur Dioxide-

Coal-burning operations, particularly those that provide electric power and space heating, are major contributors of sulphur dioxide. Sulfur dioxide penetrates the leaves mostly through stomata (microscopic apertures), resulting in either immediate or chronic damage. Sulfur dioxide absorption at high quantities in a short period of time causes acute damage. Long-term absorption of sulphur dioxide at sub-lethal doses causes chronic damage. The symptoms include leaf yellowing or chlorosis, as well as bronzing on the underside of the leaves on rare occasions.

Fluoride-

Fluorides absorbed by leaves are carried to the edges of wide leaves (grapes) and monocotyledonous leaves’ tips. The absorption point sustains little damage, while the edges or tips of the leaves accumulate harmful quantities. The damage appears as a grey or light-green water-soaked lesion that develops into a tan to reddish-brown colour over time.

Particulate Matter-

Particulate matter deposited on plants, such as cement dust, magnesium-lime dust, and carbon soot, can obstruct the leaf’s normal respiration and photosynthetic systems. Because of the combination of a thick crust and alkaline toxicity caused by wet weather, cement dust can induce chlorosis and death of leaf tissue. Furthermore, alkaline dust collection in the soil can raise soil pH to levels that are harmful to crop development

CONCLUSION

Millions of individuals are now affected by air pollution. Ozone and PM, for example, may worsen asthma symptoms or cause premature death, especially in the elderly with pre-existing respiratory or cardiovascular problems. Plants can be harmed by air pollution in a variety of ways. Foliage damage might be obvious right away or develop over time as a yellowing of the leaf. Various parts of a plant may experience a decline in growth. Plants can be killed instantly, but they normally don’t surrender until they’ve been injured repeatedly. As a result, there is a compelling case for taking action to minimise air pollution, which can take numerous forms. Urban planning, technical advancements (e.g., the design of new automobiles that emit less pollution), and the implementation of new legislation at the national level are just a few examples.