Photochemical smog is also famous as summer smog and it is very harmful. It is produced when UV light originating from the sun interacts with the oxides of nitrogen. This smog is usually personified as a brown haze in the atmosphere. It is seen in the highly populated cities that are placed in relatively warm climates. It is most see-able during afternoons as well as mornings.
The modern world is delivering a hundred tons of waste every hour. Humans are mainly spoiling the rivers, the sea, and even the forest. All of these factors lead to the pollution of air at the end of the day. This pollution is a very pathetic thing because it is polluting the environment which is the only source of oxygen.
These factors lead to breathing problems in those who are already suffering from bronchitis and asthma. Nowadays many metropolitan cities are facing the issue of smog. It is called the mixture of smoke and fog that gets stuck in the air during the winter season. It is very risky to health and it also disrupts the ground-level ozone, sulphur dioxide, and carbon monoxide.
It becomes harmful to the senior citizens and here the most important factor is that it is linked to the pollution of the cities and towns. The classic smog pollution mainly happens when there is an excess amount of coal burning. It also increases the amount of smoke and sulphur dioxide in the air.
The result of this factor is the thick clouds of smoke which are known as smog. Photochemical smog is also known as the Los Angeles Smog. This type of smog occurs in the urban areas that contain a large number of automobiles.
Photochemical smog can be formed with a complex series of chemical reactions. The matter includes sunlight, oxides of nitrogen, and volatile organic compounds present in the atmosphere as a result of air pollution. All those reactions often result in the formation of ground-level ozone and certain airborne particles. It is also observed that the appearance of photochemical smog is closely related to the concentration of primary pollutants in the atmosphere.
Figure 1: Photochemical Smog formation
(Image Attribution: Liweichao.vivian, CC BY-SA 4.0
The factor is also related to the concentration of secondary pollutants. Some common examples of primary pollutants those are responsible for photochemical smog is nitric oxide, nitrogen dioxide, and nitrous oxide and most VOCs. Some secondary pollutants are aldehydes, troposphere ozone, and peroxyacetyl nitrates. It is seen that during the peak traffic hours in the morning, large amounts of nitrogen oxides and volatile hydrocarbons are released into the atmosphere.
All the pollutants are traced to automobile emissions and industrial discharge. The hydroxyl groups in the atmosphere are mainly responsible for some of these hydrocarbon pollutants rapidly undergo oxidation. It results in the formation of peroxy radicals and these radicals go on to convert nitric oxide into nitrogen dioxide.
Nitric oxide and nitrogen dioxide are emitted from the combustion of fossil fuels. It also reacts along with being naturally emitted from things like volcanoes and forest fires. The exposure to the ultraviolet radiation, $\mathrm{NO_2}$ goes through a complex series of reactions. The reaction happens with hydrocarbons to produce the components of photochemical smog.
It is called a mixture of ozone, nitric acid, aldehydes, peroxyacetyl nitrates, and other secondary pollutants. Here the $\mathrm{NO_2}$, ozone and PANs are called photochemical oxidants. They are called so because they can react and oxidize certain compounds in the atmosphere or within a person's lungs that are not normally oxidized. It is seen that even small traces of these chemicals can affect the respiratory tract of humans and animals, and damage crops and trees.
Figure 2: Photochemical smog effects
Photochemical smog has different negative effects on the environment as well as human beings. It contained some chemicals and they combination with hydrocarbons form molecules which cause eye irritation.
Here, the atmospheric radicals interfere with the nitrogen cycle and stop ground-level ozone from being eliminated. The ground-level ozone can prove to be extremely toxic to human beings. Other negative effects are decreased vision and shortness of breath.
Smog is mainly called a by-product of modern industrialization society. It occurs due to industry and the number of motor vehicles present in the cities. This problem is more prominent in large cities that have a warm, sunny and dry climate. Photochemical smog is also referred to as oxidizing smog and the reactions of oxidation has described in different ways. Therefore, it is seen that photochemical smog is a kind of air pollution.
Q1. What are the main reasons for Photochemical smog?
Ans. The smog turns into Photochemical smog when comes to exposure to sunlight. It reacts with the pollutants in the air and the pollutants like hydrocarbon reacts with sunlight and formed thick clouds of smoke. It does not move much and dissipates slowly and the cloud can cover a town and it can result in no sunlight in the morning.
Q2. What are the important steps for reducing smog?
Ans. Some steps can help in reducing the effects of smog. The plantation of more trees can help in the purification of the air. The concern of the citizens about reducing the number of automobiles can help in reducing smog.
Q3. What are the main compositions of photochemical smog?
Ans. Nitrogen dioxide and nitric oxide are the two main compounds of nitrogen that helps in the creation of photochemical smog. They are produced from the burning of the fossil fuels. They are released due to events such as the eruption of volcanoes and the occurrence of forest fires.
Physics
Biology
Chemistry
Mathematics
Economics
Psychology
Environmental Science
Social Studies
Fashion Studies
English