Photochemical Smog

A hundred tonnes of rubbish are produced every hour in the modern world, according to some estimates. Humans are polluting rivers, seas, and even forests with their waste products. Finally, at the end of the day, all of this contributes to polluting the atmosphere. Polluting our atmosphere is the most destructive thing we can do to our planet. It is the only supply of oxygen, and when pollution levels in the air rise, it becomes increasingly difficult to breathe. Many children and elderly people who are already suffering from bronchitis and asthma will experience breathing difficulties as a result of the illness.

Smog has been a problem in many metropolitan areas in recent years. It is a mixture of smoke that becomes trapped in the air due to the fog that occurs throughout the winter season. Our senior citizens are at risk because it interferes with the formation of ground-level ozone and other pollutants such as sulphur dioxide and carbon monoxide. Today, we’ll look into ways we may reduce smog pollution in the environment. Learn what photochemical smog is and how it is related to the pollution of our cities and towns while also learning what photochemical smog is.

An introduction to photochemical smog

The combustion of fossil fuels results in the production of nitric oxide (a nitrogen compound with the chemical formula NO) and nitrogen dioxide (another nitrogen compound with the chemical formula NO₂), both of which are toxic gases. These pollutants are also emitted in a natural setting as a result of events such as volcano eruptions and the occurrence of forest fires. Nonetheless, the high concentration of these contaminants in locations where people live in large numbers is a source of great concern. This is due to the fact that natural emissions have a tendency to continue to spread over considerably larger distances.

When the NO₂ molecule is exposed to ultraviolet radiation, it is known to undergo a complex series of hydrocarbon reactions, which results in the formation of the photochemical smog constituents. Ozone, aldehydes, nitric acid, peroxyacyl nitrates (abbreviated as PANs), and a variety of other secondary pollutants are among the contaminants that make up this mixture.

This type of smog is typically characterised by a brown haze, and it is most frequently observed in densely populated areas that are located in warm climates. Furthermore, photochemical smog is most evident in the mornings and afternoons, when the sun is highest in the sky.

Formation of Photochemical Smog 

When sunlight interacts with nitrogen oxides and volatile organic chemicals in the atmosphere as a result of air pollution, a complicated series of chemical reactions takes place, and photochemical form is the result. Because of these reactions, ground-level ozone and some airborne particles are frequently formed in the atmosphere. Primary pollutant concentrations in the atmosphere are strongly correlated with the development of photochemical haze. It is also related to the number of secondary pollutants present in the environment (in some cases).

Primary pollutants that contribute to photochemical smog include oxides of nitrogen such as nitric oxide, nitrogen dioxide, and nitrous oxide, as well as the vast majority of volatile organic compounds (VOCs) (volatile organic compounds). Aldehydes, tropospheric ozone, and peroxyacyl nitrates are all examples of secondary pollutants that contribute to the production of photochemical smog. Aldehydes and tropospheric ozone are also instances of secondary pollutants (often abbreviated to PAN).

Nitrogen oxides and volatile organic compounds (VOCs) are emitted into the atmosphere in considerable quantities during morning rush hour traffic. Automobile emissions and industrial discharge are both responsible for the release of these contaminants. When exposed to hydroxyl groups in the environment, several of these hydrocarbon pollutants quickly oxidise and decompose, resulting in the generation of peroxy radicals. Nitric oxide is converted into nitrogen dioxide by the peroxy radicals produced as a result of this reaction.

Consequences of Photochemical Pollution

Smog caused by photochemical reactions has a variety of detrimental consequences for the environment and human beings. Because of the compounds present inside it, when coupled with hydrocarbons, they generate molecules that are irritating to the eyes. The radicals in the atmosphere interfere with the nitrogen cycle by preventing ground-level ozone from being removed from the atmosphere. Ground-level ozone has the potential to be exceedingly hazardous to human beings, according to certain studies. Additionally, poor vision and shortness of breath are two undesirable symptoms connected with photochemical pollution.

Conclusion

Between a smog cloud and photochemical smog, there isn’t much to distinguish between the two. Both of these are hazardous to us, as well as to our elderly relatives and friends. The smog that you see is simply a combination of smoke and fog, and it occurs most frequently during the winter months in urban areas that are densely populated with automobiles and trucks. The presence of smog in your location is possible if there is no wind blowing in your direction and there has been a high level of industrial activity. Smog occurs in areas that are far from its true source. This form of smog is of the sulphurous variety, and it is referred to as “London Smog” in some circles.

Meanwhile, photochemical smog occurs when UV radiation reacts with pollutants that are present in the air, whereas photochemical smog does not occur. Nitrogen oxides and hydrocarbons are two of the most common contaminants in the air that contribute to photochemical smog. Photochemical smog cannot occur without the presence of sunlight. Farmers in northern Indian states such as Delhi, Punjab, and Haryana burn their fields after the harvesting season is through, and this practise is most frequent in those states.