Photochemical smog (fog) is a fairly new type of air pollution. This is an urgent problem of modern large cities, in which a significant number of various vehicles are concentrated.
What it is?
A photochemical smog is formed as a result of concentration of aerosol particles and a mixture of gases in the atmosphere. Nitrogen and sulfur oxides and various photooxidants are distinguished as its main components.
What is the reason?
Photochemical smog, the formation of which is possible under various climatic and environmental conditions in industrial centers, is characterized by significant air pollution.
This phenomenon is especially harmful in calm, sunny weather, when the warm upper air layers cannot stop the movement of air masses in the vertical direction. Especially often, this phenomenon occurs in megacities that are protected from the winds by mountains, hills.
Photochemical smog appears as a result of photochemical reactions occurring under certain conditions when there is an increased concentration of hydrocarbons, nitrogen oxides, and other pollutants in the atmosphere.
Also, some natural processes, for example, in calm weather, with increased solar radiation in the lower atmosphere, there is a slight exchange of air masses as the cause of this phenomenon.
Chemical component
Such weather contributes to an increase in the concentration of reacting substances in the air, resulting in the formation of nitrogen oxides and atomic oxygen. It forms ozone molecules with molecular atmospheric oxygen . Nitric oxide interacts with the olefins contained in the exhaust gas, resulting in an excess of ozone and hydrocarbon radicals. Subsequent dissociation contributes to the accumulation of excess ozone in the earth's atmosphere. At night, the interaction of this species is terminated. Ozone reacts with olefins, which contributes to the accumulation of various peroxides in the atmosphere, which together form the oxidants that make up the photochemical smog. They are a source of free radicals that differ in their reactivity.
Photochemical smog is a frequent occurrence over Paris, London, New York, Los Angeles and other American and European cities.
What effect does photochemical smog have on a person? What is this phenomenon? According to its physiological effect, it is dangerous for the circulatory and respiratory systems, is the cause of the sudden death of citizens with poor health.
Important facts
Allocate dry and wet smog. The second option is typical for London, in the atmosphere of which, due to increased humidity, drops accumulate, forming dense clouds.
The problem of photochemical smog is especially acute in Japan, the USA, Great Britain, Argentina, Mexico, and Canada. For the first time, such a phenomenon was recorded in Los Angeles in 1944. Since the city is located in a depression that is surrounded by the sea and mountains, air masses stagnate, pollutants accumulate, and under favorable weather conditions, smog forms.
If its concentration is high, you can see a bluish haze, which reduces visibility, which leads to poor transport.
At lower concentrations of pollutants, it looks like a yellow-greenish haze, no continuous fog is formed. If the task "List the conditions for the formation of photochemical dry smog" is given, it is necessary to consider those gases that enter the atmosphere during the operation of industrial enterprises.
Negative influence
Photochemical smog negatively affects buildings, plants, people, a variety of materials. The appearance of such a fog leads to irritation of the mucous membranes of the nose, eyes, and throat. It causes an exacerbation of a variety of chronic diseases, has a toxic effect. Smog has a specific smell; it negatively affects beets, grapes, cereal plants, beans, and ornamental shrubs.
A typical sign that the plant was adversely affected by photochemical fog is leaf swelling. Then they have a silver and bronze hue.
Smog leads to accelerated corrosion of materials and building elements, damage to synthetic and rubber products.
Types of smog
Allocate London wet smog, which is a combination of fog and gaseous impurities, which are waste products.
Alaskan-type ice smog is formed at lower temperatures from steam from domestic gas emissions and heating systems.
Dry smog of the Los Angeles type appears as a result of photochemical reactions occurring in gas emissions under the influence of solar radiation.
Radiation fog appears during radiation cooling of the earth's surface and moist air in the lower atmosphere to the dew point. It appears at night with a slight wind, cloudless weather with an anticyclone.
Land Protection Options
The soil is an element of the biosphere, creating full conditions for the biochemical environment of humans, plants, animals. Soils accumulate precipitation, regulate water balance, ensure the purity of underground rivers and lakes. The photochemical smog negatively affects the fertility of the soil, makes it unsuitable for use, so it is so important to carry out measures to protect and protect land on a national scale.
Among the measures that should be taken today in order to preserve the ground for future generations, they highlight the reduction of land use for industrial purposes, the elimination of pollution of industrial enterprises located near the land fund.
Particular attention should be paid to the systematic restoration of land plots that are disturbed by production activities.
The environmental situation on our planet and the health of the living organisms that live on it directly depend on those effective measures that will be taken to protect land, the atmosphere at the state level.