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 is this?
Photochemical smog is formed as a result of the concentration of aerosol particles and a mixture of gases in the atmosphere. Its main components are nitrogen and sulfur oxides, various photooxidants.
What is the reason?
Photochemical smog, the formation of which is possible under various climatic and natural conditions in industrial centers, is characterized by significant air pollution.
This phenomenon is especially harmful in windless sunny weather, when the warm upper air layers cannot stop the movement of air masses in the vertical direction. This phenomenon is especially common in megacities, which are protected from winds by mountains and 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 are considered the cause of this phenomenon, for example, in calm weather, with increased solar radiation in the lower atmosphere, there is a slight exchange of air masses.
Chemical component
Such weather increases the concentration of reactants in the air, resulting in the formation of nitrogen oxides and atomic oxygen. It forms ozone molecules with molecular atmospheric oxygen. Nitric oxide reacts with olefins contained in exhaust gases, resulting in the formation of excess ozone and hydrocarbon radicals. Subsequent dissociation contributes to the accumulation of excess amounts of ozone in the earth's atmosphere. At night, the interaction of this species stops. Ozone reacts with olefins, which contributes to the accumulation of various peroxides in the atmosphere, which together form oxidants that make up photochemical smog. They are a source of free radicals, which differ in 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 humans? What is this phenomenon? He is in his own wayphysiological effect is dangerous for the circulatory and respiratory systems, is the cause of sudden death of citizens with poor he alth.
Important Facts
Separate dry and wet smog. The second option is typical for London, in the atmosphere of which, due to high humidity, droplets accumulate, forming thick clouds.
The problem of photochemical smog is especially acute in Japan, USA, Great Britain, Argentina, Mexico, Canada. This phenomenon was first recorded in Los Angeles in 1944. Since the city is located in a depression that is surrounded by sea and mountains, the air masses stagnate, pollutants accumulate, smog forms under favorable weather conditions.
If its concentration is high, you can see a bluish haze that reduces visibility, resulting in poor traffic.
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 adversely affects buildings, plants, people, various materials. The appearance of such fog leads to irritation of the mucous membranes of the nose, eyes, throat. It exacerbates a variety of chronicdisease, toxic effects. Smog has a specific smell, it negatively affects beets, grapes, cereals, beans, ornamental shrubs.
A typical sign that a plant has been adversely affected by photochemical fog is leaf swelling. Then they have a silver and bronze tint.
Smog leads to accelerated corrosion of materials and elements of buildings, damage to synthetic and rubber products.
Types of smog
Isolate London's wet smog, which is a combination of fog and gaseous impurities that are waste products.
Alaska-type ice smog is formed at low temperatures from the steam from gas emissions from household emissions and heating systems.
Dry LA-type smog occurs as a result of photochemical reactions occurring in gas emissions under the influence of solar radiation.
Radiation fog appears when the surface of the earth and moist air in the lower layers of the atmosphere are cooled by radiation to the dew point. It appears at night with a slight wind, cloudless weather with an anticyclone.
Land protection options
Soil is an element of the biosphere that creates full conditions for the biochemical environment of humans, plants, and animals. Soils accumulate precipitation, regulate water balance, and ensure the cleanliness of underground rivers and lakes. Photochemical smog negatively affects soil fertility, makesits unsuitable for use, which is why 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 to preserve the soil for future generations, there is a reduction in the use of land resources for industrial purposes, the elimination of pollution from industrial enterprises located near the land fund.
Particular attention should be paid to the systematic reclamation of areas of the earth's surface that are disturbed by industrial activity.
The ecological situation on our planet, the he alth of the living organisms that live on it directly depend on the effective measures that will be taken to protect land and the atmosphere at the state level.
