An overview on Stratospheric Pollution

Introduction

Ozone in the stratosphere is required for life to exist on Earth. It is, however, chemically unstable and susceptible to catalytic destruction by a variety of chemicals, including NOX, HOX, CIOX, and metal oxides. Even when only one part catalyst per 10,000 parts ozone is present in the stratosphere, these catalysts can be very active in ozone destruction.

Pollutants can enter the stratosphere in two ways: directly from supersonic transports, military aircraft, rockets, or nuclear bombs, or indirectly from the troposphere, which may occur for inert, water-insoluble substances that eventually work their way up into the stratosphere. The mass of catalysts required to destroy stratospheric ozone at a significant global rate is less than the annual waste products from several industrial operations. 

The mass of nitrogen oxides emitted by 500 supersonic transports, in particular, is far above the threshold for significant catalytic ozone destruction. This could have a significant impact on how the biosphere works and how it is maintained.

The stratosphere

The stratosphere is the stable layer of the atmosphere that extends from the tropopause to a height of approximately 50 km. Because the air temperature rises with height up to the stratopause, which is the height of the temperature inversion, the stratosphere is extremely stable. 

The increased temperature in this layer is primarily due to UV absorption by various chemical species in the stratosphere, including ozone and molecular oxygen. The upper part of the stratosphere experiences the most heating. Pollutant mixing is suppressed within this layer due to the stable air. As a result, natural (N2O) and synthetic (CFC) chemicals that reach the stratosphere from the troposphere tend to diffuse very slowly upward. 

ozone is formed naturally and photochemically. 

In the troposphere, ozone is considered a pollutant, but in the stratosphere, it is necessary for life on Earth because it absorbs biologically harmful UV radiation.

The mesosphere and thermosphere are two additional atmospheric layers that exist above the stratosphere.

Ozone layer

The Earth’s atmosphere is divided into layers. The troposphere is the lowest layer, extending from the Earth’s surface to about 6 miles or 10 kilometres (km) in altitude. Almost all human activities take place in the troposphere. Mt. Everest, the world’s tallest mountain, is only about 5.6 miles (9 km) high. The stratosphere is the next layer, which extends from 6 miles (10 km) to approximately 31 miles (50 km). The majority of commercial aeroplanes fly in the stratosphere’s lower layers.

The majority of atmospheric ozone is concentrated in a stratospheric layer 9 to 18 miles (15 to 30 km) above the Earth’s surface (see the figure below). In the stratosphere, ozone molecules are constantly formed and destroyed. During the decades that it has been measured, the total amount has remained relatively stable.

The ultraviolet radiations

UV radiation (UV) is classified into four wave bands. Vacuum UV, UV-C (200–280 nm), UV-B (280–315 nm), and UV-A (315–400 nm) are the four wavelengths. Because of absorption by various gases such as oxygen and ozone, vacuum UV and UV-C are not present at the earth’s surface. The evolution of life on Earth required the formation of atmospheric oxygen and a stratospheric ozone layer. Unfortunately, anthropogenic emissions of chlorofluorocarbons (CFCs) and other gases have harmed the ozone layer. It has thinned and formed “holes” in the polar regions.

As a result, there is a possibility of increased UV radiation hitting the earth’s surface. UV rays can cause serious, and sometimes irreversible, damage. It can cause mutations in cellular DNA, which can eventually lead to significant changes in cells, which is the primary cause of cancer. UV rays can also cause premature ageing, blindness, and sterilisation. UV radiation can also kill microorganisms, plants, and animals, making them more susceptible to disease by compromising immune systems. UV radiation, in addition to having direct biological effects, can have complex effects on biogeochemical processes.

How does the atmosphere shield us from UV rays?

The ozone layer, also known as the ozone shield, is a region of the Earth’s stratosphere that absorbs the majority of the Sun’s ultraviolet (UV) radiation.

It has high ozone concentrations. It’s a pale blue gas with a distinct pungent odour. It is a much less stable oxygen allotrope than the diatomic allotrope. Ozone is formed from dioxygen by the action of ultraviolet light as well as atmospheric electrical discharges, and it is found in low concentrations throughout the Earth’s atmosphere.

Although the concentration of ozone in the ozone layer is very low, it is critical to life because it absorbs biologically harmful ultraviolet radiation from the sun. UV-C, which is extremely harmful to all living things, is completely blocked out by a combination of dioxygen (200 nm) and ozone (> about 200 nm) at around 35 kilometres altitude. UV light, such as UV-B, is also important. Some UV-B reaches the skin’s surface, particularly at its longest wavelengths, and is necessary for vitamin D production.

Conclusion

The stratosphere is the stable layer of the atmosphere that extends from the tropopause to a height of approximately 50 km. Because the air temperature rises with height up to the stratopause, which is the height of the temperature inversion, the stratosphere is extremely stable. The increased temperature in this layer is primarily due to UV absorption by various chemical species in the stratosphere, including ozone and molecular oxygen. The upper part of the stratosphere experiences the most heating. Ozone is formed naturally and photochemically. In the troposphere, ozone is considered a pollutant, but in the stratosphere, it is necessary for life on Earth because it absorbs biologically harmful UV radiation.