Stratospheric pollution - class-XII

Ozone layer depletion is caused due to CFC's. So, chlorine nitrate, which is found in the stratosphere causes break down of the ozone layer. Chlorine is highly reactive and it interacts with ozone and hence destroys the ozone layer.

Freons are chlorofluorocarbons and are responsible for depletion of ozone layer. 

The severe depletion of the Antarctic ozone layer known as the ozone hole occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSCs) to form. These clouds contain Chlorine nitrate $(ClNO _3)$

Option (B) is correct.

The ozone layer protects us from harmful ultraviolet rays of the sun.

Ozone is formed as a result of the action of U.V. light on oxygen and it forms a layer in upper layers of the atmosphere. 

Ozone is a form of elemental oxygen. In its most stable form, elemental oxygen exists as diatomic molecules (O2). The molecules of ozone contain three oxygen atoms (O3) and are unstable with respect to O2. Ozone is a very reactive gas, and even at low concentrations it is irritating and toxic. It occurs naturally in small amounts in the Earth's upper atmosphere, and in the air of the lower atmosphere after a lightning storm. 

Ozone has been implicated to have an adverse effect on plant growth: "... ozone reduced total chlorophylls, carotenoid and carbohydrate concentration, and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production. In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and solute leakage were significantly higher than in ozone-free controls. 

Ozone, along with reactive forms of oxygen such as superoxide, singlet oxygen, hydrogen peroxide superoxide, singlet oxygen, hydrogen peroxide, and hypochlorite ions, is naturally produced by white blood cells and other biological systems (such as the roots of marigolds) as a means of destroying foreign bodies. 

Thus Option B is correct.

Ozone is an allotropic form of oxygen. 

The presence of the layer of ozone prevents the UV rays from reaching the surface of the earth.

The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres (12 to 19 mi) above Earth.

Chlorofluorocarbons are cause depletion of the atmospheric ozone layer.

UV is radiation increases the chances of skin cancer.

Ozone, an allotrope of oxygen is the primary absorber of UV solar radiation in earth's atmosphere.

Ozone is $O _3$ present in stratosphere region of the atmosphere, which protects us by absorbing harmful Ultraviolet radiation released by the sun that causes a variety of health problems in humans, plants, and other animals which leads to the damage in ecosystems. Plants do not and grow in heavy ultraviolet radiation.

Hence option $A$ is correct.

Ozone layer of stratosphere require protection from indiscriminate use of aerosols and high flying jet because they produce gases which react with ozone layer and depletion of ozone occurs.

Chlorofluorocarbon is responsible for the depletion of ozone layer.

UV radiation from the sun on reaction produces ozone.

The proposal to ban supersonic jet planes in Russia is because of toxic gases which reacts with ozone layer and damage it.

Ozone is a greenhouse gas that absorbs and emits radiant energy within thermal infrared range. The increase in ozone in the troposphere because of surface pollution gases have increased the warming effect on the earth's surface and contributed to a greenhouse effect.

This is because of ozone layer.Ozone is a gas in the atmosphere that protects everything living on the Earth from harmful ultraviolet (UV) rays from the Sun.The ozone layer absorbs ultraviolet (UV) radiation from the sun, preventing most of it from reaching the earth's surface. 

We know that, UV-B radiation is very harmful. 

Chlorofluorocarbons (CFCs) and other halogenated ozone-depleting substances (ODS) are mainly responsible for ozone depletion.

The ozone layer is important because it absorbs ultraviolet (UV) radiation from the sun, preventing most of it from reaching the earth's surface. Radiation in the UV spectrum has wavelengths just shorter than those of visible light.

The ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (UVR) from the sun, protecting life on Earth from its potentially harmful effects. When the sky is clear, there is an inverse relationship between stratospheric ozone and solar UVR measured at the Earth’s surface. That is,the lower the ozone levels, the higher the solar UVR.

Ozone in stratosphere is depleted by chlorofluorocarbon, such as $CF _2Cl _2$.
It is dichlorodifluoromethane also known as freon-12.

Air pollution is formed through the reaction of solar radiation with airborne pollutants like nitrogen oxides and volatile organic compounds. These compounds, which are called primary pollutants, are often introduced into the atmosphere through automobile emissions and industrial processes. Ultraviolet light can split nitrogen dioxide into nitric oxide and monatomic oxygen; this monatomic oxygen can then react with oxygen gas to form ozone. 

Ozone $\displaystyle O _3$ gas is known to shield the earth from harmful ultraviolet radiation. 

In the stratosphere, ozone $\displaystyle O _3 $ screen out a large fraction of the ultraviolet rays of the sun. Thus, ozone acts as a protective shield. Thus, due to presence of ozone layer, the harmful ultraviolet rays cannot penetrate earth's atmosphere. Hence, they cannot reach us.

The ozone depletion was related to halogen (chlorine)-catalyzed chemical reaction which takes place in the spring season in the Antarctic polar region. The chlorine is derived from manmade chlorofluorocarbons and reacts with nitric acid forms chlorine nitrate($ClONO _2$) (CFCs) in the stratosphere.

Hence option D is correct. 

The two forms of oxygen found in the atmosphere are a diatomic molecular form that has chemical formula as O$ _2$ or oxygen, the life-giving gas that we breathe in to survive. 
Another  is a triatomic molecular form that has chemical formula as O$ _3$ called ozone gas, it protects us from harmful UV rays.
In water, oxygen is found as a compound with hydrogen molecules. The oxygen in water is dissolved oxygen used by aquatic animals and plants.
carbon dioxide has 2 molecules of oxygen with one molecule of carbon. It is formed by the reaction between carbon molecules and oxygen molecules during fermentation or respiration.
In the case of water and carbon dioxide, the oxygen does not exist independently but in association with other molecules. Whereas in the case of ozone and oxygen, the oxygen exists independently. Hence, the two forms of oxygen are ozone and oxygen.
The correct option is C (Ozone and Oxygen).

The ozone layer or ozone shield refers to a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone ($O _3$) relative to other parts of the atmosphere, although still very small relative to other gases in the stratosphere.