Ozone Layer Depletion

Ozone layer depletion

Definition:

The fragile shield of ozone is been damaged by chemicals released on earth. The main chemicals that are depleting stratospheric ozone are chlorofluorocarbons which are used in refrigerators, aerosols, and as cleaners in many industries, and halons, which are used in fire extinguishers. The damage is caused when these chemicals release highly reactive forms of chlorine and bromine .Other ozone-depleting substances (ODS), include hydro chlorofluorocarbons (HCFCs), and volatile organic compounds (VOCs)

 

 

Causes of Ozone Layer Depletion:

CFC's accounts for almost 80% of the total depletion of ozone. Other ozone-depleting substances (ODS), include hydro chlorofluorocarbons (HCFCs), and volatile organic compounds (VOCs) ODS are relatively stable in the lower atmosphere of the Earth, but in the stratosphere, they are exposed to ultraviolet radiation and thus, they break down to release a free chlorine atom.

This free chlorine atom reacts with an ozone molecule (O3), and forms chlorine monoxide (ClO), and a molecule of oxygen. Now, ClO reacts with an ozone molecule to form a chlorine atom, and two molecules of oxygen. The free chlorine molecule again reacts with ozone to form chlorine monoxide. The process continues, and this results in the depletion of the ozone layer.

Possible Effects of Ozone Depletion
As ozone depletes in the stratosphere, it forms a 'hole' in the layer. This hole enables harmful ultraviolet rays to enter the Earth's atmosphere. Ultraviolet rays of the Sun are associated with a number of health-related, and environmental issues:

Impact on Humans

Skin cancer: Exposure to ultraviolet rays poses an increased risk of developing several types of skin cancers, including malignant melanoma, basal and squamous cell carcinoma.
Eye damage: Direct exposure to UV radiations can result in photokeratitis (snow blindness), and cataracts.
Immune system damage: Effects of UV rays include impairment of the immune system. Increased exposure to UV rays weakens the response of the immune system.
Accelerated aging of skin: Constant exposure to UV radiation can cause photo allergy, which results in the outbreak of rash in fair-skinned people.
Other effects: Ozone chemicals can cause difficulty in breathing, chest pain, throat irritation, and hamper lung functioning.

Effects on Amphibians

 Some of the effects are mentioned below:
1.Hampers growth and development in larvae
2.Changes behavior and habits
3.Causes deformities in some species
4.Decreases immunity. Some species have become more vulnerable to diseases and death
5.Retinal damage and blindness in some species

Effects on Marine Ecosystems

In particular, plankton (phytoplankton and bacterioplankton) are threatened by increased UV radiation. Marine phytoplankton play a fundamental role in both the food chain as well as the oceanic carbon cycle. Plankton play an important role in converting atmospheric carbon dioxide into oxygen. Ultraviolet rays can influence the survival rates of these microscopic organisms, by affecting their orientation and mobility. This eventually disturbs and affects the entire ecosystem.

Impact on Plants

In some species of plants, UV radiation can alter the time of flowering, as well as the number of flowers.
Plant growth can be directly affected by UV-B radiation. Despite mechanisms to reduce or repair these effects, physiological and developmental processes of plants are affected.

Learning Activity:

Q1. What is the name of a common Man- made substance that causes ozone depletion?

a.       TLC 
b.      CFC 
c.       DDT 
d.      MCC

Q2.  Where is the majority of Ozone found in the atmosphere?

a.       Thermosphere 
b.      Troposphere 
c.       Mesosphere
d.      Stratosphere
 

Q3. What type of harmful radiations is blocked by ozone?

a.       Radiowaves 
b.      Infrared
c.       Ultraviolet 
d.      X-rays
 

Q4. Between what heights is the ozone layer found in the atmosphere?

a.       2-3 km 
b.      0-1km
c.       19-30 km 
d.      70-80 km