OZONE

Ozone O3 

 is a gas having low boiling point.It is present in a small  concentration throughout  the atmosphere .

UNITS

The amount of the Ozone in the atmosphere is expressed in Dobson units(DU). The normal amount of overhead ozone is about 350 DU.

PRESENCE:

The stratosphere where the ozone layer exist in the atmosphere is approximately at 15 to 40 KM altitude and is just  above the troposphere which extend to an altitude of 0-15 KM. from the earth. The temperature in the troposphere decreases with the increasing altitude from 15 to -56 degree. It is because the air near the earth is heated up by radiations re-emitted from the earth . Where as the temperature in the stratosphere increases with the increases of altitude ; -56 to -2 degree. The Ozone is the main chemical species which is present in the stratosphere which absorb the ultraviolet radiation and increases the temperature of the upper part of the ozone layer.

ADVANTAGES:

The ozone layer, 25-28 KM high , in the stratosphere surrounds the globe and filter most of the harmful ultraviolet rays in the Sun light before they could reach on the earth. Therefore , if there is substantial reduction in the ozone layer the life on the earth would be  threatened . In 1980's a large hole in the ozone over Antarctic was discovered which represent a major environmental crises.

DISADVANTAGES:
Ozone is produced in most of the tropical regions by photo-chemical reaction of the oxygen , from where it is transported to polar regions.It acts as a pollutant and cause various health problems i.e; damage eyes and aggravates asthma, decrease the elasticity of lung tissue, coughing, chest discomfort etc.

                  It is harmful to the plants and other materials . i.e; attack rubber, reduce durability and appearance of paints and cause fabric  dyes to fade. 

OZONE HOLE:

The thickness of ozone layer has been decreasing over Antarctic during the spring time since in mid 1970's . By the mid 1980's loss in ozone at some altitude over Antarctica result in about 50% depletion of the total over head amount . The region in which amount of ozone depletes substantially in every year during September -November is now termed as : Ozone Hole.