212
Sulfuric Acid (H2SO4)
Nitric Acid (HNO3)
Water Vapor & Cloud
Chemistry
    
Sulfur Dioxide &
Nitrogen Oxide
Emissions
:::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::
::::::Dry Fallout ::
:::::::::::::::::::::::::::::::
Acid Rain
::Acid Fog
:::::::::::::::::::::::::::::
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
………
Dieoff of Aquatic life
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
………...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
…………...
Water
Dry Fallout
……………Condensation
……………
………
Damage to
Acid Dew
 
  
   
     
 Acid Snow 

   
   
   
  
Acid Snow
Melt
Acid Leaching
Aluminum Toxicity
Vegetation
Figure 5: Acid precipitation. Emissions of sulfur and nitrogen
oxides react with water vapor in the atmosphere to form
their respective acids which come back down as dry acid
deposition or mixed with water, causing the precipitation to
be abnormally acidic. Various effects are noted.
213
Atmospheric Turbidity
One of the more obvious indications of atmospheric
pollution is the presence of solid or liquid particles
called aerosols dispersed in the air. These aerosols
include dust, soot, salt crystals, organics, smoke,
sulfates, ash, and a variety of microscopic particles.
Collectively, they are often regarded as equivalent to air
pollution although many of the materials involved are
produced naturally by volcanic activity, forest and grass
fires,
evaporation,
local
atmospheric
turbulence
and
biological processes (Fig. 6). The presence of aerosols
provides a measure of atmospheric turbidity, a property
which can be considered as an indication of dustiness or
dirtiness of the atmosphere. Aerosols produced by human
activities cannot match the volume of material produced
naturally.
STRATOSPHERE
--------------------------------------TROPOSPHERE
::::::::::::::::::::
::::: soot::::::::
dust::::::::::::::
::dust::
::::::::::
Forest fires
Slash & burn
:::::::::::::::::::
hydrocarbons:
::pollen:::::::::
spores:::::::::::
:
H2O
nitrates --------------- 
hydrocarbons
Aviation
:::::::::::::::::::
hydrocarbons:
::::::::::::::::::
nitrates::::::::::
::::sulphates:::
:::
H2O ::: soot
:::::::::dust::::
Soil
particles
Volcanic Activity
dust
Mining &
Quarrying
Natural organic
emissions
Urban &
industrial
activities
Agriculture
H2O ::::::::::
Salt particles
Ocean
s
Figure 6: Diagrammatic representation of the sources and
types of atmospheric aerosols
214
Any increase in the turbidity of the atmosphere should
cause global temperature to decline, as the proportion of
solar radiation reaching the earth’s surface is reduced by
scattering and absorption. In addition, the condensation of
water vapor around atmospheric aerosols would lead to
increased
cloudiness
and
further
reduction
in
the
transmission of incoming radiation (Kemp, 1990). However,
Mitchel (1975) proposed that although there is reduction in
isolation, it is also considered that there would be a
concomitant
reduction
in
the
amount
of
terrestrial
radiation escaping into space, which would offset the
cooling effect resulting in some warming of the lower
atmosphere.
Ozone Layer Depletion
A layer of ozone gas in the upper atmosphere keeps the
ultraviolet radiation within manageable limits. This ozone
is a relatively minor constituent of the atmosphere. It is
diffused through the stratosphere between 10 and 50 km
above the surface reaching its maximum concentration at an
altitude of 20-25 km. This small amount of a minor gas,
with ability to filter out a very high proportion of the
incoming UV radiation is essential for the survival of life
on earth.
Human activities has been found out to bring about
sufficient degradation of the ozone layer of which recovery
way never occur. These gases which destroy the ozone layer
are the hydrogen oxides, nitrogen oxides, chlorine oxides
and CFCs. The threat has been seen to come from four main
sources- modern technological development in warfare,
aviation, life-style and agriculture (Fig. 7).
In addition, since UV radiation is an integral part of
the earth’s energy budget, changes in the ultraviolet
levels have the potential to contribute to climate change
(Kemp, 1990; Cicerone, 1989).
215
Figure 7: Diagrammatic representation of the sources of
natural and anthropogenic ozone-destroyers
ENVIRONMENTAL IMPACTS OF CLIMATE CHANGE
Physical Impact
Mathematical models of the potential climate impact of
a change in greenhouse gases concentrations have been
developed by various groups (Rosenberg, 1989; Sinha, et al,
1989). The model attempt to predict changes in critical
climate variable with a doubling of CO2 concentrations.
While there is little agreement between various models
about specific magnitudes of the changes at the regional
level during the next 50-100 years, there is considerable
agreement in the nature of such changes at the global
level.
1. Atmosphere
*Large Stratospheric Cooling
A reduction in the upper stratosphere ozone by
chlorine compounds means less absorption of solar radiation
and
thus
less
heating.
This
also
means
increased
concentration of trace stratosphere. The combination of
decreased heating and decreased cooling will decrease the
upper stratospheric temperature perhaps by 10C to 20C
(Silver & DeFries, 1990; Sinha et al, 1989).