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A number of people have heard of acid rain. But
what is acid rain? Where does it come from? Has it ever
rained acid anywhere in any part of the world? And more
important, what can we do to minimise its effects?
A hundred years ago in Britain the term acid rain was
coined by some residents in the town of Manchester when they
realised that the air was not only filthy by also acidic
which was attacking vegetation, stones and iron metal. In
addition through the years incidents of acid rain have been
reported in several industrialised countries.
Acid rain is the rain that contains more than the required
amount of acid in it. The culprits in acid are sulphur
dioxides, nitrogen oxides and nitric oxides, which reaches
the atmosphere in many different ways. Rain is naturally
slightly acidic. It reacts with carbon dioxide in the air to
produce weak carbonic acid, which has little or no effects
on the environment. Without human intervention there would
be no acid rain problem.
The gases are introduced into the atmosphere through human
activities such as burning of fossil fuels (coal and oil) in
industries, power generating stations, residential heating
and motor vehicles.
Once these gases reach the atmosphere, then react with
moisture in the air to form acids (sulphur dioxide to
sulphuric acid, nitric oxides to nitric acid). These gases
can travel long distances by wind from point of source
before they can come down as acid rain and as a result can
transcend national boundaries. Hence acid rain can occur at
any place in the world. Here in Malawi samples of rain
collected from an air pollution monitoring station at LIA
(Lilongwe International Airport) have shown traces of acid.
The most commonly cited environmental effects of acid rain
include:
Acidification of lakes, streams and groundwater resulting
in destruction to aquatic life, damage to forests and crops
and corrosion of man-made materials such as buildings and
metal structures.
The way out from this problem is the reduction in the
emission of these gases into atmosphere, which can be done
by strict enforcement of existing air pollution control
measures.
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