The term 'acid rain' is commonly used to mean the
deposition of acid component in rain, snow, fog, dew, or dry particles. They
are the result of air pollution. When any type of fuel is burnt, lots of
different chemicals are produced. The smoke that comes from a fire or the fumes
that come out of a car exhaust don't just contain the sooty grey particles that
you can see - they also contains lots of invisible gases. Some of these gases (especially
nitrogen oxides and sulphur dioxide) react with the tiny droplets of water in
clouds to form sulphuric and nitric acids. The rain from these clouds then
falls as very weak acid - which is why it is known as "acid rain".
Acid rain has an adverse effect on forest,
freshwater and soil, killing off insects and aquatic life forms as well as
causing damage to building and having possible impact on human health.
It is thought that acid rain can cause tree to
grow more slowly or even to die. As it falls on a forest it trickles through
the leaves of the trees and run down into the soil below. Some of it find its
way into streams and then on into the river and lakes, thus effecting its
On other hand acid rain can affect trees by
dissolving and washing way the nutrients and minerals in the soil which help in
their growth. It is one of the major causes of the release of harmful
substances such as aluminum into the soil. Somewhere, acid rain wear away the
waxy protective coating of leaves, damaging them and preventing them from being
able to photosynthesize properly.
On lakes and river water, acid rain has a diverse
effect. Both the lower Ph and higher aluminum concentration in the surface
water that occur as a result of the acid rain can cause damage to fish and
other aquatic animals. At pHs lower than 5 most fish eggs will not hatch and
lower pHs can kill adult fish. As lakes become more acidic biodiversity is
reduced. Acid rain has eliminated insect life and some fish species.
Soil biology can also be seriously damaged by
acid rain. Some tropical microbes can quickly consume acids but other microbes
are unable to tolerate low pHs and are killed. The hydronium ions of acid rain
also mobilize toxins and leach away essential nutrients and minerals of the
soil. The effects of acid rain can last for generations, as the effects of pH
level change can stimulate the continued leaching of undesirable chemicals into
otherwise pristine water sources, killing off vulnerable insect and fish
species and blocking efforts to restore native life.
On human health, acid rain have
been shown to cause illness and premature deaths. Acid rain can also cause
damage to certain building materials and historical monuments. Acid rain can
cause weathering on ancient and valuable statues and has caused considerable
damage. This is because the sulfuric acid in the rain chemically reacts with
the calcium compounds in the stones (limestone, sandstone, marble and granite)
to create gypsum, which then flakes off. This is also commonly seen on old
gravestones where the acid rain can cause the inscription to become completely
illegible. Acid rain also causes an increased rate of oxidation for iron.
Visibility is also reduced by sulfate and nitrate in the atmosphere.
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