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INTRODUCTION: Acid rain is a great problem in our world. It causes fish and
plants to die in our waters. As well it causes harm to our own race as well,
because we eat these fish, drink this water and eat these plants. It is a
problem that we must all face together and try to get rid of. However acid
rain on it’s own is not the biggest problem. It cause many other problems such
as aluminum poisoning. Acid Rain is deadly.
WHAT IS ACID RAIN?
Acid rain is all the rain, snow, mist etc that falls from the sky onto our
planet that contains an unnatural acidic. It is not to be confused with
uncontaminated rain that falls, for that rain is naturally slightly acidic. It
is caused by today’s industry. When products are manufactured many chemicals
are used to create it. However because of the difficulty and cost of properly
disposing of these products they are often emitted into the atmosphere with
little or no treatment.
The term was first considered to be important about 20 years ago when
scientists in Sweden and Norway first believed that acidic rain may be causing
great ecological damage to the planet. The problem was that by the time that
the scientist found the problem it was already very large. Detecting an acid
lake is often quite difficult. A lake does not become acid over night. It
happens over a period of many years, some times decades. The changes are
usually to gradual for them to be noticed early.
At the beginning of the 20th century most rivers/lakes like the river Tovdal
in Norway had not yet begun to die. However by 1926 local inspectors were
noticing that many of the lakes were beginning to show signs of death. Fish
were found dead along the banks of many rivers. As the winters ice began to
melt off more and more hundreds upon hundreds more dead fish (trout in
particular) were being found. It was at this time that scientist began to
search for the reason. As the scientists continued to work they found many
piles of dead fish, up to 5000 in one pile, further up the river. Divers were
sent in to examine the bottom of the rivers. What they found were many more
dead fish. Many live and dead specimens were taken back to labs across Norway.
When the live specimens were examined they were found to have very little
sodium in their blood. This is typical a typical symptom of acid poisoning.
The acid had entered the gills of the fish and poisoned them so that they were
unable to extract salt from the water to maintain their bodies sodium levels.
Many scientist said that this acid poising was due to the fact that it was
just after the winter and that all the snow and ice was running down into the
streams and lakes. They believed that the snow had been exposed to many
natural phenomena that gave the snow it’s high acid content. Other scientists
were not sure that this theory was correct because at the time that the snow
was added to the lakes and streams the Ph levels would change from around 5.2
to 4.6. They believed that such a high jump could not be attributed to natural
causes. They believed that it was due to air pollution. They were right. Since
the beginning of the Industrial revolution in England pollution had been
affecting all the trees,soil and rivers in Europe and North America.
However until recently the loses of fish was contained to the southern parts
of Europe. Because of the constant onslaught of acid rain lakes and rivers
began to lose their ability to counter act their affects. Much of the alkaline
elements; such as calcium and limestone; in the soil had been washed away. It
is these lakes that we must be worried about for they will soon become
extinct. A fact that may please fishermen is that in lakes/rivers they tend to
catch older and larger fish. This may please them in the short run however
they will soon have to change lakes for the fish supply will die quickly in
these lakes. The problem is that acid causes difficulties the fish’s
reproductive system. Often fish born in acid lakes do not survive for they are
born with birth defects such as twisted and deformed spinal columns. This is a
sign that they are unable to extract enough calcium from the water to fully
develop their bone. These young soon die. With no competition the
older,stronger can grow easily. However there food is contaminated as well by
the acid in the water. Soon they have not enough food for themselves and turn
to cannibalism. With only an older population left there is no one left to
regenerate themselves. Soon the lake dies.
By the late 1970s many Norwegian scientists began to suspect that it was not
only the acid in the water that was causing the deaths. They had proved that
most fish could survive in a stream that had up to a 1 unit difference in PH.
After many experiments and research they found that their missing link was
aluminum. Aluminum is one of the most common metals on earth. It is stored in
a combined form with other elements in the earth. When it is combined it
cannot dissolve into the water and harm the fish and plants. However the acid
from acid rain can easily dissolve the bond between these elements. The
Aluminum is then dissolved into a more soluble state by the acid. Other metals
such as Copper (Cu), iron (Fe) etc can cause such effects upon the fish as
well however it is the aluminum that is the most common.
For example: CuO + H2SO4 ----------> CuSO4 + H2O
In this form it is easily absorbed into the water. When it comes in contact
with fish it causes irritation to the gills. In response the fish creates a
film of mucus in the gills to stop this irritation until the irritant is gone.
However the aluminum does not go always and the fish continues to build up
more and more mucus to counteract it. Eventually there is so much mucus that
it clogs the gills. When this happens the fish can no longer breath. It dies
and then sinks to the bottom of the lake. Scientists now see acid, aluminum
and shortages of calcium as the three determining factors in the extinction of
fish.
As well there is the problem of chlorine. In many parts of the world it is
commonly found in the soil. If it enters the fish’s environment it can be
deadly. It affects many of the fish’s organisms and causes it to die. As well
it interferes in the photosynthesis process in plants.
NaOH + HCl ----> NaCl + H2O
The carbon in the water can become very dangerous for fish and plants in the
water if the following reaction happens:
CaCO3 + 2HCl ---> CaCl2 + H2CO3 then
H2CO3 ---> H2O + CO2
The salt created by this reaction can kill. It interferes directly with the
fish’s nervous system. Acid lakes are deceivingly beautiful. The are crystal
clear and have a luscious carpet of green algae on the bottom. The reason that
these lakes are so clear is because many of the decomposers are dead. They
cannot break down that material such as leaves and dead animals. These
materials eventually sink to the bottom instead of going through the natural
process of decomposition. In acid lakes decomposition is very slow. "The whole
metabolism of the lake is slowed down." During this same period of time the
Canadian department of fisheries spent eight years dumping sulfuric acid
(H2SO4) into an Ontario lake to see the effects of the decrease in the PH over
a number of years. At the PH of 5.9 the first organisms began to disappear.
They were shrimps. They started out at a population of about seven million,
but at the pH of 5.9 they were totally wiped out. Within a year the minnow
died because it could no longer reproduce it’s self. At this time the pH was
of 5.8. New trout were failing to be produced because many smaller organisms
that served as food to it had been wiped out earlier. With not enough food the
older fish did not have the energy to reproduce. Upon reaching the pH of 5.1
it was noted that the trout became cannibals. It is believed this is due to
the fact that the minnow was nearly extinct.
At a pH of 5.6 the external skeletons of crayfish softened and they were soon
infected with parasites, and there eggs were destroyed by fungi. When the pH
went down to 5.1 they were almost gone. By the end of the experiment none of
the major species had survived the trials of the acid. The next experiment
conducted by the scientists was to try and bring the lake back to life. They
cut in half the amount of acid that they dumped to simulate a large scale
cleanup. Soon again the cuckers and minnows began to reproduce again. The lake
eventually did come back; to a certain extent; back to life. THE NEW THEORY:
A scientist in Norway had a problem believing that it was the acid rain on
it’s own that was affecting the lakes in such a deadly way. This scientist was
Dr Rosenqvist. "Why is it that during heavy rain, the swollen rivers can be up
to fifteen times more acid than the rain? It cannot be the rain alone that is
doing it, can it?" Many scientist shunned him for this however they could not
come up with a better answer. Soon the scientists were forced to accept this
theory.
Sulfuric acid is composed of two parts, know as ions. The hydrogen ion is what
make a substance acid. The other ion is sulphate. When there are more hydrogen
ions then a substance is acid. It is this sulphate ion that we are interested
in. When the rain causes rivers to overboard onto the banks the river water
passes through the soil. Since the industrial revolution in britain there has
been an increasing amount of sulphur in the soil. In the river there is not
enough sulphur for the acid to react in great quantities. However in the soil
there is a great collection of sulphur to aid the reaction. When it joins the
water the pH becomes much lower. This is the most deadly effect of acid rain
on our water!!! The water itself does not contain enough sulphur to kill off
it’s population of fish and plants. But with the sulphur in the soil it does.
CONCLUSION:
Acid rain is a big problem. It causes the death of our lakes, our rivers, our
wild life and most importantly us. As well it causes other problems that are
very serious as well such as the release of aluminium and lead into our water
supplies. We are suffering because of it. In Scotland there are many birth
defects being attributed to it. We must cut down the releases of chemicals
that cause it. But it will take time, even if we were to stop today we would
have the problem for years to come because of the build up in the soil. Let’s
hope we can do something.
Science Essays
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