|
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.
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.
The carbon in the water can become very dangerous for fish and
plants in the water if the following reaction happens: CaCl2 + H2CO3
then 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.
BIBLIOGRAPHY
Penguin Publishing House, 1987 , Pearce Fred Acid Rain.
What is it and what is it doing to us?
New York Publishers, 1989,
William Stone Acid Rain. Fiend or Foe?
Lucent books, Inc. 1990, Steward
Gail Acid Rain.
|
(0 vote)