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Acid rain pollution comes in various forms. Whether it’s toxic
waste, CFC’s, or sewage, they are all hazardous to the earth. These can
deplete the earth and it’s inhabitants of resources, causing a harmful
change. A product of pollution is acid rain. We shall see that
acidification is harmful to all forms of life. Acid rain is any form of
precipitation that is polluted by sulphur dioxide (SO2), and nitrogen
oxides (NOX).
This acid precipitation can be in the form of rain, snow,
sleet, fog, or cloud vapors. The acidity of substances dissolved in
water are measured by their pH levels. Normal precipitation pH levels
fall between 5.0-5.6.2 When levels fall below these numbers, then the
precipitation is said to be acidic. There are two ways in which acid
deposition can form. The first way occurs when nitrogen oxides and
sulphur dioxide land on the Earth’s surface, and interact with frost or
dew. The second way takes place due to the oxidation of nitrogen oxides
or sulphur dioxide gases that are released into the air.3 Since it may
take up to several days for the gases to be altered into their acid
counter-parts, the pollutants can travel miles away from their original
source.
Emissions of (SO2) are responsible for the majority of the acid
deposition, which falls to Earth. When we burn coal, we are releasing
(SO2), into the air, since coal is slight made up of sulphur. Volcanic
eruptions can add a great deal of sulphur into the atmosphere. Everyday
organic decay adds sulphur into the air as well. (SO2) can hit the
Earth’s surface in dry forms or wet forms, by undergoing the following
reactions: (SO2 + H20 *** H2SO3) (SO2 + ½O2 *** SO3 + H2SO4)2. Human
activity is the major cause for nitrogen oxides’ presence in our
atmosphere, such as forest fires and the combustion of oil, coal, and
gas. The other causes are due to nature. Lightning, volcanic action,
and bacteria in soil are just to name a few. The following chemical
reactions show how acids of nitrogen form: (NO2 + ½O2 *** NO2) (2NO2 +
H2O *** HNO2 + HNO3) (NO2 + OH *** HNO3)2.
Acid rain can affect plant life directly when the surface of leaves
and needles come into contact with acid vapor or fog. This causes a
reduction in the tree’s ability to withstand the cold. A direct result
would be the tree's incapability of reproduction. It can also harm
plant life indirectly, by the acidification of soils. Acid rain can
cause soil to loose nutrients such as calcium, potassium, and
magnesium. In very acidic conditions, aluminum becomes soluble, and is
released from the soil. At high enough concentrations, aluminum can
cause damage to roots. Acid rain causes a nutrient imbalance, in soil.
Although it is true that nitrogen promotes forest growth, plant life
also needs other nutrients. Precipitation polluted by nitrogen can
contain heavy metals, such as mercury, cadmium, and lead. This process
is known as nitrogen saturation.1 These too, can cause damage to tree
roots. Besides trees, plants are also affected by acid rain. Reductions
in pH levels can cause seed germination to be inhibited. Plant
structures become weak, due to the loss of nutrients to the plant’s
tissues.4 Flowering of certain plants may not occur due to lack of
essential minerals.
Marine life is also greatly affect by acid rain. Acid water can
leach high levels of aluminum from the bedrock. Rocks that contain
great amounts of calcium or magnesium can act as a neutralizer. Those
rocks and soils that lack some sort of buffers can cause grave damage
to marine fish and plants. There are two ways in which aluminum can
harm aquatic environments. It can cause a fish to suffocate, because
aluminum precipitates in gills, thus interfering in the transport of
oxygen. Secondly, fish produce mucus to combat the aluminum, in their
gills. The mucus then builds up a clogs the fish’s gills.5 In middle
latitudes many bodies of water experience what is called “acid shock.”4
Over the winter acid deposits can build up on snow. As the snow melts,
the acids are released. Most fish can survive shock, but their eggs
cannot adapt to acidification. When there is a change in the chemistry
of water, the ecology of the water begins to change. The number and
variety of species are altered. At a pH level of 6.0 certain types of
zooplankton and green algae begin to disappear. The loss of green
plants allows more UV light to penetrate to further depths, so certain
types of snails and phyto-plankton disappear.
Frogs, toads, and salamanders are also affected by acid rain.5 The
low pH stunts their growth. Not only does acid rain kill species, but
also it alters the food supply for higher fauna. If there is a decrease
in the number of bottom dwelling organisms (benthos), there can be a
decline in the number of insects, such as mosquitoes and flies. This
puts a stress on carnivorous fish. Birds that eat these fish, which may
contain high levels of aluminum, will then produce eggs with
soft-shells. Their young will most likely not survive. Humans are not
immune to the effects of acid rain. People that are exposed to high
concentrations of acidic pollution are known to have respiratory
problems. SO2 can react with water vapor to form fine particles of
sulphate. If inhaled, these particles can cause severe damage to lung
tissue. The affect can be a simple cough or chest cold, or as dangerous
as asthma or chronic bronchitis. Humans can consume aluminum by
drinking water or eating crops that have contaminated by acid
precipitation. If ingested in large quantities, it can have toxic
effects on human health. Many doctors believe that aluminum consumption
can lead to Alzheimer’s disease.1
We see the effects of acidification everyday. All forms of acid
precipitation may damage automotive coatings. The damaged is mostly
observed on newly painted vehicles. It is the evaporation of acidic
moisture that causes the damage. Many headstones and buildings and
statues, such as the Statue of Liberty, are affected in the same way.
Acid deposition can cause fading of these structures. Churches and
cathedrals also suffer. The United States is trying to take care of
this problem through environmental legislation. Title IV of the Clean
Air Act Amendments of 1990, calls for a 10 million ton reduction in the
number of emissions of sulfur dioxide. One way of reducing emissions is
lowering the production of sulphate aerosol cans. Since this act was
passed, hospitals have witnessed a significantly lower number of cases
of respiratory problems. There are other ways that we can alleviate the
problems of acid deposition. A process known as liming can increase the
pH levels of bodies of water. Large quantities of hydrated lime are
added to the water. The best way to solve the problems caused by acid
deposition is for industries to try to limit the emissions of
pollutants. There has been two ways in which industries have done this.
Several companies have switched to using fuels that have a low sulphur
content. Other industries have used buffers on the tops of their
smokestacks, to reduce the amount of (SO2) in the air.4 There is no way
that we can totally eliminate acid deposition. We as humans, are not
the only creators of this problem. Over the years, there has been an
increase in the amount of annual precipitation. We can change our ways
of production to help decrease the amount of acid precipitation, but
then that would be greatly affecting our way of life. More then the
acid rain itself does. Just like the cycle of affects the acid rain has
on aquatic and terrestrial systems, there is the same type of cycle
viewed when it comes to human life.
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