FREE ESSAY ON ACID RAIN

ACID RAIN

Acid Rain Acid rain is a serious problem with disastrous effects. Each day this serious
problem increases, many people believe that this issue is too small to deal with right
now this issue should be met head on and solved before it is too late. In the following
paragraphs I will be discussing the impact has on the wildlife and how our atmosphere is
being destroyed by acid rain. STATISTICS Although there is very little data, the evidence
indicates that in the last twenty to thirty years the acidity of rain has increased in
many parts of the United States. Presently, the United States annually discharges more
than 26 million tons of suffer dioxide into the atmosphere. Just three states, Ohio,
Indiana, and Illinois are responsible for nearly a quarter of this total. Overall,
two-thirds of the suffer dioxide into the atmosphere over the United States comes from
coal-fired and oil fired plants. Industrial boilers, smelters, and refineries contribute
26%; commercial institutions and residences 5%; and transportation 3%. The outlook for
future emissions of suffer dioxide is not a bright one. Between now and the year 2000,
United States utilities are expected to double the amount of coal they burn. The United
States currently pumps some 23 million tons of nitrogen oxides into the atmosphere in the
course of the year. Transportation sources account for 40%; power plants, 30%; industrial
sources, 25%; and commercial institutions and residues, 5%. What makes these figures
particularly distributing is that nitrogen oxide emissions have tripled in the last
thirty years. CAUSES Acid rain is a cancer eating into the face of Eastern Canada and the
North Eastern United States. One of the main causes of acid rain is sulphur dioxide.
Natural sources which emit this gas are volcanoes, sea spray , rotting vegetation and
plankton. However, the burning of fossil fuels, such as coal and oil, are largely to be
blamed for approximately half of the emissions of this gas in the world. When sulphur
dioxide reaches the atmosphere, it oxidizes to first form a sulfate ion. It then becomes
sulphuric acid as it joins with hydrogen atoms in the air and falls back down to earth.
Oxidation occurs the most in clouds and especially in heavily polluted air where other
compounds such as ammonia and ozone help to catalyze the reaction, converting more
sulphur dioxide to sulphuric acid. However, not all of the sulphur dioxide is converted
to sulphuric acid. In fact, a substantial amount can float up into the atmosphere, move
over to another area and return to earth unconverted. The following are the
stoichiometric equations for the formation of sulphuric acid: S (in coal) + O2"_ SO2 2
SO2 + O2"_ 2 SO3 SO3"_ + H2O H2SO4 Nitric oxide and nitric dioxide are also components of
acid rain. Its sources are mainly from power stations and exhaust fumes. Like sulfur
dioxide, these nitrogen oxides rise into the atmosphere and are oxidized in clouds to
form nitric acid. These reactions are also catalyzed in heavily polluted clouds where
iron, manganese, ammonia and hydrogen peroxide are present. In Canada, the main sulfuric
acid sources are non-ferrous smelters and power generation. On both sides of the border,
cars and trucks are the main sources for nitric acid(about 40% of the total), while power
generating plants and industrial commercial and residential fuel combustion together
contribute most of the rest. In the air, the sulfur dioxide and nitrogen oxides can be
transformed into sulfuric acid and nitric acid, and air current can send them thousands
of kilometers from the source. When the acids fall to the earth in any form it will have
large impact on the growth or the preservation of certain wildlife. NO DEFENSE One of the
direct effects of acid rain is on lakes and its aquatic ecosystems. There are several
routes through which acidic chemicals can enter the lakes. Some chemical substances exist
as dry particles in the air while others enter the lakes as wet particles such as rain,
snow, sleet, hail, dew or fog. In addition, lakes can almost be thought of as the sinks
of the earth, where rain that falls on land is drained through the sewage systems
eventually make their way into the lakes. Acid rain that falls onto the earth washes off
the nutrients out of the soil and carries toxic metals that have been released from the
soil into the lakes. Another harmful way in which acids can enter the lakes is spring
acid shock. When snow melts in spring rapidly due to a sudden temperature change, the
acids and chemicals in the snow are released into the soils. The melted snow then runs
off to streams and rivers, and gradually make their way into the lakes. The introduction
of these acids and chemicals into the lakes causes a sudden drastic change in the pH of
the lakes - hence the term spring acid shock. The aquatic ecosystem has no time to adjust
to the sudden change. Areas in Ontario mainly southern regions that are near the Great
Lakes, such substances as limestone or other known antacids can neutralize acids entering
the body of water thereby protecting it. However, large areas of Ontario that are near
the Pre-Cambrian Shield, with quartzite or granite based geology and little top soil,
there is not enough buffering capacity to neutralize even small amounts of acid falling
on the soil and the lakes. Therefore over time, the basic environment shifts from an
alkaline to a acidic one. This is why many lakes in the Muskoka, Haliburton, Algonquin,
Parry Sound and Manitoulin districts could lose their fisheries if sulphur emissions are
not reduced substantially. WHAT IS ACID RAIN? Acidity is measured using a pH scale, with
the number 7 being neutral. Consequently, a substance with a pH value of less than 7 is
acidic, while one of a value greater than 7 is basic. It is also worthwhile to note that
the pH scale is logarithmic; that is, a substance of pH of 6 is 10 times more acidic than
another with a pH of 7. Generally, the pH of 5.6 has been used as the baseline in
identifying acid rain, although there has been much debate over the acceptance of this
value. Interestingly enough, a pH of 5.6 is the pH value of carbon dioxide in equilibrium
with distilled water. Hence, acid ran is defined as any rainfall that has an acidity
level beyond what is expected in non-polluted rainfall. In essence, any precipitation
that has a pH value of less than 5.6 is considered to be acid precipitation. The average
mean of pH rainfall in Ontario's Muskoka-Haliburton lake country ranges between 3.95 and
4.38 about 40 times more acidic than normal rainfall, while storms in Pennsilvania have
rainfall pH at 2.8 it almost has the same rating for vinegar. Already 140 Ontario lakes
are completely dead or dying. An additional 48 000 are sensitive and vulnerable to acid
rain due to the surrounding concentrated acidic soils. ACID RAIN CONSISTS OF....? Canada
does not have as many people, power plants or automobiles as the United States, and yet
acid rain there has become so severe that Canadian government officials called it the
most pressing environmental issue facing the nation. But it is important to bear in mind
that acid rain is only one segment, of the widespread pollution of the atmosphere facing
the world. Each year the global atmosphere is on the receiving end of 20 billion tons of
carbon dioxide, 130 million tons of suffer dioxide, 97 million tons of hydrocarbons, 53
million tons of nitrogen oxides, more than three million tons of arsenic, cadmium, lead,
mercury, nickel, zinc and other toxic metals, and a host of synthetic organic compounds
ranging from polychlorinated biphenyls(PCBs) to toxaphene and other pesticides, a number
of which may be capable of causing cancer, birth defects, or genetic imbalances. COST OF
ACID RAIN Interactions of pollutants can cause problems. In addition to contributing to
acid rain, nitrogen oxides can react with hydrocarbons to produce ozone, a major air
pollutant responsible in the United States for annual losses of $2 billion to 4.5 billion
worth of wheat, corn, soyabeans, and peanuts. A wide range of interactions can occur many
unknown with toxic metals. In Canada, Ontario alone has lost the fish in an estimated
4000 lakes and provincial authorities calculate that Ontario stands to lose the fish in
48 500 more lakes within the next twenty years if acid rain continues at the present
rate.Ontario is not alone, on Nova Scotia's Eastern most shores, almost every river
flowing to the Atlantic Ocean is poisoned with acid. Further threatening a $2 million a
year fishing industry. THE DYING Acid rain is killing more than lakes. It can scar the
leaves of hardwood forest, wither ferns and lichens, accelerate the death of coniferous
needles, sterilize seeds, and weaken the forests to a state that is vulnerable to disease
infestation and decay. In the soil the acid neutralizes chemicals vital for growth,
strips others from the soil and carries them to the lakes and literally retards the
respiration of the soil. The rate of forest growth in the White Mountains of New
Hampshire has declined 18% between 1956 and 1965, time of increasingly intense acidic
rainfall. Acid rain no longer falls exclusively on the lakes, forest, and thin soils of
the Northeast it now covers half the continent. EFFECTS There is evidence that the rain
is destroying the productivity of the once rich soils themselves, like an overdose of
chemical fertilizer or a gigantic drenching of vinegar. The damage of such overdosing may
not be repairable or reversible. On some croplands, tomatoes grow to only half their full
weight, and the leaves of radishes wither. Naturally it rains on cities too, eating away
stone monuments and concrete structures, and corroding the pipes which channel the water
away to the lakes and the cycle is repeated. Paints and automobile paints have its life
reduce due to the pollution in the atmosphere speeding up the corrosion process. In some
communities the drinking water is laced with toxic metals freed from metal pipes by the
acidity. As if urban skies were not already gray enough, typical visibility has declined
from 10 to 4 miles, along the Eastern seaboard, as acid rain turns into smogs. Among one
of the serious side effects of acid pollution on humans is respiratory problems. The SO2
and NO2 emissions give rise to respiratory problems such as asthma, dry coughs,
headaches, eye, nose and throat irritations. An indirect effect of acid precipitation on
humans is that the toxic metals dissolved in the water are absorbed in fruits, vegetables
and in the tissues of animals. Although these toxic metals do not directly affect the
animals, they have serious effects on humans when they are being consumed. For example,
mercury that accumulates in the organs and tissues of the animals has been linked with
brain damage in children as well as nerve disorders, brain damage and death. Similarly,
another metal, Aluminum, present in the organs of the animals, has been associated with
kidney problems and recently, was suspected to be related to Alzheimer's disease. Acid
particles are also deposited on to buildings and statues, causing corrosion. For example,
the Capitol building in Ottawa has been disintegrating because of excess sulphur dioxide
in the atmosphere. Limestone and marble turn to a crumbling substance called gypsum upon
contact with the acid, which explains the corrosion of buildings and statues. In
addition, bridges are corroding at a faster rate, and the railway industry as well as the
airplane industry have to expend more money in repairing the corrosive damage done by
acid rain. Not only is this an economically taxing problem caused by acid rain, but also
a safety hazard to the general public. PREVENTION There are three main sources of acid
deposition: coal in electricity, base metal smelting, and fuel combustion in vehicles.
There are several ways to reduce SO2 emissions and NOx emissions: 1. Reducing NOx
emissions: During Combustion NOx emissions are reduced during combustion are reduced
primarily by a process called Overfire Air. In this procedure, a portion of the total air
required for the combustion process is diverted from the burners to an upper furnace.
This causes the combustion to occur with less O2 than that required, hence slowing down
the conversion of atmospheric nitrogen to NO. The process of Low NOx Concentric Firing
operates under the same principal, but involves increases separation of the fuel air and
secondary air. After Combustion The catalytic reduction system - This system involves the
injection of ammonia gas upstream of the catalytic reaction chamber. This gas will react
with NO by the following reaction: 4NO + 4NH3 + O2"_ 4N2 + 6H2O It will react with NO2 by
the following reaction: 2NO2 + 4NH3 + O2"_ 3N2 + 6H20 The harmless nitrogen gas can then
be released into the atmosphere. 2. Reducing SO2 emissions: Before Combustion 1. Coal
Cleaning - The cleaning of coal was originally used to reduce costs from transporting
inert material and improving the quality and uniformity of the coal. However, it has been
found to be useful in reducing sulfur content. The cleaning process is performed
gravitationally and is dependent on the density of the sulfur. The process is therefore
successful in removing pyritic sulfur (FeS2) due to its high specific gravity, and
relatively unsuccessful in removing chemically bound organic sulfur. This method is
therefore limited by its dependence on the percent of pyritic sulfur in the coal. The
pyritic sulfur content varies from region to region, so those with the highest percentage
will be in the highest demand. 2. Burning of Low Sulfur Coals - Some power plants have
chosen to reduce their sulfur dioxide emissions by burning coal of low sulfur content.
(Subbituminous coal is of lower sulfur content than bituminous coal.) A process is very
expensive, due to the high demand for subbituminous coal. During Combustion 1. FBC -
Fluidized Bed Combustion - This process allows sulfur dioxide emissions to be reduced
during the combustion process. A limestone or sand bed are crushed and fluidized. It is
essential that a balance is established between the heat liberated within the bed from
fuel combustion, and the heat removed by the flue gas as it leaves. The limestone is able
to react with the SO2 and reduce emissions by over 90%. After Combustion 1. Wet Flue Gas
Desulfurization - This is a highly effective and cost efficient system of flue gas
desulfurization. The wet scrubber is located downstream of the boiler, and consists of
either limestone, lime, or sodium hydroxide. Limestone is the most popular choice and
reacts with the gas by the following reaction: CaCO3 + SO2 + H2O + O2"_ CaSO3 + CaSO4 +
CO2 + H2O The flue gas enters the absorber and is re-emitted after being scrubbed, at
which time the waste solids are removed and disposed of. 2. Dry Scrubbing - The process
of dry scrubbing involves the contact between drying gas and the atomized liquid
(alkaline based). Upon contacting the flue gas, the drying gas will convert the atomized
droplets into a dry product that can be separated and disposed of. The dry scrubbing
process requires less power to complete than wet scrubbing. FINAL THOUGHTS Acid rain is
very real and a very threatening problem. Action by one government is not enough. In
order for things to be done we need to find a way to work together on this for at least a
reduction in the contaminates contributing to acid rain. Although there are right steps
in the right directions but the government should be cracking down on factories not using
the best filtering systems when incinerating or if the factory is giving off any other
dangerous fumes. 
Bibliography
sorry, no biblio.