project on acit rain

8/14/2019 Project on Acit Rain

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PROJECT ON ACIT RAIN

Acid rain describes any form of precipitation with high levels of nitric and

sulfuric acids. It can also occur in the form of snow, fog, and tiny bits of drymaterial that settle to Earth.

Rotting vegetation and erupting volcanoes release some chemicals that

can cause acid rain, but most acid rain falls because of human activities.

The biggest culprit is the burning of fossil fuels by coal-burning power

plants, factories, and automobiles.

When humans burn fossil fuels, sulfur dioxide (SO2) and nitrogen oxides

(NOx) are released into the atmosphere. These chemical gases react with

water, oxygen, and other substances to form mild solutions of sulfuric and

nitric acid. Winds may spread these acidic solutions across the

atmosphere and over hundreds of miles. When acid rain reaches Earth, it

flows across the surface in runoff water, enters water systems, and sinks

into the soil.

Acid rain has many ecological effects, but none is greater than its impact

on lakes, streams, wetlands, and other aquatic environments. Acid rain

makes waters acidic and causes them to absorb the aluminum that makes

its way from soil into lakes and streams. This combination makes waters

toxic to crayfish, clams, fish, and other aquatic animals.

Some species can tolerate acidic waters better than others. However, in an

interconnected ecosystem, what impacts some species eventually impacts


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many more throughout the food chainincluding non-aquatic species

such as birds.

Acid rain also damages forests, especially those at higher elevations. It

robs the soil of essential nutrients and releases aluminum in the soil,

which makes it hard for trees to take up water. Trees' leaves and needles

are also harmed by acids.

The effects of acid rain, combined with other environmental stressors,

leave trees and plants less able to withstand cold temperatures, insects,

and disease. The pollutants may also inhibit trees' ability to reproduce.

Some soils are better able to neutralize acids than others. In areas where

the soil's "buffering capacity" is low, the harmful effects of acid rain are

much greater.

The only way to fight acid rain is by curbing the release of the pollutants

that cause it. This means burning fewer fossil fuels. Many governments

have tried to curb emissions by cleaning up industry smokestacks and

promoting alternative fuel sources. These efforts have met with mixed

results. But even if acid rain could be stopped today, it would still take

many years for its harmful effects to disappear.

Individuals can also help prevent acid rain by conserving energy. The less

electricity people use in their homes, the fewer chemicals power plants

will emit. Vehicles are also major fossil fuel users, so drivers can reduce

emissions by using public transportation, carpooling, biking, or simply

walking wherever possible.


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A stand of withered red spruce and Fraser fir trees blights a green vista inNorth Carolina's Mount Mitchell State Park. The trees fell victim to balsam

wooly aphids after being weakened by the effects of acid rain.

Over the years acid deposition, commonly referred to as "acid rain," hasrendered dozens of lakes in the Adirondacks uninhabitable for fish and

other wildlife. Now, Rensselaer Polytechnic Institute researchers at the

Darrin Fresh Water Institute (DFWI) have indicated that some of the most

severely affected lakes in that region are showing signs of recovery.

"In about half of the 30 lakes under study, an increase in the pH has been

observed, a sign that acidic levels are decreasing," says Director Sandra

Nierzwicki-Bauer.

Levels of nitrogen influenced by nitric oxide, a primary source of acid rain,

have decreased moderately in 18 of the 30 lakes the DFWI has monitored

since 1994 through its federally funded Adirondack Effects Assessment

Program. There also has been an overall reduction of sulfuric acid,

another main contributor of acid rain that comes from industry

pollutants.


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The reductions may be correlated with the 1990 Clean Air Act, a federal

mandate to significantly reduce emissions that cause acidification, says

Nierzwicki-Bauer.

More research is needed to pinpoint the exact reasons for the apparent

changes seen in the lakes in the southwestern part of the Adirondack Park,

an area hardest hit by acid rain.

"Recovery doesn't happen overnight," says Charles Boylen, professor of

biology and DFWI associate director. "One of the reasons we need long-

term data is that other factors can come into play. More or less rainfall in

a year, for instance, can lead to a temporary shift in acid-rain levels. You

need to track specific data over 10 to 15 years."

The DFWI's long-term strategy recently has led to a $2.36 million grantfrom the Environmental Protection Agency. The five-year grant will allow

the DFWI and its collaborators to study acid rain effects in four more lakes

in addition to monitoring the other 30. During a workshop in June at the

Institute, researchers will announce the most up-to-date results in the

acid-rain studies to leading scientists around the country.

The Darrin Fresh Water Institute, established more than 25 years ago, hashelped increase public awareness concerning the protection of land, water

and air. The Institute's all-encompassing study of fresh water systems and

ecological processes has earned it high regard in the national scientific

community and high marks from the general public.


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Rensselaer Polytechnic Institute, founded in 1824, is the nation's oldesttechnological university. The school offers degrees in engineering, the

sciences, information technology, architecture, management, and the

humanities and social sciences. Institute programs serve undergraduates,

graduate students, and working professionals around the world.

Rensselaer faculty are known for pre-eminence in research conducted in a

wide range of research centers that are characterized by strong industry

partnerships. The Institute is especially well known for its success in the

transfer of technology from the laboratory to the marketplace so that newdiscoveries and inventions benefit human life, protect the environment,

and strengthen economic development.

History

Since the Industrial Revolution, emissions of sulfur dioxide and nitrogen

oxides to the atmosphere have increased.[2] [3] In 1852, Robert Angus

Smith was the first to show the relationship between acid rain and

atmospheric pollution in Manchester, England.[4] Though acidic rain was

discovered in 1852, it was not until the late 1960s that scientists began

widely observing and studying the phenomenon. The term "acid rain" was

generated in 1972.[5] Canadian Harold Harvey was among the first to

research a "dead" lake. Public awareness of acid rain in the U.S increased

in the 1970s after the New York Times promulgated reports from the

Hubbard Brook Experimental Forest in New Hampshire of the myriad

deleterious environmental effects demonstrated to result from it.[6][7]

Occasional pH readings in rain and fog water of well below 2.4 (the acidity

of vinegar) have been reported in industrialized areas.[2] Industrial acid


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rain is a substantial problem in Europe, China,[8][9] Russia and areas

down-wind from them. These areas all burn sulfur-containing coal to

generate heat and electricity.[10] The problem of acid rain not only hasincreased with population and industrial growth, but has become more

widespread. The use of tall smokestacks to reduce local pollution has

contributed to the spread of acid rain by releasing gases into regional

atmospheric circulation.[11][12] Often deposition occurs a considerable

distance downwind of the emissions, with mountainous regions tending to

receive the greatest deposition (simply because of their higher rainfall).

An example of this effect is the low pH of rain (compared to the local

emissions) which falls in Scandinavia.[13]

[edit] History of Acid Rain in the United States

In 1980, the U.S. Congress passed an Acid Deposition Act. This Act

established a 10-year research program under the direction of the

National Acidic Precipitation Assessment Program (NAPAP). NAPAP

looked at the entire problem. It enlarged a network of monitoring sites to

determine how acidic the precipitation actually was, and to determine

long term trends, and established a network for dry deposition. It looked

at the effects of acid rain and funded research on the effects of acid

precipitation on freshwater and terrestrial ecosystems, historical

buildings, monuments, and building materials. It also funded extensive

studies on atmospheric processes and potential control programs.

In 1991, NAPAP provided its first assessment of acid rain in the United

States. It reported that 5% of New England Lakes were acidic, with

sulfates being the most common problem. They noted that 2% of the lakes


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could no longer support Brook Trout, and 6% of the lakes were unsuitable

for the survival of many species of minnow. Subsequent Reports to

Congress have documented chemical changes in soil and freshwaterecosystems, nitrogen saturation, decreases in amounts of nutrients in soil,

episodic acidification, regional haze, and damage to historical

monuments.

Meanwhile, in 1990, the US Congress passed a series of amendments to the

Clean Air Act. Title IV of these amendments established a program

designed to control emissions of sulfur dioxide and nitrogen oxides. Title

IV called for a total reduction of about 10 million tons of SO2 emissions

from power plants. It was implemented in two phases. Phase I began in

1995, and limited sulfur dioxide emissions from 110 of the largest power

plants to a combined total of 8.7 million tons of sulfur dioxide One power

plant in New England (Merrimack) was in Phase I. Four other plants

(Newington, Mount Tom, Brayton Point, and Salem Harbor) were added

under other provisions of the program. Phase II began in 2000, and affects

most of the power plants in the country.

During the 1990s, research has continued. On March 10, 2005, EPA issued

the Clean Air Interstate Rule (CAIR) . This rule provides states with a

solution to the problem of power plant pollution that drifts from one state

to another. CAIR will permanently cap emissions of SO2 and NOx in the

eastern United States. When fully implemented, CAIR will reduce SO2

emissions in 28 eastern states and the District of Columbia by over 70

percent and NOx emissions by over 60 percent from 2003 levels.[14]


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[edit] Emissions of chemicals leading to acidification

The most important gas which leads to acidification is sulfur dioxide.Emissions of nitrogen oxides which are oxidized to form nitric acid are of

increasing importance due to stricter controls on emissions of sulfur

containing compounds. 70 Tg(S) per year in the form of SO2 comes from

fossil fuel combustion and industry, 2.8 Tg(S) from wildfires and 7-8 Tg(S)

per year from volcanoes.[15]

[edit] Natural phenomena

The principal natural phenomena that contribute acid-producing gases to

the atmosphere are emissions from volcanoes and those from biological

processes that occur on the land, in wetlands, and in the oceans. The major

biological source of sulfur containing compounds is dimethyl sulfide.

Acidic deposits have been detected in glacial ice thousands of years old in

remote parts of the globe.[16]

[edit] Human activity

The coal-fired Gavin Power Plant in Cheshire, OhioThe principal cause of

acid rain is sulfur and nitrogen compounds from human sources, such as

electricity generation, factories, and motor vehicles. Coal power plants are


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one of the most polluting. The gases can be carried hundreds of kilometres

in the atmosphere before they are converted to acids and deposited. In the

past, factories had short funnels to let out smoke, but this caused manyproblems locally; thus, factories now have taller smoke funnels. However,

dispersal from these taller stacks causes pollutants to be carried farther,

causing widespread ecological damage.

[edit] Chemical processes

Combustion of fuels creates sulfur dioxide and nitric oxides. They are

converted into sulfuric acid and nitric acid.[17]

[edit] Gas phase chemistry

In the gas phase sulfur dioxide is oxidized by reaction with the hydroxyl

radical via an intermolecular reaction [4]:

SO2 + OHHOSO2

which is followed by:

HOSO2 + O2HO2 + SO3

In the presence of water, sulfur trioxide (SO3) is converted rapidly to

sulfuric acid:


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SO3 (g) + H2O (l)

H2SO4 (l)

Nitrogen dioxide reacts with OH to form nitric acid:

NO2 + OHHNO3

[edit] Chemistry in cloud droplets

When clouds are present, the loss rate of SO2 is faster than can be

explained by gas phase chemistry alone. This is due to reactions in the

liquid water droplets.

Hydrolysis

Sulfur dioxide dissolves in water and then, like carbon dioxide, hydrolyses

in a series of equilibrium reactions:

SO2 (g) + H2O SO2H2O

SO2H2O H+ + HSO3

HSO3-H+ + SO32

Oxidation

There are a large number of aqueous reactions that oxidize sulfur from

S(IV) to S(VI), leading to the formation of sulfuric acid. The most

important oxidation reactions are with ozone, hydrogen peroxide and


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oxygen (reactions with oxygen are catalyzed by iron and manganese in the

cloud droplets).

For more information see Seinfeld and Pandis (1998).[4]

[edit] Acid deposition

Processes involved in acid deposition (note that only SO2 and NOx play a

significant role in acid rain).

[edit] Wet deposition

Wet deposition of acids occurs when any form of precipitation (rain, snow,

etc.) removes acids from the atmosphere and delivers it to the Earth'ssurface. This can result from the deposition of acids produced in the

raindrops (see aqueous phase chemistry above) or by the precipitation

removing the acids either in clouds or below clouds. Wet removal of both

gases and aerosols are both of importance for wet deposition.

[edit] Dry deposition

Acid deposition also occurs via dry deposition in the absence of

precipitation. This can be responsible for as much as 20 to 60% of total

acid deposition.[18] This occurs when particles and gases stick to the

ground, plants or other surfaces.


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[edit] Adverse effects

This chart shows that not all fish, shellfish, or the insects that they eat can

tolerate the same amount of acid; for example, frogs can tolerate water

that is more acidic (i.e., has a lower pH) than trout.Acid rain has been

shown to have adverse impacts on forests, freshwaters and soils, killing

insect and aquatic life-forms as well as causing damage to buildings and

having impacts on human health.

[edit] Surface waters and aquatic animals

Both the lower pH and higher aluminum concentrations in surface waterthat occur as a result of 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 and rivers become more acidic

biodiversity is reduced. Acid rain has eliminated insect life and some fish

species, including the brook trout in some lakes, streams, and creeks in

geographically sensitive areas, such as the Adirondack Mountains of the

United States.[19] However, the extent to which acid rain contributes

directly or indirectly via runoff from the catchment to lake and riveracidity (i.e., depending on characteristics of the surrounding watershed) is

variable. The United States Environmental Protection Agency's (EPA)

website states: "Of the lakes and streams surveyed, acid rain caused

acidity in 75 percent of the acidic lakes and about 50 percent of the acidic

streams".[19]


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Other plants can also be damaged by acid rain, but the effect on food crops

is minimized by the application of lime and fertilizers to replace lost

nutrients. In cultivated areas, limestone may also be added to increase theability of the soil to keep the pH stable, but this tactic is largely unusable in

the case of wilderness lands. When calcium is leached from the needles of

red spruce, these trees become less cold tolerant and exhibit winter injury

and even death.[24][25]

[edit] Human health

Scientists have suggested direct links to human health.[26] Fine particles,

a large fraction of which are formed from the same gases as acid rain

(sulfur dioxide and nitrogen dioxide), have been shown to cause illness

and premature deaths such as cancer and other diseases.[27] For more

information on the health effects of aerosols see particulate health effects.

[edit] Other adverse effects

Effect of acid rain on statuesAcid rain can also cause damage to certain

building materials and historical monuments. This results when 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.


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CaCO3 (s) + H2SO4 (aq) CaSO4 (aq) + CO2 (g) + H2O (l)

This result is also commonly seen on old gravestones where the acid raincan cause the inscription to become completely illegible. Acid rain also

causes an increased rate of oxidation for iron.[28] Visibility is also reduced

by sulfate and nitrate aerosols and particles in the atmosphere.[29]

[edit] Affected areas

Particularly badly affected places around the globe include most of Europe

(particularly Scandinavia with many lakes with acidic water containing

no life and many trees dead) many parts of the United States (states like

New York are very badly affected) and South Western Canada. Other

affected areas include the South Eastern coast of China and Taiwan.

[edit] Potential problem areas in the future

Places like much of South Asia (Indonesia, Malaysia and Thailand),

Western South Africa (the country), Southern India and Sri Lanka and

even West Africa (countries like Ghana, Togo and Nigeria) could all be

prone to acidic rainfall in the future.

[edit] Prevention methods


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[edit] Technical solutions

In the United States, many coal-burning power plants use Flue gasdesulfurization (FGD) to remove sulfur-containing gases from their stack

gases. An example of FGD is the wet scrubber which is commonly used in

the U.S. and many other countries. A wet scrubber is basically a reaction

tower equipped with a fan that extracts hot smoke stack gases from a

power plant into the tower. Lime or limestone in slurry form is also

injected into the tower to mix with the stack gases and combine with the

sulfur dioxide present. The calcium carbonate of the limestone produces

pH-neutral calcium sulfate that is physically removed from the scrubber.That is, the scrubber turns sulfur pollution into industrial sulfates.

In some areas the sulfates are sold to chemical companies as gypsum

when the purity of calcium sulfate is high. In others, they are placed in

landfill. However, 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 offvulnerable insect and fish species and blocking efforts to restore native

life.

Automobile emissions control reduces emissions of nitrogen oxides from

motor vehicles.

The term acid rain refers to what scientists call acid deposition. It is

caused by airborne acidic pollutants and has highly destructive results.


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Scientists first discovered acid rain in 1852, when the English chemist

Robert Agnus invented the term. From then until now, acid rain has been

an issue of intense debate among scientists and policy makers.

Acid rain, one of the most important environmental problems of all,

cannot be seen. The invisible gases that cause acid rain usually come from

automobiles or coal-burning power plants.

Acid rain moves easily, affecting locations far beyond those that let out the

pollution. As a result, this global pollution issue causes great debates

between countries that fight over polluting each other's environments.

For years, science studied the true causes of acid rain. Some scientists

concluded that human production was primarily responsible, while others

cited natural causes as well. Recently, more intensive research has been

done so that countries have the information they need to prevent acid rain

and its dangerous effects.

The levels of acid rain vary from region to region. In Third World nations

without pollution restrictions, acid rain tends to be very high. In Eastern

Europe, China, and the Soviet Union, acid rain levels have also risen

greatly. However, because acid rain can move about so easily, the problem

is definitely a global one.

For many years, there was considerable debate and disagreement over

what caused acid rain. Recent scientific work, however, has helped to

clarify this

The primary causes of acid rain are sulfur dioxide and nitrogen oxides.

These chemicals are released by certain industrial processes, and as a
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result, the more industrialized nations ofEurope as well as the US suffer

severely from acid rain.

Most sulfur dioxide comes from power plants that use coal as their fuel.

These plants emit 100 million tons of sulfur dioxide, 70% of that in the

world.

Automobiles produce about half of the world's nitrogen oxide. As the

number of automobiles in use increases, so does the amount of acid rain.

Power plants that burn fossil fuels also contribute significantly to nitrogen

oxide emission.

Though human causes are primarily responsible for acid rain, natural

causes exist as well. Fires, volcanic eruptions, bacterial decomposition,

and lightening also greatly increase the amount of nitrogen oxide on the

planet. However, even the gigantic explosion ofMt. St. Helens released

only about what one coal power plant emits in a year.

Once the tiny pollutant molecules have entered the atmosphere, they can

travel for thousands of miles. Eventually, the particles will combine with

other compounds to produce new, often harmful, chemicals.

Acid rain comes down to the earth in the form of rain, snow, hail, fog, frost,

or dew. Once it reaches the ground, the acidity in the substance can harm

and even destroy both naturalecosystems and man-made products, such

as car finishes.

Acid rain is having harmful effects both on people and on the natural

ecosystems of the world. Scientists today are convinced that acid rain is

severe in many areas, and that it is having an adverse effect on the

environments of those locations.
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The problem of acid rain is rapidly spreading. Because it is mainly caused

by industrial processes, automobiles, and power plants, those countries

that are developed have the most severe acid rain problems. However, asthe undeveloped nations begin to industrialize, acid rain will increase

greatly.

Determining just how much the planet is being hurt by acid rain is very

difficult because the ecosystems that it affects are so diverse and complex.

Many ecosystems are affected by acid rain. Bodies of water, such as lakes

and rivers, see many of their inhabitants die off due to rising acidity levels.

Acidic water also ruins plant nutrients, hurting plants' ability to survive

and to give life to other organisms.

Human-made products are also experiencing degradation from acid rain.

Cars can lose their finishes, and outdoor statues are beginning to rust.

Acid rain's effects are destructive and long lasting. Though scientists have

studied lakes, streams, and many other natural ecosystems to prove its

negative effects, acid rain continues to be produced and is increasing inmany parts of the world.

Modern science has proven that acid rain is a dangerous and highly

destructive problem. As a result, various ways to limit acid rain have been

invented, and some are now being used.

Debate over acid rain and ways of preventing it have raged between

environmentalists and corporations. Businesses such as power companies
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and car makers oppose controlling acid rain because they fear the effects

on their profits.

But in some cases, industries have attempted to curb acid rain production.

The Northern States Power company began working to reduce acid rain in

the 1980s, and has invested over a billion dollars to that end.

There are many ways that power plant companies like Northern States

can reduce acid rain creation. They can use coal with a low sulfur content,

they can remove the sulfur from smoke their plants release, and they can

limit processes known to generate high levels of acid rain.

Policy makers and environmental experts are now looking into the best

methods to limit acid rain.

Environmentalists advocate the installation of sulfur cleaning scrubbers

in factories, washing sulfur out of coal, and finding new methods of

burning coal. Power plant operators are looking for less expensive

solutions to the problem.

Individuals can help by conserving energy or driving their cars less.Governments can pass laws restricting pollution levels, or can use a

variety of methods such as tradable emission permits to reduce acid rain.

Whatever way it is done, acid rain will certainly have to be limited in the

future.

Acid Rain--A Contemporary World Problem

Acid rain is one of the most dangerous and widespread forms of pollution.

Sometimes called "the unseen plague," acid rain can go undetected in an
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area for years. Technically, acid rain is rain that has a larger amount of

acid in it than what is normal. The acidity of rain in parts of Europe and

North America has dramatically increased over the past few decades. It isnow common in many places for rain to be ten to seventy times more acid

than unpolluted rain. Many living and non-living systems become harmed

and damaged as a result of acid rain. This website gives an informational,

in-depth look at acid rain--it's causes and effects; and solutions to the acid

rain problem.

Causes of Acid Rain

Acid rain is caused by smoke and gases that are given off by factories and

cars that run on fossil fuels. When these fuels are burned to produce

energy, the sulfur that is present in the fuel combines with oxygen and

becomes sulfur dioxide; some of the nitrogen in the air becomes nitrogen

oxide. These pollutants go into the atmosphere, and become acid.

Sulfur dioxide and nitrogen oxide are produced especially when coal is

burnt for fuel. Burning coal produces electricity, and the more electricity

that people use, the more coal is burnt. Of course, nowadays people

probably couldn't live without electricity, so coal will continue to be burnt;

but electricity and energy are constantly being overused. Think of it this

way: every time you turn on a light switch or the television set without

really needing to, you're indirectly contributing to the acid rain problem.

Automobiles produce nitrogen oxides (which cause acid rain), so everytime you don't carpool when you can, you are helping to cause acid rain.

So now that we know what causes acid rain, here's a look at how acid rain

can hurt you and the world around you. . .

project on acit rain

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