Effects of acid rain

1. EFFECTS OF ACID RAIN
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2. What is Acid Rain ?
Acid rain, also called acid precipitation or acid deposition, precipitation possessing
a pH of about 5.2 or below primarily produced from the emission of sulfur dioxide(SO2)
and nitrogen oxides (NOx; the combination of NO and NO2) from human activities,
mostly the combustion of fossil fuels.
Fig.1: Acid Rain cycle.
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3. Chemistry Of Acid Rain :
• Acid rain is a popular expression for the more scientific term acid deposition, which refers to the
many ways in which acidity can move from the atmosphere to Earth’s surface.
• Acid deposition includes acidic rain as well as other forms of acidic wet deposition—such
as snow, sleet, hail, and fog (or cloud water).
• Acid deposition also includes the dry deposition of acidic particles and gases, which can affect
landscapes during dry periods. Thus, acid deposition is capable of affecting landscapes and the
living things that reside within them even when precipitation is not occurring.
• Normal rainwater is weakly acidic because of the absorption of carbon dioxide (CO2) from
the atmosphere—a process that produces carbonic acid—and from organic acids generated from
biological activity.
• In addition, volcanic activity can produce sulfuric acid (H2SO4), nitric acid (HNO3),
and hydrochloric acid (HCl) depending on the emissions associated with specific volcanoes.
• Other natural sources of acidification include the production of nitrogen oxides from the conversion
of atmospheric molecular nitrogen (N2) by lightning and the conversion of organic nitrogen
by wildfires.
• However, the geographic extent of any given natural source of acidification is small, and in most
cases it lowers the pH of precipitation to no more than about 5.2.
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4. Effects Of Acid Rain
Human
Health Environment Materials
1.Soil :Plants and Trees
2.Water bodies:Marine life
Direct Effects Indirect Effects
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5. Effects Of Acid Rain : Human Health:
1. Direct Effect of Acid Rain on Humans
While acid tends to bring to mind the image of corrosive chemicals dissolving metals and other
materials, acid precipitation does not have direct effects on human health. Acid rain does not have
an acidic enough pH to burn human skin.
While acid rain cannot burn your skin, it is linked to several indirect health effects.
2. Indirect Effects of Acid Rain:
• Effects of Sulfur Dioxide:
Everything is connected in air quality. While acid rain cannot harm humans directly, the sulfur
dioxide that creates it can cause health problems. Specifically, sulfur dioxide particles in the air
can encourage chronic lung problems, like asthma and bronchitis.
• Effects of Nitrogen oxides:
The nitrogen oxides that create acid rain promote the formation of ground-level ozone.
While ozone high above the Earth helps block ultraviolet radiation, ground-level ozone promotes
severe lung problems like chronic pneumonia and emphysema.
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6. 3. Other Effects : on Humans
• Visibility When acid rains fall at places located at higher altitudes, acid rains lead to thick
acidic fog that hangs low, affecting visibility and causing irritation to eyes and nose.
• Animals that humans eat, eat grass and plants that could have been adulterated by acid
rain.Whatever contaminated the plants contaminated the animal, that could contaminate
us.
Fig.2 Effects of SO2 on lungs :
Asthma
Fig.3 Effects of NO x on
lungs:Emphysema
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7. Effect of Acid Rain : On Soil
When acid rain falls to the earth, it undergoes a new round of physical and chemical changes. These
changes may reduce the acidity and change the chemical characteristics of the water reaching the
streams and lakes.
• Alkaline or basic soils, such as those rich in limestone, calcium carbonate, can neutralize the acid
directly. The extent to which soils can neutralize acid rain depends on several factors:
• Type of soil
• Thickness
• Weather
• Water flow patterns.
• If the ground is frozen, as in the winter, soil process cannot work, the acid is not neutralized. If the
soil is mainly quartz, such as sand, it is resistant to weathering and no bases are present to neutralize
acid. If the soil has very little base such as limestone, the acid is neutralized only slightly or with the
passage of time, not at all. The acid can be immobilized as the soil or vegetation retains the sulfate
and nitrate ions (from sulfuric and nitric acids). Very deep soils have a large capacity to retain sulfate
and nitrate ions.
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8. Effects of Acid Rain : Plants and Trees:
Trees are depended upon soil for getting nutrition for growth from soil so anything affecting soil
will affect trees in following way:
1.Leaching:
• Trees derive their nutrition primarily from element ions such as calcium, Ca, magnesium, Mg,
and potassium, K that have dissolved from rocks into the soil.
• Acid deposition adds hydrogen ions, which displace these important nutrients in a process
called leaching. Leaching means that the ions are washed deeper into the subsoil or washed out
of the top soil. If ions are leached from the soil, they are no longer available to the roots of the
plants.
• Calcium ion is used in the cells of a tree for cell formation and in the processes that transport
sugars, water, and other nutrients from the roots to the leaves.
• Magnesium ion is a vital element in photosynthesis and as a carrier of phosphorus which is
important in the production of DNA.
• These ions may be unavailable to the tree roots because they have been leached away.
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9. 2. Aluminum Mobilization :
• Increasing amounts of acids can "mobilize" aluminum ions which are normally present in an
insoluble nontoxic form of aluminum hydroxide.
• It appears that when the soil pH dips to 5 or lower, aluminum ions are dissolved into the water and
become toxic to plants. Aluminum ions cause a stunting of the root growth and prevent the roots
from taking up calcium.
• The result may be the overall slowing of the growth of the entire tree.
• Lower soil pH and aluminum mobilization can reduce populations of soil microorganisms.
• Soil bacteria have the job of breaking down the dead and decaying leaves and other debris on the
forest floor.
• The effect of this action is to release nutrients such as calcium, magnesium, phosphate, nitrate, and
others.
• Low pH and high aluminum ion concentrations inhibit this process.
• Higher amounts of acids can mobilize other toxic metals from the insoluble to the soluble ion forms
in the same fashion as aluminum.
The toxic metals include lead, mercury, zinc, copper, cadmium, chromium, manganese, and
vanadium.
• These may all contribute to slow the growth of a tree. In addition, this combination of toxic metals
may also adversely effect the growth of soil bacteria, mosses, algae, fungi, and earthworms.
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10. Aluminum Hydroxide
Neutralization:
The sulfuric acid reacts with
the aluminum hydroxide in a
neutralization reaction.
Limestone: Al(OH)3 + H2SO4 --
> Al2(SO4 )3 + H2CO3
The aluminum sulfate is
soluble in water and are thus
released from the soil particles.
Fig.4 : Leaching Fig.5: Aluminium
mobilization
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11. Effects of Acid Rain : Water bodies and marine life :
• The ecological effects of acid rain are most clearly seen in aquatic environments,
such as streams, lakes, and marshes where it can be harmful to fish and other
wildlife. As it flows through the soil, acidic rain water can leach aluminum from
soil clay particles and then flow into streams and lakes.
• The more acid that is introduced to the ecosystem, the more aluminum is released.
• Some types of plants and animals are able to tolerate acidic waters and moderate
amounts of aluminum.
• Others, however, are acid-sensitive and will be lost as the pH declines. Generally,
the young of most species are more sensitive to environmental conditions than
adults. At pH 5, most fish eggs cannot hatch.
• At lower pH levels, some adult fish die. Some acidic lakes have no fish. Even if a
species of fish or animal can tolerate moderately acidic water, the animals or plants
it eats might not. For example, frogs have a critical pH around 4, but the mayflies
they eat are more sensitive and may not survive pH below 5.5.
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12. Fig. 6 This figure illustrates the pH level at which key organisms may be lost as their
environment becomes more acidic. Not all fish, shellfish, or the insects that they eat can
tolerate the same amount of acid.
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13. Effects of Acid Rain on Materials
• Not all acidic deposition is wet. Sometimes dust particles can become acidic as well,
and this is called dry deposition.
• When acid rain and dry acidic particles fall to earth, the nitric and sulfuric acid that
make the particles acidic can land on statues, buildings, and other manmade
structures, and damage their surfaces. The most notable effects occur
on marble and limestone, which are common building materials found in many
historic structures, monuments, and gravestones.
• The acidic particles corrode metal and cause paint and stone to deteriorate more
quickly. They also dirty the surfaces of buildings and other structures such as
monuments.
• The consequences of this damage can be costly:
• damaged materials that need to be repaired or replaced,
• increased maintenance costs, and
• loss of detail on stone and metal statues, monuments and tombstones.
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14. Effects of Acid Rain : Materials
• Effect on Taj Mahal:
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