Acid Rain

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Acid Rain
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Educational Objectives

• To understand how the pH level of an environment
  affects living organisms.
• To understand the relationship between the pH
  level and CO2 concentration of distilled water.

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What is Acid Rain ?

• Acid Rain is any form of rain that is more acidic
  than normal
• Generally, rain water has a pH value of a little
  less than 7
• Pure water has a pH of 7
• Any rainfall that has a pH value less than 5.6 (
  about 5.0-5.5 ) is defined as acid rain.
• Northeastern United States pH in range of 4.

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History of Pollution

• From Industrial Revolution to the Space Age,
  humans have produced inventions that use many of
  the earths varied energy resources to make
  living easier.
• Often, energy comes from fossil fuels - coal,
  oil and natural gas !
• These inventions and using fossil fuels lead to
  pollution !

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How does Acid Rain Form ?

• Gas pollutants e.g. carbon dioxide, sulphur
  dioxide, or nitrogen dioxide dissolve in rain
  water.
• Acids are formed when gases, such as CO2 , SO2
  and NO2 react with the water in the atmosphere

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Pollutants

• Nitrogen oxides can also be produced naturally by
  lightning strikes
• Sulfur dioxide is produced by volcanic
  eruptions.
• Human activities ( burning fossil fuels
  Carbon dioxide )such as electricity generation,
  factories, and motor vehicles also release lots
  of acid vapour into the atmosphere.

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How does Acid Rain form ?

• Smoke and fumes from burning fossil fuels rise
  into the atmosphere and combine with the moisture
  in the air to form acid rain.
• Acid rain usually forms high in the clouds
• Sunlight increases the rate of these acid forming
  reactions.
• Rainwater, snow, fog, and other forms of
  precipitation containing acids fall to earth as
  acid rain.

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Pollution

• The chemical reactions that change air pollution
  to acid rain can take from several hours to
  several days.
• Many years ago, smokestacks were only a few
  stories high, pollution stayed near the ground
  causing unhealthy conditions for plants and
  animals

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Pollution

• To reduce this pollution, government passed a law
  permitting construction of very tall smokestacks
• However, sending pollution high into the sky,
  increases the time that pollution stays in the
  air
• The longer the pollution is in the air, the
  greater the chances that pollutants can form acid
  rain.
• In addition, wind can carry pollutants for
  hundreds of miles before they combine with water
  droplets and form acid rain.

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What is Acid Rain ?

• CO2 H2O ? H2CO3 (carbonic acid)
• SO2 H2O ? H2SO3 (sulphorous acid)
• NO2 H2O ? HNO2 (nitrous acid) HNO3
  (nitric acid)
• The pH of Rain drops

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Examples

• When CO2 reacts with water, carbonic acid is
  formed.
• CO2 (g)H2O(l)-?H2CO3(aq)
• When SO2 reacts with water, sulfurous acid is
  formed.
• SO2 (g)H2O(l)-?H2SO3(aq)
• When NO2 reacts with water, nitric acid and
  nitric acid is formed.
• 2NO2(g)H2O(l)-?HNO2(aq)HNO3(aq)

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Causes of Acid Rain
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How does Acid Rain effect us ?

• Harmful effects on plants, aquatic animals and
  human beings.
• It kills micro-organisms
• It poisons plants
• It damages metals and limestone
• It kills fish

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Effects of Acid Rain

• harmful to plants acid rain destroys the
  nutrients in the soil which the plants need to
  survive.

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Effects of Acid Rain

• harmful to aquatic animals - fish eggs will not
  hatch and adult fishes will die when acid rain
  enters lakes or rivers

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Effects of Acid Rain

• harmful to human beings, although the acid in the
  rainwater is too dilute to have direct effect on
  us humans, increased amount of sulfur dioxide and
  nitrogen oxides in the air do contribute to heart
  and lung problems including asthma and
  bronchitis.

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Effects of Acid Rain

• Urban areas of cities acid rain affects
  buildings, statues, monuments, and cars.
• Chemicals found in acid rain can cause paint to
  peel and stone statues to begin to appear old and
  worn down, which reduces their value and beauty.

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Effects of Acid Rain

• Most building materials made of limestone and
  marble.
• The acid rain water mainly sulphuric acid will
  react with calcium carbonate from limestone and
  marble to form calcium sulphate.

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Acid Rain on Earth

• Region of Continental US most affected by acid
  rain is Northeast ( pH levels between 4 -4.5 )
• Most rapid increase in acid precipitation in US
  seems to be Southeast.
• West of Mississippi rain neutral or alkaline.
• Exceptions Colorado, Los Angeles Basin, San
  Francisco Bay area, Tucson, Spokane, Portland (
  pH 4-5 )

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