ACID RAIN

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ACID RAIN
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• WHAT IS ACID RAIN?
• The term "acid rain" is commonly used to mean the
  deposition of acidic components in rain, snow,
  fog, dew, or dry particles. Distilled water,
  which contains no carbon dioxide, has a neutral
  pH of 7. "Clean" or unpolluted rain has a
  slightly acidic pH of 5.6, because carbon dioxide
  and water in the air react together to form
  carbonic acid, a weak acid.
• CO2 H2O H2CO3

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• The extra acidity in rain comes from the reaction
  of air pollutants, primarily sulfur oxides and
  nitrogen oxides, with water in the air to form
  strong acids (like sulfuric and nitric acid). The
  main sources of these pollutants are vehicles and
  industrial and power-generating plants.

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LAKES AND STREAMS Most lakes and streams have a
pH between 6 and 8, although some lakes are
naturally acidic even without the effects of acid
rain. Lakes and streams become acidic (pH value
goes down) when the water itself and its
surrounding soil cannot buffer the acid rain
enough to neutralize it. In areas where buffering
capacity is low, acid rain also releases aluminum
from soils into lakes and streams aluminum is
highly toxic to many species of aquatic
organisms CaCO3 ---gt Ca(2) CO3(-2)

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• How Does Acid Rain Affect Ecosystems?
• The plants and animals living within an ecosystem
  are highly interdependent. For example, frogs may
  tolerate relatively high levels of acidity, but
  if they eat insects like the mayfly, they may be
  affected because part of their food supply may
  disappear. Because of the connections between the
  many fish, plants, and other organisms living in
  an aquatic ecosystem, changes in pH or aluminum
  levels affect biodiversity as well. Thus, as
  lakes and streams become more acidic, the numbers
  and types of fish and other aquatic plants and
  animals that live in these waters decrease.
  FOREST KILLED BY ACID RAIN

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• EFFECTS OF ACID RAIN ON FORESTS
• Over the years, scientists, foresters, and others
  have watched some forests grow more slowly
  without knowing why. The trees in these forests
  do not grow as quickly at a healthy pace. Leaves
  and needles turn brown and fall off when they
  should be green and healthy. In extreme cases,
  individual trees or entire areas of the forest
  simply die off without an obvious reason.

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• How Acid Rain Harms Trees
• Acid rain does not usually kill trees directly.
  Instead, it is more likely to weaken trees by
  damaging their leaves, limiting the nutrients
  available to them, or exposing them to toxic
  substances slowly released from the soil. Quite
  often, injury or death of trees is a result of
  these effects of acid rain in combination with
  one or more additional threats.

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• How Acid Rain Affects Other Plants
• Acid rain can harm other plants in the same way
  it harms trees. Although damaged by other air
  pollutants such as ground level ozone, food crops
  are not usually seriously affected because
  farmers frequently add fertilizers to the soil to
  replace nutrients that have washed away. They may
  also add crushed limestone to the soil. Limestone
  is an alkaline material and increases the ability
  of the soil to act as a buffer against acidity.

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• Effects of Acid Rain Materials
• Acid rain and the dry deposition of acidic
  particles contribute to the corrosion of metals
  (such as bronze) and the deterioration of paint
  and stone (such as marble and limestone). These
  effects seriously reduce the value to society of
  buildings, bridges, cultural objects (such as
  statues, monuments, and tombstones), and cars.

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• Dry deposition of acidic compounds can also dirty
  buildings and other structures, leading to
  increased maintenance costs. To reduce damage to
  automotive paint caused by acid rain and acidic
  dry deposition, some manufacturers use
  acid-resistant paints, at an average cost of 5
  for each new vehicle (or a total of 61 million
  per year for all new cars and trucks sold in the
  U.S.) The Acid Rain Program will reduce damage to
  materials by limiting SO2 emissions.

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• Effects of Acid Rain Visibility Reduction
• Sulfates and nitrates that form in the atmosphere
  from sulfur dioxide (SO2) and nitrogen oxides
  (NOx) emissions contribute to visibility
  impairment, meaning we can't see as far or as
  clearly through the air. Sulfate particles
  account for 50 to 70 percent of the visibility
  reduction in the eastern part of the United
  States, affecting our enjoyment of national
  parks, such as the Shenandoah and the Great Smoky
  Mountains.

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• Effects of Acid Rain Human Health
• Acid rain looks, feels, and tastes just like
  clean rain. The harm to people from acid rain is
  not direct. Walking in acid rain, or even
  swimming in an acid lake, is no more dangerous
  than walking or swimming in clean water. However,
  the pollutants that cause acid rain (sulfur
  dioxide (SO2) and nitrogen oxides (NOx)) also
  damage human health. Many scientific studies have
  identified a relationship between elevated levels
  of fine particles and increased illness and
  premature death from heart and lung disorders,
  such as asthma and bronchitis. Effects can be
  similar to smoking.

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• Based on health concerns, SO2 and NOx have
  historically been regulated under the Clean Air
  Act, including the Acid Rain Program. In the
  eastern United States, sulfate aerosols make up
  about 25 percent of fine particles.By lowering
  SO2 and NOx emissions from power generation, the
  Acid Rain Program will reduce the levels of fine
  sulfate and nitrate particles and so reduce the
  incidence and the severity of these health
  problems.asthma and bronchitis. When fully
  implemented by the year 2010, the public health
  benefits of the Acid Rain Program are estimated
  to be valued at 50 billion annually, due to
  decreased mortality, hospital admissions, and
  emergency room visits.