UCPEL Fevereiro 2011

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[1] ACID RAIN

[2] Acid rain is a form of precipitation containing a heavy
[3] concentration of sulfuric and nitric acids. When fossil
[4] fuels such as coal, gasoline, and fuel oils are burned,
[5] they emit oxides of sulfur, carbon, and nitrogen into the
[6] air. These oxides combine with moisture in the air to
[7] form sulfuric acid, carbonic acid, and nitric acid. The
[8] term acid rain is also applied to other forms of
[9] precipitation - snow, hail, sleet, and fog - that are
[10] similarly acidic. Such precipitation has become an
[11] increasingly serious environmental problem in many
[12] areas of North America, Europe, and Asia. Although
[13] this form of pollution is most severe in and around large
[14] urban and industrial areas, substantial amounts of acid
[15] precipitation may be transported great distances.
[16] The process that results in the formation of acid rain
[17] generally begins with emissions into the atmosphere of sulfur dioxide and nitrogen oxide. These gases are released by
[18] automobiles, certain industrial operations, and electric power plants that burn fossil fuels such as coal and oil. The
[19] gases combine with water vapour in clouds to form sulfuric and nitric acids. When precipitation falls from the clouds,
[20] it is highly acidic, having a pH value of about 5.6 or lower.
[21] Precipitation and fog of high acidity contaminate lakes and streams; they are particularly harmful to fish and other
[22] aquatic life in regions with thin soil and granitic rock, which provide little buffering to acidic inputs. It also has been
[23] discovered that aluminum is leached from the soil in regions subjected to such acid precipitation, and that dissolved
[24] aluminum seems to be extremely toxic to aquatic organisms. All forms of acid precipitation have been found to
[25] damage various kinds of vegetation, including agricultural crops and trees, chiefly by inhibiting nitrogen fixation and
[26] leaching nutrients from foliage. ________, these pollutants can corrode the external surfaces of buildings and other
[27] man-made structures; marble structures and statues are especially vulnerable to their damaging effects.
[28] The problem of acid rain has been mainly dealt with in two ways. Adherents to the “cost-sharing” principle believe acid
[29] rain is a regional problem that should be dealt with collectively by all countries affected by the problem. Supporters of
[30] the “polluter pays” approach highlight the actions and responsibility of the polluter, which they believe should pay for
[31] the damages caused by its habits and institutions.

[32] From the Encyclopædia Britannica
[33] http://www.britannica.com/EBchecked/topic/3761/acid-rain