Acid Rain
Acid rain is a rain or any other form of precipitation that
is unusually acidic, meaning that it possesses elevated levels of hydrogen
ions (low pH). It can have harmful effects on plants, aquatic animals and
infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen
oxide, which react with the water molecules in the atmosphere to
produce acids. Governments have made efforts since the 1970s to reduce the
release of sulfur dioxide into the atmosphere with positive results.
Nitrogen oxides can also be produced naturally by lightning strikes
and sulfur dioxide is produced by volcanic eruptions. The chemicals
in acid rain can cause paint to peel, corrosion of steel structures
such as bridges, and erosion of stone statues.
Acid rain is rain consisting of water droplets that are
unusually acidic because of atmospheric pollution - most notably the excessive
amounts of sulfur and nitrogen released by cars and industrial processes. Acid
rain is also called acid deposition because this term includes other forms of
acidic precipitation such as snow.
Wet deposition refers to acidic rain, fog, and snow. If
the acid chemicals in the air are blown into areas where the weather is wet,
the acids can fall to the ground in the form of rain, snow, fog, or mist. As
this acidic water flows over and through the ground, it affects a variety of
plants and animals. The strength of the effects depends on several factors,
including how acidic the water is; the chemistry and buffering capacity of
the soils involved; and the types of fish, trees, and other living things that
rely on the water.
In areas where the weather is dry, the acid chemicals may
become incorporated into dust or smoke and fall to the ground through dry
deposition, sticking to the ground, buildings, homes, cars, and trees. Dry
deposited gases and particles can be washed from these surfaces by rainstorms,
leading to increased runoff. This runoff water makes the resulting mixture more
acidic. About half of the acidity in the atmosphere falls back to earth through
dry deposition.
Because of these problems and the adverse effects air
pollution has on human health, a number of steps are being taken to reduce
sulfur and nitrogen emissions. Most notably, many governments are now requiring
energy producers to clean smoke stacks by using scrubbers which trap pollutants
before they are released into the atmosphere and catalytic converters in cars
to reduce their emissions. Additionally, alternative energy sources are gaining
more prominence today and funding is being given to the restoration of
ecosystems damaged by acid rain worldwide.
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