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The
changing view from Skyline drive
When
the Skyline drive in Shenandoah
National Park
was built between 1931 and 1939, the 105-mile long drive
provided magnificent views of the surrounding country.
These magnificent views are still there, but sometimes
you won't be able to enjoy them in all their splendor
because of the haze that is hanging over the landscape.
Take
a look at the photo below. The photo shows the view on
a clear day in the Shenandoah National Park, but if you
move your mouse over the picture, you will see what's
left of this view on a hazy day when air pollution is
clouding the skies.
Picture:
View on a clear and on a hazy day in Shenandoah National
Park. Move
your mouse over the picture to see the difference between
a clear and hazy day.
Picture
courtesy of EPA, Office of Air and Radiation To
the original photo.
You
don't have to go to the Skyline drive to notice that the
skies are sometimes very hazy. Haze, or "visibility
impairment" is one of the most obvious effects of
air pollution and
obscures the clarity, color, texture and form of what
we see, making it harder to look into the distance.
What
causes haze_
Haze
is created by tiny pollution particles (sulfates, nitrates,
organic carbon, soot, and soil dust) and some gases (nitrogen
dioxide) in the air. These particles and gases absorb
and scatter sunlight before the light can reach our eyes.
More pollutants means more absorption and scattering of
light, resulting in more haze. Humidity (especially prevalent
in the East) magnifies the haze problem because some particles,
such as sulfates, attract water and grow in size, scattering
the light even more.
Where
are these particles coming from_
Some
haze-causing particles are formed from gases that could
have been released into the air many miles away from where
you see the haze. Particles that are formed from gases
include sulfates, nitrates, and some organic carbon particles.
Other haze-causing pollutants (mostly small particles)
are emitted to the atmosphere from sources such as electric
utilities and industrial fuel burning, manufacturing processes,
and vehicle
emissions. Natural sources such as forest fires and
windblown dust also contribute to haze.
Do
these pollutants cause more than a haze_
The
haze you see is only the visible part of the pollution
caused by these particles and gases. The same pollutants
that cause haze also cause or contribute to significant
health and environmental problems across the United States.
Exposure
to very small particles has been linked to increased respiratory
illness, damage to lung tissue, and premature death. The
haze-causing sulfate and nitrate particles also contribute
to the formation of acid rain, which damages forests,
erodes building materials and monuments, and causes lakes
and streams to become acidic, making them unsuitable for
many fish.
Other
pollutants that contribute to haze also help form ground-level
ozone (smog) that can trigger serious respiratory problems
and cause significant damage to forests and ecosystems.
Nitrogen oxide gases from electric utilities and cars
are a major contributor to increased nitrogen loading
in water bodies, particularly estuaries, which upsets
the chemical balance of nutrients used by aquatic plants
and animals.
What
can you do_
You
can reduce your contribution to air pollution by saving
energy and becoming a responsible
driver. For more information, visit the EPA website:
What you can
do about air pollution.
References
and further reading
Related
Watershed Radio programs
About
Shenandoah National Park
About
air pollution and visibility reduction
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