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AnonymousInactiveU.S. exports its air pollution to Europe
Study reveals how emissions have global impact
On Nov.14, 2001,a
low-pressure system caused a large mass of air Huddled over the eastern half of
the United States to rise up several miles, where it was then carried by the jet
stream to Europe.This plume brought
with it carbon monoxide, ozone and other pollutants from North American cars,
smokestacks and forest fires.It took five days
for the package to show up in the skies over Scandinavia. It later touched down
in the Alps, where ozone levels jumped by 33 percent. The effect was not
noticeable at lower altitudes, since background pollution levels there are
higher.An analysis of the
event was presented last month in the Journal of Geophysical
Research.Going
global
The event was recorded by a coordinated effort between
environmental researchers on both sides of the Atlantic. Recently, there has
been a heightened interest in the intercontinental transport of
pollution.“Ten to 20 years
ago, pollution studies were all on the scale of cities,” said Owen Cooper of the
Cooperative Institute for Research in Environmental Sciences. “Now, it has all
gone global.”A study in 2002
used a computer model to estimate the amount of pollution that travels over the
Atlantic. Although the research showed that a majority of pollution is
manufactured locally, it was found that one-fifth of the European ozone
violations in the summer of 1997 would not have occurred in the absence of
emissions from North America.“What you see is an
elevated background pollution level from upwind countries, which leaves downwind
countries less room to pollute,” Cooper told LiveScience.Our continent is
not alone in blowing its bad breath around. European pollution has been tracked
to Asia, as well as the Arctic. Asian plumes have been recorded over
California.Conveyor
belt
Taking into account which way the wind blows, it makes sense that
North American pollution ends up in Europe at some point. But if the air stays
close to the surface, Cooper explained, it moves very slowly, and the pollution
tends to dissipate before reaching the Old World’s shores.But occasionally a
weather pattern develops, called a warm conveyor belt, which lifts surface air
to an altitude where the winds ferry it two to three times faster. The pollution
hitches a ride.“This is the
fastest way that pollution travels,” Cooper said.In November 2001,
Cooper and his colleagues monitored the weather patterns over North America,
waiting for the right conditions — like a warm conveyor belt — to develop.
Once a “pollution
event” formed, they had computer simulations that predicted where and when the
air mass would show up in the skies over Europe. A research aircraft then made
measurements of pollution levels in targeted areas.“We used the model
to make a pollution forecast because it is too expensive to have the plane
flying around randomly,” Cooper said.Detected in the
mountains
In the case of the plume from Nov. 14, the plane was flown over
Sweden on Nov. 19. Elevated levels of carbon monoxide, ozone, nitrous oxides,
acetone, and sulfur dioxide were detected. Some other pollutants did not make
it. Sulfuric and nitric acid tend to be washed out of the air – in the form of
acid rain – before traveling long distances.“But ozone and
carbon monoxide are not water-soluble, so they keep going for a long time,”
Cooper explained.The plume was later
detected at Alpine air monitoring sites. Whether it had any effect at lower
altitudes, where pollution levels are higher to begin with, is more difficult to
tell.“It is hard to
pinpoint a pollution event where people live,” Cooper said.Over the
researchers’ monthlong observing period, the Nov. 14 plume caused the most
observable change. It is too soon to say if this event is typical of
trans-Atlantic pollution transport, according to Cooper.“We’ve only made
the first baby steps in measuring this,” he said. -
AuthorFebruary 11, 2005 at 11:04 AM
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