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 user 2005-02-11 at 11:04:00 am Views: 89
  • #10185

    U.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

    An analysis of the
    event was presented last month in the Journal of Geophysical

    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

    “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

    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
    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

    “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.