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 ir pollution from Asia could violate new federal ozone
standard. A plume of pollution that crossed the Pacific Ocean
from Asia earlier this year contained ozone at levels high enough
to violate a new federal ozone standard.
 "This
is air that has health implications," said Daniel Jaffe,
an atmospheric scientist at the University of Washington, Bothell,
whose team of researchers discovered evidence of the high pollution
content in data collected during a research flight off the Washington
coast on April 9. He presented his findings last December at
the American Geophysical Union's fall meeting in San Francisco.
Equipment
aboard the plane detected an ozone level of 85 parts per billion
at about 20,000 feet. That would exceed a new US Environmental
Protection Agency standard of 80 parts per billion (or 0.08 parts
per million). That standard, which was formulated in 1997 but
is under legal challenge and has not yet taken effect, includes
time limits for how long ozone levels can remain at or above
80 parts per billion. It would replace the current standard that
allows concentrations of 120 parts per billion.
Eventually,
air at 20,000 feet is likely to mix into the lower atmosphere,
but it is uncertain where it might come to ground level and create
a health risk, Jaffe said.
The research
flight also found an ozone level of 72 parts per billion at about
10,000 feet, an altitude lower than the tops of many peaks in
the Cascade Range. At that concentration, ozone is known to damage
vegetation, he said. A meteorological analysis of the plume shows
it came from East Asia, though the exact source is unknown, he
said. At the same time, elevated levels of other pollutants,
including hydrocarbons, carbon monoxide and a key smog ingredient
called PAN (peroxyacetylnitrate), proved that the ozone-rich
air mass had not come from the upper atmosphere because those
pollutants do not exist at high concentrations in the upper atmosphere.
At the AGU
meeting in 1997, Jaffe presented computer modeling indicating
the likelihood that, under the proper springtime conditions,
air pollution from East Asia could make its way across the Pacific
relatively undiluted within a matter of days. Data collected
from the UW's Cheeka Peak Observatory on Washington's northwest
coast in 1997 and 1998 confirmed the model's prediction, though
that data did not indicate heightened ozone levels.
To gather
this year's data, Jaffe's team used a University of Wyoming plane
that is part of a fleet of research aircraft operated by the
National Science Foundation. The plane was outfitted with essentially
the same equipment used at Cheeka Peak. On 14 flights between
March 15 and April 28, the plane gathered data from several equally
spaced levels between 1,500 feet (the same elevation as Cheeka
Peak) and 23,000 feet. Pollution layers were observed on about
one-third of the flights.
"This
was a day when we could really see haze layers out there,"
Jaffe said of the April 9 flight. Other scientists involved in
the research are from the UW, Seattle; the University of California,
Irvine; the National Oceanic and Atmospheric Administration;
and the Atmospheric Environment Service of Canada.
Jaffe's previous
research has shown that Asian pollution travels to North America
when meteorological conditions over the Pacific are just right,
typically during the spring. A low-pressure system over the Aleutian
Islands and a high-pressure cell near Hawaii, which remain stable
and in place for at least several days, work in concert to quickly
move air from East Asia directly across the ocean to North America.
The process, which the researchers have dubbed "The Asian
Express," takes four to 10 days, too little time for the
air to be cleansed over the ocean.
"For
us to see what we're seeing, I think we have to be talking about
a fairly large region of pollutants that remain intact and get
transported across in one big blob," Jaffe said. 
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