|
 ew research by a University of Florida professor suggests
the complex computer models underlying regulations on pollution
from cars and other sources in many of the nation's largest cities
may significantly underestimate pollution levels.
 Jean Andino,
a University of Florida assistant professor of environmental
engineering, said the models are based in part on studies of
how gases combine to form smog in clean laboratory environments.
Her research, set to appear in a leading international atmospheric
environmental science journal this spring, indicates some of
these gases may react far more quickly when mixed with tiny particles
often found in urban and natural atmospheres.
"Traditionally,
researchers have done studies in laboratories in what I call
pristine atmospheres,'" Andino said. "The problem is
that the real atmosphere is not pristine -- it not only has gaseous
compounds, it also has particles -- and we've found these particles
can act as catalysts for the reactions and actually increase
reaction rates of some gases."
Andino
said her results, which will appear in the British-based journal
Atmospheric Environment, indicate the particles may speed
up the reactions of a selection of smog-forming gases as much
as 26 percent. Tests of simple models based on the sped-up reactions
have resulted in increases as high as 30 percent in the models'
predicted levels of ozone, a crucial ingredients of smog, she
said.
"We
just looked at the chemistry, so our models were very simple
compared with the real models, which consider meteorology and
many other factors," she said. "Still, we think that
30 percent is a fairly significant increase, and further study
is warranted."
Many of
the nation's large cities and urban regions use air quality models
to predict the outcome of pollution control efforts such as requiring
vehicle inspections or providing special lanes for carpooling,
said Roger Atkinson, a professor in the departments of environmental
sciences and chemistry and director of the Air Pollution Research
Center at the University of California at Riverside. The models
also are used to forecast future pollution levels and help policy-makers
decide whether regulations may be required in advance to keep
a city or region within federal pollution standards.
The models
take into account the reactions of smog-forming chemicals such
as a myriad array of volatile organic compounds emitted by cars,
Andino said. But they ignore another pollutant especially common
in urban environments: tiny particles emitted in diesel engine
exhaust, aerosol sprays or from a range of other sources.
"Particles
can come directly from sources such as diesel trucks or they
can be formed in the atmosphere," Andino said. "Gases
can react to form compounds that essentially condense and form
very small, liquid particles."
Her experiments
show the introduction of different types of small particles sped
up the reaction rates of several types of alcohol that are ingredients
of gasoline. Other gasoline ingredients, including an aromatic
compound and an alkane, did not react more quickly, but only
a few varieties were tested, Andino said. The particles in the
tests included ammonium nitrate and ammonium sulfate aerosols,
both common particles in urban areas, she said.
Atkinson
said Andino's results would have little impact on the computer
models in use by cities currently, but they are intriguing. "If
it's true for more alcohols, then it could be beginning to be
important," he said. "I think the other line is that
it probably needs to be confirmed by other labs."
Future
research will examine a much broader array of smog constituents
with the hope of improving the accuracy of the air quality models,
Andino said. "The next step is really to look at a whole
series of compounds to see if we can generate some kind of nice
correction factor for the data used for these models," she
said.
Andino's
research, part of a five-year project funded with more than $280,000
from the National Science Foundation, is in its third year. She
received the grant as part of an NSF Faculty Early Career Award,
designed to help promising scientists and engineers develop simultaneously
their contributions to research and education early in their
careers. 
|
ufl.edu.