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Amid heightened anti-terrorism vigilance in New York City's subways, a mammoth
Department of Homeland Security-sponsored project starting as early as Saturday
will seek to answer how harmful gases might disperse through midtown's streets
and the warren of subway tunnels beneath them.
The simulation, which will use colorless, odorless and harmless "tracer"
gases, follows a smaller effort in March that focused on the Madison Square
Garden area. This time, a team of more than 150 researchers and volunteers working
on the Urban Dispersion Program's second field study will fan out over a much
larger section of midtown, ranging from 37th to 59th streets and from 10th to
Third avenues, and including stations along the Broadway subway line and other
lines in the area.
Scientists will release the gases at four of eight possible locations above ground,
depending on the wind, within an office building and on a subway platform of the
Broadway line at 50th Street and Seventh Avenue.
Six separate experiments are planned over the next three weeks, with specific
dates dependent on the weather, and the subway portion planned for the final
three release dates.
"We'll be looking at the interaction of the subways in how the gases are
dispersed," said Paul Kalb, a senior research engineer at Brookhaven National
Laboratory. "If we release on the ground level, the street level, some
of the material may be drawn into the subways and moved around that way."
Likewise, releasing a gas in the subway will tell researchers whether that
gas remains within the tunnel system or drifts up to street level, and how it
disperses.
One of the substances is known as PFT, or perfluorocarbon tracer gas, a safe
and extensively used labeling compound. Jerry Allwine, the project's lead scientist
and an engineer with the Pacific Northwest National Laboratory in Richland,
Wash., said the second type of benign tracer gas, known as sulfur hexafluoride,
also has been used for years. With it, scientists can measure exposure rates
at one-second intervals.
To collect the reams of data expected from the experiments, electronic monitors
will be positioned on rooftops, in subway stations, in baskets hanging from
lampposts, in a half-dozen unmarked vans, and in the pockets of volunteers simulating
the movements of pedestrians and subway riders.
Another experiment in a midtown office building will analyze how air flows
inside and exchanges with the air outside.
For more information, see http://urbandispersion.pnl.gov.
