Brookhaven Scientists Aid in Homeland Security Field Study

Data on how tracer gases move through “urban canyons” will help first responders plan for and respond to potential terrorist attacks and accidents involving harmful airborne contaminants.
- by Kay Cordtz

If an industrial accident or a terrorist act released dangerous contaminants into the atmosphere in New York City, the city’s first responders would have to decide quickly whether people should shelter in place or be evacuated, and what evacuation routes should be considered. In the future they will be aided in making those decisions by information gathered during the New York City Urban Dispersion Program field studies, conducted in the city’s urban canyons in March and August of 2005.

The field studies were part of the $10 million Urban Dispersion Program, sponsored by the U.S. Department of Homeland Security, the Defense Department’s Defense Threat Reduction Agency, the Environmental Protection Agency (EPA), and the Department of Energy (DOE). Data gathered from the study will help improve existing models of how a gas or chemical release might move around Manhattan’s tall buildings and canyons. Emergency management, law enforcement, and intelligence personnel use these models to plan for, train for, and respond to potential terrorist attacks and accidents involving harmful airborne contaminants.

Brookhaven scientists collect data from the roving van.

“We are interested in how contaminants behave in very complicated urban canyon environments like New York City,” said Paul Kalb of Brookhaven Lab’s Environmental Sciences Department. “Anyone who’s been to the city has observed that the flags on one side of the street may be blowing one way while those on the other side of the street are blowing in the complete opposite direction.”

The March field study consisted of two days of detailed meteorological observations while scientists released a colorless, odorless, harmless “tracer” gas near Madison Square Garden. In six days of August experiments, the scientists released either perfluorocarbon (PFT) or sulfur hexafluoride at a number of outdoor locations. On several of those test days, small amounts of the gases were also released and tracked inside a Manhattan office building and in several subway stations.

“Many people may not realize that a few days of actual experimentation requires months of planning and preparation,” said Brookhaven’s John Heiser, the tracer team’s principal investigator for the project. “Hundreds of samplers, thousands of sample tubes, scores of approvals, in addition to the placement of meteorological equipment, route planning and many other details all require a massive, unseen effort by all involved.”