Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) are participating in a study sponsored by the U.S Department of Homeland Security (DHS) in conjunction with the Massachusetts Bay Transportation Authority (MBTA) to determine how airborne contaminants would spread if released into Boston's subway system. During the study, which rans from December 5-11, the Berkeley Lab researchers measured how gas gets dispersed throughout tunnels and subway cars.

"The data we're collecting will help in the development of the next generation of biological and chemical agent detector systems," says Melissa Lunden, a chemist with the Environmental Energy Technologies Division (EETD) who leads Berkeley Lab's participation. "The information will also provide a better understanding of airflow characteristics in subway systems that should be useful for planning responses to fires, unintentional chemical or fuel spills, and other emergencies."

In addition to Lunden, other Berkeley Lab EETD researchers working on this DHS study include Doug Black, William Delp, Toshifumi Hotchi, Jennifer Logue, Ann McDonagh, Richard Sextro, and Tracy Thatcher.

While Boston's MBTA subway system has never been threatened or attacked, terrorists have threatened subway systems in New York and elsewhere. In 1995, a sarin gas attack on the Tokyo subway system by domestic terrorists killed a dozen people and injured dozens more.

"Proactively studying and preparing for possible threats is one of our most effective strategies for fortifying our critical infrastructure," said DHS Secretary Janet Napolitano in announcing this study. "DHS is undertaking many studies such as this across the country to inform our emergency response planning in preparation for chemical or biological terrorist attacks."

The MBTA study involved the release of common, harmless tracer gases used for indoor and outdoor air testing (sulfur hexafluoride and perfluoro-carbon); an inert particle tracer tagged with a biologically inert, non-toxic organic dye used in medical imaging applications; and, a common chemical often used as a brightening agent in laundry detergents and paper manufacturing. Particle and gas concentrations are being sampled in more than 20 stations and in subway cars, but normal MBTA operations are not being disrupted by the activities of the researchers.

Joining Berkeley Lab in this effort were scientists from Argonne National Laboratory, ICx Technologies of Arlington, Virginia, the Defence Science and Technology Laboratory of the United Kingdom, and the Chemistry Centre of Australia.

"The Argonne team, under David Brown, has created a computational model for predicting the behavior of airborne contaminants in subway systems," says Lunden. "We will now have actual subway data measurements that can be compared to the model's predictions and used to refine it."

Because air temperature is a driver of airflow, Lunden and her colleagues will return to Boston in the summer of 2010 to conduct further measurements. Berkeley Lab EETD researchers were part of a similar study conducted in 2007 and 2008 by DHS of the "Metro" subway system that serves the Washington, D.C. metropolitan area.

Source: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory