Air Today . . . Gone Tomorrow Article|
Rolling dust cloud
filled USGS scientists with a sense of urgency
By Andrew Schneider,
Post-Dispatch, February 9, 2002
DENVER - Chemists, geophysicists, astrophysicists and other
scientists cloistered in the sprawling U.S. Geological Survey complex here are not
emergency responders. Their work is detailed, methodical, with little room for haste or
need for spontaneity. They track water poisoned by mining, search for cracks in the
Earth's crust, and explore for minerals on Mars and Saturn.
But when a terrorist attack leveled the World Trade Center on
Sept. 11, that all changed. "We sat at home, watched that gray-white cloud roll over
lower Manhattan, and knew damned well that the dust was going to hurt a lot of
people," said Gregg Swayze, a USGS geophysicist. "I knew we had the best
technology in the world to determine precisely what was in that dust."
For more than a month, about two dozen men and women shelved
their ongoing projects and found themselves worried about fighter intercepts and White
House demands and people they didn't know. Many worked 18-hour days, speeded up normally
slow-moving science and used the most sophisticated analytical equipment to help the
people of New York.
Part of that technology was a remote-sensing unit designed for
use in exploring planets, called Airborne Visible Infrared Spectrometer. AVIRIS, the size
of a Volkswagen Beetle, reads the infrared signatures of minerals reflected from the
ground into its sensors. Then, they are compared with the unique peaks and curves -
similar to a fingerprint - of the signatures of thousands of minerals and materials in the
Geological Survey's vast database.
When used by NASA, the device is often strapped inside a modified
U-2 plane that flies 12.5 miles above the Earth's surface. But when the USGS team uses
AVIRIS, it's most often poking through a hole in the belly of a de Havilland Twin Otter
prop plane. On Sept. 11, the twin-engine aircraft was on a science mission along the East
Coast before it was grounded in Atlanta, ordered to land like every other aircraft that
morning. "We needed to get that aircraft up and over New York if we were going to
accomplish anything," said Roger Clark, the astrophysicist who heads USGS' portion of
the AVIRIS program in Denver. But first they needed approval from NASA, which owned the
plane, the AVIRIS and the crews that operate it.
Step 1: Avoid getting shot down
On Sept. 12, Clark contacted his counterpart, Robert
Green, who heads the AVIRIS program at NASA's Jet Propulsion Laboratory in Pasadena. By
Sept. 13, Green had permission from NASA to fly the mission. The Federal Emergency
Management Agency and the White House Office of Science and Technology Policy had signed
off on the flight. And the Air Force had agreed not to shoot the Twin Otter down. With
permission granted, Clark's team had to determine exactly how many passes over Manhattan
would be needed to survey the spread of the dust.
Swayze rushed three blocks to building 810, the USGS store in
Denver. He grabbed the four topographic maps of Manhattan and spent the next two hours
with pencil and ruler precisely plotting how many flights would be needed to cover the
disaster area and surrounding apartments and offices. "We knew the age of the World
Trade buildings and that it likely was built with much asbestos-containing material in the
concrete, the floor tiles, the fireproofing and walls," said Clark, who is a member
of the team running NASA's Mars Global Surveyor and the Cassini flight to Saturn. "We
wanted to see how far the dust had spread."
Airborne at high noon
As they prepared for the flight, the Denver team determined that
14 passes would be needed, going from Central Park to Jersey City, N.J., to cover lower
Manhattan. The longitude and latitude of each starting and ending point was e-mailed to
NASA pilots Bill Clark and John Longenecker. In the cabin of the Otter, Betina Pavri and
Charles Sarture had fine-tuned AVIRIS and had prepared the vessels of liquid nitrogen
needed to cool its infrared detectors.
On Sept. 16, around noon when the sun was highest, lighting as
much of the dark canyons between the buildings as possible, the first of the USGS missions
was flown. The first pass was at 6,500 feet above Manhattan; the second pass at an
altitude of 12,500 feet. The data tapes were loaded on a FEMA jet and flown to the Jet
Propulsion Lab at Pasadena. They arrived at 2 a.m., where Green and Frank Loiza were
The first evaluation of the data on Sept. 17 cut through the
heavy smoke and clearly showed 34 fires burning deep in the bowels of the collapsed World
Trade Center complex. That was more than anyone had anticipated. Maps were prepared and
shipped to emergency response teams in New York. Based on this information, firefighters
redeployed their equipment and changed how they were attacking the fires, which AVIRIS
measured at heat ranging between 800 degrees and 1,000 degrees. "Everything we were
finding went through the White House first," Clark said.
Collecting dust on the ground
For AVIRIS' data to be most useful, measurements for
calibration must be taken on the ground under the flight path. So Swayze and Todd Hoefen,
another USGS geophysicist, flew to New York on Sept. 17. Their backpacks filled with
respirators, protective clothing, dozens of sampling bags and a hand-held version of
AVIRIS - something like a Star Trek tricorder - they set out to get the calibration data.
Somehow, they said, they got through airport security without a second glance.
For three days, they took calibration sightings during the day
and at night. Taking the ferry across the Hudson from New Jersey, they collected samples
of dust in zipper-lock freezer bags from window ledges, flower pots, car windshields -
anyplace it was collecting. They hoofed it out two miles - or to the river's edge - in
each direction of the compass from the collapsed towers and gathered three dozen samples.
They found an all-night Kinko's and shipped the special calibrations back to Denver over
Worried that a rainstorm the night of Sept. 14 might have altered
the dust, Swayze and Hoefen found dry samples - dust from an apartment on the 30th floor
about three blocks from the World Trade Center and a gymnasium in the World Financial
Center across from the smoldering ruins.
Finding and analyzing the dry dust was crucial, the scientists
said, because it presented an accurate picture of what risks workers and residents would
face if they encountered dust that hadn't been rained upon or splashed with wash water.
"AVIRIS offers a bird's-eye view - coarse and broad," Clark said. "The
ground samples that Gregg and Todd collected gave us up-close, specific information on
specific points." But the mission wasn't over. The White House science office asked
that AVIRIS be flown again because more information was needed, Green said. On Sept. 18,
22 and 23, the Twin Otter and its $15 million-plus sensor crisscrossed Manhattan.
Inside the USGS anthill
By the afternoon of Sept. 20, the ground samples were back in
Denver, being split among the different laboratories that dotted the rat's maze of
hallways. "The place looked like an anthill that someone kicked," said Gregory
Meeker, head of the agency's mircobeam laboratory. "Everyone was grabbing their
samples and running."
Clark, Swayze, Hoefen and Eric Livo were in the Imaging
Spectroscopy Lab. Meeker was running the scanning electron microscope and doing energy
dispersive spectroscopy. Steve Sutley was conducting X-ray diffraction on his sample of
dust. Joe Taggart was doing X-ray fluorescence. And Geoffrey Plumlee and Phil Hageman were
doing chemical analysis and chemical leach testing.
Sam Vance, an environmental scientist with the EPA who is liaison
to the Geological Survey, was notifying his agency, New York health officials and the U.S.
Public Health Service of the preliminary results of tests and what his colleagues were
doing next. "All of these techniques are used to define the composition of the dust,
and we were looking at 40 different minerals," Swayze said. "They each back each
other up. Some techniques can see more than others, and we were throwing in every
technique we had in house." Clark said: "We didn't know what we were going to
find. We've never had a pulverized World Trade Center to analyze before."
Within hours, some results started coming back. They did find the
asbestos they were searching for. But they also found an alphabet soup of heavy metals.
But the real surprise was the pH of the dust. It registered a high of 12.1 on the samples
taken indoors. Ammonia has a pH of 10. The degree of acidity or alkalinity in a material
is expressed as a pH measurement. Neutral pH - like water - is 7 on a 15-point scale. From
less than 7 to zero is an indication of acid. From higher than 7 to 14, the top of the
scale, is alkaline. Levels near either end of the pH scale can harm health.
Plumlee was mixing one part of dust to 20 parts of water.
"We simulated the rain mixing with the dust, which gives an idea of what the dust
will do when it contacts tissue that is consistently moist like lungs, throat, eyes and
such," the geochemist said. "We were startled at the pH level we were
finding," he added. "We knew that the cement dust was caustic, but we were
getting pH readings of 12 and higher. It was obvious that precautions had to be taken to
protect the workers and people returning to their homes from the dust." Significant
efforts are being made at ground zero to keep the work area wet, to suppress the dust, but
this has minimal effect on the hazards of pockets of dust just below the surface.
Environmental cleanup specialists say that large amounts of water, a week or two of heavy
rain, are needed to neutralize the high pH.
Bringing in the health experts
While the USGS team is considered the world's leading authority
in mineral composition, its members are not health experts. They took their findings to
toxicologists and emergency coordinators from the EPA and physicians from the U.S. Public
Health Service and the Centers for Disease Control. These medical authorities agreed that
the Geological Survey's findings, especially the high pH levels, must be available to
those setting rules for worker safety and those considering whether and when to permit
people to return to their homes and offices, the scientists said.
All scientific reports go through a cumbersome and extensive peer
review. The USGS team broke all records and had their findings reviewed and on a
"government-only" Web site within a week. "It was important to get the
information out to those who needed it," Clark said. "What we wanted to indicate
to emergency response workers and those making decisions about people returning to their
homes and offices was that in addition to the high pH, there were heavy metals, especially
chromium and aluminum, in the dust which could be released by water."
On Sept. 27, the information was e-mailed to all the government
contacts the team had. "Then it was sent to EPA, FEMA, OSHA and everyone else that
seemed to be in charge," Clark said. "It was just obvious that people needed to
know what was in that dust." But even today, most New Yorkers have never been told
what the USGS team found in the dust.
The public version of the USGS report can be found at http://speclab.cr.usgs.gov/
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