!! History Commons Alert, Exciting News
Profile: DELTA Group
DELTA Group was a participant or observer in the following events:
A team of specialists from UC Davis, known as the Detection and Evaluation of Long-range Transport of Aerosols (DELTA) Group, conducts air sampling from the roof of 201 Varick St., located one mile north-northeast of the WTC site, at the request of the Department of Energy. Regional meteorology will suggest that the monitoring equipment’s location at Varick Street probably receives material from the World Trade Center site about half the time. The group’s analysts use seven different techniques to analyze the data including synchrotron-induced X-ray fluorescence, scanning transmission ion microscopy and proton elastic scattering analysis, and soft beta mass measurements and scanning electron microscopy (SEM). DELTA will examine the samples for dozens of substances including carbon-based compounds from burning wood, plastic and carpets; glass shards; and asbestos. DELTA will release summary reports in December (see Early November 2001) and February (see February 11, 2002). [JOM, 12/1/2001; Dateline (Univ of Calif, Davis), 2/15/2002; Chemical and Engineering News, 2/18/2002]
A team of specialists from UC Davis, the Detection and Evaluation of Long-range Transport of Aerosols (DELTA) Group, sends the results from their first samples (see October 2, 2001-Mid-December, 2001) to the Lawrence Berkeley National Laboratory’s Advanced Light-Source Lab. Since October 2, the group has been conducting air sampling from the roof of 201 Varick St., located one mile north-northeast of the WTC site, at the request of the Department of Energy. According to the team, data indicates that the WTC plume “in many ways [resembles] those seen from municipal waste incinerators and high temperatures processes in coal-fired power plants.” A summary report of the data concludes: “The size fractions above 1 micrometer contained finely powdered concrete gypsum, and glass, with soot-like coatings and anthropogenic metals, but little asbestos. Composition in the very fine size range (0.26 > Dp > 0.09) was dominated by sulfuric acid and organic matter, but, including polycyclic aromatic hydrocarbons (PAHs) and their derivatives, and glasslike silicone containing aerosols.” [JOM, 12/1/2001; Dateline (Univ of Calif, Davis), 2/15/2002; Chemical and Engineering News, 2/18/2002]
The Delta Group releases a final report on air quality data collected in Manhattan between October and December, 2001 (see October 2, 2001-Mid-December, 2001). Thomas Cahill, PhD, Delta Group member, is a noted expert on composition and transport of ultra-fine airborne particles. Dr. Cahill explains that World Trade Center aerosols contained high levels of sulfur, sulfur-based compounds, and very fine silicon that probably came from the thousands of tons of glass that had been in the WTC buildings. The presence of these fine particles decreased during the month of October. The largest spike in very fine particle levels measured 58 micrograms per cubic meter which Cahill says was “an extremely high peak.” The sampling also indicated that there were almost always high concentrations of coarse particles—those about 12 micrometers to 5 micrometers in diameter—present in the air near the WTC site. “These particles simply should not be there,” Cahill says. “It had rained, sometimes heavily, on six days in the prior three weeks. That rain should have settled these coarse particles.” He says their presence suggests the hot debris pile was continually generating the larger particles. The study also determined the chemical composition of the dust it sampled. Some of the metals found in the air occurred at the highest levels ever recorded in the United States. Metals present at high levels included iron, titanium (some associated with powdered concrete), vanadium and nickel (often associated with fuel-oil combustion), copper and zinc. Mercury, lead, and asbestos were present at low levels. [On Earth, 2002; Dateline (Univ of Calif, Davis), 2/15/2002; Chemical and Engineering News, 2/18/2002]
A team of scientists from the University of California at Davis, known as the DELTA group, complete a study on the composition of the toxic gases released during fires burning at the World Trade Centers following the September 11 attacks. DELTA scientists release their report at a meeting of the American Chemical Society in New York. The study concludes that samples taken from the World Trade Center site contained four types of particles that the EPA considers harmful to human health: ultra-fine particulate matter composed of heavy metals known to cause lung damage, sulfuric acid harmful to pulmonary cells, ultra-fine glass particles that can travel through the lungs to the bloodstream and heart, and high-temperature carcinogenic organic matter. [Reuters, 9/11/2003]
Receive weekly email updates summarizing what contributors have added to the History Commons database
Developing and maintaining this site is very labor intensive. If you find it useful, please give us a hand and donate what you can.
If you would like to help us with this effort, please contact us. We need help with programming (Java, JDO, mysql, and xml), design, networking, and publicity. If you want to contribute information to this site, click the register link at the top of the page, and start contributing.