VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

the estimated dilution would have been relative to WTC Ground Zero concentrations. During periods when emissions from Ground Zero were low, any increases in concentrations within the plume would also be low. Other inputs (e.g., evaluation of surface-level PM measurements at various sites and/or photos of the WTC plume) are also needed to aid in characterizing likely occurrences of plumes affecting the surface and/or possible human exposures.

In addition to the above expanded EPA and New York State government PM monitoring and modeling efforts, numerous other investigators (e.g., some from other Federal government agencies, academia, and commercial firms or sponsored by nongovernmental organizations) collected data aimed at in estimating likely PM exposures associated with the WTC attack and ensuing fires and recovery operations. Limited published reports from such studies are becoming available, and a few salient points from these reports are alluded to here. More thorough discussion of these and other reports that become available in the coming months will be included in any subsequent, fuller EPA/ORD evaluation.

One important set of newly available findings are those reported by Lioy et al. (2002), based on work done cooperatively with EPA/ORD and also partly funded by NIEHS. Direct air measurements of the composition of WTC-generated airborne particles by EPA/ORD did not begin until September 21,2001. Before that date, only bulk samples of settled dust were available for chemical analyses. Lioy et al. (2002) measured the mass of particles in several size ranges in the settled dust and analyzed their composition. Also, detailed chemical analyses of fine fraction particles (< 2.5 pm diameter) from settled WTC dust has recently been reported (McGee et al., 2002). Although the bulk samples do not provide direct data on ambient air PM concentrations, they do provide strong clues as to the likely composition of airborne PM in lower Manhattan and the size distribution of particles in the suspended dust immediately after the collapse of WTC buildings. Small amounts of WTC-derived settled dust were also provided by New York University investigators for laboratory toxicity testing by EPA scientists (EPA, 2002c; Gavett et al., 2002) in EPA/ORD’s National Health and Environmental Effects Research Laboratory (NHEERL).

Also, in a cooperative U.S. Department of Energy (DOE)/University of California study, measurements of the size distribution of particles in 10 channels from 0.09 to 12 pm were made on the roof of the Federal Building on Varick Street, using the rotating drum impactor developed at the University of California, Davis (Cahill et al., 2002). This Varick Street DOE site is about 2.0 km north of the WTC (see Figure 2). Sampling began October 2, 2001 and continued into December 2001. Elemental analyses of samples collected approximately every 3 hours were done by synchrotron radiation-induced X-ray emission (SRIXE).

IV.a.2. Particulate Matter Air Monitoring/Modeling Results 1. Particulate Matter Mass Measurements and Plume Trajectory Plots The collapse of the WTC buildings and the associated fires resulted in the initial dispersion of large quantities of various-size particles in the massive dust/smoke cloud that enveloped lower Manhattan. It is clear from Figures 3 and 4 (and other photographs) that the densest portion of the dust/smoke cloud initially spread in all directions and impacted most of lower Manhattan, especially below Chambers Street. On the basis of the size classifications (by

DRAFT-DO NOT QUOTE OR CITE 28 October 2002

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