VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

the 40 pg/m’ AQILOC value; many of the 24-hour PM2 5 levels for such sites were below 20 pg/m\ PM,o values (not graphically depicted here) observed at the same NYSDEC lower Manhattan locations around the WTC were also consistently below the daily PM2 5 NAAQS (150 pg/m\ 24-h) and showed a general decreasing trend from October 1 to November 30 and beyond, with 24-hour values decreasing from ~ 50-90 pg/m’ at some sites in early October to generally less than 50 pg/m^ in November (except for ~114-135 pg/m’ on October 25-26 for Park Row and 55-75 pg/m^ on November 15-16, 2001 for all the sites).

Overall, then, the PM2.5 data appear to support the following conclusions:

(1) Notable PM2 5 elevations occurred in the immediate vicinity of the World Trade Center Ground Zero during late September/early October, with concentrations at ORD WTC perimeter sites on some days exceeding the 24-hr PM2 5 NAAQS. However, PM concentrations at the WTC perimeter sites fell to typical background levels by late November/early December, 2001.

(2) Such high PM2 5 elevations were not observed at other lower Manhattan monitoring sites within 3 to 10 blocks of WTC Ground Zero. On only a few sporadic occasions did daily PMj ^ concentrations approach or exceed the AQI LOC (40 pg/m’) at one or two sites (e.g., 290 Broadway or PS 64) along the WTC plume path in addition to elevations seen at WTC perimeter sites. The frequency of such excursions were not out of line with historical frequency of PM2.5 values approaching or exceeding 40 pg/m’ either before the Sept. 11 WTC attack or since the WTC fires ended. See Figure 13, for example, where post September 11 PM2 5 24-h values for PS 64 are compared to historic levels seen at PS 64 during the previous two years.

(3) No notable elevations in PM2 5 concentrations were seen at NYSDEC lower Manhattan sites located 3-10 blocks to the north, east, and south from the WTC, with no PM2 5 values exceeding either the PM2 5 daily NAAQS or the AQI LOC from the start-up of PM monitoring on October 1 onward.

2. Measurements ofParticle Composition Analyses of bulk samples of dust produced by the collapse of the WTC towers were performed by EOHSI at Rutgers University (Lioy et al., 2002). Two bulk dust samples were collected on September 16 and another on September 17. The samples were collected at weather-protected sites located less than 1 km to the east of the WTC. The particle samples were separated according to size by aerodynamic and gravimetric methods. As noted earlier, results of the aerodynamically separated samples indicate that only a very small fraction (about 1%) of PM was in the PM25 size range and less than 0.5% was in the PM,0.2.5 size range. The overwhelming fraction of the mass of PM was found in settled dust particles larger than 10 gm. Most of the mass consisted of pulverized building and construction materials such as cement and glass fibers and office building materials such as cellulose. High concentrations of inorganic constituents such as silica, calcium, and sulfate components of building material and metals such as lead and zinc, were found. Also, total polycyclic aromatic hydrocarbons (PAHs), which are products of incomplete combustion, constituted more than 0.1% of the total mass of dust. The fraction of adsorbed PAHs in each size fraction is expected to be roughly related to the relative surface area in each size fraction. According to this criterion, smaller particles would have contained proportionately greater concentrations of PAHs than indicated by their relative

DRAFT-DO NOT QUOTE OR CITE 32 October 2002

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