VOC sampling locations table for Ground Zero area, Jan 2002

NYC 9/11 Public Portal Document

and at the 290 Broadway site, in contrast with coarse (PM,0.2.5) silicon elevations (generally in the 1000-3000 ng/m’ range) seen at 290 Broadway on a number of days well into late November. The coarse fraction calcium and silicon enrichments most likely reflect (a) windblown re-entrainment of calcium and silicon-contaminated dust remaining on rooftops or window ledges, for example, after hazardous material cleanup of WTC-derived dust in lower Manhattan during the two weeks after September 11, and/or (b) calcium and silicon particle re-entrainment into ambient air associated with WTC recovery operations and transport of debris away from Ground Zero.

Data for concentrations of elemental carbon and total organic compounds in the aerosol phase based on analyses of paired filter samples are not yet available. However, ORD nephelometer results and the results of analyses of bulk dust composition mentioned below suggest that the WTC emissions contained substantial quantities of carbon produced by incomplete combustion. Surprisingly low total carbon levels (1.5 to 8.5%) were found in aerodynamically size-separated PM2 5 samples from the bulk dust samples collected on September 12 and 13 (McGee et al., 2002). These results indicate that crushed building materials were the dominant sources of fine PM immediately after the collapse of the towers, whereas combustion from ongoing fires was a relatively more important source of PM2 5 in later emissions from the WTC disaster site. Potassium enrichments were also especially notable for ORD Site A measurements into early October (consistent with combustion of organic materials such as wooden furniture, paper, etc.); but much lower potassium concentrations occurred at 290 Broadway, and air levels of potassium at all ORD sites returned to very low background levels by late November.

Elevations of sulfur, chlorine, and bromine (shown in Figure 15) were clearly evident at ORD Groimd Zero perimeter sites and sometimes at 290 Broadway during late September and decreasingly so into October, again consistent with the notable enrichments seen by Lioy et al. in WTC dust particles. The sulfur was likely in oxidized form, some perhaps having been converted from primary emissions of SO2 into secondary sulfate particles, consistent again with both reports of elevated sulfate levels in settled WTC dust particles (Lioy et al., 2002; McGee et al., 2002) or airborne particles (including very fine fraction particles) collected at the DOE Varick St. site on October 3 (Cahill et al., 2002). Also consistent with the Lioy et al. findings of chlorine and bromine enrichments in WTC settled dust are ORD measurements of unusually elevated chlorine and bromine at Ground Zero perimeter sites. The WTC sources of these halides are not clear, but chlorine from burning plastics is not unlikely. The specific enrichment in fine particles of chlorine (versus more typical sodium chloride present as coarse particles) and no notable sodium enrichment rule out attribution of the chlorine levels simply to airborne sea salt influxes into the WTC fire site.

As seen in Figures 16-18, lead and certain other metals (copper, zinc, antimony, palladium, and cadmium) were notably elevated on some days in late September and into early October at EPA/ORD Site A, as compared with concentrations at Sites C and K, but the concentrations of these metals had generally decreased to background levels by mid-October. The late September/early October, elevations at Site A on the WTC north perimeter indicate that the WTC fires were likely a common source of emissions of these metals, because the winds were mainly from the southwest at this time. The detection of elevated levels of arsenic and

DRAFT-DO NOT QUOTE OR CITE 34 October 2002

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