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CONCENTRATIONS AND SPECIATION OF PM AT GROUND ZERO AND LOWER MANHATTAN FOLLOWING THE COLLAPSE OF THE WTC
Citation:
Vette, A F., M S. Landis, R W. Williams, D. LaPosta, M. Kantz, J. Filippelli, L. Webb, T G. Ellestad, AND D A. Vallero. CONCENTRATIONS AND SPECIATION OF PM AT GROUND ZERO AND LOWER MANHATTAN FOLLOWING THE COLLAPSE OF THE WTC. Presented at International Society of Exposure Analysis 2002 Conference, Vancouver, Canada, August 11-15, 2002.
Impact/Purpose:
The primary study objectives are:
1.To quantify personal exposures and indoor air concentrations for PM/gases for potentially sensitive individuals (cross sectional, inter- and intrapersonal).
2.To describe (magnitude and variability) the relationships between personal exposure, and indoor, outdoor and ambient air concentrations for PM/gases for different sensitive cohorts. These cohorts represent subjects of opportunity and relationships established will not be used to extrapolate to the general population.
3.To examine the inter- and intrapersonal variability in the relationship between personal exposures, and indoor, outdoor, and ambient air concentrations for PM/gases for sensitive individuals.
4.To identify and model the factors that contribute to the inter- and intrapersonal variability in the relationships between personal exposures and indoor, outdoor, and ambient air concentrations for PM/gases.
5.To determine the contribution of ambient concentrations to indoor air/personal exposures for PM/gases.
6.To examine the effects of air shed (location, season), population demographics, and residential setting (apartment vs stand-alone homes) on the relationship between personal exposure and indoor, outdoor, and ambient air concentrations for PM/gases.
Description:
The U.S. EPA National Exposure Research Laboratory (NERL), in conjunction with our Regional offices, established a network of air monitoring sites to characterize ambient air concentrations of gases and particles in lower Manhattan following the collapse of the World Trade Center (WTC). Monitoring at these sites was conducted on a daily basis from September 21, 2001 through February, 2002. Integrated 24-hour PM2.5 concentrations and continuous measurements of PM concentrations were made at three ground-level sites within 100-200 m of the WTC (Ground Zero). The Ground Zero sites triangulated the WTC in order to characterize both upwind and downwind concentrations. Another monitoring site was located about 500 m from Ground Zero on the 16th floor of a building at 290 Broadway. Measurements at this site included integrated 24-hour PM2.5 and PM10 concentrations as well as continuous PM and black carbon concentrations. The integrated PM2.5 and PM10 aerosols collected at these sites were analyzed for mass concentrations as well as elemental composition using X-ray fluorescence (XRF). In early October, 2001 two additional sites located about 500-1000m from Ground Zero were equipped to measure airborne concentrations of 17 dioxin and furan congeners. Concentrations of PM2.5 surrounding Ground Zero were elevated and highly variable through late October, 2001. In general, concentrations of PM2.5 during this period were highest at the Ground Zero site located north of the WTC (96 ? 85 ug/m3; mean ? SD) and lowest at the southeast site (36 ? 18 ug/m3). Concentrations of PM2.5 at the 290 Broadway site (25 ? 22 ug/m3) were generally lower than those measured at Ground Zero through late October, 2001. Beginning in November, 2001, levels of PM2.5 decreased and were generally similar at the Ground Zero sites, but still somewhat higher than those measured at 290 Broadway. Dioxin and furan concentrations at a site located north of the WTC behaved similarly with elevated concentrations observed during October, 2001 that decreased and stabilized beginning in November, 2001. Analysis of the elemental composition of PM2.5 aerosols indicated elevated concentrations of crustal elements generally associated with building materials (e.g. Ca, Si, and K.) suggesting that concrete and other building materials were pulverized. In addition, elevated concentrations of Pb were observed initially as were elements normally associated with iron and steel (Fe, Cr, Ni and Mn). Typically, PM2.5 levels at 290 Broadway were similar to upwind concentrations measured at Ground Zero indicating the regional background contribution to PM2.5. However, when downwind of the plume, PM2.5 levels measured at 290 Broadway were considerably higher, a possible indication that the site was being impacted by the WTC plume. For example, the maximum integrated 24-hour PM2.5 concentrations were measured at Ground Zero (403 ug/m3) and 290 Broadway (100 ug/m3) during one such plume event. The event occurred in the early morning and was characterized by a peak in the 5-min. PM concentration of 1000 ug/m3 and a black carbon concentration of 180 ug/m3.
This work has been funded wholly or in part by the United States nvironmental Protection Agency under contract #68-D-00-206 to Mantech International. It has been subjected to Agency review and approved for publication.