NYC-WTC_000232959

NYC 9/11 Public Portal Document

curve and other methodological interference. Therefore, these data will only be considered semiquantitative and should be treated as estimated values, noted by the “J” qualifier.

Due to changes in sample volume, the detection limit of minerals in each fraction varied, allowing lower concentrations to be recorded in the PMIO and PMIOO fractions compared to the PM4 fraction. Care must be taken when comparing results between fractions for this reason. Additionally, although the PM4 fraction should be a subset of the PMIO and PMIOO fractions, PM4 results are sometimes higher than PMIO or PMIOO from the same location. Therefore, due to uncertainties in the quantification and general quality assurance/quality control concerns, data will not be associated to a specific building sampling location or correlated between size fractions at the same location.

The comparison air samples, taken in areas above 59th Street, contained no quartz, cristobalite, tridymite, calcite, portlandite, mica, or halite above method detection hmits (Table 11). Gypsum was found at least once in all size fractions collected in the comparison areas above 59th Street. Gypsum concentrations were estimated at 3 ug/m\l (PM2.5), 5 ug/m\l (PM4), 3 ug/mil (PMIO), and 3 ug/mj (PMIOO) (Table 11).

All of the minerals found in the settled surface dust were seen in at least one air sample from lower Manhattan (Table 11). Quartz, calcite, portlandite, and gypsum were detected at similar frequencies in each of the larger size fractions, PMIOO, PMIO, and PM 4. Table 11 shows the frequency of detection and the range of estimated values for each size fraction sampled. Quartz and gypsum were each detected once in the PM 2.5 fraction. The PM 2.5 size fraction was only collected toward the end of the project, and there are fewer samples for this size fraction.

Approximate quartz levels in air ranged from 4 ug/rn' 19 ug/m',1 in the respirable fraction (PM4), Estimated levels of minerals in 3 Lig/n? 12 pg/m^J in the thoracic fraction (PMIO) air, including quartz, calcite, and 3 ug/n? 13 pg/rn^J in the inhalable fraction gypsum, and portlandite, appear (PMIOO). Detection frequencies were similar in higher in some areas of lower these fractions at 11%, 10%, and 14% respectively. Manhattan than in the However, quartz was only seen in one of the PM2.5 comparison areas above 59th samples (3%) at an estimated 3 ug/m\l. Cristobalite, Street. a different crystalline form of crystalline silica, was found in one lower Manhattan air sample at 15 ug/m)l in the PMIOO fraction. Cristobalite was not seen in any other sample, either air or settled surface dust. Across the size fractions, quartz was detected in air samples taken in lower Manhattan; it was not detected in the comparison areas above 59th Street. Therefore, the estimated airborne levels of quartz appear to be higher in some air samples from lower Manhattan than the chosen comparison areas above 59th Street.

Similar observations can be seen in the results for calcite and portlandite. Calcite and portlandite occur at a similar frequency to quartz (Table 11) and tend to be present in the same air samples (Appendix C.) Both minerals are present in PM4, PMIO, and PMIOO size fractions. Calcite was estimated at 3 ug/m\l 14 pg/rn^J and portlandite at 14 pg/m^J-95

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