NYC-WTC_000232959

NYC 9/11 Public Portal Document

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

Quartz, calcite, portlandite, and gypsum were the most abundant minerals detected (see Table 7). Mica was detected with less frequency than the other minerals, and generally estimated at approximately 0.1% J of the dust. Halite (salt) was also detected at trace levels.

Quartz was detected in all 14 outdoor dust samples, 21 of the 26 common area samples, and only 30 of the 57 samples from Mineral components of concrete residences in lower Manhattan. Neither (quartz calcite, and portlandite) and cristobalite nor tridymite, other forms of other building materials (gypsum, crystalline silica, were found in any of the mica, and halite) in the indoor settled settled surface dust samples. For this surface dust of some areas of lower discussion quartz will refer to the alpha- Manhattan were estimated at higher quartz form of crystalline silica. Levels of percentages than for the comparison quartz were estimated as from 0.05%J to areas above 59th Street. 31%J in residences, and from 0.03%J to 25%J in common areas. Estimated quartz content in outdoor samples ranged from 1%J to 27%J. Because quartz is a common material (i.e., silica sand), finding this mineral in the city where there is a lot of concrete building material is not unusual. However, quartz in dust from the comparison areas above 59th Street was estimated from nondetect to 1%J in the common areas and from nondetect to 2%J in the residences. Figure 16 shows the locations where the estimated maximum quartz content in settled surface dust was greater than or similar to estimated quartz content in the dust samples from the comparison areas above 59th Street. Fifteen residences, six common areas, and 12 outdoor areas had estimated quartz levels higher than the associated comparison areas above 59th Street. Therefore, quartz was elevated in some indoor areas of lower Manhattan relative to the comparison areas above 59th Street. Outdoor dust samples were not taken from the comparison areas, due to insufficient amounts of dust. Figures 13-16 compare the indoor and outdoor locations in lower Manhattan to the indoor samples above 59th to show the relative distribution of the minerals.

Calcite (calcium carbonate) and portlandite (calcium hydroxide) are also components of concrete. They occurred with similar frequency in the dust samples and were often co­ located with the quartz. Calcite ranged from an estimated 0.8% J to 19% J in outdoor areas, and from 0.02%J to 21%J in indoor areas. Portlandite ranged from an estimated 0.07%J to 6%J in outdoor areas and from 0.04%J to 8%J in indoor areas. In contrast, the maximum levels found in indoor comparison areas above 59th Street were 0.9%J calcite and 0.08%J portlandite. Figures 13 and 15 show the locations where the estimated calcite and portlandite content in settled surface dust was higher than to that estimated in dust samples from the comparison areas above 59th Street. For calcite, 13 residence and 9 common area samples had estimated levels higher than those found in the comparison areas above 59th Street. Similarly for portlandite, 17 residence and 9 common area samples were estimated

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