Health Assessment Document for Diesel Emissions - NSCEP | US ...
Health Assessment Document for Diesel Emissions - NSCEP | US ...
Health Assessment Document for Diesel Emissions - NSCEP | US ...
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1 polarity, more than 65% of the mutagenic activity <strong>for</strong> HDD particulate extract is concentrated in<br />
2 the most polar fraction. However, because of the serious analytical difficulties, only preliminary<br />
3 data exist on the identification of compounds that are responsible <strong>for</strong> the mutagenic activity of<br />
4 this fraction (so-called "polar mutagens"). Schuetzle and co-workers (1985) employed the<br />
5 concept of"bioassay directed chemical analysis" (see Section 2.6) <strong>for</strong> the isolation and<br />
6 identification of polar P AH derivatives from the extracts of HDD particulate matter (National<br />
7 Institute of Standards and Technology [NIST] standard reference material SRM 1650). Several<br />
8 hydroxynitro-PAHs, hydroxy-PAHs, and nitrated heterocyclic compounds were tentatively<br />
9 identified in the polar fraction. It has to be noted, however, that NIST SRM.1650 was not<br />
10 intended to be representative ofHDD engines but was a material made available to investigators<br />
11 <strong>for</strong> the purpose of methods development.<br />
12 In another study (Bayona et al., 1988), the polar HPLC fractions ofthe same NIST SRM<br />
13 1650 were analyzed by fused silica capillary GC with low- and high-resolution mass MS, using ·<br />
14 electron impact (EI) and negative ion chemical ionization (NICI) techniques. In addition, direct-<br />
15 probe EI and NICI-MS analyses were per<strong>for</strong>med. More than 80 polycyclic aromatic compounds<br />
16 (PAC) belonging to several different chemical classes (anhydrides, carboxaldehydes, diazaarenes,<br />
17 cyclic imides, hydroxynitro-PAH, nitroaza-PAC, nitrolactones, and quinones) were tentatively.<br />
18 identified. Ten were positively identified by comparison ·of retention times with authentic<br />
19 standards. Among them, phenazine and phthalic anhydride were positively identified <strong>for</strong> the first<br />
20 time in diesel exhaust particles. In addition, cyclic imides and their alkylated derivatives were<br />
21 tentatively identified.<br />
22<br />
23 2.3.3. Gaseous-/Particulate-Phase Emission Partitioning of Polycyclic Aromatic<br />
24 Hydrocarbons<br />
25 The distribution of the emissions between the gaseous and particulate phases is<br />
26 determined by the vapor pressure of the individual species, by the amount and type of the<br />
27 particulate matter present (adsorption surface available), and by the temperature (Ligocki and<br />
28 Pankow, 1989). Table 2-11 gives the vapor pressures at 25 oc of some representative PAHs<br />
29 ranging from naphthalene to benzo[ a ]pyrene.<br />
30 The factor of"' 10 7 in the range of vapor pressures is reflected in the fact that, at<br />
31 equilibrium at ambient temperature, naphthalene exists almost entirely in the gas phase, whereas<br />
32 B [a ]P, other five-ring P AHs, and higher-ring P AHs are predominantly adsorbed on particles.<br />
33 The intermediate three- and four-ring P AHs are distributed between the two phases.<br />
34 However, the vapor pressures of these intermediate P AHs can be significantly reduced by<br />
35 their adsorption on various types of surfaces. Because of this phenomenon, the amount and type<br />
2/1198 2-23 DRAFT--DO NOT CITE OR QUOTE