James N. Pitts

Mutagens in diesel exhaust particulate identification and direct activities of 6-nitrobenzo[a]pyrene, 9-nitroanthracene, 1-nitropyrene and 5H-phenanthro[4,5-bcd]pyran-5-one

Organic extracts of ambient particulate matter are directly mutagenic in the Ames Salmonella assay (Pitts et al., 1975, 1977a, b; Talcott and Wei, 1977; Tokiwa et al., 1977; Chrisp and Fisher, 1980; Hoffmann et al., 1980) with the activity concentrated in particles < 1 #m in diameter (i.e., in the respirable size range) (Pitts et al., 1978a, b; Pitts, 1979; Talcott and Harger, 1980). Thus the rapidly increasing use of diesel engines in light-duty motor vehicles is of concern (NAS, 1980) because they emit high levels of respirable particulate organic matter (POM) which will significantly increase the existing atmospheric burden of POM. As with ambient particles, organic extracts of this diesel POM not only contain carcinogenic and promutagenic PAH such as benzo[a]pyrene (BP) (NAS, 1972), but also chemicals which are strong, direct** mutagens in the Ames test (Huisingh et al., 1978; NAS, 1980; Pepelko et al., 1980). Currently, this direct activity cannot be explained by the presence of any known carcinogens and attention is being focussed on nitroarenes as possible major contributors (NAS, 1980; Rosenkranz et al., 1981; Mermelstein et al., 1981). Certain members of this chemical class (e.g., l-nitropyrene) are strong, direct mutagens and have been found (or tentatively identified) in POM from ambient air (J~iger, 1978; Wang et al., 1980), simulated atmospheres (Pitts et al., 1978, b; Pitts, 1979), carbon black used in toners (LOfroth et al., 1980; Rosenkranz et al., 1980) and typewriter ribbons (Alfheim et al., 1981), and diesel exhaust particulate (Pederson and Siak,

Determination of 2-nitrofluoranthene and 2-nitropyrene in ambient particulate organic matter: Evidence for atmospheric reactions

Abstract We have identified and quantified 2-nitrofluoranthene (2-NO2-FL) and 2-nitropyrene (2-NO2-PY), both strong, direct mutagens in paniculate organic matter (POM) samples collected in polluted ambient air in southern California. Samples were collected during four consecutive 6-h periods on 18–19 September 1984, during which the ambient concentrations of gaseous co-pollutants were characterized by long pathlength spectroscopic techniques and conventional analyzers. Concentrations ranged up to 0.3 ng m−3 for 2-NO2-FL and 0.02 ng m−3 for 2-NO2-PY. The 2-nitro isomers of fluoranthene and pyrene have not been observed in direct emissions of POM (e.g. diesel exhaust and wood smoke). However, we recently observed these isomers from laboratory reactions involving N2O5 or OH radicals and the parent compounds. Thus the identification of 2-NO2-FL and 2-NO2-PY in ambient POM suggests that chemical transformations of fluoranthene and pyrene may take place in polluted atmospheres.

Spectroscopic identification and measurement of gaseous nitrous acid in dilute auto exhaust

We report here the direct spectroscopic detection of gaseous nitrous acid (HONO) in exhaust emissions from certain light duty motor vehicles (LDMV). Co-pollutants such as nitrogen dioxide (NO2), formaldehyde (HCHO), benzaldehyde (C6H5CHO) and sulfur dioxide (SO2) were also readily determined. Nitric oxide (NO) was measured too, but with reduced accuracy. To avoid possible artifactual formation of HONO on the surfaces of conventional dilution and sampling systems (e.g. Federal and California constant volume sampling systems), an instrument was developed consisting of a multiple reflection cell without walls coupled to a u.v. differential optical absorption spectrometer (DOAS), the entire system being placed in the open air ~ 2 m from the tailpipe of the LDMV. At an optical path of 31.2 m, detection limits (in parts per 109, ppb) were: HONO-12; HCHO-78; C6H5CHO-13; NO2-57; and SO2-11. With this instrument, HONO levels observed in diluted exhaust ranged from nondetectable (< 12 ppb) for a 1982 California car with an effective 3-way catalyst (and associated low NOx emissions), to ~ 300 ppb for a heavily used 1974 station wagon having high NOx emissions and run on leaded gasoline. While the number of LDMV tested was too small for statistical treatment, our results show that the older portion of the total LDMV population (i.e. without current emission control devices) may be a significant primary source of gaseous HONO, a key precursor to photochemical air pollution and an inhalable nitrite.

A Possible formation pathway for the 2-nitrofluoranthene observed in ambient particulate organic matter

Abstract The reaction of N2O5 with gaseous fluoranthene has been shown to be a possible formation pathway for the 2-nitrofluoranthene observed in ambient particulate organic matter.

Temperature dependence of the unimolecular decomposition of pernitric acid and its atmospheric implications

Abstract The decay of pernitric acid (HO 2 NO 2 ) in the presence of excess nitric oxide has been studied in a 5800-liter, Teflon-lined chamber over the temperature range 254 to 283 K at 1 atm pressure of N 2 by Fourier transform infrared spectroscopy. A heterogeneous reaction of NO 2 and H 2 O 2 was used to generate HO 2 NO 2 with less than 20% HNO 3 and less than 5% NO 2 present as impurities. The HO 2 NO 2 had lifetimes of 5 to 20 h in our chamber, presumably determined by heterogeneous loss to the walls. Two paths have been proposed for the reaction of NO 2 with HO 2 : (1), NO 2 + HO 2 → HONO + O 2 (2). In this study the ratio k 1 / k 2 was calculated to be greater than 10 3 throughout the temperature range studied. The homogeneous unimolecular decay of the HO 2 NO 2 , reaction (3), was investigated by adding excess NO in order to remove HO 2 by reaction (4). (3), HO 2 + NO → NO 2 + OH (4). The rate constant k 3 was determined to be 1.4 × 10 14 exp(−20700 ± 500/ RT )s −1 . The thermal decomposition lifetimes of HO 2 O 2 at 1 atm total pressure calculated from k 3 are 12 s at 298 K, 5 min at 273 K and 1 month at 220 K. Implications of these results for the role of pernitric acid in the lower and upper atmosphere are discussed.

The gas-phase reaction of naphthalene with N2O5 to form nitronaphthalenes

Abstract While the formation of nitroarenes from the reaction of NO 2 , containing traces of HNO 3 , in air with polycyclic aromatic hydrocarbons (PAH) adsorbed on combustion generated particles is now well recognized, little is known about the gas-phase reactions of PAH. In this study, the gas-phase reactions in air of N 2 O 3 with part-per-million levels of naphthalene have been studied at room temperature and atmospheric pressure in a 5800V Teflon-coated environmental chamber. The kinetic data obtained showed that in these N 2 O 5 -NO 3 -NO 2 -air mixtures studied, naphthalene did not react with the NO 3 radical at an observable rate, but that it reacted with N 2 O 5 with a rate constant of ~ (2–3) × 10 −17 cm 3 molecule −1 s −1 . Significant yields of 1-nitronaphthalene and 2-nitronaphthalene ( ~ 18 and ~ 7.5%, respectively) were obtained from this reaction. The latter is a procarcinogen capable of being metabolized in animals to the carcinogen β-naphthylamine. These results and their atmospheric implications are discussed.

Pressure and temperature dependence of the unimolecular decomposition of HO2NO2

The pressure and temperature dependence of the unimolecular decomposition of pernitric acid HO2NO2→NO2+HO2 have been studied in the presence of excess nitric oxide by Fourier transform infrared spectroscopy in a 5800 liter, Teflon‐lined chamber over the temperature range 261 to 295°K with N2 or O2 pressures between 1 and 760 torr. The rate constant in the second‐order kinetic regime was determined to be 5.2×10−6 exp[−19 900±500/RT] cm3 molecule−1 sec−1 for N2 pressures up to ∼7 torr. The pressure dependence of the reaction between the second‐order region and 1 atm pressure was determined for N2 and O2 at 278°K and for N2 at 261°K and fitted to an empirical rate constant expression for use in atmospheric modeling calculations. Extrapolation of the data at 278°K gave a limiting first‐order high pressure rate constant of ∼0.018 sec−1. The relative efficiency of O2 as an M gas relative to N2 (1.0) between 1 and 760 torr was 0.83±0.12. The implications of these results for the reaction of HO2 with NO2 and for ...

Effects of Wavelength and Temperature on Primary Processes in the Photolysis of Nitrogen Dioxide and a Spectroscopic—Photochemical Determination of the Dissociation Energy

The quantum yields of oxygen production in the photolysis of nitrogen dioxide have been determined at a series of wavelengths at room temperature and as a function of temperature at 3660, 4047, and 4358 A. These values were satisfactorily correlated with the extent of dissociation into NO and O atoms by means of 18–18O2 tracer techniques. On the basis of the above correlation and inert gas experiments, a general mechanism is proposed for the photolysis of NO2 from 3130 to 4047 A. Temperature effects are discussed in terms of a theoretical calculation based on the population of the rotational energy levels of NO2. This leads to a spectroscopic—photochemical determination of the dissociation energy of NO2 in good agreement with that calculated from thermodynamic data.

Factors influencing the reactivity of polycyclic aromatic hydrocarbons adsorbed on filters and ambient POM with ozone

Abstract Five polycyclic aromatic hydrocarbons (PAH), pyrene (PY), fluoranthene (FL), benz(a)anthracene (BaA), benzo(a)pyrene (BaP), and benzo(e)pyrene (BeP) adsorbed on glass fiber (GF) and Teflon impregnated glass fiber (TIGF) filters and on ambient particulate organic matter (POM) were exposed to ozone (50–300 ppb) passively in a 360-liter Teflon chamber and actively in a flow system. The influence of ozone concentration, exposure time and relative humidity (RH) on the degree of degradation of these PAH was established. The most reactive PAH both on filters and in ambient POM were PY, BaA and BaP. Up to 50–80% of these PAH degraded in 3-hr exposures to 200 ppb of ozone at ∼1% RH; in a flow system, most of the degradation occurred within the first 10 minutes of exposure. With the exception of BaP, the degradation of the PAH tested on GF and TIGF filters were much lower at 50% RH than at 1% RH, whether they were exposed to ozone in an active or passive mode. Interestingly, RH did not significantly affect the reactivity of PAH present in ambient POM passively exposed to ozone. Our results show that PAH are susceptible to ozone degradation under many typical atmospheric conditions.

Evidence for alkoxy radical isomerization in photooxidations of C4C6 alkanes under simulated atmospheric conditions

Abstract We have calculated approximate room temperature rate constants for intramolecular hydrogen shift isomerizations of alkyl, alkoxy and alkylperoxy radical intermediates in photochemical smog and found that alkoxy radicals with δ hydrogens appear to undergo 1,5 hydrogen shifts at ambient conditions. Product distributions observed during irradiations of alkane (n-butane, n-pentane and n-hexane)NOxair systems in two quite-different ≈6000-liter environmental chambers were found to be consistent with this prediction. For example, in the n-pentaneNO xair system the observed large yields of 3-pentanone relative to 2-pentanone were consistent with room temperature rate constants which we have estimated for the corresponding hydrogen shift isomerizations. While such isomerizations have been well recognized in studies of free radicals and high temperature hydrocarbon oxidations, they are not taken into account in current kinetic mechanisms for alkane oxidation under ambient atmospheric conditions. This has implications for the construction of computer models of photo-chemical smog formation.