An outdoor smog chamber and modeling study of toluene–NO_x photooxidation

Abstract

An experimental investigation of the gas-phase photooxidation of toluene-NO,-air mixtures a t part-per-million concentrations has been carried out in a 6B-m3, outdoor smog chamber to assess our understanding of the atmospheric chemistr,y of toluene. In addition, six CO-NO,-air irradiations were conducted to characterize the chamber with regard to any wall radical sources. Measured parameters in the toluene-NO, experiments included 0 3 , NO, NO,, HN03, peroxyacetyl nitrate (PAN), CO, toluene, benzaldehyde, o-cresol, m-nitrotoluene, peroxybenzoyl nitrate (PBZN), temperature, relative humidity, aerosol size distributions, and particulate organic carbon. Predictions of the reaction mechanism of Leone and Seinfeld [71 are found to be in good agreement with the data under a variety of initial conditions. Additional simulations are used to investigate various mechanistic pathways in areas where our understanding of toluene chemistry is still incomplete.

Formation of ring‐retaining products from the OH radical‐initiated reactions of benzene and toluene

“…The ring-retaining products observed in this work have been previously reported from several studies [8,9,11,12,15,16,18-21, 23,24,27]. For benzaldehyde, the present formation yield is in reasonable agreement with those of Atkinson et al [15,19], Shepson et al [20), Leone et al [23], Bandow et al [24], and Gery et al [27]. The benzaldehyde yields reported by Spicer and Jones [8] and O'Brien et al [ll] are widely divergent and must be judged to be incorrect.…”

“…The formation of the cresol isomers has been reported previously [8,9,11,12,15,16,19,20,23,27], although, as in this work, m-+ p-cresol Nitrotoluenes have been identified as products of the OH radical reaction with toluene under simulated atmospheric conditions in several previous studies [9,12,15,21,23,27] (in some of these studies, only m-nitrotoluene was reported [ 15,231). Hoshino et al [9] observed m-and p-nitrotoluene, but no o-nitrotoluene, with the p-nitrotoluene yield generally being less than that of the m-nitrotoluene isomer.…”

Design and characterization of a smog chamber for studying gas-phase chemical mechanisms and aerosol formation

“…Smog chambers were initially constructed for developing and evaluating atmospheric gasphase chemical mechanisms or models for predicting secondary pollutants (Akimoto et al, 1979;Carter et al, 1982;Jeffries et al, 1982Jeffries et al, , 1985. In the mid-1980s, Seinfeld and colleagues at the California Institute of Technology in Pasadena developed a 65 m 3 outdoor chamber made of fluorinated ethylene propylene (FEP) Teflon film to study the aerosol formation from gas-phase precursors such as aromatic and biogenic hydrocarbons (Leone et al, 1985;Stern et al, 1987). In the subsequent three decades, outdoor and indoor chambers have been widely used to study formation of secondary pollutants such as ozone (Hess et al, 1992;Simonaitis et al, 1997;Carter, 2000;Dodge, 2000) and secondary organic aerosols (SOA) (Odum et al, 1996,Paulsen et al, 2005Rollins et al, 2009) and evolution of SOA (Donahue et al, 2012).…”

“…Many simulation experiments on SOA formation have been carried out in large outdoor chambers (Leone et al, 1985;Stern et al, 1987;Pandis et al, 1991;Johnson et al, 2004;Martín-Reviejo and Wirtz, 2005;Rollins et al, 2009). However, diurnal variations of the actinic flux and temperature make it difficult to model experimental data and to reproduce the experiments.…”

Assessing the degree of plug flow in oxidation flow reactors (OFRs): a study on a potential aerosol mass (PAM) reactor

“…Accurate kinetic measurements were possible due to the high pipe aspect ratios, which encouraged a high degree of plug flow behavior (Keyser, 1984). The design of these miniature tubular reactors, with volumes on the order of a few cm 3 , was different from that of significantly larger, batch-type or semi-continuous type well-mixed reactors, with volumes on the order of several m 3 , built to understand aerosol formation in the troposphere (Crump et al, 1982;Crump and Seinfeld, 1980;Leone et al, 1985). To study aerosol formation and growth chemistry, the dynamics of atmospheric circulation and transport needed to be excluded.…”