Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: implications for oxidation of intermediate volatility organic compounds (IVOCs)

Abstract

Abstract. Current atmospheric models do not include secondary organic aerosol (SOA) production from gas-phase reactions of polycyclic aromatic hydrocarbons (PAHs). Recent studies have shown that primary emissions undergo oxidation in the gas phase, leading to SOA formation. This opens the possibility that low-volatility gas-phase precursors are a potentially large source of SOA. In this work, SOA formation from gas-phase photooxidation of naphthalene, 1-methylnaphthalene (1-MN), 2-methylnaphthalene (2-MN), and 1,2-dimethylnaphthalene (1,2-DMN) is studied in the Caltech dual 28-m 3 chambers. Under high-NO x conditions and aerosol mass loadings between 10 and 40 µg m −3 , the SOA yields (mass of SOA per mass of hydrocarbon reacted) ranged from 0.19 to 0.30 for naphthalene, 0.19 to 0.39 for 1-MN, 0.26 to 0.45 for 2-MN, and constant at 0.31 for 1,2-DMN. Under low-NO x conditions, the SOA yields were measured to be 0.73, 0.68, and 0.58, for naphthalene, 1-MN, and 2-MN, respectively. The SOA was observed to be semivolatile under high-NO x conditions and essentially nonvolatile under low-NO x conditions, owing to the higher fraction of ring-retaining products formed under low-NO x conditions. When applying these measured yields to estimate SOA formation from primary emissions of diesel engines and wood burning, PAHs are estimated to yield 3-5 times more SOA than light aromatic compounds over photooxidation timescales of less than 12 h. PAHs can also account for up to 54% of the total SOA from oxidation of diesel emissions, representing a potentially large source of urban SOA.

The influence of semi-volatile and reactive primary emissions on the abundance and properties of global organic aerosol

“…The yield, when compared at a C OA of 1 µg m −3 , is much higher than the aerosol mass yields observed for biogenic VOCs like alpha-pinene (4 %) and isoprene (1 %) in smog chamber experiments (Farina et al, 2010). However, the yield is similar to those of aromatics like benzene (33 %) and naphthalene (66 %) (Ng et al, 2007;Chan et al, 2009). Hence, the mechanism used in this work to represent the gas-phase chemistry of POC would be similar to a traditional mechanism, which treated all POC like aromatics.…”

Naphthalene SOA: redox activity and naphthoquinone gas–particle partitioning

“…For example, it has been estimated that naphthalene, 1-and 2-methylnaphthalene, acenaphthalene and acenaphthylene from mobile sources could contribute 37-162 kg m −3 d −1 of SOA in Houston, Texas, compared to a total SOA estimate of 268 kg m −3 d −1 from mobile sources, with a substantial fraction (36-48 %) of the PAH SOA mass coming from naphthalene oxidation (Shakya and Griffin, 2010). For diesel exhaust, it was estimated that of SOA production from oxidation of light aromatics, PAHs, and long-chain alkanes, 58 % of the aerosol produced arises from PAH precursor species (Chan et al, 2009). With a significant amount of naphthoquinone production from naphthalene oxidation and sufficient organic aerosol mass loading available for gas-particle partitioning, naphthoquinones may have a significant impact in terms of the redox behaviour and toxicity of ambient particles.…”

“…To correct for particle bounce due to the low relative humidities used in the experiments, a collection efficiency of 0.5 was used for all AMS data. To verify the suitability of this choice, AMS mass loadings were compared to mass loadings calculated from SMPS-measured particle volumes using a particle density of 1.55 g cm −3 (Chan et al, 2009); good agreement between the two values was obtained using 0.5 as the AMS collection efficiency.…”

“…To start with as simple a system as possible by using only one SOA precursor, naphthalene was chosen for its ability to form aerosol in relatively high yield -particularly under low NO x conditions (Chan et al, 2009) -which was advantageous for the small size of our photoreaction chamber. The mass spectrum of the SOA generated in the chamber was fairly invariable from day-to-day and consisted mostly of hydrocarbon (C x H y ) and oxidised hydrocarbon (C x H y O z ) fragments; elemental composition information is given in Table 2, as obtained using established methods (DeCarlo et al, 2006;Aiken et al, 2007), and the average AMS mass spectrum from two representative experiments is shown Table 2.…”

“…They may also be produced as secondary products of polycyclic aromatic hydrocarbon (PAH) oxidation. Naphthalene (Bunce et al, 1997;Chan et al, 2009;Kautzman et al, 2010;Lee and Lane, 2009;Sasaki et al, 1997), phenanthrene (Lee and Lane, 2010;Wang et al, 2007), and anthracene (Kwamena et al, 2006) all generate their corresponding quinone species (naphthoquinone, phenanthrenequinone, and anthraquinone, respectively) via reaction with gas-phase oxidants. Formation of these species from PAH precursors in the atmosphere could increase the redox activity of ambient particles during photochemical aging in locations with PAH emission sources.…”