Identification and Quantification of 4-Nitrocatechol Formed from OH and NO₃ Radical-Initiated Reactions of Catechol in Air in the Presence of NO_x: Implications for Secondary Organic Aerosol Formation from Biomass Burning

Abstract

Catechol (1,2-benzenediol) is emitted from biomass burning and produced from a reaction of phenol with OH radicals. It has been suggested as an important secondary organic aerosol (SOA) precursor, but the mechanisms of gas-phase oxidation and SOA formation have not been investigated in detail. In this study, catechol was reacted with OH and NO radicals in the presence of NO in an environmental chamber to simulate daytime and nighttime chemistry. These reactions produced SOA with exceptionally high mass yields of 1.34 ± 0.20 and 1.50 ± 0.20, respectively, reflecting the low volatility and high density of reaction products. The dominant SOA product, 4-nitrocatechol, for which an authentic standard is available, was identified through thermal desorption particle beam mass spectrometry and Fourier transform infrared spectroscopy and was quantified in filter samples by liquid chromatography using UV detection. Molar yields of 4-nitrocatechol were 0.30 ± 0.03 and 0.91 ± 0.06 for reactions with OH and NO radicals, and thermal desorption measurements of volatility indicate that it is semivolatile at typical atmospheric aerosol loadings, consistent with field studies that have observed it in aerosol particles. Formation of 4-nitrocatechol is initiated by abstraction of a phenolic H atom by an OH or NO radical to form a β-hydroxyphenoxy/o-semiquinone radical, which then reacts with NO to form the final product.

Measurements of I/SVOCs in biomass-burning smoke using solid-phase extraction disks and two-dimensional gas chromatography

“…Potential breakthrough of such volatile compounds through the SPE filter was probed by collecting smoke samples from a campfire-style burn in Riverside, CA onto a PTFE-SPE-SPE sampling train. Any compounds present on the backup SPE filter were below detection limit despite very high concentrations observed on the front SPE filter, consistent with the negligible breakthrough observed in previous studies using sorbent-impregnated filters (Galarneau et al, 2006) and SPE filters (Tollback et al, 2006). These observations demonstrate the ability of SPE filters to trap relatively volatile compounds, although more work is needed to optimize the recovery and quantification of such compounds.…”

“…All such compounds were oxygenated and will therefore exhibit very different chemistry and SOA yields than I/SVOCs in vehicular emissions, which have generally been characterized as almost entirely hydrocarbons, particularly alkanes (Tkacik et al, 2012;Zhao et al, 2014Zhao et al, , 2016. Of the identified compounds, only catechol has been studied with respect to gas-phase oxidation and SOA formation (Finewax et al, 2018;Nakao et al, 2011;Yee et al, 2013). Therefore more work is needed to better understand the relative importance of gas-phase vs. heterogeneous reaction pathways for biomass-burning-derived I/SVOCs.…”

“…All of the offline I/SVOC characterization studies cited above collected samples using a filter and polyurethane foam (PUF) plug (or PUF/XAD-sorbent/PUF sandwich) to trap particle-and gas-phase I/SVOCs, respectively. Due to the drawbacks of PUF/XAD sampling and analysis, including high solvent needs and a relatively large physical size that exacerbates shipping costs and storage demands (Galarneau et al, 2006), alternative approaches, such as sorbent-impregnated filters (SIFs), have been investigated. Galarneau et al (2006) custom-coated glass-fiber filters with XAD resin and found that the collection and recovery of compounds from ambient samples compared well to PUF measurements.…”

“…Due to the drawbacks of PUF/XAD sampling and analysis, including high solvent needs and a relatively large physical size that exacerbates shipping costs and storage demands (Galarneau et al, 2006), alternative approaches, such as sorbent-impregnated filters (SIFs), have been investigated. Galarneau et al (2006) custom-coated glass-fiber filters with XAD resin and found that the collection and recovery of compounds from ambient samples compared well to PUF measurements. Similarly Paolini et al (2016) functionalized glass-fiber filters with phenyl moieties for targeted collection of gaseous PAHs and found recoveries of PAHs comparable to PUF plugs.…”

Evolution of the chemical fingerprint of biomass burning organic aerosol during aging

“…Iinuma et al (2010), Kelly et al (2010), and Finewax et al (2018) demonstrated their formation through the oxidation of cresol in the presence of NO x . The aerosol formation of nitrocatechols varies between 7 and 65 mg kg −1 for 4-NC, between 0.3 and 6 mg kg −1 for 4M5NC, and between 0.4 and 10 mg kg −1 for 3M5NC.…”