Secondary organic aerosol formation from photooxidation of furan: effects of NO<sub><i>x</i></sub> and humidity

Abstract

Abstract. Atmospheric furan is a primary and secondary pollutant in the atmosphere, and its emission contributes to the formation of ultrafine particles. We investigate the effects of NOx level and humidity on the formation of secondary organic aerosol (SOA) generated from the photooxidation of furan in the presence of NaCl seed particles. SOA mass concentration and yield were determined under different NOx and humidity levels. A significant difference is observed both in the variation of SOA mass concentration and SOA yield with the initial experimental conditions. Varying VOC (volatile organic compound) ∕ NOx ratios over the range 48.1 to 8.2 contributes to the effective formation of SOA in the presence of NaCl seed particles, with the SOA mass concentration and SOA yield ranging from 0.96 to 23.46 µg m−3 and from 0.04 % to 1.01 %, respectively. We found that there was a favourable relationship between the SOA yields and NOx concentration. In particular, the increase in SOA yield with increasing NOx concentration was continuously observed at high NOx levels owing to a corresponding increase in the amount of low-volatility hydroxyl nitrates and dihydroxyl dinitrates that can partition into the particle phase. In addition, varying relative humidity (RH) from 5 % to 88 % increased the SOA yield from 1.01 % to 5.03 %. The enhanced SOA formation from humid conditions may result from the high OH concentration, rapid furan decay rate, enhanced carbonyl-rich products condensation, and the aqueous-phase reactions. Using hybrid quadrupole-orbitrap mass spectrometer equipped with electrospray ionization (HESI-Q Exactive-Orbitrap MS), three carbonyl-rich products and three kinds of organonitrates were identified in the collected SOA. Based on the HESI-Q Exactive-Orbitrap MS analysis and Fourier transform infrared spectroscopy (FTIR), the reaction mechanism of furan photooxidation was proposed. This study demonstrates the effects of NOx and humidity on SOA formation during the furan–NOx–NaCl photooxidation and provides new insights into the oxidation regime and SOA composition in furan photooxidation. The results also illustrate the importance of studying SOA formation over a comprehensive range of environmental conditions. Only such evaluations can induce meaningful SOA mechanisms to be implemented in air quality models.

Effects of Nitrate Radical Levels and Pre-Existing Particles on Secondary Brown Carbon Formation from Nighttime Oxidation of Furan

“…Alvarez et al 22 reported that OH-initiated oxidation of furans can produce a large set of unsaturated 1,4-dicarbonyls in the aerosol phase, while Joo et al 23 suggested that nitrate radical (NO 3 )-initiated oxidation of 3methylfuran can not only generate a variety of carbonyls but also dimers and oligomers. Strollo and Ziemann 24 indicated that oligomerization is the key to SOA formation during 3methylfuran daytime oxidation, while Jiang et al 25 highlighted the potentially important role of multifunctional dihydroxyl organonitrate products in SOA formation in the furan−NO x − NaCl system. However, our understanding of the chemical composition of reaction products in furan oxidations is still limited, making it difficult to evaluate the physicochemical properties of furan SOA.…”

Evolution of Organic Aerosol From Wood Smoke Influenced by Burning Phase and Solar Radiation

“…Figure 3b gives an example for the furanic group that the precursors (such as furan, methyl-furan, and furfural) decreased in light but not in dark experiments (Figure S6). Furanic compounds have been widely reported to be the main precursors of SOA in biomass (Hartikainen et al, 2018) and solid fuel burning emission (Ahern et al, 2019), and could have an SOA yield of up to 5% (Jiang et al, 2019). Table S2 (in red) summarized all gaseous precursors, including some aromatics (benzene, toluene, and C8-aromatics), carbonyl (acrolein, MVK, and 3-methyl-3-butene-2-one), and phenolic (phenol and cresol for SM) compounds.…”

Secondary organic aerosol formation from the ozonolysis and oh-photooxidation of 2,5-dimethylfuran

“…RO radicals generally fragment into smaller more volatile products, resulting in small amounts of SOA (Sarrafzadeh et al, 2016). It should also be noted that the presence of sufficient seed surface area at the start of the reaction largely suppresses the effects of vapour wall losses of low-volatility compounds, including multifunctional nitrates (Schwantes et al, 2019), which promotes their partition into the particle phase and increases the SOA mass concentration (Jiang, 2019).…”

“…These compounds can be absorbed into the humid surface of the hygroscopic SOA at high RH, contributing to the formation of low volatility products and increasing the SOA mass yields. Moreover, these hydrophilic functional groups at the SOA surface, could also absorb the water molecules and hence, the produced SOA could partition into new wet particles (Jiang et al, 2019).…”

“…Although the SOA formation potential of furanes has been studied in recent years (Gomez-Alvarez et al, 2009;Jiang et al, 2019;Strollo and Ziemann, 2013;Joo et al, 2019), the SOA formation mechanisms are still poorly known. In this sense, the present study was initiated with the aim of studying the OH radical photooxidation and ozonolysis of 2,5-DMF to characterize the conditions that lead to the formation and growth of new particles.…”