Formation of secondary organic aerosol from nitrate radical oxidation of phenolic VOCs: Implications for nitration mechanisms and brown carbon formation

Atmospheric nitrophenols are pollutants of concern due to their toxicity and light-absorption characteristics and their low reactivity resulting in relatively long residence times in the environment. We investigate multiphase nitrophenol formation from guaiacol in a simulated atmospheric aerosol and support observations with the corresponding chemical mechanisms. The maximal secondary organic aerosol (SOA) yield (42%) is obtained under illumination at 80% relative humidity. Among the identified nitrophenols, 4-nitrocatechol (3.6% yield) is the prevailing species in the particulate phase. The results point to the role of water in catechol and further 4-nitrocatechol formation from guaiacol. In addition, a new pathway of dark nitrophenol formation is suggested, which prevailed in dry air and roughly yielded 1% nitroguaiacols. Furthermore, the proposed mechanism possibly leads to oligomer formation via a phenoxy radical formation by oxidation with HONO.

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“…Similar products have been recently observed in the dark GUA nitration experiments by NO 3 and confirmed in real BB-affected PM samples. 16 …”

Section: Resultsmentioning

confidence: 99%

Guaiacol Nitration in a Simulated Atmospheric Aerosol with an Emphasis on Atmospheric Nitrophenol Formation Mechanisms

Kroflič

Anders

Drventić

et al. 2021

ACS Earth Space Chem.

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“…However, other studies show fragmentation of chromophores on exposure to O3 in a NOx-free environment led to a decrease in BrC absorption (Pillar-Little and Guzman, 2017;Sun et al, 2019). Additionally, the reaction of NO2 with O3 produces the NO3 radical, which has been identified to be an important factor in BrC formation at night (Cheng et al, 2020;Mayorga et al, 2021;Selimovic et al, 2020). In dark optically thick smoke plumes where the nitrate radical loss by photolysis may be suppressed, high O3 and NOx could also be linked to increases in BrC (Cheng et al, 2020;Mayorga et al, 2021;Selimovic et al, 2020).…”

Section: Possible Role Of O3mentioning

confidence: 98%

“…The light absorption of 4-nitrocatechol exhibited a wavelength-dependent change; a decrease in absorption between wavelengths of 300 and 380 nm and an increase in absorption below 300 nm or above 380 nm with increasing illumination time (Zhao et al, 2015). Reactions with the NO3 radical produced nitrated organics, such as nitroaromatics, that contributed to aerosol particle BrC (Bluvshtein et al, 2017;Lin et al, 2017;Jiang et al, 2019;Li et al, 2020;Mayorga et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…CC BY 4.0 License. Lin et al, 2017;Jiang et al, 2019;Li et al, 2020;Mayorga et al, 2021), but atmospheric observations from wildfires show more complex behaviors. For relatively fresh smoke, Palm et al (2020) conclude that a balance between dilution-driven evaporation of primary wildfire smoke chromophores and formation of secondary BrC led to the observation in nine fire plumes of a near-constant level of light absorption by BrC for smoke up to at least 6 hours old.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics and Evolution of Brown Carbon in Western United States Wildfires

Zeng

Dibb

Scheuer

et al. 2022

Preprint

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Abstract. Brown carbon (BrC) associated with aerosol particles in western United States wildfires was measured between Jul. and Aug. 2019 onboard the NASA DC-8 research aircraft during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study. Two BrC measurement methods are investigated; highly spectrally-resolved light absorption in solvent (water and methanol) extracts of particles collected on filters and in-situ bulk aerosol particle light absorption measured at three wavelengths (405, 532, 664 nm) with a photo acoustic spectrometer (PAS). A light absorption closure analysis for wavelengths between 300 and 700 nm was performed. The combined light absorption of particle pure black carbon material, including enhancements due to internally mixed materials, plus soluble BrC and a Mie-predicted factor for conversion of soluble BrC to aerosol particle BrC, was compared to absorption spectra from a power law fit to the three PAS wavelengths. For the various parameters used, at a wavelength of roughly 400 nm they agreed, at lower wavelengths the individual component-predicted particle light absorption significantly exceeded the PAS and at higher wavelengths the PAS absorption was consistently higher, but more variable. Limitations with extrapolation of PAS data to wavelengths below 405 nm and missing BrC species of low solubility that more strongly absorb at higher wavelengths may account for the differences. Based on measurements closest to fires, the emission ratio of PAS measured BrC at 405 nm relative to carbon monoxide (CO) was on average 0.13 Mm−1 ppbv−1, emission ratios for soluble BrC are also provided. As the smoke moved away from the burning regions the evolution over time of BrC was observed to be highly complex; BrC enhancement, depletion, or constant levels with age were all observed in the first 8 hours after emission in different plumes. Within 8 hours following emissions, 4-nitrocatechol, a well characterized BrC chromophore commonly found in smoke particles, was largely depleted relative to the bulk BrC. In a descending plume where temperature increased by 15 K, 4-nitrocatechol dropped possibly due to temperature-driven evaporation, but bulk BrC remained largely unchanged. Evidence was found for reactions with ozone, or related species, as a pathway for secondary formation of BrC under both low and high oxides of nitrogen (NOx) conditions, while BrC was also observed to be bleached in regions of higher ozone and low NOx, consistent with complex behaviors of BrC observed in laboratory studies. Although the evolution of smoke in the first hours following emission is highly variable, a limited number of measurements of more aged smoke (15 to 30 hours) indicate a net loss of BrC. It is yet to be determined how the near-field BrC evolution in smoke affects the characteristics of smoke over longer time and spatial scales, where its environmental impacts are likely to be greater.

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“…Mass spectrometry plays a crucial role in its high sensitivity and molecular specificity (Johnston and Kerecman 2019). Utilization of exquisite mass spectroscopy like electrospray ionization mass spectrometry (ESI-MS), ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), and proton transfer reaction mass spectrometry sees increasing owing to the requirement of further insight into organics in particulate matter (Cai et al, 2020;Mayorga et al, 2021). Isotopic ratio mass spectroscopy (IRMS) and accelerate mass spectroscopy (AMS) are always used to distinguish fossil combustion sources and biogenic sources by carbon isotopic (Masalaite et al, 2018;Zhao et al, 2019;Huang et al, 2020).…”

mentioning

confidence: 99%

Particle size-dependent fluorescence properties of water-soluble organic compounds (WSOC) and their atmospheric implications on the aging of WSOC

Qin

Tan

Zhou

et al. 2021

Preprint

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Abstract. Water-soluble organic compounds (WSOC) are essential in atmospheric particle formation, migration, and transformation processes. Size-segregated atmospheric particles were collected in a rural area of Beijing. Excitation-emission matrix (EEM) fluorescence spectroscopy was used to investigate the sources and optical properties of WSOC. Sophisticated data analysis on EEM data was performed to characteristically estimate the underlying connections among aerosol particles in different sizes. The WSOC concentrations and average fluorescence intensity (AFI) showed monomodal distribution in winter and bimodal distribution in summer, with dominant mode between 0.26 to 0.44 µm for both seasons. The EEM spectra of size-segregated WSOC were different among variant particle sizes, which could be the results of changing sources and/or chemical transformation of organics. Size distributions of fluorescence regional intensity (region Ⅲ and Ⅴ) and HIX indicate that humification degree or aromaticity of WSOC was highest between 0.26 to 0.44 µm. The Stokes shift (SS) and the harmonic mean of the excitation and emission wavelengths (WH) reflected that π-conjugated systems were high between 0.26 to 0.44 µm as well. The parallel factor analysis (PARAFAC) results showed that humic-like substances were abundant in fine particles (< 1 µm) and peaked at 0.26–0.44 µm. All evidence supported that the humification degree of WSOC increased in submicron mode (< 0.44 µm) and decreased gradually. Thus, it was conjectured that condensation of organics still goes on in submicron mode, resulting in the highest humification degree exhibit in particle size between 0.26 to 0.44 µm rather than < 0.26 µm. Synthetically analyzing 3-dimensional fluorescence data could efficiently present the secondary transformation processes of WSOC.

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Formation of secondary organic aerosol from nitrate radical oxidation of phenolic VOCs: Implications for nitration mechanisms and brown carbon formation

Cited by 67 publications

References 81 publications

Guaiacol Nitration in a Simulated Atmospheric Aerosol with an Emphasis on Atmospheric Nitrophenol Formation Mechanisms

Guaiacol Nitration in a Simulated Atmospheric Aerosol with an Emphasis on Atmospheric Nitrophenol Formation Mechanisms

Characteristics and Evolution of Brown Carbon in Western United States Wildfires

Particle size-dependent fluorescence properties of water-soluble organic compounds (WSOC) and their atmospheric implications on the aging of WSOC

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