A combined gas- and particle-phase analysis  of highly oxygenated organic molecules  (HOMs) from <i>α</i>-pinene ozonolysis

Zhao, Jian; Häkkinen, Ella; Graeffe, Frans; Krechmer, Jordan E.; Canagaratna, Manjula R.; Worsnop, Douglas R.; Kangasluoma, Juha; Ehn, Mikael

doi:10.5194/acp-23-3707-2023

Cited by 13 publications

(6 citation statements)

References 98 publications

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“…This is consistent with the understanding that the buffering effect due to gas-wall partitioning mainly influences species with moderate-volatility species that exist in both phases with comparable concentrations , as high-volatility species mainly exist in the gas phase, and the evaporation of low-volatility species affects their gas-phase concentrations minorly due to the low saturation vapor pressure. We also note that aerosol production was not intentionally suppressed in this experiment, which also affected the variation of OOM concentrations according to our previous experiments …”

Section: Resultsmentioning

confidence: 74%

“…Integrating selective ionization chemistry at atmospheric pressure and high-resolution mass spectrometry has successfully addressed the specific needs for low detection limits, enabling direct online detection of trace species in complex gaseous samples with concentrations down to 10 4 molecules cm –3 . These advances have led to revolutions in, e.g., atmospheric chemistry in the past decade. , Coupled with inlets that can vaporize sample molecules, CIMS can also be used to analyze liquid/solid samples such as explosives, , pesticide residues, and aerosol particles. , …”

Section: Introductionmentioning

confidence: 99%

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Extending the Range of Detectable Trace Species with the Fast Polarity Switching of Chemical Ionization Orbitrap Mass Spectrometry

Cai,

Mikkilä,

Bengs

et al. 2024

Anal. Chem.

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Chemical ionization (CI) atmospheric pressure interface mass spectrometry is a unique analytical technique for its low detection limits, softness to preserve molecular information, and selectivity for particular classes of species. Here, we present a fast polarity switching approach for highly sensitive online analysis of a wide range of trace species in complex samples using selective CI chemistries and high-resolution mass spectrometry. It is achieved by successfully coupling a multischeme chemical ionization inlet (MION) and an Orbitrap Fourier transform mass spectrometer. The capability to flexibly combine ionization chemistries from both polarities effectively extends the detectability compared to using only one ionization chemistry, as commonly used positive and negative reagent ions tend to be sensitive to different classes of species. We tested the performance of the MION-Orbitrap using reactive gaseous organic species generated by αpinene ozonolysis in an environmental chamber and a standard mixture of 71 pesticides. Diethylammonium and nitrate are used as reagent ions in positive and negative polarities. We show that with a mass resolving power of 280,000, the MION-Orbitrap can switch and measure both polarities within 1 min, which is sufficiently fast and stable to follow the temporal evolution of reactive organic species and the thermal desorption profile of pesticides. We detected 23 of the 71 pesticides in the mixture using only nitrate as the reagent ion. Facilitated by polarity switching, we also detected 47 pesticides using diethylammonium, improving the total number of detected species to 59. For reactive organic species generated by α-pinene ozonolysis, we show that combining diethylammonium and nitrate addresses the need to measure oxygenated molecules in atmospheric environments with a wide range of oxidation states. These results indicate that the polarity switching MION-Orbitrap can promisingly serve as a versatile tool for the nontargeted chemical analysis of trace species in various applications.

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Section: Resultsmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Extending the Range of Detectable Trace Species with the Fast Polarity Switching of Chemical Ionization Orbitrap Mass Spectrometry

Cai,

Mikkilä,

Bengs

et al. 2024

Anal. Chem.

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“…The details of the conducted experiments are provided in Table 1. The UV LED lights (wavelength ∼ 400 nm, manufactured by LEDlightmake Inc., Shenzhen, China) (Zhao et al, 2023a) used for photolyzing NO 2 were kept on throughout each experiment, while the input concentrations of the precursors NO 2 , O 3 and α-pinene were varied across experiments and stages to map out a wide range of different conditions. The photolysis rate was varied by using varying numbers of LED light strips (1, 3, or 5).…”

Section: Methodsmentioning

confidence: 99%

On the potential use of highly oxygenated organic molecules (HOM) as indicators for ozone formation sensitivity

Zhang,

Zhao,

Luo

et al. 2023

Preprint

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Abstract. Ozone (O3), an important and ubiquitous trace gas, protects lives from harm of solar ultraviolet (UV) radiation in the stratosphere but is toxic to living organisms in the troposphere. Additionally, tropospheric O3 is a key oxidant, and source of other oxidants (e.g, OH and NO3 radicals) for various volatile organic compounds (VOC). Recently, highly oxygenated organic molecules (HOM) were identified as a new compound group formed from oxidation of many VOC, making up a significant source of secondary organic aerosol (SOA). The pathways forming HOM from VOC involve autoxidation of peroxy radicals (RO2), formed ubiquitously in many VOC oxidation reactions. The main sink for RO2 is bimolecular reactions with other radicals, HO2, NO or other RO2, and this largely determines the structure of the end products. Organic nitrates form solely from RO2 + NO reactions while accretion products (“dimers”) solely from RO2 + RO2 reactions. The RO2 + NO reaction also converts NO into NO2, making it a net source for O3 through NO2 photolysis. There is a highly nonlinear relationship between O3, NOx, and VOC. Understanding the O3 formation sensitivity to changes in VOC and NOx is crucial for making optimal mitigation policies to control O3 concentrations. However, determining the specific O3 formation regimes (either VOC-limited or NOx-limited) remains challenging in diverse environmental conditions. In this work we assessed whether HOM measurements can function as a real-time indicator for the O3 formation sensitivity based on the hypothesis that HOM compositions can describe the relative importance of NO as a terminator for RO2. Given the fast formation and short lifetimes of the low-volatile HOM (timescale of minutes), they describe the instantaneous chemical regime of the atmosphere. In this work, we conducted a series of monoterpene oxidation experiments in our chamber while varying the concentrations of NOx and VOC under different NO2 photolysis rates. We also measured the relative concentrations of HOM of different types (dimers, nitrate-containing monomers, and non-nitrate monomers) and used ratios between these to estimate the O3 formation sensitivity. We find that for this simple system, the O3 sensitivity could be described very well based on the HOM measurements. Future work will focus on determining to what extent this approach can be applied in more complex atmospheric environments. Ambient measurements of HOM have become increasingly common during the last decade, and therefore we expect that there already are a large amount groups with available data for testing this approach.

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“…The O3 level started to accumulate when the NO concentration decreased to nearly 0, reaching quickly its maximum and then decreasing slowly. Previous studies have demonstrated that SOA could be produced through the reaction of α-pinene with O3 [12,[30][31][32]. Therefore, the decreasing rates were determined not only by oxidation of OH radicals, but also more and more by O3, which was accumulating during photooxidation.…”

Section: Evolutions Of Gas-phase Species During Photooxidationmentioning

confidence: 98%

Differences in Secondary Organic Aerosol Formation from α-Pinene Photooxidation in a Chamber with Purified Air and Ambient Air as Matrices: Preliminary Results

Li,

Ren,

Zhang

et al. 2024

Atmosphere

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α-Pinene is a biogenic volatile organic compound (BVOC) that significantly contributes to secondary organic aerosols (SOA) in the atmosphere due to its high emission rate, reactivity, and SOA yield. However, the SOA yield measured in chamber studies from α-pinene photooxidation is limited in a purified air matrix. Assessing SOA formation from α-pinene photooxidation in real urban ambient air based on studies conducted in purified air matrices may be subject to uncertainties. In this study, α-pinene photooxidation and SOA yield were investigated in a smog chamber in the presence of NO and SO2 under purified air and ambient air matrices. With the accumulation of ozone (O3) during the photooxidation, an increasing part of α-pinene was consumed by O3 and finally nearly half of the α-pinene was oxidized by O3, facilitating the production of highly oxidized organic molecules and thereby SOA formation. Although the ambient air we introduced as matrix air was largely clean, with initial organic aerosol mass concentrations of ~1.5 μg m−3, the α-pinene SOA yield in the ambient air matrix was 42.3 ± 5.3%, still higher than that of 32.4 ± 0.4% in the purified air matrix. The chemical characterization of SOA by the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) revealed that CxHy accounted for 53.7 ± 1.1% of the total signal in the ambient air matrix experiments, higher than 48.1 ± 0.3% in the purified air, while CxHyO and CxHyO>1 together constituted 45.0 ± 0.9% in the ambient air matrix, lower than 50.1 ± 1.0% in the purified air. The O:C ratio in the ambient air matrix experiments was 0.41 ± 0.01, lower than 0.46 ± 0.01 in the purified air. The higher SOA yield of α-pinene in the ambient air matrix compared to that in the purified air matrix was partly due to the presence of initial aerosols in the ambient air, which facilitated the low volatile organic compounds produced from photochemical oxidation to enter the aerosol phase through gas-particle partitioning. The in-situ aerosol acidity calculated by the ISORROPIA-II model in the ambient air matrix experiments was approximately six times higher than that in purified air, and the higher SOA yield in the ambient air matrix experiments might also be attributed to acid-catalyzed SOA formation.

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A combined gas- and particle-phase analysis of highly oxygenated organic molecules (HOMs) from α-pinene ozonolysis

Cited by 13 publications

References 98 publications

Extending the Range of Detectable Trace Species with the Fast Polarity Switching of Chemical Ionization Orbitrap Mass Spectrometry

Extending the Range of Detectable Trace Species with the Fast Polarity Switching of Chemical Ionization Orbitrap Mass Spectrometry

On the potential use of highly oxygenated organic molecules (HOM) as indicators for ozone formation sensitivity

Differences in Secondary Organic Aerosol Formation from α-Pinene Photooxidation in a Chamber with Purified Air and Ambient Air as Matrices: Preliminary Results

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