Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; radical
formation and aerosol growth

Palacios, Laura González; Arroyo, Pablo Corral; Aregahegn, Kifle Z.; Steimer, Sarah S.; Bartels-Rausch, Thorsten; Nozière, Barbara; George, Christian; Ammann, Markus; Volkamer, Rainer

doi:10.5194/acp-16-11823-2016

Cited by 48 publications

(61 citation statements)

References 51 publications

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“…This needs to be considered when attempts for quantification are made. As mentioned before, previous studies 2‐imidazolecarboxaldehyde suggested as a photosensitiser, that is, it might trigger secondary reactions in the atmosphere, which could lead to aerosol particle growth . The identification of further imidazolecarboxaldehydes is interesting, since they might be involved in similar processes.…”

Section: Resultsmentioning

confidence: 79%

“…In 2013, a laboratory study showed that 2‐imidazolecarboxaldehyde is a potential photosensitiser, that is, it might trigger further reactions in the atmosphere . This discovery led to an increasing interest in 2‐imidazolecarboxaldehyde and a number of follow‐up studies were published that seem to confirm its importance in the atmosphere the knowledge about its ambient concentrations is still scarce. The method developed in the present study might therefore facilitate the quantification of imidazolecarboxaldehyde and its hydrated form to get new insights into the impact that these compounds might have in the atmosphere.…”

Section: Resultsmentioning

confidence: 99%

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Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Teich

Schmidtpott

Pinxteren

et al. 2019

J of Separation Science

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A method using ultra-high performance liquid chromatography coupled to a high resolution Orbitrap mass spectrometer was developed to identify and quantify imidazoles in aqueous extracts of aerosol particles. The aqueous particle extract was used without further enrichment or sample clean-up. Five columns were tested for efficient separation of ten imidazoles and the Acquity HSS T3 column was chosen for further optimization. Low limits of detection (<25 nM) and good intraday and interday repeatability (<1.6 and <6%, respectively) were achieved. Investigation of matrix effects showed that external calibration is applicable when the loading of organic carbon in the sample is below 10 μg m −3 . The developed method was applied to ten real samples, and six out of the ten test imidazoles were successfully quantified, while six further imidazoles were qualitatively identified, among them 4-imidazolecarboxaldehyde and 4-methyl-5-imidazolecarboxaldehyde. Advantages of the method are the minimal sample preparation, the short run time for each sample, and the low detection limits. These allow for a fast and reliable quantification of imidazoles even in a large number of aqueous particle extract samples. K E Y W O R D Sbrown carbon, high resolution mass spectrometry, imidazoles, method development, organic aerosolsThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Teich

Schmidtpott

Pinxteren

et al. 2019

J of Separation Science

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“…The film was composed of Fe III (Cit)/CA, and deposited inside the tubular glass flow tube with a thickness between 0.15 − 0.2 µm and an error of about 20 %. Details of the film preparation are described previously (Corral Arroyo et al, 2018;González Palacios et al, 2016). Seven UV lamps (UV-A range, Philips Cleo Effect) were mounted surrounding the glass reactor held at 298.15 K.…”

Section: Ho 2 Production Determined By Cwftmentioning

confidence: 99%

Photochemical degradation of iron(III)-citrate/citric acid aerosol quantified with the combination of three complementary experimental techniques and a kinetic process model

Dou¹,

Alpert²,

Arroyo³

et al. 2020

Preprint

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Abstract. Iron(III) carboxylate photochemistry plays an important role in aerosol aging, especially in the lower troposphere. These complexes can absorb light over a broad wavelength range, inducing the reduction of iron(III) and the oxidation of carboxylate ligands. In the presence of O2, ensuing radical chemistry leads to further decarboxylation, and the production of ·OH, HO2·, peroxides, and oxygenated volatile organic compounds, contributing to particle mass loss. The ·OH, HO2·, and peroxides in turn re-oxidize iron(II) back to iron(III), closing a photocatalytic cycle. This cycle is repeated resulting in continual mass loss due to the release of CO2 and other volatile compounds. In a cold and/or dry atmosphere, organic aerosol particles tend to attain highly viscous states. While the impact of reduced mobility of aerosol constituents on dark chemical reactions has received substantial attention, studies on the effect of high viscosity on photochemical processes are scarce. Here, we choose iron(III)-citrate (FeIII(Cit)) as a model light absorbing iron carboxylate complex that induces citric acid (CA) degradation to investigate how transport limitations influence photochemical processes. Three complementary experimental approaches were used to investigate kinetic transport limitations. The mass loss of single, levitated particles was measured with an electrodynamic balance, the oxidation state of deposited particles was measured with X-ray spectromicroscopy, and HO2· radical production and release into the gas phase was observed in coated wall flow tube experiments. To quantitatively compare these experiments and determine important physical and chemical parameters, a numerical multi-layered photochemical reaction and diffusion (PRAD) model that treats chemical reactions and transport of various species was developed. We observed significant photochemical degradation, with up to 80 % mass loss within 24 hours of light exposure. Interestingly, we also observed that mass loss always accelerated during irradiation, resulting in an increase of the mass loss rate by about a factor of 10. When we increased relative humidity, the observed particle mass loss rate also increased. This is consistent with strong kinetic transport limitations for highly viscous particles. The PRAD model was tuned to reproduce all experimental results and captured the essential chemistry and transport during irradiation. In particular, the photolysis rate of FeIII, the re-oxidation rate of FeII, HO2· production, and the diffusivity of O2 in aqueous FeIII(Cit)/CA system as function of relative humidity and FeIII(Cit) / CA molar ratio could be constrained. Photochemical degradation under atmospheric conditions predicted by the PRAD model shows that release of CO2 and re-partitioning of organic compounds to the gas phase may be very significant to accurately predict organic aerosol aging processes.

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“…Halogen activation is driven by the oxidation of halides by ozone (Carpenter et al, 2013;Schmidt et al, 2016) and radicals (e.g., OH or NO 3 ) (Sander and Crutzen, 1996), N 2 O 5 (Behnke et al, 1997) or photochemical oxidation (Wang and Pratt, 2017;Wren et al, 2013). These volatile compounds can also be emitted to the atmosphere in the form of biogenic halogencontaining organic species (Org-X) (Hepach et al, 2016;Vogt et al, 1999) or by volcanos, among other processes (Simpson et al, 2015). AHS are precursors of reactive halogen species (RHS) such as the X atom or XO (Sherwen et al, 2016a), which affect oxidative processes in the gas phase .…”

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confidence: 99%

Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry

Arroyo

Aellig²,

Alpert

et al. 2019

Atmos. Chem. Phys.

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Abstract. Atmospheric aerosol particles can contain light-absorbing organic compounds, also referred to as brown carbon (BrC). The ocean surface and sea spray aerosol particles can also contain light-absorbing organic species referred to as chromophoric dissolved organic matter (CDOM). Many BrC and CDOM species can contain carbonyls, dicarbonyls or aromatic carbonyls such as imidazole-2-carboxaldehyde (IC), which may act as photosensitizers because they form triplet excited states upon UV–VIS light absorption. These triplet excited states are strong oxidants and may initiate catalytic radical reaction cycles within and at the surface of atmospheric aerosol particles, thereby increasing the production of condensed-phase reactive oxygen species (ROS). Triplet states or ROS can also react with halides, generating halogen radicals and molecular halogen compounds. In particular, molecular halogens can be released into the gas phase, which is one halogen activation pathway. In this work, we studied the influence of bromide and iodide on the photosensitized production and release of hydroperoxy radicals (HO2) upon UV irradiation of films in a coated wall flow tube (CWFT) containing IC in a matrix of citric acid (CA) irradiated with UV light. In addition, we measured the iodine release upon irradiation of IC ∕ CA films in the CWFT. We developed a kinetic model coupling photosensitized CA oxidation with condensed-phase halogen chemistry to support data analysis and assessment of atmospheric implications in terms of HO2 production and halogen release in sea spray particles. As indicated by the experimental results and confirmed by the model, significant recycling of halogen species occurred via scavenging reactions with HO2. These prevented the full and immediate release of the molecular halogen (bromine and iodine) produced. Recycling was stronger at low relative humidity, attributed to diffusion limitations. Our findings also show that the HO2 production from BrC or CDOM photosensitized reactions can increase due to the presence of halides, leading to high HO2 turnover, in spite of low release due to the scavenging reactions. We estimated the iodine production within sea salt aerosol particles due to iodide oxidation by ozone (O3) at 5.0×10-6 M s−1 assuming O3 was in Henry's law equilibrium with the particle. However, using an O3 diffusion coefficient of 1×10-12 cm2 s−1, iodine activation in an aged, organic-rich sea spray is estimated to be 5.5×10-8 M s−1. The estimated iodine production from BrC photochemistry based on the results reported here amounts to 4.1×10-7 M s−1 and indicates that BrC photochemistry can exceed O3 reactive uptake in controlling the rates of iodine activation from sea spray particles under dry or cold conditions where diffusion is slow within particles.

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Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO<sub>2</sub> radical formation and aerosol growth

Cited by 48 publications

References 51 publications

Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Photochemical degradation of iron(III)-citrate/citric acid aerosol quantified with the combination of three complementary experimental techniques and a kinetic process model

Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry

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Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO&lt;sub&gt;2&lt;/sub&gt; radical formation and aerosol growth

Cited by 48 publications

References 51 publications

Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Separation and quantification of imidazoles in atmospheric particles using LC–Orbitrap‐MS

Photochemical degradation of iron(III)-citrate/citric acid aerosol quantified with the combination of three complementary experimental techniques and a kinetic process model

Halogen activation and radical cycling initiated by imidazole-2-carboxaldehyde photochemistry

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Heterogeneous photochemistry of imidazole-2-carboxaldehyde: HO<sub>2</sub> radical formation and aerosol growth