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Dai Y, Chen Z, Qin X, Dong P, Xu J, Hu J, Gu L, Chen S. Hydrolysis reactivity reveals significant seasonal variation in the composition of organic peroxides in ambient PM 2.5. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 927:172143. [PMID: 38569967 DOI: 10.1016/j.scitotenv.2024.172143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 03/24/2024] [Accepted: 03/30/2024] [Indexed: 04/05/2024]
Abstract
Atmospheric organic peroxides (POs) play a key role in the formation of O3 and secondary organic aerosol (SOA), impacting both air quality and human health. However, there still remain technical challenges in investigating the reactivity of POs in ambient aerosols due to the instability and lack of standards for POs, impeding accurate evaluation of their environmental impacts. In the present study, we conducted the first attempt to categorize and quantify POs in ambient PM2.5 through hydrolysis, which is an important transformation pathway for POs, thus revealing the reactivities of various POs. POs were generally categorized into hydrolyzable POs (HPO) and unhydrolyzable POs (UPO). HPO were further categorized into three groups: short-lifetime HPO (S-HPO), intermediate-lifetime HPO (I-HPO), and long-lifetime HPO (L-HPO). S-HPO and L-HPO are typically formed from Criegee intermediate (CI) and RO2 radical reactions, respectively. Results show that L-HPO are the most abundant HPO, indicating the dominant role of RO2 pathway in HPO formation. Despite their lower concentration compared to L-HPO, S-HPO make a major contribution to the HPO hydrolysis rate due to their faster rate constants. The hydrolysis of PM2.5 POs accounts for 19 % of the nighttime gas-phase H2O2 growth during the summer observation, constituting a noteworthy source of gas-phase H2O2 and contributing to the atmospheric oxidation capacity. Seasonal and weather conditions significantly impact the composition of POs, with HPO concentrations in summer being significantly higher than those in winter and elevated under rainy and nighttime conditions. POs are mainly composed of HPO in summer, while in winter, POs are dominated by UPO.
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Affiliation(s)
- Yishuang Dai
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Zhongming Chen
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
| | - Xuan Qin
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Ping Dong
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Jiayun Xu
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Jingcheng Hu
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Linghao Gu
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
| | - Shiyi Chen
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
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2
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Guo X, Chan YC, Gautam T, Zhao R. Autoxidation of glycols used in inhalable daily products: implications for the use of artificial fogs and e-cigarettes. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2023; 25:1657-1669. [PMID: 37728872 DOI: 10.1039/d3em00214d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/21/2023]
Abstract
The use of glycols is seen in various industries and occupations. In the past few decades, the health implications of inhalable glycols have gained public attention. Inhalable glycols may cause adverse health effects, especially for workers in occupations receiving frequent exposure and consumers of glycol-based daily products. Our previous work highlighted the rapid accumulation of formaldehyde and glycolaldehyde in fog juice, thus proposing the occurrence of glycol autoxidation. However, the fundamentals of glycol autoxidation remained unclear and unexplored. Our goal is to investigate the autoxidation of common glycols during indoor storage. Carbonyls were quantified using liquid chromatography-mass spectrometry (LC-MS), and peroxides from autoxidation were monitored via iodometry and UV-Vis spectrometry. The impact of certain factors such as the water mixing ratio and antioxidants (vitamin C) was also investigated. Formation of aldehydes in many glycols was weekly monitored, such as e-cigarette juice and triethylene glycol (TEG). Occurrence of autoxidation was confirmed by the increase in the total peroxide concentration. Additionally, we highlighted the dependence of the carbonyl formation rate on the TEG-water mixing ratio, demonstrating the complex role of water in glycol autoxidation. We have also tested the effectiveness of vitamin C and made suggestions for minimizing the formation of toxic carbonyls in consumer products.
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Affiliation(s)
- Xinyang Guo
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Ya-Chun Chan
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Tania Gautam
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
| | - Ran Zhao
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
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3
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Wang S, Zhao Y, Chan AWH, Yao M, Chen Z, Abbatt JPD. Organic Peroxides in Aerosol: Key Reactive Intermediates for Multiphase Processes in the Atmosphere. Chem Rev 2023; 123:1635-1679. [PMID: 36630720 DOI: 10.1021/acs.chemrev.2c00430] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Organic peroxides (POs) are organic molecules with one or more peroxide (-O-O-) functional groups. POs are commonly regarded as chemically labile termination products from gas-phase radical chemistry and therefore serve as temporary reservoirs for oxidative radicals (HOx and ROx) in the atmosphere. Owing to their ubiquity, active gas-particle partitioning behavior, and reactivity, POs are key reactive intermediates in atmospheric multiphase processes determining the life cycle (formation, growth, and aging), climate, and health impacts of aerosol. However, there remain substantial gaps in the origin, molecular diversity, and fate of POs due to their complex nature and dynamic behavior. Here, we summarize the current understanding on atmospheric POs, with a focus on their identification and quantification, state-of-the-art analytical developments, molecular-level formation mechanisms, multiphase chemical transformation pathways, as well as environmental and health impacts. We find that interactions with SO2 and transition metal ions are generally the fast PO transformation pathways in atmospheric liquid water, with lifetimes estimated to be minutes to hours, while hydrolysis is particularly important for α-substituted hydroperoxides. Meanwhile, photolysis and thermolysis are likely minor sinks for POs. These multiphase PO transformation pathways are distinctly different from their gas-phase fates, such as photolysis and reaction with OH radicals, which highlights the need to understand the multiphase partitioning of POs. By summarizing the current advances and remaining challenges for the investigation of POs, we propose future research priorities regarding their origin, fate, and impacts in the atmosphere.
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Affiliation(s)
- Shunyao Wang
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai200240, China
- School of Environmental and Chemical Engineering, Shanghai University, Shanghai200444, China
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, OntarioM5S 3E5, Canada
| | - Yue Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai200240, China
| | - Arthur W H Chan
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, OntarioM5S 3E5, Canada
- School of the Environment, University of Toronto, Toronto, OntarioM5S 3E8, Canada
| | - Min Yao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai200240, China
| | - Zhongming Chen
- State Key Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing100871, China
| | - Jonathan P D Abbatt
- Department of Chemistry, University of Toronto, Toronto, OntarioM5S 3H6, Canada
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Ge Y, Guo X, Zhou D, Liu J. Construction and excellent photoelectric synergistic anticorrosion performance of Z-scheme carbon nitride/tungsten oxide heterojunctions. NANOSCALE 2022; 14:12358-12376. [PMID: 35972035 DOI: 10.1039/d2nr03246e] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The use of heterojunctions for metal corrosion protection is a highly innovative and challenging task. Based on the composition and structure of tungsten oxide-based heterojunctions, Z-scheme heterojunctions were designed and synthesized by the electrostatic self-assembly method using energy band-matched g-C3N4 and WO3 materials. Applied in the field of anticorrosion, they overcame the problems of poor reduction ability and transmission inefficiency of traditional materials. The Z-scheme heterojunctions ensured unidirectional electron transfer, while the aggregation of the retained strongly reduced electrons on the surface of the iron substrates provided a strong driving force for retarding corrosion occurrence. Meanwhile, the inherent shielding properties of the two-dimensional material g-C3N4 and the confinement of chloride ions as an electroactive layer hindered the penetration of the corrosive solution. After being corroded for 72 h, the corrosion impedance of the g-C3N4/WO3 heterojunction system was improved by 640.11% compared with the epoxy resin coating. In addition, the g-C3N4/W18O49 heterojunction was synthesized by using mixed valence tungsten oxide, which overcame the problems of photogenerated electron yield and lifetime, and enhanced the anticorrosion performance compared with a single g-C3N4 phase. This research provided ideas for designing efficient and environmentally friendly heterojunction anticorrosion materials.
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Affiliation(s)
- Yunxiao Ge
- Key Laboratory for Advanced Materials, School of Chemistry and Molecular Engineering, East China University of Science and Technology (ECUST), Shanghai, 200237, P.R. China.
| | - Xiaojiao Guo
- Key Laboratory for Advanced Materials, School of Chemistry and Molecular Engineering, East China University of Science and Technology (ECUST), Shanghai, 200237, P.R. China.
| | - Dan Zhou
- Key Laboratory for Advanced Materials, School of Chemistry and Molecular Engineering, East China University of Science and Technology (ECUST), Shanghai, 200237, P.R. China.
| | - Jinku Liu
- Key Laboratory for Advanced Materials, School of Chemistry and Molecular Engineering, East China University of Science and Technology (ECUST), Shanghai, 200237, P.R. China.
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Qiu J, Fujita M, Tonokura K, Enami S. Stability of Terpenoid-Derived Secondary Ozonides in Aqueous Organic Media. J Phys Chem A 2022; 126:5386-5397. [PMID: 35921086 PMCID: PMC9393869 DOI: 10.1021/acs.jpca.2c04077] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1,2,4-Trioxolanes, known as secondary ozonides (SOZs), are key products of ozonolysis of biogenic terpenoids. Functionalized terpenoid-derived SOZs are readily taken up into atmospheric aerosols; however, their condensed-phase fates remain unknown. Here, we report the results of a time-dependent mass spectrometric investigation into the liquid-phase fates of C10 and C13 SOZs synthesized by ozonolysis of a C10 monoterpene alcohol (α-terpineol) in water:acetone (1:1 = vol:vol) mixtures. Isomerization of Criegee intermediates and bimolecular reaction of Criegee intermediates with acetone produced C10 and C13 SOZs, respectively, which were detected as their Na+-adducts by positive-ion electrospray mass spectrometry. Use of CD3COCD3, D2O, and H218O solvents enabled identification of three types of C13 SOZs (aldehyde, ketone, and lactol) and other products. These SOZs were surprisingly stable in water:acetone (1:1) mixtures at T = 298 K, with some persisting for at least a week. Theoretical calculations supported the high stability of the lactol-type C13 SOZ formed from the aldehyde-type C13 SOZ via intramolecular rearrangement. The present results suggest that terpenoid-derived SOZs can persist in atmospheric condensed phases, potentially until they are delivered to the epithelial lining fluid of the pulmonary alveoli via inhaled particulate matter, where they may exert hitherto unrecognized adverse health effects.
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Affiliation(s)
- Junting Qiu
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Michiya Fujita
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Kenichi Tonokura
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
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6
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Endo Y, Sakamoto Y, Kajii Y, Enami S. Decomposition of multifunctionalized α-alkoxyalkyl-hydroperoxides derived from the reactions of Criegee intermediates with diols in liquid phases. Phys Chem Chem Phys 2022; 24:11562-11572. [PMID: 35506905 DOI: 10.1039/d2cp00915c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxidation of volatile organic compounds in the atmosphere produces organic hydroperoxides (ROOHs) that typically possess not only -OOH but also other functionalities such as -OH and -C(O). Because of their high hydrophilicity and low volatility, such multifunctionalized ROOHs are expected to be taken up in atmospheric condensed phases such as aerosols and fog/cloud droplets. However, the characteristics of ROOHs that control their fates and lifetimes in liquid phases are poorly understood. Here, we report a study of the liquid-phase decomposition kinetics of multifunctionalized α-alkoxyalkyl-hydroperoxides (α-AHs) that possessed an ether, a carbonyl, a hydroperoxide, and two hydroxy groups. These ROOHs were synthesized by ozonolysis of α-terpineol in water in the presence of 1,3-propanediol, 1,4-butanediol, or 1,5-pentanediol. Their decomposition products were detected as chloride anion adducts by electrospray mass spectrometry as a function of reaction time. Experiments using H218O and D2O revealed that hemiacetal species were α-AH decomposition products that further transformed into other products. The result that the rate coefficients (k) of the decomposition of C15 α-AHs increased exponentially from pH 5.0 to 3.9 was consistent with an H+-catalyzed decomposition mechanism. The temperature dependence of k and an Arrhenius plot yielded activation energies (Ea) of 15.7 ± 0.8, 15.0 ± 2.4, and 15.9 ± 0.3 kcal mol-1 for the decomposition of α-AHs derived from the reaction of α-terpineol CIs with 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, respectively. The determined Ea values were compared with those of related ROOHs. We found that alkyl chain length is not a critical factor for the decomposition mechanism, whereas the presence of additional -OH groups would modulate the reaction barriers to decomposition via the formation of hydrogen-bonding with surrounding water molecules. The derived Ea values for the decomposition of the multifunctionalized, terpenoid-derived α-AHs will facilitate atmospheric modeling by serving as representative values for ROOHs in atmospheric condensed phases.
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Affiliation(s)
- Yasuyuki Endo
- Graduate School of Global Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan
| | - Yosuke Sakamoto
- Graduate School of Global Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan.,Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8316, Japan.,National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan.
| | - Yoshizumi Kajii
- Graduate School of Global Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan.,Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8316, Japan.,National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan.
| | - Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan.
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7
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Yao M, Li Z, Li C, Xiao H, Wang S, Chan AWH, Zhao Y. Isomer-Resolved Reactivity of Organic Peroxides in Monoterpene-Derived Secondary Organic Aerosol. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:4882-4893. [PMID: 35357822 DOI: 10.1021/acs.est.2c01297] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Organic peroxides play a vital role in the formation, evolution, and health impacts of atmospheric aerosols, yet their molecular composition and fate in the particle phase remain poorly understood. Here, we identified, using iodometry-assisted liquid chromatography mass spectrometry, a large suite of isomer-resolved peroxide monomers (C8-10H12-18O5-8) and dimers (C15-20H22-34O5-14) in secondary organic aerosol formed from ozonolysis of the most abundant monoterpene (α-pinene). Combining aerosol isothermal evaporation experiments and multilayer kinetic modeling, bulk peroxides were found to undergo rapid particle-phase chemical transformation with an average lifetime of several hours under humid conditions, while the individual peroxides decompose on timescales of half an hour to a few days. Meanwhile, the majority of isomeric peroxides exhibit distinct particle-phase behaviors, highlighting the importance of the characterization of isomer-resolved peroxide reactivity. Furthermore, the reactivity of most peroxides increases with aerosol water content faster in a low relative humidity (RH) range than in a high RH range. Such non-uniform water effects imply a more important role of water as a plasticizer than as a reactant in influencing the peroxide reactivity. The high particle-phase reactivity of organic peroxides and its striking dependence on RH should be considered in atmospheric modeling of their fate and impacts on aerosol chemistry and health effects.
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Affiliation(s)
- Min Yao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ziyue Li
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Chenxi Li
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Huayun Xiao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Shunyao Wang
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto Ontario M5S 3E5, Canada
| | - Arthur W H Chan
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto Ontario M5S 3E5, Canada
| | - Yue Zhao
- School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
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8
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Hu M, Chen K, Qiu J, Lin YH, Tonokura K, Enami S. Decomposition mechanism of α-alkoxyalkyl-hydroperoxides in the liquid phase: temperature dependent kinetics and theoretical calculations. ENVIRONMENTAL SCIENCE: ATMOSPHERES 2022; 2:241-251. [PMID: 35419522 PMCID: PMC8929293 DOI: 10.1039/d1ea00076d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/17/2022] [Indexed: 11/21/2022]
Abstract
Organic hydroperoxides (ROOHs) play key roles in the atmosphere as a reactive intermediate species. Due to the low volatility and high hydrophilicity, ROOHs are expected to reside in atmospheric condensed phases such as aerosols, fogs, and cloud droplets. The decomposition mechanisms of ROOHs in the liquid phase are, however, still poorly understood. Here we report a temperature-dependent kinetics and theoretical calculation study of the aqueous-phase decompositions of C12 or C13 α-alkoxyalkyl-hydroperoxides (α-AHs) derived from ozonolysis of α-terpineol in the presence of 1-propanol, 2-propanol, and ethanol. We found that the temporal profiles of α-AH signals, detected as chloride-adducts by negative ion electrospray mass spectrometry, showed single-exponential decay, and the derived first-order rate coefficient k for α-AH decomposition increased as temperature increased, e.g., k(288 K) = (5.3 ± 0.2) × 10-4 s-1, k(298 K) = (1.2 ± 0.3) × 10-3 s-1, k(308 K) = (2.1 ± 1.4) × 10-3 s-1 for C13 α-AHs derived from the reaction of α-terpineol Criegee intermediates with 1-propanol in the solution at pH 4.5. Arrhenius plot analysis yielded an activation energy (E a) of 12.3 ± 0.6 kcal mol-1. E a of 18.7 ± 0.3 and 13.8 ± 0.9 kcal mol-1 were also obtained for the decomposition of α-AHs (at pH 4.5) derived from the reaction of α-terpineol Criegee intermediates with 2-propanol and with ethanol, respectively. Based on the theoretical kinetic and thermodynamic calculations, we propose that a proton-catalyzed mechanism plays a central role in the decomposition of these α-AHs in acidic aqueous organic media, while water molecules may also participate in the decomposition pathways and affect the kinetics. The decomposition of α-AHs could act as a source of H2O2 and multifunctionalized species in atmospheric condensed phases.
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Affiliation(s)
- Mingxi Hu
- Graduate School of Frontier Sciences, The University of Tokyo 5-1-5 Kashiwanoha Kashiwa 277-8563 Japan
| | - Kunpeng Chen
- Department of Environmental Sciences, University of California Riverside California 92521 USA
| | - Junting Qiu
- Graduate School of Frontier Sciences, The University of Tokyo 5-1-5 Kashiwanoha Kashiwa 277-8563 Japan
| | - Ying-Hsuan Lin
- Department of Environmental Sciences, University of California Riverside California 92521 USA
| | - Kenichi Tonokura
- Graduate School of Frontier Sciences, The University of Tokyo 5-1-5 Kashiwanoha Kashiwa 277-8563 Japan
| | - Shinichi Enami
- National Institute for Environmental Studies 16-2 Onogawa Tsukuba 305-8506 Japan +81-29-850-2770
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9
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Hu M, Tonokura K, Morino Y, Sato K, Enami S. Effects of Metal Ions on Aqueous-Phase Decomposition of α-Hydroxyalkyl-Hydroperoxides Derived from Terpene Alcohols. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:12893-12901. [PMID: 34525797 DOI: 10.1021/acs.est.1c04635] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We report the results of a mass spectrometric study of the effects of atmospherically relevant metal ions on the decomposition of α-hydroxyalkyl-hydroperoxides (α-HHs) derived from ozonolysis of α-terpineol in aqueous solutions. By direct mass spectrometric detection of chloride adducts of α-HHs, we assessed the temporal profiles of α-HHs and other products in the presence of metal ions. In addition, reactions between α-HHs and FeCl2 in the presence of excess DMSO showed that the amount of hydroxyl radicals formed in a mixture of α-terpineol, O3, and FeCl2 was 5.7 ± 0.8% of the amount formed in a mixture of H2O2 and FeCl2. The first-order rate constants for the decay of α-HHs produced by ozonolysis of α-terpineol in the presence of 5 mM acetate buffer at a pH of 5.1 ± 0.1 were determined to be (4.5 ± 0.1) × 10-4 s-1 (no metal ions), (4.7 ± 0.2) × 10-4 s-1 (with 0.05 mM Fe2+), (4.7 ± 0.1) × 10-4 s-1 (with 0.05 mM Zn2+), and (4.8 ± 0.2) × 10-4 s-1 (with 0.05 mM Cu2+). We propose that in acidic aqueous media, the reaction of α-HHs with Fe2+ is outcompeted by H+-catalyzed decomposition of α-HHs, which produces the corresponding aldehydes and H2O2, which can in turn react with Fe2+ to form hydroxyl radicals.
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Affiliation(s)
- Mingxi Hu
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Kenichi Tonokura
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Yu Morino
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
| | - Kei Sato
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
| | - Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
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10
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Abstract
The fates of organic hydroperoxides (ROOHs) in atmospheric condensed phases are key to understanding the oxidative and toxicological potentials of particulate matter. Recently, mass spectrometric detection of ROOHs as chloride anion adducts has revealed that liquid-phase α-hydroxyalkyl hydroperoxides, derived from hydration of carbonyl oxides (Criegee intermediates), decompose to geminal diols and H2O2 over a time frame that is sensitively dependent on the water content, pH, and temperature of the reaction solution. Based on these findings, it has been proposed that H+-catalyzed conversion of ROOHs to ROHs + H2O2 is a key process for the decomposition of ROOHs that bypasses radical formation. In this perspective, we discuss our current understanding of the aqueous-phase decomposition of atmospherically relevant ROOHs, including ROOHs derived from reaction between Criegee intermediates and alcohols or carboxylic acids, and of highly oxygenated molecules (HOMs). Implications and future challenges are also discussed.
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Affiliation(s)
- Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
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11
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Hu M, Qiu J, Tonokura K, Enami S. Aqueous-phase fates of α-alkoxyalkyl-hydroperoxides derived from the reactions of Criegee intermediates with alcohols. Phys Chem Chem Phys 2021; 23:4605-4614. [PMID: 33620039 DOI: 10.1039/d0cp06308h] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In the atmosphere, carbonyl oxides known as Criegee intermediates are produced mainly by ozonolysis of volatile organic compounds containing C[double bond, length as m-dash]C double bonds, such as biogenic terpenoids. Criegee intermediates can react with OH-containing species to produce labile organic hydroperoxides (ROOHs) that are taken up into atmospheric condensed phases. Besides water, alcohols are an important reaction partner of Criegee intermediates and can convert them into α-alkoxyalkyl-hydroperoxides (α-AHs), R1R2C(-OOH)(-OR'). Here, we report a study on the aqueous-phase fates of α-AHs derived from ozonolysis of α-terpineol in the presence of methanol, ethanol, 1-propanol, and 2-propanol. The α-terpineol α-AHs and the decomposition products were detected as their chloride adducts by electrospray mass spectrometry as a function of reaction time. Our discovery that the rate of decomposition of α-AHs increased as the pH decreased from 5.9 to 3.8 implied that the decomposition mechanism was catalyzed by H+. The use of isotope solvent experiments revealed that a primary decomposition product of α-AHs in an acidic aqueous solution was a hemiacetal R1R2C(-OH)(-OR') species that was further transformed into other products such as lactols. The proposed H+-catalyzed decomposition of α-AHs, which provides H2O2 and multifunctional species in ambient aerosol particles, may be faster than other degradation processes (e.g., photolysis by solar radiation).
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Affiliation(s)
- Mingxi Hu
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Junting Qiu
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Kenichi Tonokura
- Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8563, Japan
| | - Shinichi Enami
- National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan.
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