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Peng W, Le C, Porter WC, Cocker DR. Variability in Aromatic Aerosol Yields under Very Low NO x Conditions at Different HO 2/RO 2 Regimes. Environ Sci Technol 2022; 56:750-760. [PMID: 34978436 DOI: 10.1021/acs.est.1c04392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Current chemical transport models generally use a constant secondary organic aerosol (SOA) yield to represent SOA formation from aromatic compounds under low NOx conditions. However, a wide range of SOA yields (10 to 42%) from m-xylene under low NOx conditions is observed in this study. The chamber HO2/RO2 ratio is identified as a key factor explaining SOA yield variability: higher SOA yields are observed for runs with a higher HO2/RO2 ratio. The RO2 + RO2 pathway, which can be increasingly significant under low NOx and HO2/RO2 conditions, shows a lower SOA-forming potential compared to the RO2 + HO2 pathway. While the traditional low-NOx chamber experiments are commonly used to represent the RO2 + HO2 pathway, this study finds that the impacts of the RO2 + RO2 pathway cannot be ignored under certain conditions. We provide guidance on how to best control for these two pathways in conducting chamber experiments to best obtain SOA yield curves and quantify the contributions from each pathway. On the global scale, the chemical transport model GEOS-Chem is used to identify regions characterized by lower surface HO2/RO2 ratios, suggesting that the RO2 + RO2 pathway is more likely to prove significant to overall SOA yields in those regions. Current models generally do not consider the RO2 + RO2 impacts on aromatic SOA formation, but preliminary sensitivity tests with updated SOA yield parameters based on such a pathway suggest that without this consideration, some types of SOA may be overestimated in regions with lower HO2/RO2 ratios.
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Affiliation(s)
- Weihan Peng
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, Riverside, California 92507, United States
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, 1084 Columbia Avenue, Riverside, California 92507, United States
| | - Chen Le
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, Riverside, California 92507, United States
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, 1084 Columbia Avenue, Riverside, California 92507, United States
| | - William C Porter
- Department of Environmental Sciences, University of California, Riverside, Riverside, California 92521, United States
| | - David R Cocker
- Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, Riverside, California 92507, United States
- Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, 1084 Columbia Avenue, Riverside, California 92507, United States
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Zhang Y, He B, Wang Z, Huang B, Zhou Y. Atmospheric chemistry of CF 2ClO 2: a theoretical study on mechanisms and kinetics of the CF 2ClO 2 + HO 2 reaction. Environ Sci Pollut Res Int 2020; 27:33965-33974. [PMID: 32557062 DOI: 10.1007/s11356-020-09580-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 06/02/2020] [Indexed: 06/11/2023]
Abstract
The singlet and triplet potential energy surfaces of the HO2 with CF2ClO2 reaction have been probed at the BMC-CCSD/cc-pVTZ level according to the B3LYP/6-311++G(d,p) level obtained geometrical structure. On the singlet PES, the association/dissociation, direct H- abstraction, and SN2 displacement mechanisms have been taken into account. On the triplet PES, SN2 displacement and indirect H- abstraction reaction mechanisms have been investigated and the H- abstraction channel makes more contribution to the CF2ClO2 with HO2 reaction. The rate constants have been computed at 10-10 to 1010 atm and 200-3000 K by RRKM-TST theory. The results show that at T ≤ 600 K, the generation of IM1 (CF2ClO4H) by collisional deactivation is dominant pathway; at high temperatures, the production of P8 (CF2ClOOH + O2(3Σ)) becomes predominate. The predicted data for CF2ClO2 + HO2 agrees closely with available experimental value. Moreover, OH radicals act as inhibitors in the CF2ClOOH→CF2O + HOCl and CF2ClOOH→CFClO + HOF reactions. The dominant products for the reaction of CF2ClOOH + OH are CF2ClO2 + H2O.
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Affiliation(s)
- Yunju Zhang
- Key Laboratory of Photoinduced Functional Materials, Mianyang Normal University, Mianyang, 621000, People's Republic of China.
| | - Bing He
- College of Chemistry and Life Science, Institute of Functional Molecules, Chengdu Normal University, Chengdu, 611130, Sichuan, People's Republic of China
| | - Zhiguo Wang
- Key Laboratory of Photoinduced Functional Materials, Mianyang Normal University, Mianyang, 621000, People's Republic of China
| | - Baomei Huang
- Key Laboratory of Photoinduced Functional Materials, Mianyang Normal University, Mianyang, 621000, People's Republic of China
| | - Yan Zhou
- Key Laboratory of Photoinduced Functional Materials, Mianyang Normal University, Mianyang, 621000, People's Republic of China
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Tang Y, Lu C, Sun J, Shao Y, Gao Y, Fu Z. Computational investigations on the HO 2 + CHBr 2O 2 reaction: mechanisms, products, and atmospheric implications. Environ Sci Pollut Res Int 2019; 26:2345-2352. [PMID: 30467745 DOI: 10.1007/s11356-018-3767-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 11/14/2018] [Indexed: 06/09/2023]
Abstract
Using quantum chemistry methods, mechanisms and products of the CHBr2O2 + HO2 reaction in the atmosphere were investigated theoretically. Computational result indicates that the dominant product is CHBr2OOH + O2 formed on the triplet potential energy surface (PES). While CBr2O + OH + HO2 produced on the singlet PES is subdominant to the overall reaction under the typical atmospheric condition below 300 K. Due to higher energy barriers surmounted, other products including CBr2O2 + H2O2, CBr2O + HO3H, CH2O + HO3Br, CHBrO + HO3 + Br, and CHBr2OH + O3 make minor contributions to the overall reaction. In the presence of OH radical, CHBr2OOH generates CHBr2O2 and CBr2O2 + H2O subsequently, which enters into new Br-cycle in the atmosphere. The substitution effect of alkyl group and halogens plays negligible roles to the dominant products in the RO2 + HO2 (X = H, CH3, CH2OH, CH2F, CH2Cl, CH2Br, CH2Cl, and CH2Br) reactions in the atmosphere.
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Affiliation(s)
- Yizhen Tang
- School of Environmental and municipal engineering, Qingdao University of Technology, Fushun Road 11, Qingdao, Shandong, 266033, People's Republic of China.
| | - Chenggang Lu
- School of Environmental and municipal engineering, Qingdao University of Technology, Fushun Road 11, Qingdao, Shandong, 266033, People's Republic of China
| | - Jingyu Sun
- College of Chemistry and Environmental engineering, Hubei Normal University, Cihu Road 11, Huangshi, Hubei, 435002, People's Republic of China
| | - Youxiang Shao
- School of Materials Science and Engineering, PCFM Lab, Sun Yat-sen University, Guangzhou, 510275, People's Republic of China
| | - Ying Gao
- School of Environmental and municipal engineering, Qingdao University of Technology, Fushun Road 11, Qingdao, Shandong, 266033, People's Republic of China
| | - Zhihao Fu
- School of Environmental and municipal engineering, Qingdao University of Technology, Fushun Road 11, Qingdao, Shandong, 266033, People's Republic of China
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Wu NN, Zhang MZ, Ou-Yang SL, Li L. Theoretical Study of the C₂H₅ + HO₂ Reaction: Mechanism and Kinetics. Molecules 2018; 23:E1919. [PMID: 30071619 DOI: 10.3390/molecules23081919] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 07/26/2018] [Accepted: 07/27/2018] [Indexed: 11/16/2022] Open
Abstract
The mechanism and kinetics for the reaction of the HO2 radical with the ethyl (C2H5) radical have been investigated theoretically. The electronic structure information of the potential energy surface (PES) is obtained at the MP2/6-311++G(d,p) level of theory, and the single-point energies are refined by the CCSD(T)/6-311+G(3df,2p) level of theory. The kinetics of the reaction with multiple channels have been studied by applying variational transition-state theory (VTST) and Rice–Ramsperger–Kassel–Marcus (RRKM) theory over wide temperature and pressure ranges (T = 220–3000 K; P = 1 × 10−4–100 bar). The calculated results show that the HO2 radical can attack C2H5 via a barrierless addition mechanism to form the energy-rich intermediate IM1 C2H5OOH (68.7 kcal/mol) on the singlet PES. The collisional stabilization intermediate IM1 is the predominant product of the reaction at high pressures and low temperatures, while the bimolecular product P1 C2H5O + OH becomes the primary product at lower pressures or higher temperatures. At the experimentally measured temperature 293 K and in the whole pressure range, the reaction yields P1 as major product, which is in good agreement with experiment results, and the branching ratios are predicted to change from 0.96 at 1 × 10−4 bar to 0.66 at 100 bar. Moreover, the direct H-abstraction product P16 C2H6 + 3O2 on the triplet PES is the secondary feasible product with a yield of 0.04 at the collisional limit of 293 K. The present results will be useful to gain deeper insight into the understanding of the kinetics of the C2H5 + HO2 reaction under atmospheric and practical combustion conditions.
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Fahr A, Braun W, Kurylo MJ. Optimizing Complex Kinetics Experiments Using Least-Squares Methods. J Res Natl Inst Stand Technol 1993; 98:181-190. [PMID: 28053465 PMCID: PMC4909176 DOI: 10.6028/jres.098.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 10/22/1992] [Indexed: 06/06/2023]
Abstract
Complex kinetic problems are generally modeled employing numerical integration routines. Our kinetics modeling program, Acuchem, has been modified to fit rate constants and absorption coefficients generically to real or synthesized "laboratory data" via a least-squares iterative procedure written for personal computers. To test the model and method of analysis the self- and cross-combination reactions of HO2 and CH3O2 radicals of importance in atmospheric chemistry are examined. These radicals as well as other species absorb ultraviolet radiation. The resultant absorption signal is measured in the laboratory and compared with a modeled signal to obtain the best-fit to various kinetic parameters. The modified program generates synthetic data with added random noise. An analysis of the synthetic data leads to an optimization of the experimental design and best-values for certain rate constants and absorption coefficients.
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Affiliation(s)
- A Fahr
- National Institute of Standards and Technology, Gaithersburg, MD 20899-0001
| | - W Braun
- National Institute of Standards and Technology, Gaithersburg, MD 20899-0001
| | - M J Kurylo
- National Institute of Standards and Technology, Gaithersburg, MD 20899-0001
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