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Jayasekharan T. Hg-Hg bonding and its influence on the stability of (HgS) n clusters. Phys Chem Chem Phys 2024; 26:23468-23486. [PMID: 39221613 DOI: 10.1039/d4cp02531h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
Pulsed laser ablation of a HgS(s) precursor shows the formation of small cluster ions, (HgS)n=2-4+, together with HgSn=1-8± and [(HgS)n + Sm]±. The computed structure, atomization energy, and HOMO-LUMO gap energy values of the lowest energy ring singlet show stable (HgS)n=2-8. However, the computed bond conductance of the Hg-Hg bond in (HgS)n shows a high value for (HgS)n=2-4 (ξ = 1.072-0.122), whereas it is low for (HgS)n=5-8 (ξ = 0.039-0.006) and decreases significantly as the ring expands, indicating that (HgS)n≥5 is unstable. It evidences that the weak chemical bonding between Hg2+-Hg2+ closed shell (5d10-5d10) electrons plays a significant role in the stability of ring (HgS)n=2-4. Thus, it validates the experimental observation of stable cluster ions up to (HgS)4+. In contrast, the low energy chain triplet (HgS)n=2-8 shows a progressive increase in stability and bond conductance with chain length, indicating sustained mercurophilic interactions in long chain clusters like its crystal structure. Furthermore, the lowest/low energy isomers of HgSn=1-8 have been computed for their energetics, HOMO-LUMO gaps, and electron affinity using DFT-B3LYP/PBE0 methods.
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Affiliation(s)
- Thankan Jayasekharan
- Atomic and Molecular Physics Division, Physics Group Bhabha Atomic Research Centre Trombay, Mumbai-400085, India.
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2
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Shah V, Jacob DJ, Thackray CP, Wang X, Sunderland EM, Dibble TS, Saiz-Lopez A, Černušák I, Kellö V, Castro PJ, Wu R, Wang C. Improved Mechanistic Model of the Atmospheric Redox Chemistry of Mercury. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:14445-14456. [PMID: 34724789 DOI: 10.1021/acs.est.1c03160] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We present a new chemical mechanism for Hg0/HgI/HgII atmospheric cycling, including recent laboratory and computational data, and implement it in the GEOS-Chem global atmospheric chemistry model for comparison to observations. Our mechanism includes the oxidation of Hg0 by Br and OH, subsequent oxidation of HgI by ozone and radicals, respeciation of HgII in aerosols and cloud droplets, and speciated HgII photolysis in the gas and aqueous phases. The tropospheric Hg lifetime against deposition in the model is 5.5 months, consistent with observational constraints. The model reproduces the observed global surface Hg0 concentrations and HgII wet deposition fluxes. Br and OH make comparable contributions to global net oxidation of Hg0 to HgII. Ozone is the principal HgI oxidant, enabling the efficient oxidation of Hg0 to HgII by OH. BrHgIIOH and HgII(OH)2, the initial HgII products of Hg0 oxidation, respeciate in aerosols and clouds to organic and inorganic complexes, and volatilize to photostable forms. Reduction of HgII to Hg0 takes place largely through photolysis of aqueous HgII-organic complexes. 71% of model HgII deposition is to the oceans. Major uncertainties for atmospheric Hg chemistry modeling include Br concentrations, stability and reactions of HgI, and speciation and photoreduction of HgII in aerosols and clouds.
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Affiliation(s)
- Viral Shah
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Daniel J Jacob
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Colin P Thackray
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Xuan Wang
- School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, China
| | - Elsie M Sunderland
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
- Department of Environmental Health, Harvard T.H. Chan School of Public Health, Harvard University, Boston, Massachusetts 02115, United States
| | - Theodore S Dibble
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, New York 13210, United States
| | - Alfonso Saiz-Lopez
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain
| | - Ivan Černušák
- Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 84215 Bratislava, Slovakia
| | - Vladimir Kellö
- Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 84215 Bratislava, Slovakia
| | - Pedro J Castro
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, New York 13210, United States
| | - Rongrong Wu
- Department of Physics and Astronomy, Mississippi State University, Starkville, Mississippi 39759, United States
| | - Chuji Wang
- Department of Physics and Astronomy, Mississippi State University, Starkville, Mississippi 39759, United States
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3
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Wu R, Wang C, Dibble TS. First experimental kinetic study of the atmospherically important reaction of BrHg + NO2. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137928] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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4
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Lam KT, Wilhelmsen CJ, Dibble TS. BrHgO• + C2H4 and BrHgO• + HCHO in Atmospheric Oxidation of Mercury: Determining Rate Constants of Reactions with Prereactive Complexes and Bifurcation. J Phys Chem A 2019; 123:6045-6055. [DOI: 10.1021/acs.jpca.9b05120] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Khoa T. Lam
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Dr., Syracuse, New York 13210, United States
| | - Curtis J. Wilhelmsen
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Dr., Syracuse, New York 13210, United States
| | - Theodore S. Dibble
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Dr., Syracuse, New York 13210, United States
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Lam KT, Wilhelmsen CJ, Schwid AC, Jiao Y, Dibble TS. Computational Study on the Photolysis of BrHgONO and the Reactions of BrHgO• with CH4, C2H6, NO, and NO2: Implications for Formation of Hg(II) Compounds in the Atmosphere. J Phys Chem A 2019; 123:1637-1647. [DOI: 10.1021/acs.jpca.8b11216] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Khoa T. Lam
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
| | - Curtis J. Wilhelmsen
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
| | - Abraham C. Schwid
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
| | - Yuge Jiao
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
| | - Theodore S. Dibble
- Department of Chemistry, State University of New York-College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
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Jiao Y, Dibble TS. First kinetic study of the atmospherically important reactions BrHg˙ + NO 2 and BrHg˙ + HOO. Phys Chem Chem Phys 2018; 19:1826-1838. [PMID: 28000816 DOI: 10.1039/c6cp06276h] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We use computational chemistry to determine the rate constants and product yields for the reactions of BrHg˙ with the atmospherically abundant radicals NO2 and HOO. The reactants, products, and well-defined transition states are characterized using CCSD(T) with large basis sets. The potential energy profiles for the barrierless addition of HOO and NO2 to BrHg˙ are characterized using CASPT2 and RHF-CCSDT, and the rate constants are computed as a function of temperature and pressure using variational transition state theory and master equation simulations. The calculated rate constant for the addition of NO2 to BrHg˙ is larger than that for the addition of HOO by a factor of up to two under atmospheric conditions. For the reaction of HOO with BrHg˙ the addition reaction entirely dominates competing HOO + BrHg˙ reaction channels. The addition of NO2 to BrHg˙ initially produces both BrHgNO2 and BrHgONO, but after a few seconds under atmospheric conditions the sole product is syn-BrHgONO. A previously unsuspected reaction channel for BrHg˙ + NO2 competes with the addition to yield Hg + BrNO2. This reaction reduces the mercury oxidation state in BrHg˙ from Hg(i) to Hg(0) and slows the atmospheric oxidation of Hg(0). While the rate constant for this reduction channel is not well-constrained by the present calculations, it may be as much as 18% as large as the oxidation channel under some atmospheric conditions. As no experimental kinetic or product yield data are available for the reactions studied here, this work will provide guidance for atmospheric modelers and experimental kineticists.
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Affiliation(s)
- Yuge Jiao
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Dr, Syracuse, NY 13210, USA.
| | - Theodore S Dibble
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Dr, Syracuse, NY 13210, USA.
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Jiao Y, Dibble TS. Structures, Vibrational Frequencies, and Bond Energies of the BrHgOX and BrHgXO Species Formed in Atmospheric Mercury Depletion Events. J Phys Chem A 2017; 121:7976-7985. [DOI: 10.1021/acs.jpca.7b06829] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yuge Jiao
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
| | - Theodore S. Dibble
- Department of Chemistry, State University of New York, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York 13210, United States
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9
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Sun G, Sommar J, Feng X, Lin CJ, Ge M, Wang W, Yin R, Fu X, Shang L. Mass-Dependent and -Independent Fractionation of Mercury Isotope during Gas-Phase Oxidation of Elemental Mercury Vapor by Atomic Cl and Br. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:9232-41. [PMID: 27501307 DOI: 10.1021/acs.est.6b01668] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
This study presents the first measurement of Hg stable isotope fractionation during gas-phase oxidation of Hg(0) vapor by halogen atoms (Cl(•), Br(•)) in the laboratory at 750 ± 1 Torr and 298 ± 3 K. Using a relative rate technique, the rate coefficients for Hg(0)+Cl(•) and Hg(0)+Br(•) reactions are determined to be (1.8 ± 0.5) × 10(-11) and (1.6 ± 0.8) × 10(-12) cm(3) molecule(-1) s(-1), respectively. Results show that heavier isotopes are preferentially enriched in the remaining Hg(0) during Cl(•) initiated oxidation, whereas being enriched in the product during oxidation by Br(•). The fractionation factors for (202)Hg/(198)Hg during the Cl(•) and Br(•) initiated oxidations are α(202/198) = 0.99941 ± 0.00006 (2σ) and 1.00074 ± 0.00014 (2σ), respectively. A Δ(199)Hg/Δ(201)Hg ratio of 1.64 ± 0.30 (2σ) during oxidation of Hg(0) by Br atoms suggests that Hg-MIF is introduced by the nuclear volume effect (NVE). In contrast, the Hg(0) + Cl(•) reaction produces a Δ(199)Hg/Δ(201)Hg-slope of 1.89 ± 0.18 (2σ), which in addition to a high degree of odd-mass-number isotope MIF suggests impacts from MIF effects other than NVE. This reaction also exhibits significant MIF of (200)Hg (Δ(200)Hg, up to -0.17‰ in the reactant) and is the first physicochemical process identified to trigger (200)Hg anomalies that are frequently detected in atmospheric samples.
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Affiliation(s)
- Guangyi Sun
- University of Chinese Academy of Sciences, Beijing 100190, China
| | | | | | - Che-Jen Lin
- Center for Advances in Water and Air Quality, Lamar University , Beaumont, Texas 77710, United States
| | - Maofa Ge
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Weigang Wang
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China
| | - Runsheng Yin
- Environmental Chemistry and Technology Program, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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10
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Dibble TS, Schwid AC. Thermodynamics limits the reactivity of BrHg radical with volatile organic compounds. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.07.065] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Jiao Y, Dibble TS. Quality Structures, Vibrational Frequencies, and Thermochemistry of the Products of Reaction of BrHg• with NO2, HO2, ClO, BrO, and IO. J Phys Chem A 2015; 119:10502-10. [DOI: 10.1021/acs.jpca.5b04889] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuge Jiao
- Department of Chemistry,
College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States
| | - Theodore S. Dibble
- Department of Chemistry,
College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States
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12
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Ariya PA, Amyot M, Dastoor A, Deeds D, Feinberg A, Kos G, Poulain A, Ryjkov A, Semeniuk K, Subir M, Toyota K. Mercury Physicochemical and Biogeochemical Transformation in the Atmosphere and at Atmospheric Interfaces: A Review and Future Directions. Chem Rev 2015; 115:3760-802. [DOI: 10.1021/cr500667e] [Citation(s) in RCA: 228] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
| | - Marc Amyot
- Department
of Biological Sciences, Université de Montréal, 90
avenue Vincent-d’Indy, Montreal, Quebec, Canada, H3C 3J7
| | - Ashu Dastoor
- Air
Quality Research Division, Environment Canada, 2121 TransCanada Highway, Dorval, Quebec, Canada, H9P 1J3
| | | | | | | | - Alexandre Poulain
- Department
of Biology, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada, K1N 6N5
| | - Andrei Ryjkov
- Air
Quality Research Division, Environment Canada, 2121 TransCanada Highway, Dorval, Quebec, Canada, H9P 1J3
| | - Kirill Semeniuk
- Air
Quality Research Division, Environment Canada, 2121 TransCanada Highway, Dorval, Quebec, Canada, H9P 1J3
| | - M. Subir
- Department
of Chemistry, Ball State University, 2000 West University Avenue, Muncie, Indiana 47306, United States
| | - Kenjiro Toyota
- Air
Quality Research Division, Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada, M3H 5T4
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13
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Steffen A, Lehnherr I, Cole A, Ariya P, Dastoor A, Durnford D, Kirk J, Pilote M. Atmospheric mercury in the Canadian Arctic. Part I: a review of recent field measurements. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 509-510:3-15. [PMID: 25497576 DOI: 10.1016/j.scitotenv.2014.10.109] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Revised: 10/27/2014] [Accepted: 10/31/2014] [Indexed: 06/04/2023]
Abstract
Long-range atmospheric transport and deposition are important sources of mercury (Hg) to Arctic aquatic and terrestrial ecosystems. We review here recent progress made in the study of the transport, transformation, deposition and reemission of atmospheric Hg in the Canadian Arctic, focusing on field measurements (see Dastoor et al., this issue for a review of modeling studies on the same topics). Redox processes control the speciation of atmospheric Hg, and thus impart an important influence on Hg deposition, particularly during atmospheric mercury depletion events (AMDEs). Bromine radicals were identified as the primary oxidant of atmospheric Hg during AMDEs. Since the start of monitoring at Alert (NU) in 1995, the timing of peak AMDE occurrence has shifted to earlier times in the spring (from May to April) in recent years, and while AMDE frequency and GEM concentrations are correlated with local meteorological conditions, the reasons for this timing-shift are not understood. Mercury is subject to various post-depositional processes in snowpacks and a large portion of deposited oxidized Hg can be reemitted following photoreduction; how much Hg is deposited and reemitted depends on geographical location, meteorological, vegetative and sea-ice conditions, as well as snow chemistry. Halide anions in the snow can stabilize Hg, therefore it is expected that a smaller fraction of deposited Hg will be reemitted from coastal snowpacks. Atmospheric gaseous Hg concentrations have decreased in some parts of the Arctic (e.g., Alert) from 2000 to 2009 but at a rate that was less than that at lower latitudes. Despite numerous recent advances, a number of knowledge gaps remain, including uncertainties in the identification of oxidized Hg species in the air (and how this relates to dry vs. wet deposition), physical-chemical processes in air, snow and water-especially over sea ice-and the relationship between these processes and climate change.
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Affiliation(s)
- Alexandra Steffen
- Environment Canada, Air Quality Processes Research, Toronto M3H 5T4, Ontario, Canada.
| | - Igor Lehnherr
- University of Waterloo, Department of Earth and Environmental Sciences, Waterloo N2L 3G1, Ontario, Canada
| | - Amanda Cole
- Environment Canada, Air Quality Processes Research, Toronto M3H 5T4, Ontario, Canada
| | - Parisa Ariya
- McGill University, Department of Chemistry, 801 Sherbrooke St. W., Montreal H3A 2K6, Quebec, Canada; McGill University, Department of Atmospheric and Oceanic Sciences, 801 Sherbrooke St. W., Montreal H3A 2K6, Quebec, Canada
| | - Ashu Dastoor
- Environment Canada, National Prediction Development Division, Dorval H9P 1J3, Quebec, Canada
| | - Dorothy Durnford
- Environment Canada, National Prediction Development Division, Dorval H9P 1J3, Quebec, Canada
| | - Jane Kirk
- Environment Canada, Aquatic Contaminants Research Division, Burlington L7R 4A6, Ontario, Canada
| | - Martin Pilote
- Environment Canada, Aquatic Contaminants Research Division, Montreal H2Y 2E7, Quebec, Canada
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Dibble TS, Zelie MJ, Jiao Y. Quantum Chemistry Guide to PTRMS Studies of As-Yet Undetected Products of the Bromine-Atom Initiated Oxidation of Gaseous Elemental Mercury. J Phys Chem A 2014; 118:7847-54. [DOI: 10.1021/jp5041426] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Theodore S. Dibble
- Department of Chemistry,
College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States
| | - Matthew J. Zelie
- Department of Chemistry,
College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States
| | - Yuge Jiao
- Department of Chemistry,
College of Environmental Science and Forestry, State University of New York, Syracuse, New York 13210, United States
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Du S, Germann TC, Francisco JS, Peterson KA, Yu HG, Lyons JR. The kinetics study of the S + S2 → S3 reaction by the chaperone mechanism. J Chem Phys 2011; 134:154508. [PMID: 21513396 DOI: 10.1063/1.3572226] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The recombination of S atoms has been found to be stepwise from the smallest unit, the elemental S atom, to the most abundant molecule S(8). The reaction between S + S(2) → S(3) has not been reported either experimentally or by theory, but may be a key intermediate step in the formation of sulfur aerosols in low-O(2) atmospheres. In this work, the kinetics of this reaction is reported with Ar gas used as the chaperone molecule in the production of S(3) via two complex intermediates: SAr + S(2) and S(2)Ar + S. Quasi-classical and classical trajectory methods are used. The rate constant of the S + S(2) + Ar → S(3) + Ar reaction is determined to be 2.66 × 10(-33) cm(6) mol(-1) s(-1) at 298.15 K. The temperature dependence of the reaction is found to be 2.67 × 10(-33) exp[143.56(1∕T-1∕298.15)]. The second-order rate constant of S + S(2) → S(3) is 6.47 × 10(-14) cm(3) molecule(-1) s(-1) at 298.15 K and the Arrhenius-type rate constant is calculated to be 6.25 × 10(-14) exp[450.15(1∕T-1∕298.15)] cm(3) molecule(-1) s(-1). This work provides a rate coefficient for a key intermediate species in studies of sulfur formation in the modern Venus atmosphere and the primitive Earth atmosphere, for which assumed model rate coefficients have spanned nearly 4 orders of magnitude. Although a symmetry-induced mass-independent isotope effect is not expected for a chaperone mechanism, the present work is an important step toward evaluating whether mass-independence is expected for thiozone formation as is observed for ozone formation.
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Affiliation(s)
- Shiyu Du
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Schofield K. Fuel-mercury combustion emissions: an important heterogeneous mechanism and an overall review of its implications. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:9014-9030. [PMID: 19174866 DOI: 10.1021/es801440g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
An extensive examination of combustion gases containing trace amounts of mercury shows unambiguously mercury's propensity for heterogeneous chemistry. Although additional mechanisms for the oxidation chemistry of mercury have been implied by the continuing inadequacy of modeling attempts, details of the specific chemistry have remained unknown. Now it is shown that mercury can efficiently chemi-deposit onto surfaces encountered in practical combustors. If sulfur is present, condensed mercuric sulfate forms momentarily. This is then converted by gaseous HCl to HgCl2 that may sublime into the flow or be retained. This elusive and efficient noncatalytic mechanism most likely explains the observed fractional conversions to the dichloride observed in coal combustors. A receptive surface acts solely as an intermediary, facilitating the conversion while disguising its role. Without sulfur, a corresponding mechanism occurs but via HgO that is similarly converted to the dihalide. Such heterogeneous dynamics have significant repercussions for both full-scale combustors and bench-type experiments, which data have been reassessed and reviewed. Conclusions imply that observations concerning mercury will be system dependent and no two combustors can be exactly alike. The re-examination of prior work provides significant support for these conclusions. This fundamental understanding now lays a foundation for meaningful interpretations and program planning. It has indicated also the extreme care needed in sampling and monitoring the speciation of mercury in such combustion flows for reliable results. It now points to a simple low-cost surface-induced mitigation method for effectively converting the mercury in flue gases to the water-soluble dichloride. It is in essence no more than an optimization of the natural process that is currently occurring in combustors but to only limited degrees.
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Affiliation(s)
- Keith Schofield
- Materials Research Laboratory, University of California at Santa Barbara, Santa Barbara, California 93106, USA.
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17
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Seigneur C, Lohman K. Effect of bromine chemistry on the atmospheric mercury cycle. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008jd010262] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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18
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Cremer D, Kraka E, Filatov M. Bonding in Mercury Molecules Described by the Normalized Elimination of the Small Component and Coupled Cluster Theory. Chemphyschem 2008; 9:2510-21. [DOI: 10.1002/cphc.200800510] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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19
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Feller D, Peterson KA, Dixon DA. A survey of factors contributing to accurate theoretical predictions of atomization energies and molecular structures. J Chem Phys 2008; 129:204105. [DOI: 10.1063/1.3008061] [Citation(s) in RCA: 312] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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20
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Maron L, Dommergue A, Ferrari C, Delacour-Larose M, Faïn X. How Elementary Mercury Reacts in the Presence of Halogen Radicals and/or Halogen Anions: A DFT Investigation. Chemistry 2008; 14:8322-9. [DOI: 10.1002/chem.200800491] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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21
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Du S, Francisco JS, Shepler BC, Peterson KA. Determination of the rate constant for sulfur recombination by quasiclassical trajectory calculations. J Chem Phys 2008; 128:204306. [DOI: 10.1063/1.2919569] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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22
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Goodsite ME, Plane JMC, Skov H. A theoretical study of the oxidation of Hg0 to HgBr2 in the troposphere. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2004. [PMID: 15074688 DOI: 10.1021/es301201c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The oxidation of elemental mercury (Hg0) to the divalent gaseous mercury dibromide (HgBr2) has been proposed to account for the removal of Hg0 during depletion events in the springtime Arctic. The mechanism of this process is explored in this paper by theoretical calculations of the relevant rate coefficients. Rice-Ramsberger-Kassel-Marcus (RRKM) theory, together with ab initio quantum calculations where required, are used to estimate the following: recombination rate coefficients of Hg with Br, I, and O; the thermal dissociation rate coefficient of HgBr; and the recombination rate coefficients of HgBr with Br, I, OH, and O2. A mechanism based on the initial recombination of Hg with Br, followed by the addition of a second radical (Br, I, or OH) in competition with thermal dissociation of HgBr, is able to account for the observed rate of Hg0 removal, both in Arctic depletion events and at lower latitudes.
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Affiliation(s)
- M E Goodsite
- Department of Atmospheric Environment, National Environmental Research Institute, Roskilde, Denmark.
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