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Ai Y, Wang C, Videen G, Pan YL. Optically levitated, single-particle reactor for the study of surface and heterogeneous chemistry--reactions of particulate-bound mercury with ozone in air. Chem Phys Lett 2023. [DOI: 10.1016/j.cplett.2023.140428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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Castro PJ, Kellö V, Cernušák I, Dibble TS. Together, Not Separately, OH and O 3 Oxidize Hg (0) to Hg (II) in the Atmosphere. J Phys Chem A 2022; 126:8266-8279. [DOI: 10.1021/acs.jpca.2c04364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Pedro J. Castro
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York13210, United States
| | - Vladimir Kellö
- Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, 84215Bratislava, Slovakia
| | - Ivan Cernušák
- Department of Physical and Theoretical Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, 84215Bratislava, Slovakia
| | - Theodore S. Dibble
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, New York13210, United States
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Wu R, Castro PJ, Gaito C, Beiter K, Dibble TS, Wang C. Combined Experimental and Computational Kinetics Studies for the Atmospherically Important BrHg Radical Reacting with NO and O 2. J Phys Chem A 2022; 126:3914-3925. [PMID: 35686857 DOI: 10.1021/acs.jpca.2c02531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report on the first experimental determination of the absolute rate constant of the reaction of BrHg + NO in N2 bath gas using a laser photolysis-laser-induced fluorescence (LP-LIF) system. The rate constant of the reaction of BrHg + NO is determined to be 7.0-0.9+1.3 × 10-12 cm3 molecule-1 s-1 over 50-700 Torr and 315-353 K. The absence of a pressure or temperature dependence suggests that this reaction leads mainly to mercury reduction (Hg + BrNO) rather than mercury oxidation (BrHgNO). Our theoretical calculations using NEVPT2 energies on density functional theory (DFT) geometries are consistent with a barrierless reaction to form Hg + BrNO. The equilibrium constants and the rate constants of the reaction BrHg + O2 ⇌ BrHgOO are computed theoretically because they are too low to be measured in the LP-LIF system. Molecular oxygen quenches the LIF signal of BrHg with a large rate constant of (1.7 ± 0.1) × 10-10 cm3 molecule-1 s-1. Thus, different techniques that capture the absolute [BrHg(X̃)] would be advantageous for kinetics studies of BrHg reactions in the presence of O2. The computed equilibrium constant suggests a non-negligible upper limit of the fraction of BrHg stored as BrHgOO (up to 0.5) at low-temperature conditions, e.g., in the upper troposphere and in polar winters at ground level. Preliminary results indicate that BrHgOO behaves like HOO or organic peroxy radicals in reactions with atmospheric radicals.
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Affiliation(s)
- Rongrong Wu
- Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, United States
| | - Pedro J Castro
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210, United States
| | - Cameron Gaito
- Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, United States
| | - Kyle Beiter
- Department of Chemistry, State University of New York College of Environmental Science and Forestry, Syracuse, New York 13210, 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
| | - Chuji Wang
- Department of Physics and Astronomy, Mississippi State University, Mississippi State, Mississippi 39762, United States
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Gómez Martín JC, Lewis TR, Douglas KM, Blitz MA, Saiz-Lopez A, Plane JMC. The reaction between HgBr and O 3: kinetic study and atmospheric implications. Phys Chem Chem Phys 2022; 24:12419-12432. [PMID: 35575018 PMCID: PMC9131727 DOI: 10.1039/d2cp00754a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The rate constants of many reactions currently considered to be important in the atmospheric chemistry of mercury remain to be measured in the laboratory. Here we report the first experimental determination of the rate constant of the gas-phase reaction between the HgBr radical and ozone, for which a value at room temperature of k(HgBr + O3) = (7.5 ± 0.6) × 10-11 cm3 molecule s-1 (1σ) has been obtained. The rate constants of two reduction side reactions were concurrently determined: k(HgBr + O) = (5.3 ± 0.4) × 10-11 cm3 molecule s-1 and k(HgBrO + O) = (9.1 ± 0.6) × 10-11 cm3 molecule s-1. The value of k(HgBr + O3) is slightly lower than the collision number, confirming the absence of a significant energy barrier. Considering the abundance of ozone in the troposphere, our experimental rate constant supports recent modelling results suggesting that the main atmospheric fate of HgBr is reaction with ozone to form BrHgO.
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Affiliation(s)
| | - Thomas R Lewis
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain. .,School of Chemistry, University of Leeds, LS2 9JT Leeds, UK
| | | | - Mark A Blitz
- School of Chemistry, University of Leeds, LS2 9JT Leeds, UK
| | - Alfonso Saiz-Lopez
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain.
| | - John M C Plane
- School of Chemistry, University of Leeds, LS2 9JT Leeds, UK
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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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Saiz-Lopez A, Travnikov O, Sonke JE, Thackray CP, Jacob DJ, Carmona-García J, Francés-Monerris A, Roca-Sanjuán D, Acuña AU, Dávalos JZ, Cuevas CA, Jiskra M, Wang F, Bieser J, Plane JMC, Francisco JS. Photochemistry of oxidized Hg(I) and Hg(II) species suggests missing mercury oxidation in the troposphere. Proc Natl Acad Sci U S A 2020; 117:30949-30956. [PMID: 33229529 PMCID: PMC7733835 DOI: 10.1073/pnas.1922486117] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 10/26/2020] [Indexed: 11/18/2022] Open
Abstract
Mercury (Hg), a global contaminant, is emitted mainly in its elemental form Hg0 to the atmosphere where it is oxidized to reactive HgII compounds, which efficiently deposit to surface ecosystems. Therefore, the chemical cycling between the elemental and oxidized Hg forms in the atmosphere determines the scale and geographical pattern of global Hg deposition. Recent advances in the photochemistry of gas-phase oxidized HgI and HgII species postulate their photodissociation back to Hg0 as a crucial step in the atmospheric Hg redox cycle. However, the significance of these photodissociation mechanisms on atmospheric Hg chemistry, lifetime, and surface deposition remains uncertain. Here we implement a comprehensive and quantitative mechanism of the photochemical and thermal atmospheric reactions between Hg0, HgI, and HgII species in a global model and evaluate the results against atmospheric Hg observations. We find that the photochemistry of HgI and HgII leads to insufficient Hg oxidation globally. The combined efficient photoreduction of HgI and HgII to Hg0 competes with thermal oxidation of Hg0, resulting in a large model overestimation of 99% of measured Hg0 and underestimation of 51% of oxidized Hg and ∼66% of HgII wet deposition. This in turn leads to a significant increase in the calculated global atmospheric Hg lifetime of 20 mo, which is unrealistically longer than the 3-6-mo range based on observed atmospheric Hg variability. These results show that the HgI and HgII photoreduction processes largely offset the efficiency of bromine-initiated Hg0 oxidation and reveal missing Hg oxidation processes in the troposphere.
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Affiliation(s)
- Alfonso Saiz-Lopez
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, Spanish National Research Council (CSIC), 28006 Madrid, Spain;
| | - Oleg Travnikov
- Meteorological Synthesizing Centre-East of EMEP, 115419 Moscow, Russia;
| | - Jeroen E Sonke
- Géosciences Environnement Toulouse, CNRS/Observatoire Midi-Pyrénées (OMP)/Université de Toulouse, 31400 Toulouse, France
| | - Colin P Thackray
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
| | - Daniel J Jacob
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138
| | | | - Antonio Francés-Monerris
- Departamento de Química Física, Universitat de València, 46100 València, Spain
- Université de Lorraine, CNRS, Laboratoire de Physique et Chimie Théoriques (LPCT), F-54000 Nancy, France
| | - Daniel Roca-Sanjuán
- Institut de Ciència Molecular, Universitat de València, 46071 València, Spain
| | - A Ulises Acuña
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, Spanish National Research Council (CSIC), 28006 Madrid, Spain
| | - Juan Z Dávalos
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, Spanish National Research Council (CSIC), 28006 Madrid, Spain
| | - Carlos A Cuevas
- Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, Spanish National Research Council (CSIC), 28006 Madrid, Spain
| | - Martin Jiskra
- Géosciences Environnement Toulouse, CNRS/Observatoire Midi-Pyrénées (OMP)/Université de Toulouse, 31400 Toulouse, France
- Department of Environmental Sciences, University of Basel, 4056 Basel, Switzerland
| | - Feiyue Wang
- Department of Environment and Geography, Centre for Earth Observation Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Johannes Bieser
- Helmholtz-Zentrum Geethacht, Institute of Coastal Research, 21502 Geesthacht, Germany
| | - John M C Plane
- School of Chemistry, University of Leeds, LS2 9TJ Leeds, United Kingdom
| | - Joseph S Francisco
- Department of Earth and Environmental Science,University of Pennsylvania, Philadelphia, PA 19104;
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
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