Atmospheric Hydroxyl Radical Source: Reaction of Triplet SO2 and

Subscriber access provided by UNIV OF NEW ENGLAND ARMIDALE

A: Spectroscopy, Photochemistry, and Excited States 2

Atmospheric Hydroxyl Radical Source: Reaction of Triplet SO and Water Jay A. Kroll, Benjamin Normann Frandsen, Henrik Grum Kjaergaard, and Veronica Vaida J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.8b03524 • Publication Date (Web): 17 Apr 2018 Downloaded from http://pubs.acs.org on April 18, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Atmospheric Hydroxyl Radical Source: Reaction of Triplet SO2 and Water

Authors: Jay A. Kroll1,2,#, Benjamin N. Frandsen3,#, Henrik G. Kjaergaard3,*, and Veronica Vaida1,2,* Affiliations: 1

Department of Chemistry and Biochemistry, University of Colorado Boulder, UCB 215, Boulder CO 80309 2

Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, UCB 216, Boulder CO 80309 3

Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100, Copenhagen Ø, Denmark

# Joint First Authors *Corresponding Authors: Veronica Vaida: [email protected] Henrik G. Kjaergaard: [email protected]

1 ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract The reaction of electronically excited triplet state sulfur dioxide (3SO2) with water was investigated both theoretically and experimentally. The quantum chemical calculations find that the reaction leads to the formation of hydroxyl radical (OH) and hydroxysulfinyl radical (HOSO) via a low energy barrier pathway. Experimentally the formation of OH was monitored via its reaction with methane, which itself is relatively unreactive with 3SO2, making it a suitable probe of OH production from the reaction of 3SO2 and water. This reaction has implications for the formation of OH in environments that are assumed to be depleted in OH, such as volcanic plumes. This reaction also provides a mechanism for the formation of OH in planetary atmospheres with little or no oxygen (O2) or ozone (O3) present.


Page 2 of 18

Page 3 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Introduction Sulfur compounds play important roles in planetary atmospheres, particularly in the formation of aerosol, which has implications for climate.1 While our current understanding of sulfur chemistry explains much of what we observe on Earth,2-7 there are still large discrepancies between models and observation of other planetary atmospheres, particularly the Venusian atmosphere.8 For example, high mixing ratios of sulfur monoxide (SO) and sulfur dioxide (SO2) observed above 90 km in the Venusian atmosphere exceed model predictions by orders of magnitude.8-16 Recently, the high sulfur oxide mixing ratios on Venus were shown to lead to new sulfur oxides, cis- and trans-OSSO, which could explain near UV absorption and provide a missing sulfur oxide reservoir.17 However, there is still significant work needed to fully understand the sulfur chemistry in the middle atmosphere of Venus. This is particularly interesting given that the conditions in the middle atmosphere of Venus are quite similar to conditions in Earth’s stratosphere (temperature, pressure, PH2O, solar flux),12, 15 suggesting that under increased sulfur concentration scenarios, currently unknown chemistry is impacting the concentrations of sulfur oxides. Large injections of sulfur to the atmosphere by volcanic eruptions have lead to significant, short term, changes in the temperature of the Earth.18-22 Because of this, injections of sulfur dioxide and other sulfur containing species into the stratosphere have been proposed as a potential climate engineering scheme to generate aerosol that will cool the planet by scattering light and reducing incoming solar radiation to the Earth’s surface.23-27 The traditional understanding of this process is that sulfur compounds emitted to the atmosphere are oxidized to form SO2, which then reacts with OH and, through collisions with O2, forms SO3 and HO2. SO3 then goes on to react with water via a water/acid catalyzed reaction to form sulfuric acid



Page 4 of 18

(H2SO4).2, 28-35 Sulfuric acid is incredibly hygroscopic and acts as a seed for aerosol formation. 3638

This process is summarized in scheme 1.

+ → + → + /

+ + → Scheme 1 While this chemical scheme can explain much of sulfuric acid and particle formation in the Earth’s atmosphere, this chemistry is limited to regions where enough water is present to catalyze the reaction to form the sulfuric acid (scheme 1). Recently it was shown that, in addition to the traditional gas phase processes, new particle formation can also be induced by photochemical excitation of SO2 in the presence of gas phase water.39 Sunlight driven chemistry in the atmosphere can provide unique reaction pathways not previously considered.40,

41

Sulfur dioxide absorbs UV radiation that extends into the actinic

region of the solar spectrum, which allows for excitation of the electronic state of the molecule.42, 43 This absorption leads to SO2 molecules in an excited singlet state, 1SO2 (1A2), that rapidly relax to a triplet state, 3SO2 (3B1), via intersystem crossing or collisional relaxation. Previously, the singlet state has been shown to be unreactive compared to the triplet state.44 Here we show, through combined experimental and computational work, that a reaction pathway exists for electronically excited triplet SO2 and water to form hydroxyl (OH) and hydroxysulfinyl (HOSO) radicals, which then go on to do further chemistry in our experimental setup and in the atmosphere, especially at high altitudes where more UV radiation is available. Previously, HOSO has been observed using microwave spectroscopic techniques.45 In the atmosphere, HOSO has been assumed to form from oxidation of CS246 or via collision of SO2 with H atoms 4 ACS Paragon Plus Environment

Page 5 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and, in general, has been thought of as a sink for radical species.47 Because of this, HOSO has been assumed to be of importance only in localized plumes resulting from combustion of fuels and volcanic eruptions.48 Our results suggest that HOSO is also a product of the photochemical reaction of SO2 and water, greatly broadening its potential role in the atmosphere.

Methods Experimental Methods− Photochemical experiments were carried out in a glass crosscell equipped with quartz windows transparent to ultraviolet light on one axis. The perpendicular axis was equipped with either potassium bromide (KBr) windows (for dry experiments) or Germanium (Ge) windows (for wet experiments) in order to monitor the gas phase infrared spectra of reactants over the course of the experiment. This experimental setup is a modified version of experimental setup described in Reed Harris et al.49 Experimental samples were photochemically excited by illuminating the cell with broadband light from a Newport 450 Watt Xenon arc lamp filtered using a 3 mm thick, 50 mm diameter, 280 nm long pass filter (N-WG280, Edmond Optics) (Figure S-1, SI). Reactants and products were monitored using Bruker IFS 66 v/s FTIR equipped with an external, liquid nitrogen cooled MCT detector. The spectra were collected using a 90 scan average with a 0.5 cm-1 resolution. The cell and MCT detector were encased in a plastic casing that was purged with CO2 scrubbed, dry air to minimize the interference of atmospheric CO2 and H2O on the infrared measurements. The cell was cleaned with acetone and water and then pumped out overnight using an Edwards 18 rotary vane two-stage vacuum pump to remove any contaminants. Two types of experiments were conducted, dry and wet. For the dry experiments, the cell was filled with methane (ultra high purity, >99.9% purity, Matheson) to a pressure of 67.5 mTorr. Then



approximately 9.6 Torr of sulfur dioxide (Sigma-Aldrich, 99.9% purity) was added. For the wet experiments, methane was added to a pressure of 95 mTorr, then approximately 4.3 Torr of SO2 and 3.5 Torr of water were added respectively. Ultra pure 18MΩ (milli-Q) water was used and freeze/pump/thaw cycles were employed to remove any dissolved gases from the water. The water sample was then evacuated and opened to the vacuum manifold to obtain gas phase water for the experiments. For these two experiments, the leak rate of the cell was approximately 3 mTorr/min. A second wet experiment was conducted in which the pressure of methane was increased such that PCH4 ~2.9 Torr, PSO2 ~3.2 Torr and PH2O ~3.5 Torr. The leak rate for this experiment was significantly lower at approximately 0.3 mTorr/min. In each experiment, samples were allowed to mix and equilibrate with the cell for 30 minutes in the dark and then were illuminated with the 280 nm filtered UV light for 360 minutes. Spectra were collected every 3 minutes. In the dry experiments, the concentration of methane was monitored by fitting the IR absorption from 2920 to 3020 cm-1 using the MATLAB software, Main Polwin, which was developed at CEAM (Spain). The program is based on a linear least squares fitting routine that is modified to improve the filtering process in order to remove baseline and broad absorptions of unknown compounds. This software compares standardized spectra, collected with the same apodization function (Happ-Genzel) and resolution (0.5 cm–1) that were used for our experiments, to the experimental data we collected. In the wet experiments, the peaks between 2920 to 3020 cm-1 could not be used due to interference with the germanium windows. Therefore, for the wet experiments, the methane absorption peak at 1306.15 cm-1 was used to calculate the concentration of methane. This methane peak is found in the wings of the SO2 peak centered at 1360 cm-1. Due to this, the SO2 spectrum was fit using the CEAM program from 1290 to 1320 cm-1 and subtracted from the


Page 6 of 18

Page 7 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


spectrum. The methane concentration was then calculated using a reference spectrum collected using our setup. The pressures reported for water are the increase in pressure upon the addition of water to the cell and were measured using an MKS 10 Torr Baratron Pressure Transducer. The largest source of error in the spectral fits comes from the uncertainty in the pressure of the reference spectrum (± 1 mTorr). However, this error will lead to a systematic error in the concentration determined rather than random error. As such, it would be inappropriate to represent this error using error bars. Therefore, the data reported in figures 2 and 3 do not have error bars reported. Computational Methods − The reaction of 3SO2 with H2O to form the OH and HOSO radicals was studied at the CCSD(T)/aug-cc-pV(T+d)Z//ωB97X-D/aug-cc-pV(T+d)Z level of theory.50 All calculations used Gaussian16 Rev A.03.51 Optimization of structures were followed by a harmonic frequency calculation to provide zero-point vibrational energy correction. To confirm the identity of reactants and products that the transition state connected to, intrinsic reaction coordinate calculations were carried out. Transition state theory (TST) was used to calculate an estimate of the reaction rate constant and since a H atom is transferred quantum tunneling correction was included using one dimensional Eckart tunneling.52 Partition functions necessary in TST were computed using the calculated harmonic frequencies with the approximations to statistical mechanics inherent in the Gaussian16 program.51 See the SI for additional details.53



Page 8 of 18

Results and Discussion The reaction of 3SO2 with water was investigated theoretically. It was found that 3SO2 can abstract hydrogen from water leading to the formation of OH and HOSO radicals (reaction 1). 3

SO2 + H2O → HOSO + OH

(Reaction 1)

The CCSD(T)/aug-cc-pV(T+d)Z//ωB97X-D/aug-cc-pV(T+d)Z energies of this reaction are depicted Figure 1. The difference between reactants and the transition state is found to be 20.1 kJ/mol (4.8 kcal/mol) including zero point vibrational energy. The identification of this mechanism shows that photoexcitation of SO2 in the presence of water can lead directly to the formation of OH. This novel path for the formation of OH then facilitates the chemistry shown in scheme 1, particularly in environments where water is abundant.

Figure 1. Relative energies for the reaction of 3SO2 and H2O to form HOSO and OH. Energies are CCSD(T)/aug-cc-pV(T+d)Z//ωB97X-D/aug-cc-pV(T+d)Z electronic energies (not zero-point vibrational energy corrected). This predicted photochemical reaction was tested experimentally by placing an OH scavenger in the cell and monitoring its decay upon the production of OH from the reaction of 3

SO2 with water. Alkanes such as cyclohexane are often employed as OH scavengers; however,


Page 9 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


they cannot be used to test for the presence of OH here due to their direct reaction with 3SO2.39, 44, 54, 55

However, methane, which is known to react with OH, provides an excellent scavenger, as

it does not measurably react with 3SO2 on the timescales of our experiment.

Figure 2 – Pressure of methane in the cell (measured spectroscopically) during photochemical excitation of SO2 under dry conditions (red, left axis) and under wet conditions (blue, right axis). In the dry experiment the pressure of SO2 was 9.6 Torr and initial pressure of methane 67.5 mTorr (Ptotal=9.668 Torr). In the wet experiment the pressures of SO2 and H2O were ~4.3 Torr and ~3.5 Torr, respectively, with an initial pressure of methane 95 mTorr (Ptotal=7.895 Torr). The results of the photochemical experiments are summarized in Figures 2 and 3. These figures show the pressure of methane observed in the cell over the course of the experiment via illumination with 280 nm filtered UV light (Xe arc lamp + 280 nm longpass filter, see Figure S1) simulating solar flux available in the atmospheres of Earth and Venus. Photochemical reactions are initiated at time zero. It is clearly seen that under dry conditions (Figure 2, red trace) no reaction with methane is observed. A pseudo first order kinetics analysis, using previously measured rate constants from Whitehill and Ono,56 shows the rate constant for reaction of 3SO2 with CH4 under the dry conditions to be statistically indistinguishable from zero and sets an 9 ACS Paragon Plus Environment


upper limit on the rate constant of 3×10-16 cm3molecules-1s-1 (see SI). Upon the addition of water (Figure 2, blue trace), however, a clear decrease in the concentration of methane is observed when the cell is illuminated with UV light. This UV light excites SO2 into its singlet and triplet electronic states. There is no change in the pressure of methane in a cell filled with a mixture of SO2, H2O and CH4, as long as the sample is not illuminated with UV light from the xenon arc lamp. This, in combination with the lack of reaction under dark or dry conditions, demonstrates that there are no impurities in the methane or the SO2 gas that leads to reaction and provides clear evidence that the decrease in methane concentration in the wet experiment is due to reaction with OH radicals (and potentially HOSO radicals) formed from the reaction of 3SO2 and water (Reaction 1). In the wet experiments (Figure 2, blue trace) it is seen that, over time, the depletion of methane slows down. This is likely due to the relatively high leak rate of ~3 mTorr/min. Over the course of the experiment, atmospheric O2 leaking into the cell likely reacts with the radical species being formed. This likely has two major effects on the chemistry. First, the O2 can react with HOSO2 to form SO3 and HO2,57 which is less reactive than OH. Thus, the reaction of OH with SO2 to form HOSO2 becomes a fast and permanent sink of OH, rather than a reservoir. Second, the O2 may react with other species in the cell generating molecular species that are efficient at quenching the 3SO2 to the ground electronic state and thus impedes the formation of OH via reaction 1. In Figure 3, however, it can be seen that under conditions with a much lower leak rate of 0.3 mTorr/min, and an increased concentration of methane, the depletion of methane is not significantly slowed, even after 300 minutes of photochemical excitation. Under these conditions significantly less O2 is available for reaction, even at much longer time scales. Thus it can be concluded that the slowed reaction observed after approximately 100 minutes in Figure 2


Page 10 of 18

Page 11 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


is likely a result of contamination from atmospheric gases leaking into the cell. The initial increase of CH4 seen in Figures 2 and 3 is caused by an increase in temperature upon illumination with UV light. Initially when the cell is loaded with methane, the pressure drops slightly and then once the lamp is turned on, the pressure rises back up to the value it had immediately after loading the cell. This is commonly seen in our experiments as there is some wall interaction, but it is more easily seen at the higher pressure of CH4. From the 3SO2 + H2O experiments we can estimate a rate constant of k1 = 5−16×10-15cm3molecules-1s-1. We have estimated the theoretical rate constant using Transition State Theory and find a value in the range 10-14 – 10-16 cm3molecules-1s-1, in support of the experimental value (see SI for details).

Figure 3 – Pressure of methane in the cell during photochemical excitation of SO2 (~3.2 Torr) under wet conditions (PH2O ~3.5 Torr) with a high initial pressure of methane (2.975 Torr) (Ptotal=9.675 Torr)



Conclusions We have shown that reaction of 3SO2 with methane is slow and not readily observable under our experimental conditions (See SI section S.1). Upon the addition of water, however, we see a significant decrease in the concentration of methane when the SO2/H2O/CH4 mixture is illuminated with UV light (λ > 280 nm, Figure S1). With support from the quantum chemical calculations presented here, we suggest that the depletion of methane is the result of reaction with OH radicals generated from the reaction of the 3SO2 with water. This reaction provides an alternative or additional pathway for the particle formation seen in Donaldson et al.39 Current experimental results, however, cannot provide a branching ratio for the reaction described by Donaldson et al and the reactions described here. The reaction of 3SO2 with water to form OH and HOSO is of particular relevance to atmospheric chemistry where OH is typically assumed to be depleted by reaction with SO2. We have demonstrated here that UV light can, instead, excite SO2 to the excited singlet state (250 nm>λ>340nm), which rapidly relaxes to the triplet state and reacts with atmospheric water to generate OH. This would be of particular importance in areas of high concentration of SO2, such as volcanic plumes or regions where fossil fuels with high sulfur content are burned. The OH generated from this photochemical process could go on to oxidize additional SO2 through more traditional atmospheric mechanisms (see scheme 1). Additionally, this reaction provides a mechanism for the formation of OH in planetary atmospheres that contain little or no O2 or O3. This will increase the oxidative capacity of those atmospheres, which may broadly affect the potential chemical pathways accessible in such atmospheres. Generation of HOSO radicals by the reaction of 3SO2 with water is of great interest and widens the atmospheric range of HOSO beyond the previously assumed importance in localized plumes from the combustion of fuels and


Page 12 of 18

Page 13 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


volcanic eruptions to include any location where sunlight is available to excite SO2 in the presence of water. This greatly broadens the scope and importance of the role hydroxysulfinyl radical may play in our atmosphere.

Acknowledgements We thank Kurt V. Mikkelsen for helpful discussions. JAK and VV acknowledge funding from

NASA (Grant NNX15AP- ZOG) and funding from the Army Research Office (Grant W911NF1710115). BNF and HGK acknowledge the financial support from the Danish Center for Scientific Computing, University of Copenhagen, and the Center for Exploitation of Solar Energy founded by the University of Copenhagen. BNF is grateful to Augustinus Fonden for a travel grant.

Supporting Information Additional experimental details, Kinetics analysis for the reaction of 3SO2 with methane and water Additional computational details and results



Bibliography 1.

IPCC Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (Eds.)]. IPCC: Geneva, Switzerland, 2014; p 151.

2.

Tyndall, G. S.; Ravishankara, A. R., Atmospheric Oxidation of Reduced Sulfur Species, Int. J. Chem. Kinet. 1991, 23 (6), 483-527.

3.

Ravishankara, A. R.; Rudich, Y.; Talukdar, R., et al., Oxidation of Atmospheric Reduced Sulphur Compounds: Perspective from Laboratory Studies, Philos. Trans. R. Soc. Lond., B, Biol. Sci. 1997, 352 (1350), 171-182.

4.

Vaida, V.; Kjaergaard, H. G.; Hintze, P. E., et al., Photolysis of Sulfuric Acid Vapor by Visible Solar Radiation, Science 2003, 299 (5612), 1566-1568.

5.

Hintze, P. E.; Kjaergaard, H. G.; Vaida, V., et al., Vibrational and Electronic Spectroscopy of Sulfuric Acid Vapor, J. Phys. Chem. A 2003, 107 (8), 1112-1118.

6.

Mills, M. J.; Toon, O. B.; Thomas, G. E., Mesospheric Sulfate Aerosol Layer, J. Geophys. Res. 2005, 110 (D24), D24208.

7.

Mills, M. J.; Toon, O. B.; Vaida, V., et al., Photolysis of Sulfuric Acid Vapor by Visible Light as a Source of the Polar Stratospheric CN Layer, J. Geophys. Res. Atmos. 2005, 110 (D8).

8.

Mills, F. P.; Allen, M., A Review of Selected Issues Concerning the Chemistry in Venus’ Middle Atmosphere, Planet. Space Sci. 2007, 55 (12), 1729-1740.

9.

Belyaev, D. A.; Montmessin, F.; Bertaux, J.-L., et al., Vertical Profiling of SO2 and SO above Venus’ Clouds by Spicav/Soir Solar Occultations, Icarus 2012, 217 (2), 740751.

10.

Sandor, B. J.; Clancy, R. T.; Moriarty- Schieven, G., et al., Sulfur Chemistry in the Venus Mesosphere from SO2 and SO Microwave Spectra, Icarus 2010, 208 (1), 49-60.

11.

Sandor, B. J.; Clancy, R. T.; Moriarty-Schievena, G. H., Upper Limits for H2SO4 in the Mesosphere of Venus, Icarus 2012, 217, 839-844.

12.

Zhang, X.; Liang, M. C.; Mills, F. P., et al., Sulfur Chemistry in the Middle Atmosphere of Venus, Icarus 2012, 217 (2), 714-739.

13.

Zhang, X.; Liang, M. C.; Montmessin, F., et al., Photolysis of Sulphuric Acid as the Source of Sulphur Oxides in the Mesosphere of Venus, Nat. Geosci. 2010, 3 (12), 834837.

14.

Vandaele, A. C.; Korablev, O.; Belyaev, D., et al., Sulfur Dioxide in the Venus Atmosphere: I. Vertical Distribution and Variability, Icarus 2017, 295, 16-33. 14 ACS Paragon Plus Environment

Page 14 of 18

Page 15 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15.

Krasnopolsky, V., A Photochemical Model for the Venus Atmosphere at 47–112 km, Icarus 2012, 218, 230–246.

16.

Krasnopolsky, V., Sulfur Aerosol in the Clouds of Venus, Icarus 2016, 274.

17.

Frandsen, B. N.; Wennberg, P. O.; Kjaergaard, H. G., Identification of Osso as a nearUV Absorber in the Venusian Atmosphere, Geophys. Res. Lett. 2016, 43 (21), 11,14611,155.

18.

Brühl, C.; Lelieveld, J.; Höpfner, M., et al., Stratospheric SO2 and Sulphate Aerosol, Model Simulations and Satellite Observations, Atmos. Chem. Phys. Discuss. 2013, 2013, 11395-11425.

19.

Minnis, P.; Harrison, E. F.; Stowe, L. L., et al., Radiative Climate Forcing by the Mount Pinatubo Eruption, Science 1993, 259 (5100), 1411-1415.

20.

Robock, A., Volcanic Eruptions and Climate, Rev. Geophys. 2000, 38 (2), 191-219.

21.

Ridley, D. A.; Solomon, S.; Barnes, J. E., et al., Total Volcanic Stratospheric Aerosol Optical Depths and Implications for Global Climate Change, Geophys. Res. Lett. 2014, 41 (22), 7763-7769.

22.

Santer, B. D.; Bonfils, C.; Painter, J. F., et al., Volcanic Contribution to Decadal Changes in Tropospheric Temperature, Nat. Geosci. 2014, 7, 185.

23.

Shepherd, J. G., Geoengineering the Climate: An Overview and Update, Philos. Trans. Royal Soc. A 2012, 370 (1974), 4166-4175.

24.

Pierce, J. R.; Weisenstein, D. K.; Heckendorn, P., et al., Efficient Formation of Stratospheric Aerosol for Climate Engineering by Emission of Condensible Vapor from Aircraft, Geophys. Res. Lett. 2010, 37 (18).

25.

Keith, D. W.; Dowlatabadi, H., A Serious Look at Geoengineering, Eos. Trans. AGU 1992, 73 (27), 289-293.

26.

Crutzen, P. J., The Possible Importance of CSO for the Sulfate Layer of the Stratosphere, Geophys. Res. Lett. 1976, 3 (2), 73-76.

27.

Tuck, A. F.; Donaldson, D. J.; Hitchman, M. H., et al., On Geoengineering with Sulphate Aerosols in the Tropical Upper Troposphere and Lower Stratosphere, Climatic Change 2008, 90 (3), 315-331.

28.

Stockwell, W. R.; Calvert, J. G., The Mechanism of the HO-SO2 Reaction, Atmos. Environ. 1983, 17 (11), 2231-2235.

29.

Möller, D., Kinetic Model of Atmospheric SO2 Oxidation Based on Published Data, Atmos. Environ. 1980, 14 (9), 1067-1076.



30.

Eatough, D. J.; Caka, F. M.; Farber, R. J., The Conversion of SO2 to Sulfate in the Atmosphere, Isr. J. Chem. 1994, 34 (3-4), 301-314.

31.

Torrent-Sucarrat, M.; Francisco, J. S.; Anglada, J. M., Sulfuric Acid as Autocatalyst in the Formation of Sulfuric Acid, J. Am. Chem. Soc. 2012, 134 (51), 20632-20644.

32.

Lovejoy, E. R.; Hanson, D. R.; Huey, L. G., Kinetics and Products of the Gas-Phase Reaction of SO3 with Water, J. Phys. Chem. 1996, 100 (51), 19911-19916.

33.

Long , B.; Long, Z.-w.; Wang, Y.-b., et al., Formic Acid Catalyzed Gas-Phase Reaction of H2O with SO3 and the Reverse Reaction: A Theoretical Study, ChemPhysChem 2012, 13 (1), 323-329.

34.

Hazra, M. K.; Sinha, A., Formic Acid Catalyzed Hydrolysis of SO3 in the Gas Phase: A Barrierless Mechanism for Sulfuric Acid Production of Potential Atmospheric Importance, J. Am. Chem. Soc. 2011, 133 (43), 17444-17453.

35.

Morokuma, K.; Muguruma, C., Ab Initio Molecular Orbital Study of the Mechanism of the Gas Phase Reaction SO3 + H2O: Importance of the Second Water Molecule, J. Am. Chem. Soc. 1994, 116 (22), 10316-10317.

36.

Henning, S.; Ziese, M.; Kiselev, A., et al., Hygroscopic Growth and Droplet Activation of Soot Particles: Uncoated, Succinic or Sulfuric Acid Coated, Atmos. Chem. Phys. 2012, 12 (10), 4525-4537.

37.

Khalizov, A. F.; Zhang, R.; Zhang, D., et al., Formation of Highly Hygroscopic Soot Aerosols Upon Internal Mixing with Sulfuric Acid Vapor, J. Geophys. Res. Atmos. 2009, 114 (D5).

38.

Ehn, M.; Petäjä, T.; Aufmhoff, H., et al., Hygroscopic Properties of Ultrafine Aerosol Particles in the Boreal Forest: Diurnal Variation, Solubility and the Influence of Sulfuric Acid, Atmos. Chem. Phys. 2007, 7 (1), 211-222.

39.

Donaldson, D. J.; Kroll, J. A.; Vaida, V., Gas-Phase Hydrolysis of Triplet SO2: A Possible Direct Route to Atmospheric Acid Formation, Sci. Rep. 2016, (6), 30000.

40.

Rapf, R. J.; Vaida, V., Sunlight as an Energetic Driver in the Synthesis of Molecules Necessary for Life, Phys. Chem. Chem. Phys. 2016, 18 (30), 20067-20084.

41.

Vaida, V., Spectroscopy of Photoreactive Systems: Implications for Atmospheric Chemistry, J. Phys. Chem. A 2009, 113 (1), 5-18.

42.

Heicklen, J.; Kelly, N.; Partymiller, K., The Photophysics and Photochemistry of SO2, Reviews of Chemical Intermediates 1980, 3 (3), 315.

43.

Chung, K.; Calvert, J. G.; Bottenheim, J. W., The Photochemistry of Sulfur Dioxide Excited within Its First Allowed Band (3130 Å) and the “Forbidden” Band (3700– 4000 Å), Int. J. Chem. Kinet. 1975, 7 (2), 161-182.


Page 16 of 18

Page 17 of 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


44.

Badcock, C. C.; Sidebottom, H. W.; Calvert, J. G., et al., Mechanism of the Photolysis of Sulfur Dioxide-Paraffin Hydrocarbon Mixtures, J. Am. Chem. Soc. 1971, 93 (13), 3115-3121.

45.

McCarthy, M. C.; Lattanzi, V.; Martinez, O., et al., Spectroscopic Detection and Structure of Hydroxidooxidosulfur (HOSO) Radical, an Important Intermediate in the Chemistry of Sulfur-Bearing Compounds, J. Phys. Chem. Let. 2013, 4 (23), 40744079.

46.

McKee, M. L.; Wine, P. H., Ab Initio Study of the Atmospheric Oxidation of CS2, J. Am. Chem. Soc. 2001, 123 (10), 2344-2353.

47.

Rasmussen, C. L.; Glarborg, P.; Marshall, P., Mechanisms of Radical Removal by SO2, Proc. Combust. Inst. 2007, 31 (1), 339-347.

48.

Lesar, A.; Tušar, S., Structure, Stability, and Spectroscopic Properties of H-Bonded Complexes of HOSO and CH3SO with H2O, J. Phys. Chem. A 2014, 118 (36), 78557862.

49.

Reed Harris, A. E.; Doussin, J.-F.; Carpenter, B. K., et al., Gas-Phase Photolysis of Pyruvic Acid: The Effect of Pressure on Reaction Rates and Products, J. Phys. Chem. A 2016, 120 (51), 10123-10133.

50.

Dunning, T. H. J.; Peterson, K. A.; Wilson, A. K., Gaussian Basis Sets for Use in Correlated Molecular Calculations. X. The Atoms Aluminum through Argon Revisited, J. Chem. Phys. 2001, 114 (21), 9244-9253.

51.

Frisch, M. J.; Trucks, G. W.; Schlegel, H. B., et al. Gaussian 16, Revision A.03, Gaussian, Inc.: Wallingford CT, 2016., 2016.

52.

Eckart, C., The Penetration of a Potential Barrier by Electrons, Phys. Rev. 1930, 35 (11), 1303-1309.

53.

Melissas, V. S.; Truhlar, D. G., Interpolated Variational Transition State Theory and Tunneling Calculations of the Rate Constant of the Reaction OH+CH4 at 223–2400 K, J. Chem. Phys. 1993, 99 (2), 1013-1027.

54.

Dainton, F. S.; Ivin, K. J., The Photochemical Formation of Sulphinic Acids from Sulphur Dioxide and Hydrocarbons, Transactions of the Faraday Society 1950, 46, 374-381.

55.

Dainton, F. S.; Ivin, K. J., The Kinetics of the Photochemical Gas-Phase Reactions between Sulphur Dioxide and N-Butane and 1-Butene Respectively, Transactions of the Faraday Society 1950, 46, 382-394.

56.

Whitehill, A. R.; Ono, S., Excitation Band Dependence of Sulfur Isotope MassIndependent Fractionation During Photochemistry of Sulfur Dioxide Using Broadband Light Sources, Geochimica et Cosmochimica Acta 2012, 94 (Supplement C), 238-253. 17 ACS Paragon Plus Environment


57.

Gleason, J. F.; Sinha, A.; Howard, C. J., Kinetics of the Gas-Phase Reaction HOSO2 + O2 .→ HO2 + SO3, J. Phys. Chem. 1987, 91 (3), 719-724.

TOC GRAPHIC

1SO

2 3SO

2

H2O OH + HOSO

hv

Reaction

hv

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

SO2


Page 18 of 18

Atmospheric Hydroxyl Radical Source: Reaction of Triplet SO2 and

Recommend Documents