Variation of the BrO/SO2 Molar Ratio in the Plume of Tungurahua Volcano Between 2007 and 2017 and Its Relationship to Volcanic Activity

Warnach, Simon; Bobrowski, Nicole; Hidalgo, Silvana; Arellano, Santiago; Sihler, Holger; Dinger, Florian; Lübcke, Peter; Battaglia, Jean; Steele, Alexander; Galle, Bo; Platt, U.; Wagner, Thomas

doi:10.3389/feart.2019.00132

Cited by 21 publications

(22 citation statements)

References 69 publications

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“…Bromine from various sources (e.g., polar regions, salt lakes, and volcanoes) is involved in tropospheric and stratospheric ozone depletion (e.g., Wennberg, 1999;Rose et al, 2006;Simpson et al, 2007). Tropospheric ozone depletion has also been observed in volcanic plumes (e.g., Hobbs et al, 1982;Kelly et al, 2013;Surl et al, 2015;Roberts, 2018), which supports the proposed reaction mechanisms for BrO formation via autocatalytic chain reactions.…”

Section: Introductionsupporting

confidence: 59%

Halogen activation in the plume of Masaya volcano: field observations and box model investigations

et al. 2021

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Abstract. Volcanic emissions are a source of halogens in the atmosphere. Rapid reactions convert the initially emitted hydrogen halides (HCl, HBr, and HI) into reactive species such as BrO, Br2, BrCl, ClO, OClO, and IO. The activation reaction mechanisms in the plume consume ozone (O3), which is entrained by ambient air that is mixed into the plume. In this study, we present observations of the oxidation of bromine, chlorine, and iodine during the first 11 min following emission, examining the plume from Santiago crater of the Masaya volcano in Nicaragua. Two field campaigns were conducted: one in July 2016 and one in September 2016. The sum of the reactive species of each halogen was determined by gas diffusion denuder sampling followed by gas chromatography–mass spectrometry (GC-MS) analysis, whereas the total halogens and sulfur concentrations were obtained by alkaline trap sampling with subsequent ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) measurements. Both ground and airborne sampling with an unoccupied aerial vehicle (carrying a denuder sampler in combination with an electrochemical SO2 sensor) were conducted at varying distances from the crater rim. The in situ measurements were accompanied by remote sensing observations (differential optical absorption spectroscopy; DOAS). The reactive fraction of bromine increased from 0.20 ± 0.13 at the crater rim to 0.76 ± 0.26 at 2.8 km downwind, whereas chlorine showed an increase in the reactive fraction from (2.7 ± 0.7) × 10−4 to (11 ± 3) × 10−4 in the first 750 m. Additionally, a reactive iodine fraction of 0.3 at the crater rim and 0.9 at 2.8 km downwind was measured. No significant change in BrO / SO2 molar ratios was observed with the estimated age of the observed plume ranging from 1.4 to 11.1 min. This study presents a large complementary data set of different halogen compounds at Masaya volcano that allowed for the quantification of reactive bromine in the plume of Masaya volcano at different plume ages. With the observed field data, a chemistry box model (Chemistry As A Boxmodel Application Module Efficiently Calculating the Chemistry of the Atmosphere; CAABA/MECCA) allowed us to reproduce the observed trend in the ratio of the reactive bromine to total bromine ratio. An observed contribution of BrO to the reactive bromine fraction of about 10 % was reproduced in the first few minutes of the model run.

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Section: Introductionsupporting

confidence: 59%

Halogen activation in the plume of Masaya volcano: field observations and box model investigations

et al. 2021

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“…Correlations between the bromine-to-sulfur ratio and volcanic activity have been found in long-term observations (e.g. Bobrowski and Giuffrida, 2012;Dinger et al, 2018;Warnach et al, 2019;Dinger et al, 2021), suggesting that this ratio could potentially be used for monitoring and forecasting of volcanic activity.…”

Section: Introductionmentioning

confidence: 94%

“…A smaller number of measurements of in-plume ClO and OClO have also been reported. These halogen molecules have spectroscopic signatures within the ultraviolet range, meaning they can be identified from the same data that are used to monitor SO 2 , including data collected from longterm DOAS monitoring networks at volcanoes (Dinger et al, 2018;Warnach et al, 2019). As well as ground and airborne 12416 L. Surl et al: Observation and modelling of ozone-destructive halogen chemistry observations, BrO has been observed in the plumes of some larger volcanic eruptions by satellite-based instruments (e.g.…”

Section: Observationsmentioning

confidence: 99%

Observation and modelling of ozone-destructive halogen chemistry in a passively degassing volcanic plume

Surl

Roberts²,

Bekki

2021

Atmos. Chem. Phys.

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Abstract. Volcanoes emit halogens into the atmosphere that undergo complex chemical cycling in plumes and cause destruction of ozone. We present a case study of the Mount Etna plume in the summer of 2012, when the volcano was passively degassing, using aircraft observations and numerical simulations with a new 3D model “WRF-Chem Volcano” (WCV), incorporating volcanic emissions and multi-phase halogen chemistry. Measurements of SO2 – an indicator of plume intensity – and ozone were made in the plume a few tens of kilometres from Etna, revealing a strong negative correlation between ozone and SO2 levels. From these observations, using SO2 as a tracer species, we estimate a mean in-plume ozone loss rate of 1.3×10−5 molecules of O3 per second per molecule of SO2. This value is similar to observation-based estimates reported very close to Etna's vents, indicating continual ozone loss in the plume up to at least tens of kilometres downwind. The WCV model is run with nested grids to simulate the plume close to the volcano at 1 km resolution. The focus is on the early evolution of passively degassing plumes aged less than 1 h and up to tens of kilometres downwind. The model is able to reproduce the so-called “bromine explosion”: the daytime conversion of HBr into bromine radicals that continuously cycle in the plume. These forms include the radical BrO, a species whose ratio with SO2 is commonly measured in volcanic plumes as an indicator of halogen ozone-destroying chemistry. The species BrO is produced in the ambient-temperature chemistry, with in-plume BrO / SO2 ratios on the order of 10−4 mol/mol, similar to those observed previously in Etna plumes. Wind speed and time of day are identified as non-linear controls on this ratio. Sensitivity simulations confirm the importance of near-vent radical products from high-temperature chemistry in initiating the ambient-temperature plume halogen cycling. Heterogeneous reactions that activate bromine also activate a small fraction of the emitted chlorine; the resulting production of chlorine radical Cl strongly enhances the methane oxidation and hence the formation of formaldehyde (HCHO) in the plume. Modelled rates of ozone depletion are found to be similar to those derived from aircraft observations. Ozone destruction in the model is controlled by the processes that recycle bromine, with about three-quarters of this recycling occurring via reactions between halogen oxide radicals. Through sensitivity simulations, a relationship between the magnitude of halogen emissions and ozone loss is established. Volcanic halogen cycling profoundly impacts the overall plume chemistry in the model, notably hydrogen oxide radicals (HOx), nitrogen oxides (NOx), sulfur, and mercury chemistry. In the model, it depletes HOx within the plume, increasing the lifetime of SO2 and hence slowing sulfate aerosol formation. Halogen chemistry also promotes the conversion of NOx into nitric acid (HNO3). This, along with the displacement of nitrate out of background aerosols in the plume, results in enhanced HNO3 levels and an almost total depletion of NOx in the plume. The halogen–mercury model scheme is simple but includes newly identified photo-reductions of mercury halides. With this set-up, the mercury oxidation is found to be slow and in near-balance with the photo-reduction of the plume. Overall, the model findings demonstrate that halogen chemistry has to be considered for a complete understanding of sulfur, HOx, reactive nitrogen, and mercury chemistry and of the formation of sulfate particles in volcanic plumes.

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“…A11) is included in the fit. Besides its physical meaning to account for the broadband wavelength dependency of the OClO SCD due to the change of light path distribution in the atmosphere which is large at high SZAs, this Additional pseudo absorbers intensity offset (terms 1/I0, λ/I0, λ 2 /I0) shift and stretch (Beirle et al, 2013) ISRF changes (Beirle et al, 2017) BrO absorption correction subtraction of BrO absorption, retrieved in another fit window (Warnach et al, 2019), from the measurement before the fit (see Sect. A4) parameter gives more flexibility to better account for the parameter cross-correlation problem because one can calculate the final OClO SCD at a wavelength which is less affected by systematic errors caused by the imperfection of the model.…”

Section: Retrieval Settingsmentioning

confidence: 99%

Retrieval algorithm for OClO from TROPOMI by Differential Optical Absorption Spectroscopy

Puķīte

Borger

Dörner

et al. 2021

Preprint

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Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) is a UV-VIS-NIR-SWIR instrument on board of Sentinel-5P satellite developed for monitoring the Earth’s atmosphere. It was launched on 13 October 2017 in a near polar orbit. It measures spectrally resolved earthshine radiances at an unprecedented spatial resolution of around 3.5 x 7.2 km² (3.5 x 5.6 km² starting from 6 Aug 2019) (near nadir) with a total swath width of ~ 2600 km on the Earth's surface providing daily global coverage. From the measured spectra high resolved trace gas distributions can be retrieved by means of differential optical absorption spectroscopy (DOAS). Chlorine dioxide (OClO) is a by-product of the ozone depleting halogen chemistry in the stratosphere. Although being rapidly photolysed at low solar zenith angles (SZAs) it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation to chlorine oxide (ClO). Here we present a new retrieval algorithm of the slant column densities (SCDs) of chlorine dioxide (OClO) by DOAS. To achieve a substantially improved accuracy, which is especially important for OClO observations, accounting for absorber and pseudo absorber structures in optical depth even of the order of 10−4 is important. Therefore in comparison to existing retrievals, we include several additional fit parameters accounting for spectral effects like the temperature dependency of the Ring effect and Ring absorption effects, higher order term for the OClO SCD dependency on wavelength and account for the BrO absorption. We investigate the performance of different retrieval settings by an error analysis with respect to random variations, large scale systematic variations as function of solar zenith angle and also more localised systematic variations by a novel application of an autocorrelation analysis. The retrieved TROPOMI OClO SCDs show a very good agreement with ground based zenith sky measurements and are correlated well with preliminary data of the opeartional TROPOMI OClO retrieval algorithm currently being developed as part of ESA's S5p+I project.

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Variation of the BrO/SO2 Molar Ratio in the Plume of Tungurahua Volcano Between 2007 and 2017 and Its Relationship to Volcanic Activity

Cited by 21 publications

References 69 publications

Halogen activation in the plume of Masaya volcano: field observations and box model investigations

Halogen activation in the plume of Masaya volcano: field observations and box model investigations

Observation and modelling of ozone-destructive halogen chemistry in a passively degassing volcanic plume

Retrieval algorithm for OClO from TROPOMI by Differential Optical Absorption Spectroscopy

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