Modelling reactive halogen formation and ozone depletion in volcanic plumes

Roberts, Tjarda; Braban, Christine F.; Martin, R.S.; Oppenheimer, Clive; Adams, Jonathan; Cox, R. A.; Jones, R. L.; Griffiths, Paul

doi:10.1016/j.chemgeo.2008.11.012

Cited by 87 publications

(194 citation statements)

References 35 publications

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“…Current numerical models simulating halogen chemistry in volcanic plumes (3,12) are not capable of reproducing this quantitatively; the current study is no exception. Shown are the relative contributions of several bromine compounds to the sum of gas phase bromine.…”

Section: Bromine Chemistry In the Plumementioning

confidence: 78%

“…The same pathway is active for chlorine. Reaction [12] is fast as shown by Goodsite et al (28), highlighting the need for high levels of the Br radical for the production of RGM in order to compete with the dissociation of HgBr. As shown above, the model suggests that a rather large fraction of bromine is present in the early stages of volcanic plumes as a Br radical making a rapid oxidation of GEM feasible.…”

Section: Bromine Chemistry In the Plumementioning

confidence: 99%

“…The reaction mechanism for mercury is listed in SI Text. The key reactions for rapid bromine induced oxidation of GEM and uptake to the condensed phase are Hg 0 þ Br → HgBr; [11] HgBr → Hg 0 þ Br; [12] HgBr þ Br → HgBr 2 ;…”

Section: Bromine Chemistry In the Plumementioning

confidence: 99%

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Atmospheric chemistry in volcanic plumes

Glasow

2010

Proc. Natl. Acad. Sci. U.S.A.

145

126

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Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis

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Section: Bromine Chemistry In the Plumementioning

confidence: 78%

Section: Bromine Chemistry In the Plumementioning

confidence: 99%

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Atmospheric chemistry in volcanic plumes

Glasow

2010

Proc. Natl. Acad. Sci. U.S.A.

145

126

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“…Our Having now acquired a larger amount of BrO / SO 2 ratios over several distances at various volcanoes, it seems that the maximum BrO / SO 2 ratio might be reached in a much shorter time/closer distance from the vent than previously assumed (e.g. Roberts et al, 2009). Afterwards the BrO / SO 2 ratio seems to stay constant for a while at least up to a distance of 15 km from the emission source, which would account for a 25-min-old plume, assuming a wind velocity of 10 m s −1 .…”

Section: Timing Of Bromine Monoxide Formationmentioning

confidence: 85%

“…BrO is mainly formed by interaction of the volcanic plume with the atmosphere (e.g. Oppenheimer et al, 2006;Roberts et al, 2009;von Glasow et al, 2009).…”

Section: Sensitivity Studiesmentioning

confidence: 99%

Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006–2009

Bobrowski

Giuffrida

2012

Solid Earth

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Abstract. Over a 3-yr period, from 2006 to 2009, frequent scattered sunlight DOAS measurements were conducted at Mt. Etna at a distance of around 6 km downwind from the summit craters. During the same period and in addition to these measurements, volcanic observations were made by regularly visiting various parts of Mt. Etna. Here, results from these measurements and observations are presented and their relation is discussed. The focus of the investigation is the bromine monoxide/sulphur dioxide (BrO / SO2) ratio, and its variability in relation to volcanic processes. That the halogen/sulphur ratio can serve as a precursor or indicator for the onset of eruptive activity was already proposed by earlier works (e.g. Noguchi and Kamiya 1963; Menyailov, 1975; Pennisi and Cloarec, 1998; Aiuppa et al., 2002). However, there is still a limited understanding today because of the complexity with which halogens are released, depending on magma composition and degassing conditions. Our understanding of these processes is far from complete, for example of the rate and mechanism of bubble nucleation, growth and ascent in silicate melts (Carroll and Holloway, 1994), the halogen vapour-melt partitioning and the volatile diffusivity in the melt (Aiuppa et al., 2009). With this study we aim to add one more piece to the puzzle of what halogen/sulphur ratios might tell about volcanic activities. Our data set shows an increase of the BrO / SO2 ratio several weeks prior to an eruption, followed by a decline before and during the initial phase of eruptive activities. Towards the end of activity or shortly thereafter, the ratio increases to baseline values again and remains more or less constant during quiet phases. To explain the observed evolution of the BrO / SO2 ratio, a first empirical model is proposed. This model suggests that bromine, unlike chlorine and fluorine, is less soluble in the magmatic melt than sulphur. By using the DOAS method to determine SO2, we actually observe most of the emitted sulphur of Mt.~Etna. Regarding bromine, however, we are aware that by determining only the bromine monoxide (BrO) radical we might just observe a small or even a variable fraction of the total emitted bromine, which is most probable originally in the form of HBr. Therefore, we present first studies to justify the assumption that, despite the disadvantage just mentioned, the BrO / SO2 ratio can nevertheless serve as a new parameter to indicate the state of a volcano, when measurements are conducted under certain, but rather convenient, conditions.

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Active alkaline traps to determine acidic‐gas ratios in volcanic plumes: Sampling techniques and analytical methods

Wittmer

Bobrowski

Liotta

et al. 2014

Geochem Geophys Geosyst

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In situ measurements have been the basis for monitoring volcanic gas emissions for many years and-being complemented by remote sensing techniques-still play an important role to date. Concerning in situ techniques for sampling a dilute plume, an increase in accuracy and a reduction of detection limits are still necessary for most gases (e.g., CO 2 , SO 2 , HCl, HF, HBr, HI). In this work, the Raschig-Tube technique (RT) is modified and utilized for application on volcanic plumes. The theoretical and experimental absorption properties of the RT and the Drechsel bottle (DB) setups are characterized and both are applied simultaneously to the well-established Filter packs technique (FP) in the field (on Stromboli Island and Mount Etna). The comparison points out that FPs are the most practical to apply but the results are errorprone compared to RT and DB, whereas the RT results in up to 13 times higher analyte concentrations than the DB in the same sampling time. An optimization of the analytical procedure, including sample pretreatment and analysis by titration, Ion Chromatography, and Inductively Coupled Plasma Mass Spectrometry, led to a comprehensive data set covering a wide range of compounds. In particular, less abundant species were quantified more accurately and iodine was detected for the first time in Stromboli's plume. Simultaneously applying Multiaxis Differential Optical Absorption Spectroscopy (MAX-DOAS) the chemical transformation of emitted bromide into bromine monoxide (BrO) from Stromboli and Etna was determined to 3-6% and 7%, respectively, within less than 5 min after the gas release from the active vents.

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Modelling reactive halogen formation and ozone depletion in volcanic plumes

Cited by 87 publications

References 35 publications

Atmospheric chemistry in volcanic plumes

Atmospheric chemistry in volcanic plumes

Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006–2009

Active alkaline traps to determine acidic‐gas ratios in volcanic plumes: Sampling techniques and analytical methods

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