Detection of chlorine, bromine and bromine chloride (BrCl) in volcanic emissions: Studies at Mt. Etna (Italy), 2022

Halogens in volcanic plumes are important for both volcanic and environmental research. For example, changes in the composition of the volcanic plume can be an indication of changes in the activity of the volcano. Volcanic emissions consist mainly of emitted H₂O, CO₂ and SO₂ and are rapidly mixed with surrounding background atmosphere. Additionally, HF, HCl and HBr are also significant constituents of volcanic emissions.

A particularly interesting element in this context is bromine because of its atmospheric relevance. Among others BrO forms in the volcanic plume and, like SO₂, can be determined spectroscopically using remote sensing techniques, making it ideal for monitoring and surveillance of volcanoes. However, to interpret and use BrO concentrations, we need to fully understand the formation and evolution of BrO in volcanic plumes. Measuring all relevant halogen species can take us one step further in our understanding of the interaction between atmosphere and volcanic gas and particle emissions.

Currently, several methods are used to detect the various halogen compounds. Remote sensing methods exist for only a few (in general BrO, OClO, HCl, HF). We use in-situ sampling methods such as diffusion separators, filter packs or aqueous alkaline traps to collect reactive and total halogen species, respectively.

In this study, we will present results for Cl₂, Br₂ and BrCl in volcanic plumes using AV based in situ measurement with cis-Stilbene coated syringe filters for halogens and interhalogens (i.e., Cl₂ ,Br₂ and BrCl). The results are discussed considering the different degassing activities and halogen chemistry in volcanic plumes.