Quantification of volcanic reactive halogen emissions - Volcanism and Global Environmental Change - page 127

(a)

(b)

Figure 8.5 ratios (normalised) as a function of

distance from the crater for three volcanoes (Etna, Nyiragongo, Popocatepetl)
visited during 2004 and 2008 (after Bobrowski and Giuffrida, 2012 ). (b) BrO/SO 2
ratios (based on column densities) during daytime and at night at Masaya volcano,
Nicaragua. Only during daytime BrO levels signi

(a) The evolution of BrO/SO 2 -

cantly exceed zero, thus
strongly indicating that BrO-formation is a photochemical process (from Kern
et al ., 2009 ). See also colour plates section .

plume level). An example in Figure 8.5a shows data from three volcanoes for
distances up to 18 km ( t up to 30 minutes). While initially reactive bromine

abundances are very low, there appears to be a saturation level in the BrO/SO 2
ratio at distances 10 minutes) (e.g. Vogel, 2011 ; Bobrowski et al .,

2012 ; Bobrowski et al ., in press).
(3) BrO/SO 2 ratios

> 5km( t

derived from cross sections through the volcanic plume of
Mt Etna by passive-imaging DOAS (Louban et al ., 2009 ; General et al. ,
2014 )

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are clearly higher at the plume edges than in the centre, again
indicating dependence of the bromine activation on species mixed into the
plume from the surrounding air.

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