Quantification of volcanic reactive halogen emissions - Volcanism and Global Environmental Change - page 126

Figure 8.4 BrO column densities as a function of SO 2 column densities inside
the plume for eight volcanic sites visited between 2002 and 2011; the species are
well correlated for each location, but show different slopes for different sites.
(Extended version of figure in Bobrowski and Platt, 2007 ; data were re-evaluated

for SO 2 to now better account for non-linearity effects at high SO 2 concentrations,
see also Kern et al ., 2010 .)

possible to install many instruments within the framework of Network for Detec-
tion of Volcanic and Atmospheric Change (NOVAC), presently observing 25 vol-
canoes with a total of more than 60 individual spectrometers (Galle et al ., 2010 ).
Note, however, that this technology only allows measurements during daytime.

8.4. Observations at active volcanoes
Recent observations of reactive halogen species (example in Figure 8.3 ) at several
volcanoes worldwide (see Figure 8.1 ) provided quantitative insight into the vari-
ation of emission ratios and evolution of reactive halogens (in particular reactive
bromine) in volcanic plumes. These data allow the theoretical concepts presented
in Section 8.2.3 to be tested. The relative abundance of halogens in turn gives
insight into processes in volcanic plumbing systems (see the review by Aiuppa,
2009 ). The measurements and observations of RHS made to date at a series of
volcanoes can be summarised as follows:
(1) The BrO/SO 2 ratios range between 10 -6 to 10 -3 (e.g. Bobrowski et al ., 2003 ;
Oppenheimer et al ., 2006 ; Bobrowski and Platt, 2007 ; Bani et al ., 2009 ; Theys
et al ., 2012; Hörmann et al ., 2013 ; Bobrowski et al ., in press) with most
volcanic plumes showing ratios in the range of 10 -5 to 10 -4 . Some examples are
shown in Figure 8.4 .
(2) The monotonous growth of the BrO level as a function of plume age ( t )or
distance from the crater ( L P ), where t is given by t

¼ L P / v ( v ¼

wind speed at