Environmental Engineering Reference
In-Depth Information
8
Quanti
cation of volcanic reactive halogen emissions
ulrich platt and nicole bobrowski
8.1 Introduction
Volcanic gases are composed of many species; in order of abundance these are
water vapour (typically 50
-
90% of the total emissions), CO
2
(carbon dioxide,
1
-
40%), SO
2
(sulfur dioxide, 1
-
25%), H
2
S (hydrogen sul
de, 1
-
10%) and HCl
(hydrogen chloride, 1
-
10 %) (e.g. Textor
et al
.,
2004
). Trace species include CS
2
(carbon disul
de), COS (carbonyl sul
de), CO (carbon monoxide), HF (hydrogen
fluoride), HBr (hydrogen bromide), a number of volatile metal chlorides, mercury
compounds (see e.g. Carroll and Holloway,
1994
; Symonds
et al
.,
1994
) and other
heavy metals (e.g. Buat-Menard and Arnold,
1978
; Hinkley
et al
.,
1999
). Upon
mixing with ambient air, water vapour often condenses; the number of droplets is
enhanced by the availability of aerosols, both primarily emitted and condensed out
of the gas phase (e.g. Varekamp
et al
.,
1986
; Mather
et al
.,
2003
). Aerosol particles
and water droplets provide surfaces for heterogeneous reactions, which are a pre-
condition for reactive halogen chemistry. Generally there are three main motiv-
ations to study volcanic plumes and their chemical composition:
(1) It is interesting to learn about the composition of these plumes and to study
the (compared to
strange
'
chemical
processes during the evolution of such a plume, from the time of emission at
the crater until it blends into the atmospheric background.
(2) Volcanic-gas emissions in
'
usual
'
atmospheric chemistry) very
'
uence the atmosphere in a number of ways and on
different timescales (see also
Chapters 13
and
14
). In particular, on shorter
timescales this is true for the budgets of sulfur, ozone and other oxidants in the
troposphere and the stratosphere (e.g. Robock,
2000
; von Glasow
et al
.,
2009
;
Kutterolf
et al
.,
2013
) as well as the tropospheric background of reactive
