Environmental Engineering Reference
In-Depth Information
6.4.3 Halogens
Halogens have the second highest environmental impact after sulfur (Mather,
2008
). Volcanic halogens have long been studied (Symonds
et al
.,
1988
), but
precise determinations of their emissions are complicated by large heterogeneities
of SO
2
/HCl and SO
2
/HF ratios in volcanic gases. This variability has been
attributed to (i) scrubbing of water-soluble Cl and F by hydrothermal/groundwater
systems (Symonds
et al
.,
2001
) and (ii) degassing-induced fractionations due to the
greater af
nity of sulfur for volcanic gas (Aiuppa,
2009
). Pre-eruptive halogen
contents in magmas, which vary with the geological context, are likely additional
key factors (Pyle and Mather,
2009
). The understanding of Br
I recycling through
volcanism is even less complete, but a recent review (Pyle and Mather,
2009
)
yielded the following best-accepted estimates of halogen degassing
-
fluxes from
arc volcanoes: 4.3
1.0 Tg/year HCl, 0.5
0.2 Tg/year HF, 5
-
15 Gg/year HBr and
0.5
-
2.0 Gg/year HI.
6.5 Conclusions
Volcanic-gas studies have progressed enormously over the last 20 years, and new
measurement techniques with higher temporal resolutions combined with greatly
improved interpretative degassing models are improving gas-based volcano
monitoring. However, large uncertainties remain in the current volcanic-gas global
inventories, reinforcing the need for future research into obtaining higher-quality
compositional and gas-
ux data.
References
Aiuppa, A. (2009). Degassing of halogens from basaltic volcanism: insights from volcanic
gas observations.
Chem. Geol.
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Aiuppa, A., Federico, C., Giudice, G., Gurrieri, S. (2005). Chemical mapping of a
fumarolic
-
field: La Fossa Crater, Vulcano Island (Aeolian Islands, Italy).
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Aiuppa, A., Federico, C., Giudice, G.
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