Environmental Engineering Reference
In-Depth Information
(a)
(c)
(b)
(d)
Figure 6.4 (a) Interior of an INGV-type Multi-GAS unit; (b) a Multi-GAS
permanent installation (Santorini, Greece); (c) an example Multi-GAS-derived
time series of CO
2
/SO
2
ratios
(Telica volcano, Nicaragua; courtesy of
P. Robidoux, modi
ed from Conde
et al
., in press); and (d) scatter plot of CO
2
vs. SO
2
concentrations in the plume of Telica volcano (Nicaragua) on 23 March
2013, demonstrating an excellent match between FTIR and Multi-GAS CO
2
/SO
2
ratios (courtesy of V. Conde; see Conde
et al
.,
2014
). Different intercepts of
regression lines (e.g. CO
2
levels at zero SO
2
) for the two data sets re
ect the
different measurement setups of FTIR and Multi-GAS (e.g. open-path vs. punc-
tual measurements).
uxes
The environmental consequences of volcanic degassing are to a large extent
determined by the mass of gas released per unit time (gas
6.4 Volcanic-gas
flux). However, only
the SO
2
fluxes can be measured directly, which means that the exact magnitudes
of the volcanic budgets of environmentally signi
cant volatiles such as CO
2
and
halogens remain unclear.
6.4.1 SO
2
The abundance of volcanic SO
2
isrelativelyeasytoquantifybecauseitis
spectroscopically active and present in air at a much lower concentration than
in a volcanic gas/plume. Systematic efforts to quantify volcanic SO
2
began in the
late 1970s with observations made using the correlation spectrometer (COSPEC)
