Publication Date:
2021-06-30
Description:
Soil CO2 flux and 222Rn activity measurements may positively contribute to the geochemicalmonitoring of active
volcanoes. The influence of several environmental parameters on the gas signals has been substantially demonstrated.
Therefore, the implementation of tools capable of removing (or minimising) the contribution of the atmospheric
effects from the acquired time series is a challenge in volcano surveillance. Here, we present
4 years-long continuousmonitoring (fromApril 2007 to September 2011) of radon activity and soil CO2 flux collected
on the NE flank of Stromboli volcano. Both gases record higher emissions during fall–winter (up to
2700 Bq * m−3 for radon and 750 g m−2 day−1 for CO2) than during spring–summer seasons. Short-time variations
on 222Rn activity aremodulated by changes in soil humidity (rainfall), and changes in soil CO2 flux that may
be ascribed to variations in wind speed and direction. The spectral analyses reveal diurnal and semi-diurnal cycles
on both gases, outlining that atmospheric variations are capable to modify the gas release rate fromthe soil.
The long-termsoil CO2 flux shows a slow decreasing trend, not visible in 222Rn activity, suggesting a possible difference
in the source depth of the of the gases, CO2 being deeper and likely related to degassing at depth of the
magma batch involved in the February–April 2007 effusive eruption. To minimise the effect of the environmental
parameters on the 222Rn concentrations and soil CO2 fluxes, two different statistical treatments were applied: the
Multiple Linear Regression (MLR) and the Principal Component Regression (PCR). These approaches allow to
quantify theweight of each environmental factor on the two gas species and showa strong influence of some parameters
on the gas transfer processes through soils. The residual values of radon and CO2 flux, i.e. the values obtained
after correction for the environmental influence, were then compared with the eruptive episodes that
occurred at Stromboli during the analysed time span (2007–2011) but no clear correlations emerge between
soil gas release and volcanic activity. This is probably due to i) the distal location of the monitoring stations
with respect to the active craters and to ii) the fact that during the investigated period no major eruptive phenomena
(paroxysmal explosion, flank eruption) occurred. Comparison of MLR and PCR methods in time-series
analysis indicates thatMLR can bemore easily applied to real time data processing in monitoring of open conduit
active volcanoes (like Stromboli) where the transition to an eruptive phase may occur in relatively short times.
Description:
This researchwas partly funded by ItalianMinistry of University and
Research (MIUR) and by University of Torino-Fondazione Compagnia di
San Paolo. Additional fundswere provided by the Italian “Presidenza del
Consiglio dei Ministri–Dipartimento della Protezione Civile (DPC)”
through the DEVnet Project (a cooperative program between the Departments
of Earth Sciences of the University of Torino and the University
of Florence) and through the “Potenziamento Monitoraggio
Stromboli” project. Additional funds for improving our computing hardware
were provided by Fondazione Cassa di Risparmio di Torino.
Description:
Published
Description:
65-78
Description:
4V. Processi pre-eruttivi
Description:
JCR Journal
Keywords:
Stromboli volcano
;
Continuous geochemical monitoring
;
Soil CO2 flux
;
Radon activity
;
Environmental parameters
;
Time series analyses
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
