Diffuse and Visible Emission of CO2 from Etna Volcano, Italy

Puerto de la Cruz, Tenerife, Canary Islands, Spain

This work reports the first estimation of total CO2 emission
to the atmosphere (visible and non-visible) from
Etna volcano, Sicily, by means of direct methods. Until
present, only direct measurements of the CO2 emitted
by the volcanic plume of Etna had been performed, and
not data of direct soil CO2 efflux from surface environment
of this volcano were available. To estimate the total
CO2 emission, 4075 soil CO2 efflux measurements
were performed by means of the accumulation chamber
method in October-November 2008. Most of the
study area showed background levels of soil CO2 efflux
(0.53 g·m-2·d-1), while peak values (>1725 g·m-2·d-1) were
mainly identified inside the summit craters and at Torre
del Filosofo area. Other zones with relatively high CO2
efflux values were identified at Paternó, Zafferana Etnea
and Trecastagni-Viagrande. The total output of CO2 diffuse
emission from the study area (973 km2) was computed
in 20320 t·d-1, where 1671 t·d-1, about 8.3% of
CO2 diffuse emission, was emitted by an area of 87 km2
which includes the summit craters and Torre del Filosofo.
To evaluate the visible/diffuse CO2 emission ratio,
plume CO2 emission rate was estimated by multiplying
SO2 emission rate times observed CO2/SO2 plume ratio
following the methodology described by Shinohara
(2005). Total CO2 visible emission was estimated about
31.5 kt·d-1, value is in the range reported for Etna volcano
(0.9-67.5 kt·d-1; Aiuppa et al., 2006). The total output
of CO2 diffuse emission represents 39% of the total
CO2 emission from Etna volcano to the atmosphere.
These results agree with the observations of Allard et al.
(1991), who reported that diffuse and visible CO2 emissions
were in the same order of magnitude. This study
demonstrates the importance of measuring diffuse CO2
emissions from active volcanoes like Mt. Etna in order
to have a better approach on the global estimate of CO2
emission to the atmosphere from subaerial volcanoes