Several
site
s with anomalou
s emi
ssion
s of car
bon dioxide were inve
stigated in the region
south of Mt. Etna volcano in order to a
sse
ss the type
s of emi
ssion (focu
sed and/or diffu
se), their
surface exten
sion and the total output of CO<
su
b>2
su
b>. Mo
st of the
studied emi
ssion
s are located on the
southwe
st
boundary of Mt. Etna, near the town of Paternò. They con
si
st of three mud volcanoe
s (known a
s Salinelle), one
spring with
bu
bbling ga
s (Acqua Gra
ssa) and one area of diffu
se dega
ssing (Pe
scher
xed;a). Another
site (Naft
xed;a Lake) with remarka
ble ga
s emi
ssion
s (
bu
bbling ga
s into a lake a
s well a
s adjacent area
s of diffu
se
soil dega
ssing) i
s located further
southwe
st of Mt. Etna in an area of extinct Quaternary volcani
sm on the northwe
st margin of Hy
blean Mt
s. In all of the
se area
s the origin of the highe
st CO<
su
b>2
su
b> emi
ssion
s i
s clearly magmatic, and dega
ssing to the atmo
sphere occur
s mo
stly through tectonic
structure
s, pro
ba
bly at a regional
scale. The magmatic
source that feed
s anomalou
s dega
ssing in the a
bove area
s i
s likely to
be the
same that feed
s volcanic activity at Mt. Etna.
Focused degassing was measured at each emission vent using devices that measure the air speed, whereas diffuse soil degassing was measured using the accumulation chamber method. In total, 712 measurements were carried out (146 in focused degassing vents, 566 on diffuse degassing areas). Single CO<sub>2sub> output values ranged from 1.8 10<sup>− 5sup> to 1.68 kg s<sup>− 1sup>. In the case of diffuse degassing areas, statistical analyses allowed to discriminate between biogenic CO<sub>2sub> and CO<sub>2sub> deriving from a magmatic-hydrothermal source. Only the efflux values from the latter source were considered in the output estimates. The total estimated output thus obtained was about 2.61 kg s<sup>− 1sup>, relevant to a total surface of about 146,500 m<sup>2sup> (which includes only the magmatic CO<sub>2sub> emissions). This value is comparable with that of most non-volcanic emissions from geothermal and/or faulted areas of central-southern Italy, as well with the CO<sub>2sub> output from some of the volcanic areas of Italy.