Interaction between fumarolic gases and thermal groundwaters at Vulcano Island (Italy): evidences from chemical composition of dissolved gases in waters
G. Capasso et al., Interaction between fumarolic gases and thermal groundwaters at Vulcano Island (Italy): evidences from chemical composition of dissolved gases in waters, J VOLCANOL, 102(3-4), 2000, pp. 309-318
The chemical composition of some gaseous species dissolved in thermal groun
dwaters from Vulcano Island was determined directly in the field. The deter
minations were made using a methodology basted on the equilibrium partition
ing of gases between a liquid and a gaseous phase. The analyses were perfor
med with a portable gas chromatograph using a simple analytical procedure l
asting 70 s. He and CO2 partial pressures are notably higher than those of
waters in equilibrium with the atmosphere confirming an interaction between
volcanic gases and groundwaters. The highest CO2 values were recorded in w
ells located in areas of anomalous CO2 and He exhalations related to the ac
tive volcano-tectonic structures on the island. The temporal variations in
CO2 concentrations both in the crater fumarolic gases and in the dissolved
gases of some wells showed a very similar pattern. Lastly, the lowering of
the He contents in the dissolved gases that occurred in 1996-1997 was proba
bly due to a decreased interaction between the main degassing system (crate
r fumaroles) and the thermal groundwaters. (C) 2000 Elsevier Science B.V. A
ll rights reserved.