Monitoring of fumarole discharge and CO2 soil degassing in the Azores: contribution to volcanic surveillance and public health risk assessment

Abstract

Fluid geochemistry monitoring in the Azores involves the regular sampling and analysis of gas discharges from fumaroles and measurements of CO2 diffuse soil gas emissions. Main degassing areas under monitoring are associated with hydrothermal systems of active central volcanoes in S. Miguel, Terceira and Graciosa islands. Fumarole discharge analysis since 1991 show that apart from steam these gas emissions are CO2 dominated with H2S, H2, CH4 and N2 in minor amounts. Mapping of CO2 diffuse soil emissions in S. Miguel Island lead to the conclusion that some inhabited areas are located within hazard-zones. At Furnas village, inside Furnas volcano caldera, about 62% of the 896 houses are within the CO2 anomaly, 5% being in areas of moderate to high risk. At Ribeira Seca, on the north flank of Fogo volcano, few family houses were evacuated when CO2 concentrations in the air reached 8 mol%. To assess and analyse the CO2 soil flux emissions, continuous monitoring stations were installed in S. Miguel (2), Terceira and Graciosa islands. The statistical analysis of the data showed that some meteorological parameters influence the CO2 flux. The average of CO2 flux in S. Miguel stations ranges from 250 g/m 2 /d at Furnas volcano to 530 g/m 2 /d at Fogo volcano. At Terceira Island it is about 330 g/m 2 /d and at Graciosa 4400 g/m 2 /d.

Reactive astrogliosis in the dentate gyrus of mice exposed to active volcanic environments

“…Volcanic activity in Furnas village is currently marked by several hydrothermal manifestations including soil diffuse degassing, thermal and cold carbon dioxide (CO 2 )-rich springs and fumarolic fields (Viveiros et al 2010).In this village, approximately 58% of the buildings are located above anomalous soil CO 2 diffuse degassing of volcanic-hydrothermal origin (Viveiros et al 2010;. Fumarole gaseous emissions are predominantly comprised of water (steam), and CO 2 , H 2 S, H 2 , N 2 , O 2 , CH 4 , and Ar are present in lower concentrations (Ferreira et al 2005); soil gas emissions are essentially CO 2 and 222 Rn (Silva et al 2015;Viveiros et al 2010). In addition, the active degassing areas contribute to the continuous input of volatile metals into the atmosphere (Bagnato et al 2014;Durand et al 2004).…”

Soil CO2 flux maps as tools to reduce the risk on soil diffuse degassing areas

“…Two parishes from Povoação County, Furnas and Ribeira Quente, are located, respectively, inside the caldera and in the southern flank of the volcano. Currently various hydrothermal manifestations are observed in this volcanic system, which include low temperature fumaroles, thermal and cold CO 2 -rich springs (Figure 2A) (Ferreira et al, 2005;Viveiros et al, 2010;Silva et al, 2015a;Silva et al, 2015b;Caliro et al, 2015). Despite the visible gas emissions, an important CO 2 diffuse degassing area was recognized below Furnas village in the early nineties (Baxter et al, 1999).…”

Detection of Geothermal Anomalies in Hydrothermal Systems Using ASTER Data: The Caldeiras da Ribeira Grande Case Study (Azores, Portugal)

“…The island comprises seven volcanological units, including the Fogo Volcano [ 31 ]. The Fogo Volcano is a polygenetic system, with secondary volcanism manifested in cold CO 2 -rich and thermal springs [ 32 , 33 , 34 ], low temperature (<100 °C) fumarolic fields, and diffuse degassing areas, essentially located on the northern flank [ 35 ].…”