Search

Abstract: La Fossa crater on Vulcano Island is quiescent since 1890. Periodically it undergoes “crises” characterized by marked increase of temperature (T), gas output and concentration of magmatic components in the crater fumaroles (T may exceed 600°C). During these crises, which so far did not lead to any eruptive reactivation, the diffuse CO2 soil degassing also increases and in December 2005 an anomalous CO2 flux of 1350tons/day was estimated by 1588 measurements over a surface of 1.66km2 extending from La Fossa crater to the inhabited zone of Vulcano Porto. The crater area and two other anomalously degassing sites (Levante Beach and Palizzi) have been periodically investigated from December 2004 to August 2010 for diffuse CO2 soil flux. They show a marked variation with time of the degassing rate, with synchronous maxima in December 2005. Carbon dioxide soil flux and environmental parameters have been also continuously monitored for over one year by an automatic station at Vulcano Porto. In order to assess the hazard of the endogenous gas emissions, CO2 and H2S air concentrations have been measured by Tunable Diode Laser profiles near the fumaroles of the crater rim and of the Levante Beach area, where also the viscous gas flux has been estimated. In addition, CO2 air concentration has been measured both indoor and outdoor in an inhabited sector of Vulcano Porto. Results show that in some sites usually frequented by tourists there is a dangerous H2S air concentration and CO2 exceeds the hazardous thresholds in some Vulcano houses. These zones should be immediately monitored for gas hazard should a new crisis arise. [Copyright &y& Elsevier]

Abstract: A borehole drilled at Fiumicino (Rome) down to only 27 m depth in a zone where no gas emission at the surface was known, caused a gas blowout from a pressurized gas pocket confined beneath a clay cover. Gas slowly diffused from the borehole within superficial permeable sand. Seven persons living in three ground floor flats of a near building had to be hospitalized due to CO2 exposure. All the houses in the proximity were evacuated. At the request of the Fire Brigade two additional boreholes were drilled nearby, hoping that this could rapidly exhaust the gas stored underground. To the contrary the soil gas flux near houses increased and indoor CO2 air concentration rapidly rose to lethal values (15 to 30   vol.%). As a remediation we suggested to restore the continuity of the impervious gas cover by squeezing quick-setting cement into the formation through new boreholes to be drilled near the existing ones. Although the first cement squeeze reduced drastically the CO2 soil flux and indoor concentration, six additional squeezes had to be carried out in order to lower the gas emission below the gas hazard threshold. The gas was mostly made of CO2 (98   vol.%) with minor N2 and CH4. Its chemical and isotopic composition (δ 13CCO2 =− 1.55; 3He/4He=0.314   Ra) is similar to that of the gas manifestations of Mts. Sabatini and Alban Hills volcanic areas. Though being somewhat contaminated by crustal and shallow organic volatiles, these gases likely have a component originated in the mantle, that beneath the volcanic Roman Comagmatic Province is probably deeply contaminated with crustal material. The Fiumicino gas blowout indicates that the area of Central Italy characterized by strong CO2 degassing extends westerly to include the Tyrrhenian coast. [Copyright &y& Elsevier]

Natural gas hazard was assessed at Cava dei Selci, a residential neighbourhood of Marino (Rome) by a joint study of gas emissions and related health problems. Here a densely urbanized zone with 4000 residents surrounds a dangerous natural gas discharge where, along the years, dozens of animals were killed by the gas. Gas originates from Colli Albani volcano and consists mostly of CO 2 with ~ 1 vol% of H 2 S. In recent years, several gas-related accidents occurred in the urbanized zone (gas blowouts and road collapses). Some houses were evacuated because of hazardous indoor air gas concentration. Gas hazard was assessed by soil CO 2 flux and concentration surveys and indoor and outdoor air CO 2 and H 2 S concentration measurements. Open fields and house gardens release a high quantity of CO 2 (32.23 tonnes * day -1 ). Inside most houses, CO 2 air concentration exceeds 0.1 vol%, the acceptable long-term exposure range. In several houses both CO 2 and H 2 S exceed the IDLH level (Immediately Dangerous to Life and Health). An epidemiological cohort study was carried out on the residents of two Cava dei Selci zones with high (zone A) and medium (zone B) gas hazard exposure, using the rest of Marino as reference zone. We found excess mortality and emergency room visits (ERV) related to high exposure to CO 2 and H 2 S; in particular, an increased risk of mortality and ERV for diseases of central nervous system (HR 1.57, 95% CI 0.76-3.25 and HR 5.82, 95% CI 1.27-26.56, respectively) was found among men living in zone A., (© 2022. The Author(s).)