carbon dioxide

ChEBI · EMBL-EBI ↗ · Källdatum saknas · Källans villkor

A one-carbon compound with formula CO2 in which the carbon is attached to each oxygen atom by a double bond. A colourless, odourless gas under normal conditions, it is produced during respiration by all animals, fungi and microorganisms that depend directly or indirectly on living or decaying plants for food.

De RosaMaurizio; GagliardiGianluca; RoccoAlessandra; SommaRenato; De NatalePaolo; De NataleGiuseppe · Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy) ↗ · Apr 20, 2007 · Källans villkor

Continuous monitoring of gases released in volcanic areas, emitted as fumaroles or diffusive degassing from soils, can give an insight for a deeper understanding of the volcanic dynamics and its impact on global climate and human activities [1,2].

De RosaMaurizio; GagliardiGianluca; RoccoAlessandra; SommaRenato; De NatalePaolo; De NataleGiuseppe · Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy) ↗ · Apr 20, 2007 · Källans villkor

Even though in the past years different techniques have been applied to monitoring of volcanic gases, e.g., mass spectrometry and gas cromatography, they are generally performed in laboratory, after collecting sample gases on field. No reliable techniques for long-term, continuous geochemical monitoring with near-laboratory precision do actually exist. Discrete on-site field measurements are generally restricted to CO2 soil diffusive flux [5]. Remote sensing techniques were developed in the last years for several gas species, such as Differential Optical Absorption Spectroscopy (DOAS) [6], Correlation Spectroscopy (COSPEC) [7], Light Detection And Ranging (LIDAR) [8], Fourier Transform Infrared (FTIR) Spectroscopy [9,10]. Eddy-covariance [11] (EC) micrometereological method can be alternative solutions, for CO2 flux, allowing measurements over large gas emission areas. Some of these methods are able to detect few trace species (e.g. SO2, HCl, HF) while H2S, CO2 and H2O, main constituents of volcanic gases, are spectroscopically hard to determine, therefore the corresponding volcanogenic emission rates can only be derived indirectly. More recently, continuous gas and temperature measurements have been performed using a set of analytical instruments to monitor volcanic gases over weeks [12-14].

De RosaMaurizio; GagliardiGianluca; RoccoAlessandra; SommaRenato; De NatalePaolo; De NataleGiuseppe · Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy) ↗ · Apr 20, 2007 · Källans villkor

After the first field tests [20], the spectrometer has been upgraded and in this paper, we present the results of a measurement campaign carried out in August 2004 in Vulcano (Aeolian islands, Sicily). Vulcano, due to the long period of geochemical anomalies and seismicity [22,23], and the presence of high CO2 degassing [24-27], represents an ideal test site for the new spectroscopic apparatus, both for concentration and flux measurements. Further, the presence at some sites of fumaroles with very aggressive (hot and acid) components allow to test the apparatus and optics also in extreme conditions of operation. The volcanic CO2 discharges occur both from fumaroles and as diffuse soil emanations form the volcanic edifices [28].

De RosaMaurizio; GagliardiGianluca; RoccoAlessandra; SommaRenato; De NatalePaolo; De NataleGiuseppe · Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy) ↗ · Apr 20, 2007 · Källans villkor

Measurements of CO2 flux at three sites of PAL (August 28th, 18:00) resulted in rates of 0.0031, 0.00090, 0.0018 s-1 (Table 2). At the first site, in a measurement took two days before(August 26th, 17:00), we get a rate of 0.0017 s-1 (Fig. 6). The concentration of water vapour remained constant during each flux measurement and its value is the same in the three different measurements of day August 28th, while for the two measurements made in the same place but in two different days (August 26th and 28th) we observed a change in water vapour concentration. This suggests that the presence of water is merely due to umidity of air. A measurements at Porto Levante Beach (August 29, 11:00)gave a flux rate of 0.0017 s-1. During this measurement we observed an increase of water vapour concentration, however we believe it is likely due to the evaporation of water soil content due to sun at the measuring site after raining. Flux measurements at FOG, at distance of few meters from the main fumarole, showed not detectable flux (Table 2). Similar accumulation measurements in the fumarole failed for the condensation of water vapour on the mirrors which reduced the signal to zero.

De RosaMaurizio; GagliardiGianluca; RoccoAlessandra; SommaRenato; De NatalePaolo; De NataleGiuseppe · Continuous in situ measurements of volcanic gases with a diode-laser-based spectrometer: CO2 and H2O concentration and soil degassing at Vulcano (Aeolian islands: Italy) ↗ · Apr 20, 2007 · Källans villkor

We have carried out a measurement campaign in Vulcano island with a portable spectrometer based on a semiconductor laser, which can monitor in-situ concentration and flux of CO2 and H2O. The spectrometer has a response time of the order of one second which allows the monitoring of gas dynamics on a very fast time scale. The measurements obtained at Vulcano, together with several tests, performed continuosly for several days, indicate the system has no problem to be used for long-time unattended measurements as well. The only occasional problems for a long-term remote installation could be the condensation of water vapour on the mirrors; such problem could be be reduced by heating the mirrors' surface. The average values of the CO2/H2O at ground level of the different measurement sites (0.0195–0.0150) is consistent with an average value measured for example at the FO fumarole using different comparative methods (FTIR, Filter pack and direct sampling) of about 0.063 [22]. Accumulation measurements have shown the presence of non-negligible CO2 flux from the soil, at several places, which can be missed by simply monitoring the concentration in air. The measurements of gas concentration and CO2 fluxes carried out during the present field work at Vulcano have demonstrated that laser diode spectrometers represent a suitable choice for monitoring areas with anomalous high gas concentration, in different environmental conditions. Our apparatus has shown to be suitable for continuous, in-situ monitoring of both gas concentrations and fluxes, with laboratory precision. Also, it can be considered a reliable instrument useful to the local community in areas subjected to dangerous episodes of CO2 exhalation from soils (i.e., Ciampino and Marino towns in the Albani Hills, Central Italy [42]; Mefite d'Ansanto close to Avellino city, Southern Italy; Mammuth area Long Valley, California USA [43]; Lake Nyos and Monoun, Cameroon [44]).