Soil CO2 flux measurements in volcanic and geothermal areas

As part of the work of the Economic Commission for Europe of the United Nations Task Force on Emission Inventories, a new set of guidelines has been developed for assessing the emissions of sulphur, nitrogen oxides, NH3, CH4, and nonmethane volatile organic compounds (NMVOC) from biogenic and other natural sources in Europe. This paper gives the background to these guidelines, describes the sources, and gives our recommended methodologies for estimating emissions. We have assembled land use and other statistics from European or national compilations and present emission estimates for the various natural/biogenic source categories based on these. Total emissions from nature derived here amount to ∼1.1 Tg S yr−1, 6–8 Tg CH4 yr−1, 70 Gg NH3 (as N) yr−1, and 13 Tg NMVOC yr−1. Estimates of biogenic NO x emissions cover a wide range, from 140 to 1500 Gg NO x (as N) yr−1. In terms of relative contribution to total European emissions for different pollutants, then NMVOC from forests and vegetation are clearly the most important emissions source. Biogenic NO x emissions (although heavily influenced by nitrogen inputs from anthropogenic activities) are very important if the higher estimates are reliable. CH4 from wetlands and sulphur from volcanoes are also significant emissions in the European budgets. On a global scale, European biogenic emissions are not significant, a consequence of the climate and size (7% of global land area) of Europe and of the destruction of natural ecosystems since prehistoric times. However, for assessing local budgets and for photochemical oxidant modeling, natural/biogenic emissions can play an important role. The most important contributor in this regard is undoubtedly forest VOC emissions, although this paper also indicates that NMVOC emissions from nonforested areas also need to be further evaluated. This paper was originally conceived as a contribution to the collection of papers arising as a result of the Workshop on Biogenic Hydrocarbons in the Atmospheric Boundary Layer, August 24–27, 1997. (Several papers arising from this workshop have been published in Journal of Geophysical Research, 103(D19) 1998.)

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Inventorying emissions from nature in Europe

The composition of gases released from volcanoes is a function of deep processes, such as vapor-melt separation during the generation and rise of the magmas, and shallow processes, active within the volcanic structures themselves. Of the three major types of volcanic systems, those associated with andesitic magmatism are the most suitable to the application of geochemical surveillance and monitoring techniques. Volatile contents of andesitic magmas, largely representing fluids released from the subducted slab, are likely to be high enough to allow a separate, volatile-rich phase to be present during all stages of magma generation and migration. In spite of highly variable solubilities in magmatic melts, the proportions of volatiles present in the vapors discharged from volcanic fumaroles resemble closely those acquired at depth suggesting that the vapor-melt systems have attained steady-state and that the overall process active during the rise of the volatiles is effectively nonfractionating.

Chemical Composition of Volcanic Gases

Co2 fluxes from mid-ocean ridges, arcs and plumes

In the present period of quiescence, the Solfatara volcano, 1 km far from Pozzuoli, releases 1500 t d−1 of hydrothermal CO2 through soil diffuse degassing from a relatively small area (0.5 km2). This amount of gas is comparable to that released by crater plume emissions of many active volcanoes. On the basis of the CO2/H2O ratio measured in high-temperature fumaroles inside the degassing area, we computed a total thermal energy flux of 1.19×1013 J d−1 (138 MW). Most of this energy is lost by shallow steam condensation and transferred to the atmosphere through the hot soil of the degassing area. The thermal energy released by diffuse degassing at Solfatara is by far the main way of energy release from the whole Campi Flegrei caldera. It is 1 order of magnitude higher than the conductive heat flux through the entire caldera, and, during the last 20 years, it was several times higher than the energy associated with seismic crises and ground deformation events. It is possible that changes in the energy flux from a magma body seated underneath Solfatara and/or argillification processes at relatively shallow depths determine pressurization events in the hydrothermal system and consequently ground deformation and shallow seismic swarms, as recorded during the recent episodes of volcanic unrest centered at Pozzuoli.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001JB000246

CO2 Degassing and Energy Release at Solfatara Volcano, Campi Flegrei, Italy

MOUNT Etna, in Sicily, is one of the world's most actively degassing volcanoes1. Here we use data collected from 1975 to 1987 to estimate carbon dioxide emissions from the summit craters and the upper flanks of the volcano. By combining measurements of the SO2 flux in the plume (refs 1–6 and this paper) with measurements of the CO2/SO2 ratio of the plume gases, we find that the average output of CO2 from summit crater degassing is 13±3 Tg yr−1. This is an order of magnitude higher than the annual CO2 output from Kilauea7,8, Hawaii, and representative arc volcanoes9,10. Furthermore, we find that diffuse emissions of CO2 from the upper flanks of Etna are magma-derived and are of a similar magnitude to those emitted from the crater plume. This observation, as well as others11–14, verifies the idea15 that extensive diffuse release of magmatic CO2 may occur in volcanically active regions—a process that needs to be taken into account when evaluating the volatile budget of subaerial volcanism. Such degassing may be of use for monitoring volcanic activity, could provide a means for radiocarbon dating of eruptions, and may be a mechanism by which CO2 is injected into crater lakes.

Eruptive and diffuse emissions of CO2 from Mount Etna

STROMBOLI volcano in the Aeolian islands has been erupting continuously for more than 2,000 years1, and probably as many as 5,000, following a major flank collapse2,3. Here we describe air-borne measurements of the plume flux of SO2 during 1980–93, which show that the volcano emits very large amounts of gas, mostly by open-conduit degassing between explosive outbursts, while exuding little basalt. Microprobe analysis of sulphur in the K-rich (shoshonitic) basalt, along with data for primitive basalts in the region4,5, suggests that the time-averaged SO2 flux is produced by intrusive degassing of 0.01-0.02 km3 yr-1 of magma, 100-200 times more than the volume erupted. Over 5,000 years, this rate implies that 50-100 km3 of intruded basalt would have been degassed, suggesting either that the volcanic pile has grown substantially by intrusion6 or, more probably, that a large magma storage system is emplaced at a shallow level within the crustal basement. Our results indicate that Etna and Stromboli alone provide 10% of the global budget of volcanic SO2.

Sulphur output and magma degassing budget of Stromboli volcano

https://hal.archives-ouvertes.fr/hal-02326954/document

Nouvelle évaluation des flux particulaires de l'Etna: 1980

Remote sensing of volatile flows from active volcanoes together with direct measurements of concentration ratios of chemical species in volcanic plumes are highly valuable both for applied volcanology forecasts of eruptions and a better knowledge of fundamental geochemical and biochemical cycles. A method was devised on Mt Etna (CARBONNELLE et al., 1978) in order to evaluate the volcano emissions of a number of chemical species, viz. water vapor, carbon dioxide, sulfur dioxide, hydrochloric acid and hydrofluoric acid. Table 1 displays the results for those compounds which are also regarded as atmospheric pollutants. They show that the commonly admitted values concerning the contribution of volcanic eruptions to the atmosphere and hydrosphere appear to be largely underestimated when is also taken into account the worldwide mild volcanic activity. The June 1980 measurements on Mt. Etna aroused suspicions about the previous CO2 flux estimation when the carbon dioxide baseline in the ambient air on the slopes of the volcano was found to be persistently much over the normal atmospheric background (335_ 1 ppm). That the gaseous emanation of deep volcanic soils could be more important than the discharge of volcanic vents had been demonstrated for radon-222 (WILk~NING, 1974) on Hawaii and foreshadowed by SULERZHITZKY (1971) for CO 2. This latter author, trying to establish regulari-

P. Zettwoog

Papers

Eruptive and diffuse emissions of CO2 from Mount Etna

Sulphur output and magma degassing budget of Stromboli volcano

Nouvelle évaluation des flux particulaires de l'Etna: 1980

Gas Output Measurements from an Active Volcano