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1.
Imaging Differential Optical Absorption Spectroscopy (IDOAS) is an optical remote-sensing method using scattered sunlight as light source. It combines a “pushbroom” imaging spectrometer with the DOAS technique and thus allows imaging two-dimensional trace gas distributions, e.g., in volcanic plumes. The highly sensitive and specific detection of many trace gases simultaneously (specific molecules, not just elements, e.g. SO 2, BrO, NO 2, O 3, HCHO, etc.) is possible, and the temporal and spatial variation of these gases can be measured. The IDOAS system presented here enables the taking of two-dimensional images of trace gas distributions in a volcanic plume with a spatial resolution of 100 pixels horizontally × 64 pixels vertically, each with a field of view of 0.087° in horizontal and 0.208° in vertical directions. Therefore, IDOAS provides useful information about the chemical composition and chemical variability in a volcanic plume and allows studying plume dispersal and chemical transformations. The technique was applied to map the SO 2 distribution in the plume of Mt. Etna volcano for the first time in October 2003. 相似文献
2.
The simultaneous quantitative determination of two-dimensional bromine monoxide (BrO) and sulphur dioxide (SO 2) distributions in volcanic gas plumes is described. Measurements at the fumarolic field on the island Vulcano (autumn 2004)
and in the plume of Mt. Etna volcano (spring 2005) were carried out with an Imaging DOAS instrument. The SO 2 fluxes of several fumaroles were estimated from two-dimensional distributions of SO 2. Additionally, the first two-dimensional distributions of BrO within a volcanic plume were successfully retrieved. Slant
column densities of up to 2.6 × 10 14 molecules per square centimetre were detected in the plume of Mt. Etna. The investigation of the BrO/SO 2 ratio, calculated from the two-dimensional distributions of SO 2 and BrO, shows an increase from the centre to the edge of the volcanic plume. These results have significance for the involvement
of ozone during BrO formation processes in volcanic emissions. 相似文献
3.
From the magmatic emanations differentiation point of view it is possible to calculate some ratios such as F/CO 2, Cl/CO 2, SO 2/CO 2, SO 2/H 2S, H 2S/CO 2 and CO 2/N 2 in the tumarolic gases for the forecasting of volcanic activity. In order to predict the cruptions of a volcano it is needed to select several fumaroles or hot springs having different regimes of variation of the above ratios. The study of some fumaroles composition at the Asama. Mihara, Kirishima and other volcanoes in Japan showed a close connection between volcanic gas compositions and state of the volcanoes. 相似文献
4.
A field gas chromatograph, built in 1978, was used in the field to directly analyse volcanic gases before water vapor condensation. Tested in Vulcano (Italy), Kilauea (Hawaii) and Merapi (Indonesia), this field measurement technique provides the actual composition of the volcanic gas mixture. The technique avoids the depletion of sulfur gases and the dissolution of the acid gases in the condensed water during the cooling. Thus the mixture of H 2S and SO 2 in fumarolic and high temperature gases (up to 819°C) in equilibrium at the emission temperature was examined. 相似文献
5.
Here we report measurements of the chemical composition and flux of gas emitted from the central lava lake at Erta 'Ale volcano (Ethiopia) made on 15 October 2005. We determined an average SO 2 flux of ∼ 0.69 ± 0.17 kg s − 1 using zenith sky ultraviolet spectroscopy of the plume, and molar proportions of magmatic H 2O, CO 2, SO 2, CO, HCl and HF gases to be 93.58, 3.66, 2.47, 0.06, 0.19 and 0.04%, respectively, by open-path Fourier transform infrared (FTIR) spectrometry. Together, these data imply fluxes of 7.3, 0.7, 0.008, 0.03 and 0.004 kg s − 1 for H 2O, CO 2, CO, HCl and HF, respectively. These are the first FTIR spectroscopic observations at Erta 'Ale, and are also some of the very few gas measurements made at the volcano since the early 1970s (Gerlach, T.M., 1980b. Investigation of volcanic gas analyses and magma outgassing from Erta 'Ale lava lake, Afar, Ethiopia. Journal of Volcanology and Geothermal Research, 7(3–4): 415–441). We identify significant increases in the proportion of H 2O in the plume with respect to both CO 2 and SO 2 across this 30-year interval, which we attribute to the depletion of volatiles in magma that sourced effusive eruptions during the early 1970s and/or to fractional magma degassing between the two active pit craters located in the summit caldera. 相似文献
6.
Phreatic eruptions occurred at the Meakandake volcano in 1988, 1996, 1998, 2006, and 2008. We conducted geochemical surveillance
that included measurements of temperature, SO 2 emission rates, and volcanic gas composition from 2003 to 2008 at the Nakamachineshiri (NM), Northwest (NW), and Akanuma
(AK) fumarolic areas, and the 96–1 vent, where historical eruptions had occurred. The elemental compositions of the gases
discharged from the different areas are similar compared with the large variations observed in volcanic gases discharged from
subduction zones. All the gases showed high apparent equilibrium temperatures, suggesting that all these gases originated
from a common magmatic gas. The gases discharged from each area also exhibited different characteristics, which are probably
the results of differences in the conditions of meteoric water mixing, quenching of chemical reactions, and vapor-liquid separation.
The highest apparent equilibrium temperatures (about 500°C) were observed in the case of NW fumarolic gases, despite the low
outlet temperature of about 100°C at these fumaroles. Since the NW fumaroles were formed as a result of the 2006 phreatic
eruption, the high-temperature gas supply to the NW fumarole suggests that the phreatic eruption was caused by the ascent
of high-temperature magmatic gases. The temperatures, compositions, and emission rates of the NM and 96–1 gases did not show
any appreciable change after the 2006 eruption, indicating that each fumarolic system had a separate magmatic-hydrothermal
system. The temperatures, compositions, and emission rates of the NM fumarolic gases were apparently constant, and these fumaroles
are inferred to be formed by the evaporation of a hydrothermal system with a constant temperature of about 300°C. The 96–1
gas compositions showed large changes during continuous temperature decrease from 390° to 190°C occurred from 2003 to 2008,
but the sulfur gas emission rates were almost constant at about four tons/day. At the 96–1 vent, the SO 2/H 2S ratio decreased, while the H 2/H 2O ratio remained almost constant; this was probably caused by the rock-buffer controlled chemical reaction during the temperature
decrease. 相似文献
7.
Sulphur isotopic compositions of pyrite, anhydrite and native sulphur in volcanic ashes discharged by the 1979 eruption of Ontake volcano, Nagano, Japan were determined. The isotopic data indicate that sulphate in anhydrite and a part of native sulphur were produced by the disproportionation reaction of sulphite formed by dissolution of SO2 in volcanic gases into water which filled a mud reservoir probably located just below the crater zone. Some part of H2S in volcanic gases was fixed as pyrite and some was oxidised to form native sulphur. Hydrothermal alteration of country rocks to form pyrite, anhydrite and clay minerals had proceeded in the mud reservoir before eruption at temperatures ranging from 110° to 185°C which were estimated by oxygen isotopic fractionation between anhydrite and water. 相似文献
8.
The continuous measurement of molecular hydrogen (H 2) emissions from passively degassing volcanoes has recently been made possible using a new generation of low-cost electrochemical sensors. We have used such sensors to measure H 2, along with SO 2, H 2O and CO 2, in the gas and aerosol plume emitted from the phonolite lava lake at Erebus volcano, Antarctica. The measurements were made at the crater rim between December 2010 and January 2011. Combined with measurements of the long-term SO 2 emission rate for Erebus, they indicate a characteristic H 2 flux of 0.03?kg s –1 (2.8?Mg? day –1). The observed H 2 content in the plume is consistent with previous estimates of redox conditions in the lava lake inferred from mineral compositions and the observed CO 2/CO ratio in the gas plume (~0.9 log units below the quartz–fayalite–magnetite buffer). These measurements suggest that H 2 does not combust at the surface of the lake, and that H 2 is kinetically inert in the gas/aerosol plume, retaining the signature of the high-temperature chemical equilibrium reached in the lava lake. We also observe a cyclical variation in the H 2/SO 2 ratio with a period of ~10?min. These cycles correspond to oscillatory patterns of surface motion of the lava lake that have been interpreted as signs of a pulsatory magma supply at the top of the magmatic conduit. 相似文献
9.
A new continuous monitoring system has been developed for the measurement of volcanic gas from the steam well located 3 km north from the summit of Izu-Oshima volcano, Japan. After removing the water vapor using three sequential dehydration methods, CO 2 and SO 2 contents are measured using IR sensors, and O 2 and H 2 using a zirconia sensor and a semiconductor sensor, respectively. This system has been in operation without any significant trouble for 3 years.The dehydrated volcanic gas from the well consists of a mixture of CO 2, O 2 and N 2. A decreasing trend of the CO 2 content was observed from 1995 to 1998 together with a decrease of volcanic activity. Seasonal changes have also been observed in CO 2 and O 2 contents, CO 2 being higher and O 2 lower in summer, which suggests larger contribution of magmatic components in summer. While changes in short-term variation in CO 2 and O 2 are influenced by atmospheric pressure changes; the CO 2 content correlates inversely with atmospheric pressure unlike O 2 with some hours delay. In contrast, the H 2 content increased intermittently up to 1200 ppm one to several hours after a sudden drop in the atmospheric pressure and without any apparent correlation with seasonal changes.This system allows us to study temporal variation in chemical composition of volcanic gas during quiescent periods of volcanic activity of Izu-Oshima volcano, and might help us detect anomalous changes before future eruptive events. 相似文献
10.
Equilibria calculations of high-temperature volcanic gases from lava lakes are carried out on the basis of best volcanic gas samples. The equilibrium gas composition at temperatures from 800° to 1400°K and pressures up to 25 kilobars (in ideal gas system) was calculated using the free energy minimization model as well as the Newton-Raphson methods. It is shown that the juvenile «magmatic gas » of basaltic magma consists of three components: H 2O, SO 2, CO 2; the water vapor being about 60%. The increase of temperature under constant pressure results in the increase of the SO 2 concentration and in the simultaneous decrease of H 2S. Under the same conditions the ratios CO/CO 2 and H 2/H 2O are found to increase. Methane cannot be a component of «magmatic gas» corresponding to the elemental composition of basaltic lava gases. The calculated values of \(P_{O_2 } \) are in good agreement with the experimental data obtained from direct measurements of \(P_{O_2 } \) in lava lakes and experiments with basaltic melts. 相似文献
11.
The chemical and isotopic compositions of volcanic gases at a borehole and a natural fumarole in the Owakudani geothermal
area, Hakone volcano, Japan, have been repeatedly measured since 2001, when a seismic swarm occurred in the area. The CO 2/H 2O and CO 2/H 2S ratios were high in 2001. It increased in 2006 and again in 2008 when seismic swarms occurred beneath the geothermal area.
The observed increases suggest the injection of CO 2- and SO 2-rich magmatic gas into the underlying hydrothermal reservoir, implying that the magmatic gas was episodically supplied to
the hydrothermal system in 2006 and 2008. The earthquake swarms probably resulted from the injection of gas through the shallow
crust accompanying the break of the sealing zone. 相似文献
12.
Data on uncontaminated samples of volcanic gases can be counted on the fingers of one hand, yet estimation of total volcanic gas flow cannot be made without such data. In this paper the flux of gas from the lava lake to the atmosphere is calculated by a heat budget based on the excess heat loss caused by combustion of H 2 and CO and by the mass rate of loss of other gases on the basis of their ratios to H 2 and CO in the unoxidized gas samples. The estimated rates of loss of H 2O, CO 2, SO 2 and HCl are consistent with the rate of loss of heat if this heat is generated by crystallization and if the initial magma contains concentrations of gas appropriate for submarine basalt from oceanic ridges. The moderate activity of permanent degassing from the two active lava ponds studied gives a lower flux than that of other volcanoes. 相似文献
13.
Bulk atmospheric deposition of major cations (Na, K, Ca, Mg) and anions (Cl, F, SO 4) were measured at 15 sites around an active volcano, Mount Etna, from 2001 to 2003. Their composition indicates several natural
sources, among which deposition of plume-derived volcanogenic gas compounds is prevalent for F, Cl and S. Plume-derived acidic
compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano
(pH in the 2.45–5.57 range). Cation species have complex origin, including deposition of plume volcanogenic ash and aerosols
and soil-dust wind re-suspension of either volcanic or carbonate sedimentary rocks.
Variation of the deposition rates during the March 2001–March 2003 period, coupled with previous measurements from 1997 to
2000 (Appl Geochem 16:985–1000, 2001), were compared with the variation of SO 2 flux, volcanic activity and rainfall. The deposition rate was mainly controlled by rainfall. Commonly, about 0.1–0.9% of
HF, HCl and SO 2 emitted by the summit crater's plume were deposited around the volcano. We estimate that ∼2 Gg of volcanogenic sulphur were
deposited over the Etnean area during the 2002–2003 flank eruption, at an average rate of ∼24 Mg day −1 which is two orders of magnitude higher than that typical of quiescent degassing phases. 相似文献
14.
A field system for analyzing gases was installed on line in a borehole into the geothermal field associated with Gorelyi volcano, which is close to Mutnovski volcano (Kamtchatka). The system consisted of a gas chromatograph and an electrode for sensing gases. Measurements were made for the duration of one week in July 1980. Variations in H 2 concentrations were less than 50%. No correlations were observed with regional seismic activity or with volcanic activity at Gorelyi volcano (10 km away). Measurements of H 2 during a longer period of time would allow a statistical treatment of the data. 相似文献
15.
Gas emissions from Tatun volcanic group, northern Taiwan, were studied for the first time using a multi-component gas analyser system (Multi-GAS) in combination with Giggenbach flask methods at fumaroles and mud pools at Da-you-keng (DYK) and Geng-tze-ping (GZP). CO 2/S molar ratios observed at DYK ranged from 3–17, similar ratios were observed using a Multi-GAS sensor box of 8–16. SO 2 at GZP was low, higher concentrations were observed at DYK where SO 2/H 2S ratios were close to 1 for both methods. A lower CO 2/H 2S ratio was measured via Giggenbach flask sampling (7.2) than was found in the plume using the gas sensor at GZP (9.2). This may reflect rapid oxidation of H 2S as it mixes with background air. Gaseous elemental mercury (GEM) levels were observed in the fumarole gases using a portable mercury spectrometer. These are the first such measurements of mercury at Tatun. Mean GEM concentrations in the fumarole plumes were ∼ 20 ng m − 3, with much higher concentrations observed close to the ground (mean [GEM] 130 and 290 ng m − 3 at DYK and GZP, respectively). The GEM in the fumarole plume was elevated above concentrations in industrial/urban air in northern Taiwan and the increase in GEM observed when the instrument was lowered suggests high levels of mercury are present in the surrounding ground surface. The GEM/CO 2 (10 − 8) and GEM/S (10 − 6) ratios observed in the fumarole gases were comparable to those observed at other low-temperature fumaroles. Combining the Hg/CO 2 ratio with a previous CO 2 flux value for the area, the annual GEM flux from the Tatun field is estimated as 5–50 kg/year. 相似文献
16.
Despite the abundance of SO 2(g) in magmatic gases, precursory increases in magmatic SO 2(g) are not always observed prior to volcanic eruption, probably because many terrestrial volcanoes contain abundant groundwater or surface water that scrubs magmatic gases until a dry pathway to the atmosphere is established. To better understand scrubbing and its implications for volcano monitoring, we model thermochemically the reaction of magmatic gases with water. First, we inject a 915°C magmatic gas from Merapi volcano into 25°C air-saturated water (ASW) over a wide range of gas/water mass ratios from 0.0002 to 100 and at a total pressure of 0.1 MPa. Then we model closed-system cooling of the magmatic gas, magmatic gas-ASW mixing at 5.0 MPa, runs with varied temperature and composition of the ASW, a case with a wide range of magmatic–gas compositions, and a reaction of a magmatic gas–ASW mixture with rock. The modeling predicts gas and water compositions, and, in one case, alteration assemblages for a wide range of scrubbing conditions; these results can be compared directly with samples from degassing volcanoes. The modeling suggests that CO 2(g) is the main species to monitor when scrubbing exists; another candidate is H 2S (g), but it can be affected by reactions with aqueous ferrous iron. In contrast, scrubbing by water will prevent significant SO 2(g) and most HCl (g) emissions until dry pathways are established, except for moderate HCl (g) degassing from pH<0.5 hydrothermal waters. Furthermore, it appears that scrubbing will prevent much, if any, SO 2(g) degassing from long-resident boiling hydrothermal systems. Several processes can also decrease or increase H 2(g) emissions during scrubbing making H 2(g) a poor choice to detect changes in magma degassing.We applied the model results to interpret field observations and emission rate data from four eruptions: (1) Crater Peak on Mount Spurr (1992) where, except for a short post-eruptive period, scrubbing appears to have drastically diminished pre-, inter-, and post-eruptive SO 2(g) emissions, but had much less impact on CO 2(g) emissions. (2) Mount St. Helens where scrubbing of SO 2(g) was important prior to and three weeks after the 18 May 1980 eruption. Scrubbing was also active during a period of unrest in the summer of 1998. (3) Mount Pinatubo where early drying out prevented SO 2(g) scrubbing before the climactic 15 June 1991 eruption. (4) The ongoing eruption at Popocatépetl in an arid region of Mexico where there is little evidence of scrubbing.In most eruptive cycles, the impact of scrubbing will be greater during pre- and post-eruptive periods than during the main eruptive and intense passive degassing stages. Therefore, we recommend monitoring the following gases: CO 2(g) and H 2S (g) in precursory stages; CO 2(g), H 2S (g), SO 2(g), HCl (g), and HF (g) in eruptive and intense passive degassing stages; and CO 2(g) and H 2S (g) again in the declining stages. CO 2(g) is clearly the main candidate for early emission rate monitoring, although significant early increases in the intensity and geographic distribution of H 2S (g) emissions should be taken as an important sign of volcanic unrest and a potential precursor. Owing to the difficulty of extracting SO 2(g) from hydrothermal waters, the emergence of >100 t/d (tons per day) of SO 2(g) in addition to CO 2(g) and H 2S (g) should be taken as a criterion of magma intrusion. Finally, the modeling suggests that the interpretation of gas-ratio data requires a case-by-case evaluation since ratio changes can often be produced by several mechanisms; nevertheless, several gas ratios may provide useful indices for monitoring the drying out of gas pathways. 相似文献
17.
Volcanic gases such as SO 2, H 2S, HCl and COS emitted during explosive eruptions significantly affect atmospheric chemistry and therefore the Earth's climate. We have evaluated the dependence of volcanic gas emission into the atmosphere on altitude, latitude, and tectonic setting of volcanoes and on the season in which eruptions occurred. These parameters markedly influence final stratospheric gas loading. The latitudes and altitudes of 360 active volcanoes were compared to the height of the tropopause to calculate the potential quantity of volcanic gases injected into the stratosphere. We calculated a possible stratospheric gas loading based on different volcanic plume heights (6, 10, and 15 km) generated by moderate-scale explosive eruptions to show the importance of the actual plume height and volcano location. At a plume height of 15 km for moderate-scale explosive eruptions, a volcano at sea level can cause stratospheric gas loading because the maximum distance to the tropopause is 15–16 km in the equatorial region (0–30°). Eruptions in the tropics have to be more powerful to inject gas into the stratosphere than eruptions at high latitudes because the tropopause rises from ca. 9–11 km at the poles to 15–16 km in the equatorial region (0–30°N and S). The equatorial region is important for stratospheric gas injection because it is the area with the highest frequency of eruptions. Gas injected into the stratosphere in equatorial areas may spread globally into both hemispheres. 相似文献
18.
On December 1, 2007, the solar absorption infrared spectra of the Popocatépetl volcanic plume was recorded during an eruptive event and complementarily on November 17, 2008, the passive quiescent degassing was measured from the same site. A portable FTIR spectrometer with a scanning mirror for fast tracking of the sun provided the flexibility, quality, and simplicity needed for field deployment. Slant columns of the gases SO 2, HCl, HF, and SiF 4 were retrieved and strong differences could be observed when comparing gas ratios in both time periods. During the explosive eruption, the SO 2/HCl ratio was three times greater and the HF/HCl ratio was slightly smaller than during passive degassing.While the ratios among SO 2, HCl, HF, and SiF 4 describe the chemical composition of the volcanic gas mixture, the SiF 4/HF ratio provides information about the equilibrium temperatures of the stored gases which in this study were calculated at 150° and 185 °C for the explosive and quiescent degassing episodes, respectively. We conclude that cooling of lava domes in the crater precedes Vulcanian explosions as suggested by Schaaf et al (2005). Based on SO 2 flux (Grutter et al., 2008) and measurements and data from the November 2008 event, the average fluxes for HCl, HF, SiF 4, and F through quiescent degassing are estimated to be 204, 22.7, 9.8, and 31.7 tons/day, respectively. These values are similar to those reported by Love et al. (1998) more than 10 yrs ago. 相似文献
19.
Measurements of visible and diffuse gas emission were conducted in 2006 at the summit of Sierra Negra volcano, Galapagos, with the aim to better characterize degassing after the 2005 eruption. A total SO 2 emission of 11?±?2?t day ?1 was derived from miniature differential optical absorption spectrometer (mini-DOAS) ground-based measurements of the plume emanating from the Mini Azufral fumarolic area, the most important site of visible degassing at Sierra Negra volcano. Using a portable multigas system, the H 2S/SO 2, CO 2/SO 2, and H 2O/SO 2 molar ratios in the Mina Azufral plume emissions were found to be 0.41, 52.2, and 867.9, respectively. The corresponding H 2O, CO 2, and H 2S emission rates were 562, 394, and 3?t day ?1, respectively. The total output of diffuse CO 2 emissions from the summit of Sierra Negra volcano was 990?±?85?t day ?1, with 605?t day ?1 being released by a deep source. The diffuse-to-plume CO 2 emission ratio was about 1.5. Mina Azufral fumaroles released gasses containing 73.6?mol% of H 2O; the main noncondensable components amounted to 97.4?mol% CO 2, 1.5?mol% SO 2, 0.6?mol% H 2S, and 0.35?mol%?N 2. The higher H 2S/SO 2 ratio values found in 2006 as compared to those reported before the 2005 eruption reveal a significant hydrothermal contribution to the fumarolic emissions. 3He/ 4He ratios measured at Mina Azufral fumarolic discharges showed values of 17.88?±?0.25? R A , indicating a mid-ocean ridge basalts (MORB) and a Galapagos plume contribution of 53 and 47?%, respectively. 相似文献
20.
Volcán Fuego in the Central American Republic of Guatemala erupted violently in October, 1974. A remote sensing correlation spectrometer. COSPEC IV, which utilizes the characteristic molecular absorption of SO 2 in the ultraviolet was used to monitor the SO 2 content of the volcanic plume. Over a 60-day period measurements were made on 37 days between and following major eruptive phases. SO 2 emission rates corrected for atmospheric scattering of the spectral signal average 423 metric tons/day with a standard deviation of 252 metric tons/days. Late stage peaks in SO 2 emission at Fuego are consistent with the presence of anomalously high contents of soluble materials on the stratigraphically highest ashes from other Central American eruptions. Indications are that the SO 2 concentration within the volcanic plume increased as activity waned. These features imply that remote spectroscopic sensing of SO 2 and perhaps other gases in a volcanic plume may provide a relatively easy and inexpensive means of determining the cessation of violent eruptive activity. 相似文献
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