Results 1 - 10 of 46
Results 1 - 10 of 46. Search took: 0.014 seconds
|Sort by: date | relevance|
[en] Eleven representative fumarolic gases and bubbling gases of hot springs have been collected from Tatun Volcano Group, North Taiwan, for helium isotope measurements. All the samples, except one, exhibit consistent corrected helium isotope ratios with the mean value of 4.67 times of air ratios (RA). The preliminary helium data show that more than 60% of helium composition comes from deep magmatic source in this area. It implies that a relic magma reservoir may still exist underneath North Taiwan
[en] Complete text of publication follows. Iron-containing vitamins are used to prevent iron-deficiency anemia. These vitamins contain various iron compounds. Ferrous fumarate (FeC4H2O4) is one of them. The FDA requirement for ferrous fumarate (Food and Drugs, Sec. 172.350) indicates that ferric compounds should not exceed 2% in ferrous fumarate. Earlier we demonstrated the usefulness of Moessbauer spectroscopy for iron state analysis in various vitamins and dietary supplements (M.I. Oshtrakh et al., Anal. Chim. Acta, 506 (2004) 155-160; M.I. Oshtrakh et al., J, Pharm. Biomed. Anal., 40 (2006) 1281-1287). These results demonstrated the presence of various iron-containing impurities and iron-containing compounds which did not correspond to ones announced by manufacturer. Than further development of Moessbauer spectroscopy related to improvement of velocity resolution showed the first results for analysis of iron-containing vitamins and dietary supplements (M.I. Oshtrakh et al., Hyperfine Interact., 2009, DOI: 10.1007/s10751-009-9983-y). In this work we present results of the study of new series of vitamins containing ferrous fumarate using Moessbauer spectroscopy with high velocity resolution. For instance, the study of ElevitR (Bayer) with Moessbauer spectrum presentation in 1024 channels demonstrated the presence of ferrous and ferric impurities. The relative areas of these impurities spectral components in Moessbauer spectrum of ElevitR were about 3% of each compound. Thus, application of Moessbauer spectroscopy with high velocity resolution increases quality of analysis of the iron state in iron-containing vitamins and may be useful for revealing of iron-containing impurities and evaluation of vitamin quality.
[en] Anomalous fluctuations of radon content in soil gases, fumaroles or thermal sources associated with volcanic systems are considered as precursors of deep degassing phenomena. Radon measurements in soil gases were performed for several years on three active volcanoes of Costa-Rica (Arenal, Irazu, Poas), also on El Chichon and Colima volcanoes in Mexico and more recently on the Popocatepetl since its reactivation in December 1994. Data acquisition was initially performed using plastic detectors with a 15 days integration. Since 1993, autonomous automatic probes are used and give hourly measurements. A nine stations network for ground measurements is installed on the Poas since 1982. Radon and Cl-, F- and SO42- variations of the main crater lake are examined and correlated with the volcanic activity which led to the decay and disappearing of the lake in April 1989. On the Irazu, five stations were installed in 1982 and 3 automatic ones were added in November 1993. Results obtained so far are discussed according to the phreatic eruption of December 1994. The Popocatepetl measurements obtained since December 1994 are presented too. Abstract only. (J.S.)
[en] The thermal signature of Aso Volcano (Nakadake) during unrest episodes has been analyzed by combining the MODIS-MIROVA data set (2000–2017) with high-resolution images (LANDSAT 8 OLI and Sentinel 2) and ground-based thermal observations (2013–2017). The site of major activity (crater 1) is located at the summit of the volcano and is composed by a fumarole field (located in the South Area) and an acidic lake (replaced by a Central Pit during Strombolian phases). The volcanic radiative power (VRP) obtained by nighttime satellite data during the reference period was mainly below 3 MW. This thermal threshold marks the transition from high fumarole activity (HFA) to Strombolian eruptions (SE). However, periods characterized by sporadic phreatic eruptions (PE, eventually bearing phreatomagmatic episodes), which is the prevalent phase during unrest episodes, exhibit very low VRP values, being around 0.5 MW, or below. The statistical analysis of satellite data shows that the transition from HFA to Strombolian activity (which started on August 2014 and ceased in May 2015) occurs when VRP values are above the cited 3 MW threshold. In particular during marked Strombolian phases (November–December 2014), the radiative power was higher than 4 MW, reaching peak values up to 15.6 MW (on December 7, 2014, i.e., 10 days after the major Strombolian explosion of November 27). Conversely, ground-based measurements show that heat fluxes recorded by FLIR T440 Thermo-camera on the fumarole field of the South Area has been relatively stable around 2 MW until February 2015. Their apparent temperatures were fluctuating around 490–575 °C before the major Strombolian explosive event, whereas those recorded at the active vent, named Central Pit, reached their maxima slightly above 600 °C; then both exhibited a decreasing trend in the following days. During the Strombolian activity, the crater lake dried out and was then replenished by early July, 2016. Then, volcanic activity shifted back to phreatic–phreatomagmatic and the eruptive cycle was completed. During this period, the MIROVA system detected very few thermal alerts and the ground-based measurements were fluctuating around 1 MW. The most violent explosion occurred on October 8, 2016, and within the following weeks measured VRP were moderately above 2 MW. This is coeval with a thermal increase at the fumarole field of the South Area, with temperatures well above 300 °C. Thermal monitoring at Aso Volcano is an additional tool in volcano surveillance that may contribute to near-real-time hazard assessment. .
[en] The selection and use of chemical indicators to understand and possibly predict volcanic activity depends upon the geological framework and the geochemical model of the volcano in question. Monitoring of volcanic plumes is often carried out by measuring the SO2 flux. Where an hydrothermal system buffers the uprising gases released from a deep-seated magma body, gas-geobarometry is an effective tools to evaluate the risk of impending hydrothermal eruptions. At Vulcano crater, where deep magmatic gases mix with shallower hydrothermal fluids, main chemical constituents as well as radon activity indicate the extent of the mixing process, whereas minor rective species (H2, CO) re-equilibrate fast during the ascent. Most geochemical surveillance programmes currently under way are carried out through discontinuous sampling at relevant sites. Continuous monitoring is relatively new and yet not completely tested. (author). 18 refs, 8 figs
[en] Recently Popocatepetl has commenced a new active phase with several explosive events producing ash falls at large variation. For a better understanding of the processes occurring within the volcano, as well as its structure, further data of different types is required. This study will include an extensive program of soil gas measurements, including radon, carbon dioxide, methane and helium. A comparison will be made with seismic and groundwater and ash geochemical data. One goal will be an improved understanding of the mechanism whereby seismic events influence the concentration of soil gases, which is not currently well understood. Here the preliminary data are presented
[en] We have analyzed hyperspectral Airborne Visible-Infrared Imaging System (AVIRIS) imagery taken in September of 1992 in Long Valley Caldera, CA, a geothermally active region expressed surficially by hot springs and fumaroles. Geological and vegetation mapping are attempted through spectral classification of imagery. Particular hot spring areas in the caldera are targeted for analysis. The data is analyzed for unique geobotanical patterns in the vicinity of hot springs as well as gross identification of dominant plant and mineral species. Spectra used for the classifications come from a vegetation spectral library created for plant species found to be associated with geothermal processes. This library takes into account the seasonality of vegetation by including spectra for species on a monthly basis. Geological spectra are taken from JPL and USGS mineral libraries. Preliminary classifications of hot spring areas indicate some success in mineral identification and less successful vegetation species identification. The small spatial extent of individual plants demands either sub-pixel analysis or increased spatial resolution of imagery. Future work will also include preliminary analysis of a hyperspectral thermal imagery dataset and a multitemporal air photo dataset. The combination of these remotely sensed datasets for Long Valley will yield a valuable product for geothermal exploration efforts in other regions
[en] A simple and rapid technique to effectively remove volcanic smoke (vapor-dominated white plume) from visible or thermal infrared images of active craters is proposed, in which multiple photographs taken in a fixed frame are post-processed by a script-based program on a computer. This method allows us to obtain a detailed view of the surface conditions on fuming craters that is often impossible to observe by a single snapshot. It is also effective in improving an accuracy of surface temperature anomalies, and hence, heat flux from hot lakes or geothermal areas. .
[en] In this work the results of a study are described on the physico chemicals characteristic of the rain water of the surroundings of the Poas Volcano . The main objective was to establish a general profile of the gradients of some physico chemicals parameters of the rain in function of the localization and the distance of the stations rain collectors, with regard to the column of gases, aerosols and vapors that emanate through the fumaroles of the active crater of the Poas Volcano, for this reason a net of collectors of rain water settled down in four places located along the Southwest flank of the Volcano until a distance of 19 km, following the predominant address of the wind. In Heredia to place a fifth collector of rain water which I play the part of station control. The rain was gathered from to March and November of 1996, for daily precipitation events every 24 hours. To sample of rain are determined the following parameters: HP, electric conductivity, ions fluoride, chloride, nitrate and sulfate for chromatography of ions of high resolution (HPIC) ammonia by means of analysis for injection of flow (FIA), and some such metals as calcium, magnesium, sodium, potassium, iron, manganese and aluminum for spectrophotometer of atomic absorption (EAA)
[es]En este trabajo se describen los resultados de un estudio sobre las caracteristicas fisicoquimicas del agua de lluvia de los alrededores del Volcan Poas. El objetivo principal fue establecer un perfil general de los gradientes de algunos parametros fisicoquimicos de la lluvia en funcion de la localizacion y la distancia de las estaciones recolectoras de lluvia, con respecto a la columna de gases, aerosoles y vapores que emanan a traves de las fumarolas del crater activo del Volcan Poas. Para esto se establecio una red de recolectores de agua de lluvia en cuatro sitios localizados a lo largo del flanco suroeste del Volcan hasta una distancia de 19 km, siguiendo la direccion predominante del viento. En Heredia se coloco un quinto recolector de agua de lluvia el cual desempeno el papel de estacion control. La lluvia se recolecto entre marzo y noviembre de 1996, por eventos de precipitacion diarios cada 24 horas. A las muestras de lluvia se les determino los siguientes parametros: pH,conductividad electrica, iones fluoruro, cloruro, nitrato y sulfato por cromatografia de iones de alta resolucion (HPIC) amoniaco mediante analisis por inyeccion de flujo (FIA), y algunos metales tales como calcio, magnesio, sodio, potasio, hierro, manganeso y aluminio por espectrofotometria de absorcion atomica (EAA). (author)
[en] A model of the geothermal system in which deep circulating groundwater containing noble gases at air saturated water concentrations mixes with hot fluids of mantle origin at depth is described. It is proposed that the 3He/heat ratio should be similar to that observed in mid-ocean ridge systems, in which case the 3He to atmospheric argon ratio in geothermal discharges would be an indicator o the likely heat content of a system. As a first test of this hypothesis the noble gas results of Mazor et al. (1990) have been presented as the 3He/heat ratios for Wairakei and early Mokai wells and fumaroles. Their simplified boiling model has been used to correct for the effects of gas-water separation which occurs in underground boiling. At Wairakei, the resultant range of 3He/heat values is 140-8500 atoms 3He mW-1s-1, similar (except for the lowest values) to the range measured in mid ocean ridges. Further work is needed, but the available data show that the technique has promise for the modelling of deep geothermal systems and providing input to simulation models currently being used in reservoir engineering. The technique has potential to distinguish between stored heat systems and renewing systems. (author). 8 refs., 2 figs., 1 tab