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In addition to an analytical result of two gas samples, published geological and geochemical data on the Isobe gas field, which had produced CO2 commercially during about 30 years, are examined in this paper from the viewpoint of petroleum geology. Chemical and carbon isotopic compositions of gases from the field indicate that CO2 is magmatic origin and has no relationship with hydrocarbons which are derived from the thermal decomposition of organic matters. Faults are ascending paths of CO2, which is driving force for hot spring waters. Chemical and isotopic compositions of associated waters with gases which are used as hot spring waters indicate that the waters are fossil sea waters which were entrapped during deposition and undergone diagenetic alteration. Higher temperatures of the waters estimated by the Mg-Li geothermometer than a bottom temperature at 1,500 m depth suggest that the waters are formed in deeper parts and derived from there. [ABSTRACT FROM AUTHOR]

Removal of low-concentration fluoride in natural water is an important issue all over the world. Japan is a volcanic country with many hot springs, and the removal of low-concentration fluoride from hot spring drainage is desired. In this study, we attempted to prepare a novel adsorbent with high selective removal ability of fluoride from zircon sand using mechanochemical treatment, and applied it for removing fluoride from hot spring water. Mechanochemical treatment of zircon sand was carried out using a planetary ball mill, and fluoride removal of the product was examined using fluoride aqueous solution and hot spring water. The hot spring water is collected from one of the hot spring in Japan, and a typical sulfuric acid hot spring water pH 2 including high contents of SO4 2-(12000 mg• L-1) and Cl- (5000 mg • L-1) with 11 - 15 mg • L-1. Fluoride can be adsorbed selectively from hot spring water below Japanese effluent standard for fluoride (8.0 mg • L-1. Fluoride can be adsorbed selectively from hot spring water below Japanese effluent standard for fluoride (8.0 mg • L-1). [ABSTRACT FROM AUTHOR]

Electrocardiogram (ECG) electrodes are conductive pads applied to the skin to measure cardiac activity. Ag/AgCl electrodes are the commercial product which widely used to obtain ECGs. When monitoring the ECG in a hot spring, Ag/AgCl electrodes must be waterproofed; however, this is time-consuming, and the adhesive may tear the skin on removal. For solving the problem, we developed the carbon pencil lead (CPL) electrodes for use in hot springs. Both CPL and Ag/AgCl electrodes were connected to ECG100C's cables. The Performance was evaluated in three conditions as following: hot spring water with and without bubble, and in cold water. In each environment, the procedure was followed by three different protocols that are recording from the dry condition, hot spring water immersion with and without movement, post hot spring water condition. Under dry and wet conditions, both electrodes can obtain the waveform of the ECG signal in which all PQRST waves were identifiable. Nevertheless, the signal quality of both types of electrodes was different in water immersion with and without movement. The overall morphology obtained by Ag/AgCl electrodes was unstable higher than that of CPL electrodes in immersion without movement condition. The CPL electrodes provided better ECG waveform quality compared to Ag/AgCl electrodes in which the ECG signal had high waveforms distortion in water immersion with movement condition. [ABSTRACT FROM AUTHOR]

Phreatic eruptions at Nakamachineshiri and Ponmachineshiri reflect the vigorous fumarolic and hydrothermal activities of Meakandake volcano. Thus, phreatic eruptions are likely to reoccur in the future, and hydrothermal systems should be understood to mitigate the risks of potential future hazards. Here, we reveal the results of long-term geochemical monitoring of hot spring waters and fumarolic gases since 1986 and discuss the chemical and temperature changes in hot spring waters, discharging at the foot, related to volcanic unrest. In Nakamachineshiri, related to the increase in seismic and fumarolic activity since 2019, the HCl concentration of the fumarolic gas has increased, and δD and δ18O values have also increased to approach those of the andesitic water. Simultaneously, with the increase in fumarolic and hydrothermal activity, the temperature and Cl concentration of the Meakan Onsen (MO) hot spring water discharged at the western foot of Nakamachineshiri have increased. The chemical characteristics of the fumarolic gas and MO water indicate that they were derived from a hydrothermal system in the shallow subsurface of Nakamachineshiri. Thus, we can consider that the temperature and chemical increases in the MO water represent activation of the system, and monitoring the MO water provides important information for understanding the present state of Nakamachineshiri. At Ponmachineshiri, phreatic eruptions occurred in 1988, 1996, 1998, 2006, and 2008, and seismic and fumarolic activity has sometimes increased since 1986 when we began our monitoring program. At the western foot of Ponmachineshiri, hot spring water is discharged at Yunotaki (YNT_U and YNT_L) and Lake Onneto (ONT). The results of our monitoring suggest that the YNT_U water is formed by mixing thermal water with a high HCO 3 molar ratio (HCO 3 -type) and thermal water containing Cl and SO 4 (Cl-SO 4 -type), which causes temperature and chemical changes related to the mixing ratio of these thermal waters related to volcanic unrest, especially increases in seismic activity. The Cl and SO 4 concentrations in the ONT water began to increase approximately two years before the phreatic eruptions and increase in fumarolic activity. Such chemical increases can be explained by the increase in the supply of Cl-SO 4 -type thermal water and are likely to indicate precursor changes in volcanic unrest. Therefore, we expect to utilize these hot spring waters to understand the present state of Ponmachineshiri and detect precursor changes to future volcanic unrest. • Long-term monitoring for hot spring waters and fumarolic gases has been performed at Meakandake volcano. • Chemical and thermal changes related to volcanic unrest were detected in hot spring waters discharged at the foot. • Monitoring for hot spring waters is useful to understand the present state of volcanic activity. [ABSTRACT FROM AUTHOR]

Uranium- and thorium-series isotopes are able to dissolve in hot spring waters and decay into radon, which could potentially cause health risk of the public. Besides, several environmental investigations can be carried out by measuring radon concentrations in hot spring waters. Accordingly, the measurement of radon in hot spring water is a significant issue. A practical method for measuring radon in hot spring water was developed by using a silicon semiconductor detector, RAD-7. The overall effect of detection efficiency and radon leakage of the measuring system were examined to calibrate the measured concentration of radon in hot spring waters. In addition, the effect of water temperature and pH on emanation of radon from standard 226Ra solutions as well as that of the measuring time on precision of the measurement were investigated. The correlation among temperature, pH and emanation of radon was then obtained. Further, the established method was applied to in-situ measurement to investigate the concentration of radon in hot spring waters from different geological areas in Taiwan. According to the percent error of the measurement, the measuring time for environmental samples was set as 50 min. The overall effect of radon leakage and detection efficiency of the measuring system was estimated to be 99.19 ± 7.47% with a standard rock source of 222Rn from NIST. Standard sources of 222Rn were prepared from 226Ra standard solutions with different pH values. The 226Ra standard solutions were sealed and stand for 38 days in a 250 mL vial specific for the RAD-7. After measured by the WAT250 mode of the RAD-7, the data were measured as (52.5 ± 8.9)%∼(83.6 ± 11.0)% of the prepared concentration of 222Rn (from 226Ra). The emanation rate of 222Rn from standard solution under pH 1.44–9.07 was (53.2 ± 6.9)% ∼(84.3 ± 11.1)% and decreased with pH to a minimum value at 7.00. Moreover, the effect of temperature increases with pH. High correlated trend curves (r2 = 0.9829–0.9999) for 222Rn emanation rate versus pH under different temperature were obtained. A smooth curved surface fitted by the MATLAB for emanation rate of 222Rn was accordingly derived. The 222Rn concentrations in waters of the Beitou Hot Spring (acid-digestion sulfate spring on sedimentary rock strata), Wulai Hot Spring (sodium bicarbonate spring on metamorphic rock strata), Choshuitan (sodium bicarbonate spring on mudstone strata) and Zhaori Hot Spring (acid-digestion sulfate spring on andesite strata) were measured with RAD-7 by WAT250 for 50 min and then calibrated by 222Rn emanation rate estimated above, which were 215 ± 37 (Bq/m3), 6797 ± 1073 (Bq/m3), 2124 ± 577 (Bq/m3) and 26644 ± 2768 (Bq/m3). • A practical method for measuring Rn in hot spring water was developed. • Correlation among water temperature, pH and emanation of Rn was obtained. • A smooth curved surface fitted by the MATLAB for Rn emanation was derived. • This method was applied to in-situ measurement of Rn in hot spring waters in Taiwan. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to evaluate the frequency of Legionella pneumophila in three hot spring water recreation areas by conventional culture on GVPC and by Real Time-PCR. No legionellae were isolated from the spring water upstream the distribution system suggesting strongly that the thermal area was the probable source of these pathogens. L. pneumophila was present at high level in some samples, reaching values of 8.2 × 103 CFU/l at the site C. We observed a low diversity among the 18 isolated Legionella strains according to 16S DNA analysis, since only L. pneumophila and Legionella londiniensis were identified. All of the L. pneumophila strains belong to five serogroups (1, 4, 5, 6 and 8). Pulsed-field gel electrophoresis analysis identified various genotypes among these serogroups and showed that these strains had pulsotypes distinct from L. pneumophila present in the CNRL Legionella-database. These environmental strains showed higher tolerance to heat shock stress at 48 °C than L. pneumophila clinical strain, which may explain their presence in warm waters. Our data suggested that potential pathogen legionellae are present in Tunisian medicalized thermal spas and emphasized the importance of adopting control measures to prevent infection. [Copyright &y& Elsevier]

• Chemical composition and hydrogen and oxygen isotopes of hot spring waters in Toyama were determined. • The origin and underground temperature condition for geothermal exploration were discussed. • High salinity groups of hot spring waters are a mixture of fossil sea water and meteoric water. • The low salinity groups are of meteoric origin. • There are high-temperature geothermal resources in the eastern area. The chemical compositions, including hydrogen and oxygen isotopes, of 35 hot spring waters in Toyama Prefecture, central Japan, were analyzed to examine their geochemical characteristics and geothermal resources. The hot spring water samples were classified into two groups: low and high chloride (Cl−) concentrations of less than and greater than 2000 mg/L, respectively. The samples in the low-salinity group were determined to be of meteoric origin and Ca2+–HCO 3 − type. The samples in the high-salinity group were determined to be of Na+–Ca2+–Cl− type and assumed to contain a mixture of fossil seawater and meteoric water. In the eastern area of the study region, the Na+/K+ and SiO 2 concentrations were lower and higher, respectively, than those in other areas, which corresponded to high-temperature geothermal resources. Thus, the subsurface information obtained in this study enabled effective use of the low to medium geothermal resources in Toyama Prefecture. [ABSTRACT FROM AUTHOR]

• Geothermal waters from a geothermal well in the vicinity of Yakedake volcano were monitored for 1 year for chemical and D, O, and Sr compositions. • The 87Sr/86Sr ratios of hot spring waters in Shinhirayu area are lower than those in the other districts reflecting the geologic formations. • Precipitation infiltrated into the Kasagatake Rhyolite formation where the thermal waters are enriched in Ca2+, K+ and Sr2+ by interaction with reservoir rocks. • The geothermal water from well No. 7 and hot spring waters in the study area are not in chemical equilibrium with the reservoir rocks. Geothermal waters from a 1,100-m-deep geothermal well (No. 7) in the vicinity of Yakedake volcano in Gifu Prefecture, central Japan, were monitored for 1 year for chemical and isotope (D, O, and Sr) composition to examine their source. Drill cuttings from the well and surrounding hot spring waters were also analyzed for 87Sr/86Sr ratios and chemical composition. Combining the calculated reservoir temperatures for geothermal waters from well No. 7 and the 87Sr/86Sr ratios obtained, we suggest a shallow source for the geothermal waters, such as the Cretaceous to Paleogene Kasagatake Rhyolites, and propose downward-flowing meteoric waters as dominant at depth where the geothermal waters are enriched in Ca2+, K+, and Sr2+ by the interaction with reservoir rock. The 87Sr/86Sr ratios of hot spring waters in the Shinhirayu area, west of well No.7, are lower than those in three adjacent areas (Nakao, Gamada, and Hirayu), reflecting differences between the geologic formations comprising the reservoir rocks. The geothermal water from well No. 7 and hot spring waters in the study area are not in chemical equilibrium with the reservoir rocks because the reservoirs are young and not strongly altered. [ABSTRACT FROM AUTHOR]