The Uptake Coefficient of I2 on Various Aqueous Surfaces     

Akinori Takami  Teruo Kondo  Azumi Kado  Seiichiro Koda 《Journal of Atmospheric Chemistry》2001,39(2):139-153

Uptake coefficient of I₂ on aqueous surfaces was measured by using an impinging flow method. Dependence of the uptake coefficient on the gas-liquid contact time and pH was investigated. The uptake coefficient was (3.7± 2.0)×10^–4 at 120 ms, 293 K and pH = 5.6. In the alkaline region, the uptake coefficient was larger by one order of magnitude than that in the neutral and acidic region. The I₂ uptake on KI solutions and synthetic sea water solutions was also measured. According to the analysis by the reactive uptake model, the uptake of I₂ was shown to be mainly determined by liquid phase reactions and the accommodation coefficient of I₂ on aqueous surfaces was estimated to be 0.01.  相似文献   

Long-term continuous in situ potentiometrically measured redox potential in anoxic groundwater with high methane and iron contents     

Seiichiro Ioka  Toshiaki Sakai  Toshifumi Igarashi  Yoji Ishijima 《Environmental Earth Sciences》2011,64(1):143-149

The in situ redox potential (Eh) in anoxic groundwater with high methane and iron contents (approximately 12.3 and 28.4 mg/L, respectively) was potentiometrically measured to identify the processes that control Eh. The measured Eh ranged from −213 to −187 mV; it had an inverse correlation with the concentration of methane and no correlation with that of iron. The saturation indices indicate that goethite and amorphous FeS were nearly at solubility equilibrium. A comparison of the measured Eh with those calculated for the particular redox pairs indicates that either Fe²⁺/FeOOH or CH₄/CO₂, but not sulfur redox pairs, controlled the measured Eh. The inverse relationship between measured Eh and methane concentration suggests possible control of the redox conditions by the CH₄/CO₂ redox pair. Furthermore, the equilibrium solubility state of goethite, which has higher crystallinity and lower solubility than Fe(OH)₃ indicates that the iron reaction was electrochemically irreversible. This further supports the contribution of the CH₄/CO₂ pair to controlling the measured Eh of groundwater.  相似文献   

Clay Minerals in an Active Hydrothermal Field at Iheya‐North‐Knoll,Okinawa Trough          下载免费PDF全文

Youko Miyoshi  Jun‐ichiro Ishibashi  Kazuhiko Shimada  Hiroyasu Inoue  Seiichiro Uehara  Katsuhiro Tsukimura 《Resource Geology》2015,65(4):346-360

Iheya‐North‐Knoll is one of the small knolls covered with thick sediments in the Okinawa Trough back‐arc basin. At the east slope of Iheya‐North‐Knoll, nine hydrothermal vents with sulfide mounds are present. The Integrated Ocean Drilling Program (IODP) Expedition 331 studied Iheya‐North‐Knoll in September 2010. The expedition provided us with the opportunity to study clay minerals in deep sediments in Iheya‐North‐Knoll. To reveal characteristics of clay minerals in the deep sediments, samples from the drilling cores at three sites close to the most active hydrothermal vent were analyzed by X‐ray diffraction, scanning electron microscope and transmission electron microscope. The sediments are classified into Layer 0 (shallow), Layer 1 (deep), Layer 2 (deeper) and Layer 3 (deepest) on the basis of the assemblage of clay minerals. Layer 0 contains no clay minerals. Layer 1 contains smectite, kaolinite and illite/smectite mixed‐layer mineral. Layer 2 contains chlorite, corrensite and chlorite/smectite mixed‐layer mineral. Layer 3 is grouped into three sub‐layers, 3A, 3B and 3C; Sub‐layer 3A contains chlorite and illite/smectite mixed‐layer mineral, sub‐layer 3B contains chlorite/smectite and illite/smectite mixed‐layer minerals, and sub‐layer 3C contains chlorite and illite. Large amounts of di‐octahedral clay minerals such as smectite, kaolinite, illite and illite/smectite mixed‐layer mineral are found in Iheya‐North‐Knoll, which is rarely observed in hydrothermal fields in mid‐ocean ridges. Tri‐octahedral clay minerals such as chlorite, corrensite and chlorite/smectite mixed‐layer mineral in Iheya‐North‐Knoll have low Fe/(Fe + Mg) ratios compared with those in mid‐ocean ridges. In conclusion, the characteristics of clay minerals in Iheya‐North‐Knoll differ from those in mid‐ocean ridges; di‐octahedral clay minerals and Fe‐poor tri‐octahedral clay minerals occur in Iheya‐North‐Knoll but not in mid‐ocean ridges.  相似文献   

An acoustic positioning system using demodulated signals of an FM ultrasonic wave     

Mitome  H. Koda  T. Shibata  S. 《Oceanic Engineering, IEEE Journal of》1985,10(3):316-323

An acoustic positioning system using a continuous frequency-modulated (FM) ultrasonic wave transmitted from a sound source source located on the sea bottom is described in this paper. This system consists of a direction detecting system and a distance-change detecting system. The accuracy of the direction detection of the tested system was2degand the accuracy of the distance-change detection was within 0.10 m for a displacement of 50 m. Combining these two systems, it is possible to detect the change of position of the vessel sensitively. Since information from the phases of demodulated signals of the received FM ultrasonic wave is used exclusively, this system is excellent in signal-to-noise ratio (S/N) in spite of the simplicity of the electronic circuit. It was confirmed in experiments in the sea that both the direction detecting system and the distance-change detecting system worked well simultaneously, and that the combined systems would be suitable as an acoustic positioning system.  相似文献   

Cenozoic stratigraphy and sedimentation history of the northern Philippine Sea based on multichannel seismic reflection data     

Yu  Higuchi  Yutaka  Yanagimoto  Kazuyoshi  Hoshi  Sadao  Unou  Fumio  Akiba  Kunishige  Tonoike  Keita  Koda 《Island Arc》2007,16(3):374-393

Abstract To clarify the regional distribution and characteristics of the sedimentary deposits in the northern part of the Philippine Sea, multichannel seismic reflection surveys of 26 864 km in total length were performed. The seismic reflection data were interpreted and correlated with available Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) data and a general stratigraphic framework of the area was established. The sedimentary deposits in this area were divided into five layers; Units I, II, III, IV and V in ascending order. Their approximate geological ages are the Early Eocene, Middle to Late Eocene, Oligocene, Miocene and Pliocene‐Pleistocene, respectively. Seismic records were classified into three seismic facies, Facies A, B and C, on the basis of their characteristics. They were judged to represent pelagic and hemipelagic sediments of non‐volcanic origin, fine pyroclastic sediments and coarse pyroclastic or volcanic sediments, respectively, by comparing them with lithological data in the DSDP/ODP holes. From the thickness and facies distributions of these sediments, a sedimentary history in the area was reconstructed as follows. The oldest sediments in the study area, Unit I, interfinger with some parts of the Daito Ridge (acoustic basement) in the Minami Daito Basin. The geological age of the unit is estimated by microfossils in the sediment and supports the idea that this part of the Daito Ridge is composed of the Early Eocene oceanic basalt. Later, a fair amount of sediments were deposited in the Minami Daito Basin in the Middle to Late Eocene age. A large volume of volcanic materials was supplied from the Paleo‐Kyushu‐Palau Ridge in the Kita Daito Basin in the Eocene and Oligocene ages. The eastern part of the Shikoku and Parece Vela basins is characterized by volcanic sediments supplied from the Nishi Shichito and West Mariana Ridges in the Miocene age. However, pelagic and hemipelagic sediments prevail in the northern part of the Shikoku Basin in the Miocene or later. In short, the area of principal sedimentation has generally shifted from west to east through geological time, reflecting the evolution of the island arc systems with the same trend in the northern Philippine Sea.  相似文献