High-pressure phase transition and behavior of protons in brucite Mg(OH)2: a high-pressure–temperature study using IR synchrotron radiation     

K. Shinoda  M. Yamakata  T. Nanba  H. Kimura  T. Moriwaki  Y. Kondo  T. Kawamoto  N. Niimi  N. Miyoshi  N. Aikawa 《Physics and Chemistry of Minerals》2002,29(6):396-402

 Infrared absorption spectra of brucite Mg (OH)₂ were measured under high pressure and high temperature from 0.1 MPa 25 °C to 16 GPa 360 °C using infrared synchrotron radiation at BL43IR of Spring-8 and a high-temperature diamond-anvil cell. Brucite originally has an absorption peak at 3700 cm⁻¹, which is due to the OH dipole at ambient pressure. Over 3 GPa, brucite shows a pressure-induced absorption peak at 3650 cm⁻¹. The pressure-induced peak can be assigned to a new OH dipole under pressure. The new peak indicates that brucite has a new proton site under pressure and undergoes a high-pressure phase transition. From observations of the pressure-induced peak under various P–T condition, a stable region of the high-pressure phase was determined. The original peak shifts to lower wavenumber at −0.25 cm⁻¹ GPa⁻¹, while the pressure-induced peak shifts at −5.1 cm⁻¹ GPa⁻¹. These negative dependences of original and pressure-induced peak shifts against pressure result from enhanced hydrogen bond by shortened O–H···O distance, and the two dependences must result from the differences of hydrogen bond types of the original and pressure-induced peaks, most likely from trifurcated and bent types, respectively. Under high pressure and high temperature, the pressure-induced peak disappears, but a broad absorption band between 3300 and 3500 cm⁻¹ was observed. The broad absorption band may suggest free proton, and the possibility of proton conduction in brucite under high pressure and temperature. Received: 16 July 2001 / Accepted: 25 December 2001  相似文献   

Radiocesium in Ponds in the Near Zone of Fukushima Dai-ichi NPP     

A. V. Konoplev  Y. Wakiyama  T. Wada  V. N. Golosov  K. Nanba  T. Takase 《Water Resources》2018,45(4):589-597

The article presents the results of studying radiocesium concentration and distribution between dissolved and particulate forms in ponds in the near zone of Fukushima Dai-ichi NPP NPP after the 2011 accident. The total concentration of ¹³⁷Cs in pond water and its variations are shown to be largely governed by the concentration of particulate matter being as high as 68 Bq/L, compared with 5 Bq/L in solution. The values of the distribution coefficient K_d in the ponds are similar to those in rivers and in large flow-through lakes in the accidentally polluted zone at Fukushima Dai-ichi NPP. The contributions of the main competing ions K⁺ and NH ₄ ⁺ to radiocesium desorption from solid particles into solution were similar for the ponds; however, their relative effect on dissolved radiocesium concentration varied over time because of variations in ammonium concentration.  相似文献   

A theoretical interpretation of the chemical shift of Si NMR peaks in alkali borosilicate glasses     

Tokuro Nanba  Mitsunori Nishimura 《Geochimica et cosmochimica acta》2004,68(24):5103-5111

In ²⁹Si-NMR, it has so far been accepted that the chemical shifts of Qⁿ species (SiO₄ units containing n bridging oxygens) were equivalent between alkali borosilicate and boron-free alkali silicate glasses. In the sodium borosilicate glasses with low sodium content, however, a contradiction was confirmed in the estimation of alkali distribution; ¹¹B NMR suggested that Na ions were entirely distributed to borate groups to form BO₄ units, whereas a −90 ppm component was also observed in ²⁹Si-NMR spectra, which has been attributed to Q³ species associated with a nonbridging oxygen (NBO). Then, cluster molecular orbital calculations were performed to interpret the −90 ppm component in the borosilicate glasses. It was found that a silicon atom which had two tetrahedral borons (B4) as its second nearest neighbors was similar in atomic charge and Si2p energy to the Q³ species in boron-free alkali silicates. Unequal distribution of electrons in Si-O-B4 bridging bonds was also found, where much electrons were localized on the Si-O bonds. It was finally concluded that the Si-O-B4 bridges with narrow bond angle were responsible for the −90 ppm ²⁹Si component in the borosilicate glasses. There still remained another interpretation; the Q³ species were actually present in the glasses, and NBOs in the Q³ species were derived from the tricluster groups, such as (O₃Si)O(BO₃)₂. In the glasses with low sodium content, however, it was concluded that the tricluster groups were not so abundant to contribute to the −90 ppm component.  相似文献   

Natural groundwater of a gas field utilizable for a bioremediation of trichloroethylene-contamination   总被引：1，自引：0，他引：1  

Mio?TakeuchiEmail author  Kenji?Nanba  Ken?Furuya  Hisashi?Nirei  Mitsuo?Yoshida 《Environmental Geology》2004,45(7):891-898

Groundwater from a shallow aquifer in Mobara, a city in a natural gas field in Chiba Prefecture, Japan, was found to contain a significant amount of dissolved methane (<3.1 mM) along with nitrate, phosphate and methane-oxidizing bacteria (methanotrophs, <9.9×10⁶ MPN ml^–1) which can degrade trichloroethylene (TCE). This water exhibited high methanotroph growth activity and rapid degradation of TCE. This water was introduced into a TCE-contaminated aquifer. The concentration of TCE at the monitoring well 2 m down-gradient of the injection pit decreased from 128 g L^–1 before the injection to less than the lower detection limit of 12.5 g L^–1 after the injection, while it decreased only slightly (to 86 g L^–1) when control water was injected. These results demonstrate the feasibility of utilizing a natural groundwater resource containing methane and methanotrophs without any additives for bioremediation of a TCE-contaminated site.  相似文献