Decarbonation reaction of magnesite in subducting slabs at the lower mantle     

N. Takafuji  K. Fujino  T. Nagai  Y. Seto  D. Hamane 《Physics and Chemistry of Minerals》2006,33(10):651-654

High-pressure and temperature experiments (28–62 GPa, and 1,490–2,000 K, corresponding to approximately 770–1,500 km depth in the mantle) have been conducted on a MgCO₃ + SiO₂ mixture using a laser-heated diamond anvil cell combined with analytical transmission electron microscope observation of the product phases to constrain the fate of carbonates carried on the subducting basalt into the lower mantle. At these conditions, the decarbonation reaction MgCO₃ (magnesite) + SiO₂ (stishovite) → MgSiO₃ (perovskite) + CO₂ (solid) has been recognized. This indicates that above reaction takes place as a candidate for decarbonation of the carbonated subducting mid ocean ridge basalts in the Earth’s lower mantle.  相似文献   

Groundwater Level Prediction/Forecasting and Assessment of Uncertainty Using SGS and ARIMA Models: A Case Study in the Bauru Aquifer System (Brazil)     

Takafuji  Eduardo Henrique de Moraes  Rocha  Marcelo Monteiro da  Manzione  Rodrigo Lilla 《Natural Resources Research》2019,28(2):487-503

Natural Resources Research - Best water management practices should involve the prediction of the availability of groundwater resources. To predict/forecast and consequently manage these water...  相似文献   

Arsenic contamination of ground and pond water and water purification system using pond water in Bangladesh   总被引：1，自引：0，他引：1  

H. Yokota  K. Tanabe  M. Sezaki  Y. Akiyoshi  T. Miyata  K. Kawahara  S. Tsushima  H. Hironaka  H. Takafuji  M. Rahman  Sk. A. Ahmad  M. H. S. U. Sayed  M. H. Faruquee 《Engineering Geology》2001,60(1-4):323-331

This paper, firstly, shows the distribution of arsenic-contaminated groundwater in Samta village. This village, which is in Jessore district in Bangladesh, was chosen as a model village for investigating the mechanism of groundwater contamination. 90% of the tube wells in this village had arsenic concentrations above the Bangladesh standard of 0.05 mg/l. Tube wells with arsenic concentrations of over 0.50 mg/l were distributed in the southern part of the village with a belt-like shape from east to west. Secondly, groundwater distribution is discussed with respect to its flow and the high arsenic zone (As≥0.50 mg/l) agrees well with the drifting zone of the groundwater. Furthermore, arsenic-free water supply systems suitable for a small area in the village have been developed. A pond sand filter (PSF) system which purifies pond water is discussed in this paper. Prior to the construction of the PSF, the water quality in ponds was examined for arsenic levels. The inflow of drainage from the tube wells was found to be the major cause of arsenic contamination of pond water. The PSF installed in Samta is working very well and produces a good quality of treated water.  相似文献   

Study on Al2O3 content and phase stability of aluminous-CaSiO3 perovskite at high pressure and temperature     

N. Takafuji  T. Yagi  N. Miyajima  T. Sumita 《Physics and Chemistry of Minerals》2002,29(8):532-537

 In order to clarify Al₂O₃ content and phase stability of aluminous CaSiO₃-perovskite, high-pressure and high-temperature transformations of Ca₃Al₂Si₃O₁₂ garnet (grossular) were studied using a MA8-type high-pressure apparatus combined with synchrotron radiation. Recovered samples were examined by analytical transmission electron microscopy. At pressures of 23–25 GPa and temperatures of 1000–1600 K, grossular garnet decomposed into a mixture of aluminum-bearing Ca-perovskite and corundum, although a metastable perovskite with grossular composition was formed when the heating duration was not long enough at 1000 K. On release of pressure, this aluminum-bearing CaSiO₃-perovskite transformed to the “LiNbO₃-type phase” and/or amorphous phase depending on its Al₂O₃ content. The structure of this LiNbO₃-type phase is very similar to that of LiNbO₃ but is not identical. CaSiO₃-perovskite with 8 to 25 mol% Al₂O₃ was quenched to alternating lamellae of amorphous layer and LiNbO₃-type phase. On the other hand, a quenched product from CaSiO₃-perovskite with less than 6 mol% consisted only of amorphous phase. Most of the inconsistencies amongst previous studies could be explained by the formation of perovskite with grossular composition, amorphous phase, and the LiNbO₃-type phase. Received: 11 April 2001 / Accepted: 5 July 2002  相似文献   

Formal education and disaster response of children: evidence from coastal villages in Indonesia     

Shoji  Masahiro  Takafuji  Yoko  Harada  Tetsuya 《Natural Hazards》2020,103(2):2183-2205

Natural Hazards - Although children are exposed to a high mortality risk during disasters, what determines their disaster response, especially during earthquakes, remains largely unexplored. The...  相似文献