Phytotoxicity assessment of γ-Fe2O3 nanoparticles on root elongation and growth of rice plant     

Darioush Alidoust  Akihiro Isoda 《Environmental Earth Sciences》2014,71(12):5173-5182

This study was conducted to determine the phytotoxicity of 6 nm γ-Fe₂O₃ nanoparticles (IONPs) in terms of root elongation and the physiological performance of rice plants. Rice seeds (Oryza sativa L. var. Koshihikari) exposed to IONPs at 500, 1,000 and 2,000 mg/L, had a significantly higher root elongation than the control and its bulk counterparts (IOBKs), indicating that the effect can be nanospecific. In a 14-week greenhouse pot experiment, the CO₂ assimilation rate in IOBK and IONP-treated pots (500 and 1,000 mg/pot) decreased over time, with the decline (maximum 42.5 %) being less pronounced for IONPs, indicating that the effect cannot be inferred from the toxicity of nanoscale size iron oxide. Excessive adsorption of IONPs onto soil colloids with subsequent low water extractable iron was responsible for the unremarkable phytotoxic nature of IONPs in the rice plants. Amendment of IONPs coated with 20 mmol citric acid (IONPs-Cit) significantly diminished the CO₂ assimilation rate and the decrease was similar to its bulk counterpart (IOBKs-Cit). However, maximum shoot growth inhibition (37 %) was associated with the application of IOBKs-Cit. It was concluded that massive accumulations of Fe plaque on the root surfaces of IOBKs-Cit treatments due to a decline in the pH of rhizoplane soils compared to the IONPs-Cit treatments were responsible for the remarkable shoot growth reduction. This study provided evidence of the phytotoxicity of γ-Fe₂O₃ nanoparticles, demonstrating the lower toxicity of nanosized iron oxide compared to a microsized preparation under reductive conditions.  相似文献   

A measurement of H₀ from Ryle Telescope, ASCA and ROSAT observations of Abell 773     

Richard Saunders  Rüdiger Kneissl  Keith Grainge  William F. Grainger  Michael E. Jones  Alessia Maggi  Rhiju Das  †  Alastair C. Edge  Anthony N. Lasenby  G. G. Pooley  Shigeru J. Miyoshi  Taisuke Tsuruta  Koujun Yamashita  Yuzuru Tawara  Akihiro Furuzawa  Akihiro Harada  Izamu Hatsukade 《Monthly notices of the Royal Astronomical Society》2003,341(3):937-940

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Upper Eocene travertine-lacustrine carbonate in the Jianchuan basin,southeastern Tibetan Plateau: Reappraisal of its origin and implication for the monsoon climate     

Aki Sakuma  Akihiro Kano  Yoshihiro Kakizaki  Ryuji Tada  Honbo Zheng 《Island Arc》2021,30(1):e12416

The Asian monsoon is one of the largest climatic systems in the world, but age of its onset has been estimated differently ranging from the late Eocene to the Quaternary. We investigated the sedimentology and stable isotopic compositions of the upper Eocene Jiuziyan Formation, a terrestrial limestone unit in the Jianchuan basin, Yunnan Province in China. This limestone formation is restricted in several localities in the central part of the basin. Previously, this has been characterized as palustrine carbonate and the transition to the sublacustrine deposit of the overlying Shuanghe Formation was interpreted as the appearance of wetter climate during the late Eocene. Our observations of macro- and microfacies revealed sedimentary fabrics indicating rapid CaCO₃ precipitation, such as dendritic calcite and calcified reed stems, which are unlikely to develop in a simple lacustrine setting. High carbonate content (mostly >90 %) and restricted distribution of the Jiuziyan limestone indicate a depositional setting spatially limited and isolated from clastic influx. These findings, together with clearly higher δ¹³C values (−0.7 ‰ to +6.9 ‰) and lower δ¹⁸O values (−14.6 ‰ to −10.5 ‰) than those of the Shuanghe Formation, indicate that the limestone was mainly travertine, carbonate formed from endogenic spring water. The elevated δ¹³C resulted from a large amount of CO₂ degassing from spring water with high pCO₂. In addition, the occurrence of centimeter-scale lamination coupled with cyclic changes in δ¹³C and δ¹⁸O is almost identical with the modern annually-laminated travertine reported from Baishuitai in northern Yunnan Province, implying comparable amplitude of seasonal temperature and precipitation changes to the record of the modern travertine at Baishuitai. Our results do not contradict the previous interpretation of late Eocene wetting and additionally suggest the existence of the late Eocene monsoon climate in the Jianchuan basin.  相似文献   

Sequentially sampled gas hydrate water,coupled with pore water and bottom water isotopic and ionic signatures at the Kukuy mud volcano,Lake Baikal: ambiguous deep-rooted source of hydrate-forming water     

Hirotsugu Minami  Akihiro Hachikubo  Hirotoshi Sakagami  Satoshi Yamashita  Yusuke Soramoto  Tsuyoshi Kotake  Nobuo Takahashi  Hitoshi Shoji  Tatyana Pogodaeva  Oleg Khlystov  Andrey Khabuev  Lieven Naudts  Marc De Batist 《Geo-Marine Letters》2014,34(2-3):241-251

The isotopic and ionic composition of pure gas hydrate (GH) water was examined for GHs recovered in three gravity cores (165–193 cm length) from the Kukuy K-9 mud volcano (MV) in Lake Baikal. A massive GH sample from core St6GC4 (143–165 cm core depth interval) was dissociated progressively over 6 h in a closed glass chamber, and 11 sequentially collected fractions of dissociated GH water analyzed. Their hydrogen and oxygen isotopic compositions, and the concentrations of Cl^– and HCO₃ ^– remained essentially constant over time, except that the fraction collected during the first 50 minutes deviated partly from this pattern. Fraction #1 had a substantially higher Cl^– concentration, similar to that of pore water sampled immediately above (135–142 cm core depth) the main GH-bearing interval in that core. Like the subsequent fractions, however, the HCO₃ ^– concentration was markedly lower than that of pore water. For the GH water fractions #2 to #11, an essentially constant HCO₃ ^–/Cl^– ratio of 305 differed markedly from downcore pore water HCO₃ ^–/Cl^– ratios of 63–99. Evidently, contamination of the extracted GH water by ambient pore water probably adhered to the massive GH sample was satisfactorily restricted to the initial phase of GH dissociation. The hydrogen and oxygen isotopic composition of hydrate-forming water was estimated using the measured isotopic composition of extracted GH water combined with known isotopic fractionation factors between GH and GH-forming water. Estimated δD of ?126 to ?133‰ and δ¹⁸O of ?15.7 to ?16.7‰ differed partly from the corresponding signatures of ambient pore water (δD of ?123‰, δ¹⁸O of ?15.6‰) and of lake bottom water (δD of ?121‰, δ¹⁸O of ?15.8‰) at the St6GC4 coring site, suggesting that the GH was not formed from those waters. Observations of breccias in that core point to a possible deep-rooted water source, consistent with published thermal measurements for the neighboring Kukuy K-2 MV. By contrast, the pore waters of core St6GC4 and also of the neighboring cores GC2 and GC3 from the Kukuy K-9 MV show neither isotopic nor ionic evidence of such a source (e.g., elevated sulfate concentration). These findings constrain GH formation to earlier times, but a deep-rooted source of hydrate-forming water remains ambiguous. A possible long-term dampening of key deep-water source signatures deserves further attention, notably in terms of diffusion and/or advection, as well as anaerobic oxidation of methane.  相似文献   

Stratigraphy of the mid‐ to upper‐Cretaceous System in the Aridagawa area,Wakayama, Southwest Japan     

Akihiro Misaki  Haruyoshi Maeda 《Island Arc》2010,19(3):517-529

The litho‐ and biostratigraphy of the mid‐ to upper‐Cretaceous System around the Yagumaike Pond in the Aridagawa area, Wakayama, Southwest Japan, were investigated. Many Middle to Late Albian megafossils were found in the strata of a block bounded by faults. It was also revealed that the Upper Cretaceous System of other blocks ranges from the Middle Turonian to Santonian. The Albian megafossil assemblage contains few benthic organisms, in contrast with the abundance of nektons found (e.g. cephalopods). Sedimentological observations of the mudstone profiles also indicate that scarcely or weakly bioturbated, well‐laminated mudstone is dominant among the Albian deposits. These results suggest deposition of the Albian mudstone under a dysaerobic to anoxic environment. It is comparable to the extended oceanic anoxia (OAEs) in mid‐Cretaceous time. Albian deposits with similar characteristics are also known to exist in Shikoku, Southwest Japan. A wide sedimentary basin that was directly affected by global environmental events, such as OAEs, seemed to be formed on the Chichibu Belt in the Albian. The Upper Cretaceous strata in the study area are extremely thin, similar to the coeval deposits on the Chichibu Belt in Shikoku. It is suggested that the sedimentation rate in the sedimentary basin on the Chichibu Belt was extremely low during early Late Cretaceous time.  相似文献   

Aerodynamic Scaling for Estimating the Mean Height of Dense Canopies   总被引：1，自引：1，他引：0  

Taro Nakai  Akihiro Sumida  Kazuho Matsumoto  Ken’ichi Daikoku  Shin’ichi Iida  Hotaek Park  Mie Miyahara  Yuji Kodama  Alexander V. Kononov  Trofim C. Maximov  Hironori Yabuki  Toshihiko Hara  Takeshi Ohta 《Boundary-Layer Meteorology》2008,128(3):423-443

We used an aerodynamic method to objectively determine a representative canopy height, using standard meteorological measurements. The canopy height may change if the tree height is used to represent the actual canopy, but little work to date has focused on creating a standard for determining the representative canopy height. Here we propose the ‘aerodynamic canopy height’ h _a as the most effective means of resolving the representative canopy height for all forests. We determined h _a by simple linear regression between zero-plane displacement d and roughness length z ₀, without the need for stand inventory data. The applicability of h _a was confirmed in five different forests, including a forest with a complex canopy structure. Comparison with stand inventory data showed that h _a was almost equivalent to the representative height of trees composing the crown surface if the forest had a simple structure, or to the representative height of taller trees composing the upper canopy in forests with a complex canopy structure. The linear relationship between d and z ₀ was explained by assuming that the logarithmic wind profile above the canopy and the exponential wind profile within the canopy were continuous and smooth at canopy height. This was supported by observations, which showed that h _a was essentially the same as the height defined by the inflection point of the vertical profile of wind speed. The applicability of h _a was also verified using data from several previous studies.  相似文献   

Lithostratigraphy and biostratigraphy of the Campanian–Maastrichtian Toyajo Formation in Wakayama, southwestern Japan     

Akihiro Misaki  Haruyoshi Maeda 《Cretaceous Research》2009,30(6):1398-1414

The Upper Cretaceous Toyajo Formation is distributed around the Mt. Toyajo in the Aridagawa area, Wakayama, southwestern Japan. The formation is subdivided into three newly defined members, the Nakaibara Siltstone Member, Hasegawa Muddy Sandstone Member, and Buyo Sandstone Member, in ascending order. Close field observation elucidated the detailed biostratigraphy of the Toyajo Formation, and high-precision biostratigraphic correlation was made with the Yezo Group in Hokkaido (northern Japan) and Sakhalin and the Izumi Group in southwestern Japan.The Toyajo Formation contains diversified lower Campanian to upper Campanian heteromorph ammonoid assemblages, including Eubostrychoceras and Scaphites. Discovery of the heteromorph fauna demonstrates that scaphitid ammonoids survived until Campanian time in the northwestern Pacific region. Although Eubostrychoceras elongatum has been known in the northeastern Pacific region, the occurrence of this species in the northwestern Pacific region has been uncertain before. The rich occurrence of E. elongatum in the Aridagawa area indicates that this species was distributed widely in the northern Pacific realm.The Toyajo Formation is similar to the Izumi Group in various geologic features, and may indicate that the Toyajo Formation was deposited in a strike-slip basin along the Chichibu Belt formed by the movement along the Kurosegawa Tectonic Zone in the latest Cretaceous, like the Izumi Group, along the Median Tectonic Line.  相似文献   

国际全球变化研究发展态势文献计量评价   总被引：1，自引：0，他引：1  

张志强  王雪梅 《地球科学进展》2007,22(7):0-765

-全球变化研究是国际上地球系统综合研究的重大跨学科研究领域。随着全球环境问题的日益突出，国际上先后组织发起了全球环境变化研究的四大科学计划WCRP、IGBP、IHDP、DIVERSITAS及其组成的地球系统科学联盟ESSP，开展对全球变化和地球系统科学的研究。当前，全球变化问题不仅是科学界关注和研究的问题，也是政治界、经济界都关注的重大问题。 科技文献能够反映科学前沿的发展动态。对SCIE和SSCI数据库收录的全球变化研究文献进行统计，从文献计量学的角度，分析国际全球变化研究领域的发展态势，了解中国全球变化研究的国际影响力。可以看出：国际上全球变化研究的论文数量一直呈增长趋势，以地球科学多学科、生态学、环境科学、自然地理学、植物学等学科领域为主。中国自2000年以来在该领域的发文数量增长较快，特别是中国科学院的发文量已进入国际前列，但中国在该研究领域尚缺少高影响力的论文。  相似文献   

Investigation on the Performance of Pipe Roof Method Adjacent to the Underground Construction     

Ma  Peng  Shimada  Hideki  Sasaoka  Takashi  Hamanaka  Akihiro  Dintwe  Tumelo K. M.  Pan  Donjiang 《Geotechnical and Geological Engineering》2021,39(6):4677-4687

In this paper, the behaviour of the pipe roof method with different pipe roofs disposition schemes including the pipe roof gate system and L-shaped system is discussed in terms of ground settlement reduction in the condition of underground space construction adjacent to the existing structure by using numerical simulation method. Considering the construction sequences of parallel underground tunnels with rectangular cross sections, the appropriate parameters and ground response characteristics of the corresponding pipe roof methods are evaluated by the ground surface displacement. The results indicated that the construction impacts from new buildings can be reduced by the pipe roof method. However, the theoretical performance of pipe roofs is highly dependent on the spacing between two structures. Generally, the L-shaped system is more effective in case of the distance (D) that is less than or equal to 1/2 width of box culvert (R) under the condition of a new structure constructed nearby the existing building. When two structures are constructed simultaneously, the excavation and the construction of structures influence each other reciprocally. The conclusions could provide a reference for the pipe roof method with the application scenario of adjacent building protection.

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Purification of seawater contaminated with undegradable aromatic ring compounds using ozonolysis followed by titanium dioxide treatment   总被引：1，自引：0，他引：1  

Nakamura Y  Kobayashi F  Daidai M  Kurosumi A 《Marine pollution bulletin》2008,57(1-5):53-58

Treatment of aromatic ring compounds, 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichloro-phenoxy acetic acid (2,4,5-T), and bisphenol A, in the artificial seawater, i.e. Allen seawater, was carried out by ozonation and titanium dioxide (TiO2) photocatalyst treatment. Each compound was degraded and varnished within 30 min by only ozonolysis at pH 9.0 and at 20 degrees C, while the TOC value of each compound decreased gradually but reached almost constant value, i.e. about 70-80% of the initial value, at even 30 min of ozonation time. Ozonolysis (30 min of ozonation time) followed by TiO2 photocatalyst treatment (50h of reaction time) was a very effective method for decreasing the TOC values of aromatic ring compounds in the artificial seawater. In consequence, TOC values of 2,4-D, 2,4,5-T, and bisphenol A could be reduced to about 28, 21, and 34% of their initial values, respectively.  相似文献