Analysis of runoff generation and soil erosion processes by using environmental radionuclides in semiarid areas of Mongolia   总被引：1，自引：0，他引：1  

Yuichi Onda  Hiroaki Kato  Maki Tsujimura  Dambaravjaa Oyunbaatar 《Journal of Hydrology》2007,333(1):124-132

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The long-term effects of crude oil on microbial processes in subarctic marine sediments     

Robert P. Griffiths  Bruce A. Caldwell  William A. Broich  Richard Y. Morita 《Estuarine, Coastal and Shelf Science》1982,15(2):183-198

Subarctic marine sediments were exposed to fresh and ‘weathered’ crude oil from Cook Inlet, Alaska. The crude oil was thoroughly mixed with the sediment at various concentrations and some of the oil-sediment mixtures were placed on top of unamended sediments. Both sediments with added oil and those overlain by oiled sediments were investigated. These sediments were placed either in trays or aquaria. The trays were incubated in situ near the site from which the sediments were originally collected. The aquaria were maintained at simulated in situ conditions by maintaining a continuous flow of fresh seawater through them. The sediments were exposed to crude oil for periods up to 1.5 years. Sediments exposed to 50‰ fresh crude oil showed significant decreases in nitrogen fixation and denitrification rates and redox potentials. Also observed were increases in CO₂ production rates and methane concentrations. These same changes were observed in sediments exposed to 1‰. When ‘weathered’ crude oil was added to the sediments, the same changes were observed except there was no reduction in nitrogen fixation activity. In most cases, the observed effects were less marked when the sediments were amended with ‘weathered’ crude oil than with the same concentration of fresh crude oil. Untreated sediments that were overlain with treated sediments showed the same changes as those sediments that were thoroughly mixed with crude oil. The presence of fresh crude oil at 50‰ essentially eliminated burrowing activity of the benthic infauna. Under these conditions, there was an accumulation of detritus particles on the oiled sediments that was not present in the untreated controls.  相似文献   

Experimental investigation of conditions of lateral shear reinforcements in RC columns accompanied by buckling of longitudinal bars     

Yuichi Sato  HuneBum Ko 《地震工程与结构动力学》2007,36(12):1685-1699

This study presents a cyclic load test of four RC columns to obtain data on stresses and strains on lateral shear‐reinforcing bars that contact buckled longitudinal reinforcing bars. The specimens include columns laterally jacketed with all‐elastic fibre‐reinforced polymer (FRP) sheets. The buckling lengths and modes in the longitudinal bars of the four column specimens stabilized at a buckling deflection (= lateral deformation of buckled longitudinal bar) from 0.3 to 0.6 mm. The yield portion ratio r_by of shear reinforcement around the buckled longitudinal bars was introduced as an index of the development of buckling conditions. Here, the yield portion ratio r_by was defined as the ratio of the length of the region where the shear reinforcements yield l_by, to the buckling length l_b. The r_by values of the tested columns ranged from 0.45 to 0.76. The test results show that the buckling stress and the specific compressive stress of the longitudinal bars in the columns were smaller than those of the bare bars. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Distribution of the geochemical signature caused by the 2011 Tohoku-oki tsunami in Misawa harbor,northern Japan     

Frenken  Mike  Bellanova  Piero  Nishimura  Yuichi  Reicherter  Klaus  Schwarzbauer  Jan 《Natural Hazards》2022,114(1):313-333

Natural Hazards - The 2011 Tohoku-oki tsunami left a characteristic geochemical signature in the sediments of the Misawa harbor on the Aomori coastline (northern Japan), not only in vertical...  相似文献   

Occurrence of brominated flame retardants, polycyclic musks, and chlorinated naphthalenes in seal blubber from Antarctica: Comparison to organochlorines     

Alessandra Schiavone  Kurunthachalam Kannan  Yuichi Horii  Silvano Focardi  Simonetta Corsolini 《Marine pollution bulletin》2009,58(9):1415-1419

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Effects of slope gradient on runoff from bare-fallow purple soil in China under natural rainfall conditions     

Yoshitaka Komatsu  Hiroaki Kato  Bo Zhu  Tao Wang  Fan Yang  Randeep Rakwal  Yuichi Onda 《山地科学学报》2018,15(4):738-751

Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.  相似文献   

The height of the maximum ionospheric electron density over the MU radar     

Shun-Rong Zhang  Shoichiro Fukao  William L. Oliver  Yuichi Otsuka 《Journal of Atmospheric and Solar》1999,61(18):361

Ionospheric F₂-layer peak height h_mF₂ variations, as measured over 1986–1995 by the MU radar (34.85°N, 136.1°E) and as calculated with a theoretical model, are discussed. The diurnal variations of the measured peak height for different seasons and levels of solar activity are compared with those estimated from ionosonde M3000F₂ and IRI predictions. Also given are the measured ion drift velocities and meridional neutral winds needed to understand the dynamic behavior of the F₂-layer. It is found that: (1) h_mF₂ is generally higher during periods of the solar maximum than during periods of the solar minimum, and higher in summer than in winter; (2) for the solar maximum, h_mF₂ drops markedly in the morning and in the afternoon, while, for the solar minimum, the h_mF₂ minimum occurs in the morning during summer and usually in the afternoon during winter. In general, the measured h_mF₂ is well reproduced by our model when we use the observed drift velocities and plasma temperatures as inputs. Our modeling study shows that the neutral wind contributes strongly to the diurnal variation of h_mF₂ in winter by lowering the ionization layer by day, particularly for the solar maximum; it also helps to enlarge the day–night difference of h_mF₂ in summer. The northward electromagnetic drifts that usually cancel the neutral wind effect have only a minor effect for the location of the MU radar. Other features of the observed h_mF₂ variations, e.g., the solar maximum–minimum difference, the summer–winter difference, and the morning and afternoon drops, are explained by the basic processes of O⁺ production, loss and diffusion, as influenced by the atomic oxygen concentration and neutral and plasma temperatures.  相似文献   

Three–Dimensional Isotopic Characteristics of Crystalline Limestone around the Sakonishi Zn Ore Bodies in the Kamioka Mining District, Japan     

Yuichi MORISHITA 《Resource Geology》1999,49(4):243-257

Abstract: Predominant Zn-rich ore bodies were found to a deep part of the Sakonishi area in the Kamioka mining district, Japan. The ore mineralization was recognized at 230 to 300m above sea level in the Sakonishi area. Since crystalline limestone is broadly distributed over the area, and the variation in isotopic composition is easily detected, the isotopic prospecting should be powerful in surveying of the extent of the ore bodies and the related hydrothermal system. Although isotopic anomalies have been extracted two-dimensionally so far, three-dimensional information is possibly more powerful. In this paper, Zn-rich ore bodies in the Sakonishi area are treated as hydrothermal ore deposits, and the importance of the activity of hydrothermal fluids during mineralization is emphasized. Oxygen and carbon isotopic ‘iso–surfaces’ are three-dimensionally calculated for the Sakonishi area. The δ¹⁸O values of crystalline limestone from the surface and from the drill holes range from +8. 1 to +21. 1% and from –2. 7 to +20. 4%, respectively. The δ¹³C values of crystalline limestone from the surface and from the drill holes range from –1. 0 to +5. 3% and from –7. 7 to +4. 6%, respectively. The oxygen and carbon iso-topic ratios at the mineralization level are extremely low, but there are exceptions as to carbon isotopes. The oxygen isotopic ratios of crystalline limestone may decrease by isotopic exchange reaction with a hydrothermal fluid, while the carbon isotopic ratios slightly change. Since the precipitated calcite from a hydrothermal fluid has low carbon isotopic ratio and various oxygen isotopic ratio depending on the formation temperature, the bulk sample of crystalline limestone containing the precipitated calcite has oxygen and carbon isotopic ratios of relatively low values accordingly. Thus the decrease mechanism for carbon isotopic ratio of crystalline limestone is different from that for oxygen isotopic ratio. Samples with the carbon isotopic ratio of –4 to –8% are considered to be crystallized from hydrothermal fluids. Since the oxygen and carbon isotopic ratios of crystalline limestone at the ore mineralization level are low, the ore bodies are considered to have formed by a prominent hydrothermal activity. Thus oxygen and carbon isotopic ratios of crystalline limestone can be used as an indicator of the related hydrothermal activity. The alteration such as chloritization is intense near fractures in the Sakonishi area, showing that the hydrothermal system is controlled by a fracture system. It is assumed that the decreased isotopic ratios indicate the high degree of reactivity with hydrothermal fluids, and the depleted zone in oxygen and carbon isotopes may correspond to the conduit of the hydrothermal fluids.  相似文献   

Small-Amplitude Disturbances in a Radiating and ScatteringGrey MediumI. Solutions of Given Real Frequency ω     

Noboru Kaneko  Kazuhiko Morita  Tetsuya Satoh  Kiyotaka Toyama  Masaki Nishimura  Makoto Maekawa 《Astrophysics and Space Science》2000,274(3):601-641

We reanalyze the propagation of one-dimensional small-amplitude disturbances of given real frequency ω in a radiating and scattering grey medium using the Eddington approximation, which has been studied previously by us (Kaneko et al., 1976). Numerical results reveals three frequency regimes to be distinguished, and two wave modes always appear in each frequency regime. The governing equations and analytic solutions are derived for all wave modes using Whitham's method modified into quadratic form and approximate methods based on radiation thermodynamics. In the high-frequency regime appear the radiation-wave and adiabatic sound modes, which are damped by opacity and radiative cooling, respectively. Wave patterns in the intermediate-frequency and low-frequency regimes depend critically on the importance of radiation, for which the criterion is given in terms of the ratio of total specific heats at constant pressure and constant volume. When the radition overwhelms the matter (radiation-dominated case), the radiative mode in the intermediate-frequency regime is the constant-volume diffusion mode. When the matter overwhelms the radiation (matter-dominated case), damped radiation-wave and damped radiation-diffusion modes newly appear between the radiation-wave and constant-volume diffusion modes. The acoustic mode in the intermediate-frequency regime is the isothermal sound mode,which is damped by radiative cooling at higher frequencies and by radiation-thermal drag force at lower frequencies. Two modes appearing in the low-frequency regime are the isentropic radiation-acoustic and constant-pressure diffusion modes. The absorption coefficient derived for the former is shown to be a radiation-thermodynamic extension of that of Landau and Lifshitz (1987). The transition frequencies between all adjacent two modes are also derived to discuss the implications of them. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Ovo-testis and disturbed reproductive cycle in the giant abalone, Haliotis madaka: possible linkage with organotin contamination in a site of population decline.   总被引：1，自引：0，他引：1  

T Horiguchi  N Takiguchi  H S Cho  M Kojima  M Kaya  H Shiraishi  M Morita  H Hirose  M Shimizu 《Marine environmental research》2000,50(1-5):223-229

Histological examination of gonads as well as chemical analysis of organotin compounds in tissues of the giant abalone, Haliotis madaka, was conducted to evaluate possible endocrine disruption and to consider the causal factors for the decline of abalone stocks in Japan. Abalone specimens were collected from two different areas, Tsushima as a reference site and Jogashima as a site representative of declining abalone populations, each month from September 1995 to November 1996. Scores were given to the development stages of reproductive cells in the ovary and testis. The degree of sexual maturation was evaluated by calculating the mean value of a histogram of these scores for the reproductive cells of each abalone. The temporal variations in degree of sexual maturation showed that female and male abalone from Tsushima matured synchronously, while those from Jogashima did not. The observed maximum reproductive developmental score in abalone from Jogashima was much lower than that from Tsushima, because immature females were present at the former site throughout the spawing season. Approximately 20% of the abalone from Jogashima were masculinized females with an ovo-testis. The masculinization of female abalone was similar to the imposex, typically induced in other gastropod molluscs by tributyltin (TBT) and triphenyltin (TPhT) from antifouling paints. Concentrations of TBT and TPhT in the muscles of abalone from Jogashima (n = 83) of 4.9 +/- 4.4 ng/g wet wt and 6.3 +/- 6.6 ng/g wet wt, respectively, were significantly higher than those from Tsushima (n = 125) (P < 0.01) of 0.8 +/- 0.8 ng/g wet wt and 0.6 +/- 1.3 ng/g wet wt, respectively. In situ exposure of abalone from Tsushima caged near a dockyard in Jogashima for 7 months (from the immature to the mature stage) resulted in spermatogenesis in the ovary of approximately 90% of females. Endocrine disruption may be caused in the giant abalone by organotin compounds from antifouling paints, which are possibly one of the causal factors for the decline of Japanese abalone stocks.  相似文献