Heavy metals contamination in water and sediments of an urban river in a developing country     

K. M. Mohiuddin Ph.D.  Y. Ogawa Ph.D.  H. M. Zakir Ph.D.  K. Otomo Ph.D.  N. Shikazono Ph.D. 《International Journal of Environmental Science and Technology》2011,8(4):723-736

Water and sediment samples were collected from 20 location of the Buriganga river of Bangladesh during Summer and Winter 2009 to determine the spatial distribution, seasonal and temporal variation of different heavy metal contents. Sequential extraction procedure was employed in sediment samples for the geochemical partitioning of the metals. Total trace metal content in water and sediment samples were analyzed and compared with different standard and reference values. Concentration of total chromium, lead, cadmium, zinc, copper, nickel, cobalt and arsenic in water samples were greatly exceeded the toxicity reference values in both season. Concentration of chromium, lead, copper and nickel in sediment samples were mostly higher than that of severe effect level values, at which the sediment is considered heavily polluted. On average 72 % chromium, 92 % lead, 88 % zinc, 73 % copper, 63 % nickel and 68 % of total cobalt were associated with the first three labile sequential extraction phases, which portion is readily bioavailable and might be associated with frequent negative biological effects. Enrichment factor values demonstrated that the lead, cadmium, zinc, chromium and copper in most of the sediment samples were enriched sever to very severely. The pollution load index value for the total area was as high as 21.1 in Summer and 24.6 in Winter season; while values above one indicates progressive deterioration of the sites and estuarine quality. The extent of heavy metals pollution in the Buriganga river system implies that the condition is much frightening and may severely affect the aquatic ecology of the river.  相似文献   

Production and bacterial decomposition of dissolved organic matter in a fringing coral reef     

Yasuaki Tanaka  Hiroshi Ogawa  Toshihiro Miyajima 《Journal of Oceanography》2011,67(4):427-437

The concentrations of dissolved organic carbon and nitrogen (DOC and DON, respectively) were measured in Shiraho fringing reef (Japan), using a high-temperature catalytic-oxidation method. When the seawater on the reef flat (shallow lagoon) was isolated from the surrounding ocean due to the low tide, the concentrations of DOC and DON on the reef flat were 66–75 and 4.8–5.7 μmol l⁻¹, respectively. The DOC and DON concentrations were higher than those of the adjacent outer ocean (57–58 and 3.8 μmol l⁻¹, respectively), suggesting that the coral reef functioned as a net source of dissolved organic matter for the surrounding ocean. In order to investigate long-term bacterial decomposition of the reef-derived DOC (RF-DOC), the seawater samples collected on the reef flat and at the adjacent ocean were incubated in the dark for 1 year. Regression analysis using an exponential curve that considered two degradability pools (labile and refractory) fitted the mineralization of the RF-DOC very well (r ² > 0.89). According to the regression analysis, the DOC produced on the reef flat was composed of the labile fraction of 63–94% (average 77%) and the refractory fraction of 6–37% (average 23%). It was concluded that some of the DOC that was produced in the coral reef ecosystem was exported to the surrounding ocean if the reef flat had a water residence time less than several months. The exported organic matter may support microbial communities in the ocean as an energy source.  相似文献   

钻孔千斤顶压裂测量技术的发展和原地测量     

Yokoyama T  Ogawa K  Sano O  Hirata A  Mizuta Y  徐伟 《国际地震动态》2011,(1):67-76

为了测量距地表1 000 m以下位置的地壳应力状态,我们研究并开发了钻孔千斤顶压裂技术.技术的原理是:当钻孔千斤顶对钻孔壁加载时,与钻孔轴向平行的方向将会产生两个相对的新裂隙;卸载之后,如果千斤顶对钻孔壁的同一个地方进行施压,这对裂隙将会再次张开.与钻孔轴向垂直的平面上的两个主应力的大小和方向分别是由重张压力和裂隙的方...  相似文献   

http://www.sciencedirect.com/science/article/pii/S167498711200062X     

Tetsuya Tokiwa  Kimikazu Tsusaka  Makoto Matsubara  Taiki Ishikawa  Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111

This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes.  相似文献   

Olivine-rich exposures in the South Pole-Aitken Basin     

Satoru Yamamoto  Ryosuke Nakamura  Tsuneo Matsunaga  Yoshiko Ogawa  Yoshiaki Ishihara  Tomokatsu Morota  Naru Hirata  Makiko Ohtake  Takahiro Hiroi  Yasuhiro Yokota  Junichi Haruyama 《Icarus》2012,218(1):331-344

The distribution and the geological context of the olivine-rich exposures in the South Pole-Aitken (SPA) Basin on the Moon were investigated based on the spectral data obtained from the Spectral Profiler (SP) and Multiband Imager (MI) onboard the Japanese lunar explorer Kaguya/SELENE. The olivine-rich exposures are found only in the peak rings or central peaks of the Schrödinger basin and Zeeman crater, which are located in the outer region of the SPA Basin and not in the center region. On a localized scale, the olivine-rich materials are exposed on landslide features on the crater walls or sloped wall of the central peaks or the peak rings. Another observational finding is the co-existence of olivine-rich and plagioclase-rich materials on a kilometer scale spanning most of the olivine-rich sites in the Schrödinger basin. Pyroxene-rich materials are found in fresh craters outside the peak rings or the central peaks with olivine-rich materials. Based on these results, the following scenario are proposed: (1) the impact to form the SPA Basin melted a large amount of the lunar upper mantle and crust, and distributed the melted materials to the outer region; (2) local differentiation of melted materials hid the olivine-rich materials in the center region of the SPA Basin; (3) later impacts that formed the Schrödinger and Zeeman craters excavated and exposed the olivine-rich materials to the surface again; and (4) space weathering and regolith gardening obscured the olivine-rich spectra at the exposure sites, but recent, small scale impacts or landslides on the sloped wall exposed fresh olivine-rich materials, allowing the identification of the olivine-rich exposures by spectral remote-sensing. This suggests that several, different scale events play an important role in forming the surface distributions of originally deep-seated materials on the Moon, as well as on other planetary bodies.  相似文献   

Seasonal occurrence and microhabitat of the hyperparasitic monogenean Udonella fugu on the caligid Copepod Pseudocaligus fugu infecting the grass puffer Takifugu niphobles in the Seto Inland Sea, Japan     

Hiroko Okawachi  Susumu Ohtsuka  Norshida Binti Ismail  B. A. Venmathi Maran  Kazuo Ogawa 《Ocean Science Journal》2012,47(3):181-187

The seasonal occurrence and microhabitat of the monogenean Udonella fugu that hyperparasitizes exclusively on adults of the caligid copepod Pseudocaligus fugu that infects the skin of the grass puffer Takifugu niphobles were investigated in the Seto Inland Sea, western Japan from November 2004 to December 2006. The udonellids occurred and bred mostly during the occurrence of P. fugu on the fish host. The average prevalence and intensity of U. fugu on P. fugu during the whole investigation were 29% and 3.6, respectively. The main attachment sites of U. fugu were the posterior side of leg 3 and the dorsal marginal side of the cephalothorax for feeding and copulation, while eggs were predominantly located on the ventral side of the urosome to avoid detachment. More attention should be paid to the ecology of U. fugu, due to recent high prevalence of P. fugu on cultured tiger puffer in western Japan.  相似文献   

Formation age of the lunar crater Giordano Bruno     

Tomokatsu Morota  Junichi Haruyama  Hideaki Miyamoto  Chikatoshi Honda  Makiko Ohtake  Yasuhiro Yokota  Tsuneo Matsunaga  Naru Hirata  Hirohide Demura  Hiroshi Takeda  Yoshiko Ogawa  Jun Kimura 《Meteoritics & planetary science》2009,44(8):1115-1120

Abstract— Using the Terrain Camera onboard the Japanese lunar explorer, SELENE (Kaguya), we obtained new high‐resolution images of the 22‐kilometer‐diameter lunar crater Giordano Bruno. Based on crater size‐frequency measurements of small craters (<200 m in diameter) superposed on its continuous ejecta, the formation age of Giordano Bruno is estimated to be 1 to 10 Ma. This is constructive evidence against the crater's medieval age formation hypothesis.  相似文献   

Observation of wave transformation on a sloping type B shore platform under wind-wave and swell conditions     

Hiroki Ogawa 《Geo-Marine Letters》2013,33(1):1-11

An instrumented field study of the across-shore evolution of wave characteristics was conducted under wind-wave and swell-wave conditions on a sloping type B shore platform along the mesotidal, fetch-limited coast of Auckland, New Zealand, based on spectral analysis of hydrodynamic data recorded in pressure-sensor time series during a 24-h deployment on 24–25 November 2008. The results highlight the ability of the shore platform in dissipating wave energy reaching the cliff toe under wind-wave and swell-wave conditions, and the spectral redistribution of wave energy. As waves propagated onto the platform surface and towards the cliff toe, infragravity-wave energy became progressively more dominant, while gravity waves were dissipated. Wave height and period in the central sector of the platform and at the cliff toe were not markedly affected by differences in incident-wave conditions observed during the survey. The findings confirm the importance of platform morphology in modulating wave-energy delivery to the cliff toe. In contrast to previous studies, infragravity-wave height at the cliff toe did not appear to be correlated to incident-wave conditions.  相似文献   

Rocket measurements of the 6300 Å and 3914 Å dayglow features     

T. Nagata  T. Tohmatsu  T. Ogawa 《Planetary and Space Science》1965,13(12):1273-1282

Rocket results are presented on the OI 6300 Å line and on the N₂⁺ 3914 Å band in the dayglow. An altitude range of 78–335 km is covered. Theoretical interpretations are given, using results of simultaneous measurements of electron density and electron temperature. The apparent brightness of the 6300 Å line at the base of the emitting region is found to be 13 kR, of which 5.5 kR are ascribed to excitation through the Schumann-Runge dissociation of O₂ by the solar UV radiations, 0.55 kR to the dissociative recombination of O₂⁺ and NO⁺ ions, and 0.03 kR to the excitation of O by thermal electrons. An additional source of excitation above 280 km is suggested. The deactivation of O(¹D) by O₂(X³Σ_g⁻) is found to be appreciable below 200 km, and its rate coefficient is estimated to be 2 × 10⁻¹⁰ cm³/sec. The apparent brightness of the 3914 Å band at the base of the emitting region is found to be 6.5 kR, decreasing to 3.2 kR at 330 km. Assuming that fluorescent scattering of solar radiation is the mechanism involved the distribution of N₂⁺ ions is calculated. The rate coefficients for the loss of these ions are hence calculated.  相似文献   

A two-dimensional magnetotelluric inversion assuming Gaussian static shift   总被引：4，自引：0，他引：4  

Yasuo Ogawa  Toshihiro Uchida 《Geophysical Journal International》1996,126(1):69-76

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