GEOLOGY OF MT. PHULCHOKI AREA, CENTRAL NEPAL     

Funakawa Satoshi 《地学前缘》2000,(Z1)

GEOLOGY OF MT. PHULCHOKI AREA, CENTRAL NEPAL  相似文献   

The Weathering of Granodiorite Porphyry in the Thiel Mountains, Inland Antarctica   总被引：2，自引：0，他引：2  

Satoshi Ishimaru  & Kenji Yoshikawa 《Geografiska Annaler: Series A, Physical Geography》2000,82(1):45-57

The weathering of granodiorite porphyry is examined in the extremely cold and dry environment of the inland part of Antarctica. Weathering features include granular disintegration, rock varnish, and sheeting. Sheeting has gradually proceeded since the exposing of the nunatak, but the other types of weathering have not actively advanced in recent times.
Granular disintegration primarily comprises the release of individual crystals. The mechanism of this release is that cracks are created along crystal boundaries and cleavages in phenocrysts mainly due to differential thermal expansion. Plagioclase and hypersthene are released more readily than quartz. Disintegration of plagioclase has produced many prism-shaped holes, 0.5 to 2.0 mm in length, while fine-grained quartz crystals, 0.05 to 0.1 mm in diameter, are incidentally released without cracking.
The reddish brown (10R4/4) rock varnishes result from oxidation and consist of limonite, which fills cracks and penetrates into crystals. Ferrous iron in hypersthene, biotite, ilmenite and magnetite is transformed into limonite by oxidation. Manganese is not found in the varnishes. Sulfur, which is important for oxidation and which may have originated from adhered snow, is concentrated on the surface of the rock.
Sheeting has precipitated rock falls, and has gradually formed a gray mosaic on the varnished wall. The sheeting was caused by gravitational body force, which is internal stress of the rock body due to the mass of the overburden.  相似文献   

Groundwater dynamics of Fongafale Islet, Funafuti Atoll, Tuvalu     

Nakada S  Umezawa Y  Taniguchi M  Yamano H 《Ground water》2012,50(4):639-644

Geoelectric and hydrologic surveys during spring tides revealed the spatiotemporal distribution of groundwater quality produced by tidal forcing in Fongafale Islet, Funafuti Atoll, Tuvalu. The observed low resistivity showed that saline water largely immersed the surficial Holocene aquifer, indicating that there is no thick freshwater lens in Fongafale Islet, unlike in other atoll islands of comparable size. Half of the islet was constructed by reclaiming the original swamp with porous, highly permeable coral blocks; this reclaimed area should not be considered as part of the islet width for calculation of the expected thickness of the freshwater lens. The degree of aquifer salinization depends on the topographic characteristics and the hydrologic controls on the inland propagation of the tidal forcing. Large changes in bulk resistivity and the electrical conductivity of groundwater from wells indicate that periodic salinization in phase with the semidiurnal tides was occurring widely, especially in areas at lower elevation than the high-tide level and in reclaimed areas with high permeability. Thin sheets of nearly fresh and brackish water were observed in the surficial aquifer in areas above the high-tide level and in taro swamps, respectively. The thinness of the brackish and freshwater sheets suggests that the taro swamps and the fresh groundwater resources of the islet are highly vulnerable to salinization from anticipated sea-level rise. An understanding of the inherent geologic and topographic features of an atoll is necessary to evaluate the groundwater resources of the atoll and assess the vulnerability of its water resources to climate change.  相似文献   

Low-frequency variations of the Eastern Subtropical Front in the North Pacific in an eddy-resolving ocean general circulation model: roles of central mode water in the formation and maintenance     

Shusaku Sugimoto  Kimio Hanawa  Tamaki Yasuda  Goro Yamanaka 《Journal of Oceanography》2012,68(4):521-531

Temporal variations (1960–2005) of the Eastern Subtropical Front (ESTF) in the North Pacific are investigated using historical-run output data of the eddy-resolving Meteorological Research Institute Community Ocean Model, forced by atmospheric reanalysis dataset. Simulated ESTF is distributed in a region of zonal band of 24°N–30°N east of the International Date Line, and is located at the southern boundary of the central mode water (CMW) north of the front. The ESTF intensity clearly shows an interdecadal variation with a timescale of about 20?years. This variation is associated with that in the potential vorticity of CMW, which originates in the CMW formation region farther north about 3?years earlier due to changes in the surface wind forcing.  相似文献   

Relationship between the path of the Kuroshio in the south of Japan and the path of the Kuroshio Extension in the east   总被引：2，自引：0，他引：2  

Shusaku Sugimoto  Kimio Hanawa 《Journal of Oceanography》2012,68(1):219-225

A relationship between paths of the Kuroshio and Kuroshio Extension (KE) is investigated, using the satellite-derived altimetry dataset of 1993–2008. When the Kuroshio takes the nearshore nonlarge meander path or typical large meander path and resultantly goes through the deeper channel (about 2500 m) of the Izu-Ogasawara Ridge, the KE path adopts a relatively stable state with the two quasi-stationary meanders. On the other hand, when the Kuroshio takes the offshore nonlarge meander path and then passes over the shallower part of the Ridge (about 1000 m), the KE path tends to be convoluted, i.e., an unstable state.  相似文献   

Complex organic molecules in an early stage of protostellar evolution     

Nami Sakai  Takeshi Sakai  Satoshi Yamamoto 《Astrophysics and Space Science》2008,313(1-3):153-157

We have detected the rotational lines of HCOOCH₃ toward a Class 0 low-mass protostar, NGC1333 IRAS4B, which is reported to be extremely young according to the dynamical age of the molecular outflow (a few 100 yr). This suggests that the complex organic molecules appear from the very early stage of protostellar evolution. On the other hand, the complex organic molecules are not detected in a more evolved protostar, L1527. We have also found a similar trend in a massive star forming region, NGC2264. The HCOOCH₃ emission is almost absent toward IRS1, whereas it is concentrated near MMS3, which is younger than IRS1. In addition, the HCOOCH₃ intensity peak is slightly shifted from the dust emission peak, as is seen in the Orion KL Compact Ridge, giving an important clue to solve its origin.  相似文献   

A new method of snowmelt sampling for water stable isotopes   总被引：1，自引：0，他引：1       下载免费PDF全文

D. Penna  M. Ahmad  S. J. Birks  L. Bouchaou  M. Brenčič  S. Butt  L. Holko  G. Jeelani  D. E. Martínez  G. Melikadze  J. B. Shanley  S. A. Sokratov  T. Stadnyk  A. Sugimoto  P. Vreča 《水文研究》2014,28(22):5637-5644

We modified a passive capillary sampler (PCS) to collect snowmelt water for isotopic analysis. Past applications of PCSs have been to sample soil water, but the novel aspect of this study was the placement of the PCSs at the ground‐snowpack interface to collect snowmelt. We deployed arrays of PCSs at 11 sites in ten partner countries on five continents representing a range of climate and snow cover worldwide. The PCS reliably collected snowmelt at all sites and caused negligible evaporative fractionation effects in the samples. PCS is low‐cost, easy to install, and collects a representative integrated snowmelt sample throughout the melt season or at the melt event scale. Unlike snow cores, the PCS collects the water that would actually infiltrate the soil; thus, its isotopic composition is appropriate to use for tracing snowmelt water through the hydrologic cycle. The purpose of this Briefing is to show the potential advantages of PCSs and recommend guidelines for constructing and installing them based on our preliminary results from two snowmelt seasons. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Blast furnace slag can effectively remediate coastal marine sediments affected by organic enrichment     

Satoshi Asaoka 《Marine pollution bulletin》2010,60(4):573-578

There is an urgent need to control nutrient release fluxes from organically-enriched sediments into overlying waters to alleviate the effects of eutrophication. This study aims to characterize blast furnace slag (BFS) and evaluate its remediation performance on organically-enriched sediments in terms of suppressing nutrient fluxes and reducing acid volatile sulfide. BFS was mainly composed of inorganic substances such as CaO, SiO₂, Al₂O₃ and MgO in amorphous crystal phase. Container experiments showed that the phosphate concentration in the overlying water, its releasing flux from sediment and AVS of the sediment decreased by 17-23%, 39% and 16% compared to the control without BFS, respectively. The loss on ignition was significantly decreased by 3.6-11% compared to the control. Thus, the application of BFS to organically-enriched sediment has a suppressive role on organic matter, AVS concentration and phosphate releasing flux from sediments and therefore, is a good candidate as an effective environmental remediation agent.  相似文献   

Simultaneous Analysis of Natural Free Estrogens and Their Conjugates in Wastewater by GC‐MS     

Ze‐Hua Liu  Takeshi Hashimoto  Yoichi Okumura  Yoshinori Kanjo  Satoshi Mizutani 《洁净——土壤、空气、水》2010,38(2):181-188

A solid‐phase extraction (SPE)‐gas chromatography (GC)‐mass spectrometry (MS) analytical method was developed for the simultaneous analysis of natural free estrogens and their conjugates in wastewater samples. Natural free estrogens and their conjugates in wastewater were successfully separated by the oasis hydrophilic‐lipophilic balance solid phase extraction (Oasis HLB SPE) method, and the conjugates were initially enzyme hydrolyzed by β‐glucuronidase or arylsulfatase from Helix pomatia prior to derivatization. N‐methyl‐N‐(tert‐butyldimethylsilyl)trifluoroacetamide (MTBSTFA) plus 1% tert‐butyldimetheylchlorosilane (TBDMCS) was chosen as the derivatization reagent, and the most appropriate conditions of derivatization were determined to be at 95°C for 90 min. The recovery ratios of nine target chemicals were determined by spiking them in 1 L of ultra‐purified water or the influent of a wastewater treatment plant (WWTP). The recovery ratios of six out of nine for the analytes ranged from 73.3–114.9% with relative standard deviations (RSD) from 1.6–19.9%. The established method was successfully applied to environmental wastewater samples which were collected from one municipal wastewater treatment plant (WWTP) in Osaka, Japan, for the determination of natural free estrogens and their conjugates. In the influent sample, E1, E2, E1‐3S, E3‐3S, and E1‐3G were detected at concentrations of 16.6, 9.6, 8.2, 21.9, and 3.2 ng L^–1, respectively. However, only E1 was detected at a high concentration of 44 ng L^–1 in the effluent sample, suggesting that it is the dominant natural free estrogen in the effluent.  相似文献   

Simultaneous Analysis of Natural Free Estrogens and Their Sulfate Conjugates in Wastewater     

Ze‐hua Liu  Yoshinori Kanjo  Satoshi Mizutani 《洁净——土壤、空气、水》2010,38(12):1146-1151

Natural estrogens from humans increasingly attract attention because of their strong endocrine disrupting potency. The discharge of sewage water is considered as the most important source of these endocrine disrupting chemicals (EDCs) in the environment. Therefore, a GC‐MS method was developed for the simultaneous analysis of six natural free estrogens and their sulfate conjugates in municipal wastewater, in which natural free estrogens and sulfate conjugates were successfully separated from an Oasis HLB solid phase extraction (SPE) cartridge with two different eluents, and the sulfate conjugates were then transformed to their corresponding free estrogens by acid solvolysis. Before the analysis with GC‐MS, samples were derivatized by N,O‐bis (trimethylsilyl) trifluoroacetamide (BSTFA) plus 1% trimethylchlorosilane (TMCS) at 80°C for 40 min. Satisfactory recoveries ranging from 64 to 112.3% were obtained by spiking ultra‐purified water, raw, and treated municipal wastewater with the six estrogens at 50, 100, and 50 ng/L, respectively. The method was successfully applied to wastewater samples from one WWTP, which suggested that E1 was the dominant natural estrogens in effluent and E3‐3S was one of the conjugates possibly occurring in the effluent.  相似文献