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101.
102.
Masaki Inagaki Masanobu Yamamoto Yaeko Igarashi Ken Ikehara 《Journal of Oceanography》2009,65(6):847-858
We investigated marine and terrestrial environmental changes at the northern Japan margin in the northwestern Pacific during
the last 23,000 years by analyzing biomarkers (alkenones, long-chain n-alkanes, long-chain n-fatty acids, and lignin-derived materials) in Core GH02-1030. The U
37K′-derived temperature in the last glacial maximum (LGM) centered at 21 ka was ∼10°C, which was 2°C lower than the core-top
temperature (∼12°C). This small temperature drop does not agree with pollen evidence of a large air temperature drop (more
than 4°C) in the Tokachi area. This disagreement might be attributed to a bias of U
37K′-derived temperature within 2.5°C by a seasonal shift in alkenone production. The U
37K′-derived temperature was significantly low during the last deglaciation. Because this cooling was significant in the Kuroshio-Oyashio
transition zone, the temperature drops are attributable to the southward displacement of the Kuroshio-Oyashio boundary. Abundant
lignin-derived materials, long-chain n-alkanes and long-chain n-fatty acids indicate a higher contribution of terrigenous organic matter from 17 to 12 ka. This phenomenon might have resulted
from an enhanced coastal erosion of terrestrial soils due to marine transgression and/or an efficient inflow of higher plant
debris to river waters from 17 to 12 ka. 相似文献
103.
This paper presents the first report on the occurrence of eclogite from the Kumon range of the Western province in Myanmar, which is in the southeastern extension of the Himalayan orogenic belt. The eclogite is mainly composed of omphacite, garnet, hornblende/edenite/katophorite/taramite, biotite, quartz, and rutile. The garnet grains in the eclogite usually show textures of barrier reef, atoll, and table reef types, and have a wide compositional range of Alm58–70Sps1–2Prp9–16Grs14–31. Omphacite grains that occur as garnet inclusions and as isolated crystals in the matrix have similar compositions of Jd34–45 and Jd37–44, respectively. Lesser amounts of jadeitic clinopyroxene (Jd21–38), phengite, biotite, albite, and quartz occur in the lagoon of barrier reef and atoll garnet grains. The matrix omphacite is partly replaced by symplectite of sodic clinopyroxene of Jd20–29 and albite. The lower limits of the pressure/temperature during the eclogite stage, which are defined by the assemblage of garnet, omphacite (Jd40–45), and quartz, are 1.2–1.3 GPa/530–615 °C. The finding of eclogite from Myanmar suggests the possibility of a wide occurrence of high-pressure metamorphic rocks in the ophiolite zone along the southeastern extension of the Indus-Yarlung Zangbo suture in Myanmar and Indochina. 相似文献
104.
Major minerals (sulfates, sulfides, quartz) are distributed in different parts of submarine hydrothermal ore deposits. For instance, the abundance of barite increases stratigraphically upwards in the massive orebodies of the Kuroko deposits (black and yellow ores), while quartz is abundant in the lower parts (siliceous ore). The different distribution of barite and quartz in the Kuroko deposits can not be accounted for by thermochemical equilibrium calculations based on the precipitation due to mixing of ascending hydrothermal solutions with ambient cold seawater. In the present study, a coupled fluid flow‐precipitation kinetics model was used to calculate the amounts of quartz, barite, and anhydrite precipitated from a hydrothermal solution mixed with seawater, assuming reasonable values for temperature, precipitation rate, fluid flow velocity, mineral surface area/fluid mass ratio (A/M), and initial concentrations of hydrothermal solution and seawater before mixing occurred. The results indicate that barite precipitates more efficiently than quartz from discharging fluids with relatively higher flow velocity, lower temperatures and under the condition of lower A/M ratios on the seafloor (black ore), whereas quartz precipitates more effectively from solutions with lower flow velocity, higher temperatures and higher A/M ratios beneath the seafloor (siliceous ore) and in the orebody (barite ore, ferruginous chert ore). Anhydrite precipitates in shallow sub‐seafloor environments with lower precipitation rates and higher A/M ratios than barite and higher precipitation rates and lower A/M ratios than quartz. These results explain the observed occurrences of barite, anhydrite, and quartz in the Kuroko deposits. Namely, barite is abundant in black ore and barite ore which formed above the seafloor, anhydrite formed in high‐permeability tuff breccias, and quartz formed in low permeability dacite intrusive bodies in the sub‐seafloor environment. 相似文献
105.
Groundwater recharge sets a constraint on aquifer water balance in the context of water management. Historical data on groundwater and other relevant hydrological processes can be used to understand the effects of climatic variability on recharge, but such data sets are rare. The climate of the Canadian prairies is characterized by large inter-annual and inter-decadal variability in precipitation, which provides opportunities to examine the response of groundwater recharge to changes in meteorological conditions. A decadal study was conducted in a small (250 km2) prairie watershed in Alberta, Canada. Relative magnitude of annual recharge, indicated by water-level rise, was significantly correlated with a combination of growing-season precipitation and snowmelt runoff, which drives depression-focussed infiltration of meltwater. Annual precipitation was greater than vapour flux at an experimental site in some years and smaller in other years. On average precipitation minus vapour flux was 10 mm y?1, which was comparable to the magnitude of watershed-scale groundwater recharge estimated from creek baseflow. Average baseflow showed a distinct shift from a low value (4 mm y?1) in 1982–1995 to a high value (15 mm y?1) in 2003–2013, indicating the sensitivity of groundwater recharge to a decadal-scale variability of meteorological conditions. 相似文献
106.
Volatilization properties of gasoline components in soils 总被引:1,自引:0,他引:1
Junko Nishiwaki Yoshishige Kawabe Yasuhide Sakamoto Takeshi Komai Ming Zhang 《Environmental Earth Sciences》2011,63(1):87-95
Understanding the volatilization properties of gasoline components in soils is of fundamental importance in the field of geoenvironments.
A series of experiments were performed to investigate the effects of temperature, soil water content, soil organic matter
content, as well as mean particle size on volatilization rate of total petroleum hydrocarbons (TPH) and the paraffin (n-paraffin and isoparaffin), olefin, naphthene, and aromatic (PONA) components in four typical Japanese soils. The results
of this study can be summarized as follows. (1) Volatilization rate of gasoline in a soil is concentration-dependent; extensive
volatilization occurs above a certain threshold, while volatilization becomes very slow below this threshold. (2) Compared
to other factors, temperature and soil organic matter content have greater effects on volatilization rate of gasoline in soils.
The volatilization rate is proportional to temperature, but inversely related to soil organic matter content. (3) The characteristics
of time-dependent decreases of TPH and PONA components in soils are similar. The volatilization rate of olefin is higher than
those of other components. In addition, volatilization of olefin is also more sensitive to temperature as well as organic
matter content. 相似文献
107.
Based on measured stream nitrogen concentrations at outlets of 12 small sub‐areas (1·3–54·7 km2) in a largely forested catchment during the base flow period, we investigated the influences of discharges and different catchment characteristics on stream nitrogen concentration. Our field surveys were carried out during the 11‐month's period from April 2001 to February 2002 and the correlations between nitrogen concentrations and catchment characteristics were studied. The results showed that the vegetation cover was strongly correlated to total nitrogen (TN) and nitrate + nitrite ? nitrogen (NOx‐N) concentrations. That is, the TN and NOx‐N concentrations had positive correlations with mean normalized difference vegetation cover index (NDVI) of each sub‐area during dormant seasons (mean NDVI < 0 · 70) and had negative correlations during the growing season (mean NDVI ≥ 0 . 70). The significance of catchment characteristics to TN and NOx‐N concentrations was ranked as vegetation cover > soil > topography > land use, and the best models can account for 55–64% of the variance of TN and NOx‐N concentrations. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
108.
Phase relations in the system CaTiO3-CaSiO3 were experimentally examined at 5.3–14.7 GPa and 1200–1600 °C with a 6–8 type multianvil apparatus. As pressure increases, stability field of perovskite solid solution extends from CaTiO3 to CaSiO3, and the perovskite becomes stable for the entire composition range above about 12.3 GPa. The stability field of Ca(Ti1?X, SiX)2O5 (0.78<x≦1) titanite solid solution +Ca2SiO4 larnite exists in the CaSiO3-rich composition range at 9.3–12.3 GPa and 1200 °C. Perovskite solid solutions containing CaSiO3 component of 0 to 66 mol% could be quenched to 1 atm. The composition-molar volume relationship of perovskite solid solution showed that molar volume of perovskite solid solution linearly reduces from the value of CaTiO3 to that of CaSiO3. 相似文献
109.
Martin G. LOCKLEY LI Jianjun LI Rihui Masaki MATSUKAWA Jerald D. HARRIS XING Lida 《《地质学报》英文版》2013,87(1):1-20
<正>"Splitting" and "lumping" are perpetual problems in vertebrate,especially dinosaur, ichnotaxonomy.Chinese dinosaur ichnotaxonomy,which began in 1940,provides a series of interesting case studies,highlighting the dual problems of historical and dubious ichnotaxonomy. Chinese Mesozoic tetrapod track types have been placed into 63 ichnospecies(one Triassic,28 Jurassic,and 34 Cretaceous),exclusive of other,non-type ichnospecies or ichnotaxa identified from China.Fifty-two(~83%) of these 63 tetrapod ichnospecies were placed in monospecific ichnogenera. At the ichnogenus level,we prune—either by recognizing nomina dubia or by synonymy—17 from the list of 53 dinosaurian ichnogenera(a 32%reduction),leaving 36 ichnotaxa that we consider valid. Most of the cuts affect Jurassic theropod ichnotaxa,which are reduced from 23 to only nine because most ichnogenera are subjective junior synonyms of Grallator and Eubrontes.Fewer Chinese Cretaceous ichnotaxa(only six of 21 ichnogenera) are obvious nomina dubia or subjective synonyms, suggesting greater east Asian endemism during this time.Because ichnospecies differences are subtle, we provisionally retain ichnospecies as valid pending detailed comparative analyses of congeneric ichnospecies.This synthesis is long overdue and is necessary to address problems of historical and provincial ichnotaxonomy,which severely hamper comparisons of tetrapod ichnofaunas in space and time. 相似文献
110.
Measuring saturated hydraulic conductivity and anisotropy of peat by a modified split-container method 总被引:1,自引:0,他引:1
Ranjeet M. Nagare Robert A. Schincariol Aaron A. Mohammed William L. Quinton Masaki Hayashi 《Hydrogeology Journal》2013,21(2):515-520
Long-term changes in the physical and hydraulic properties of peat result from the decomposition and consolidation processes. The saturated hydraulic conductivity (K s) of peat is depth-dependent and could increase or decrease with depth; therefore, K s determination on a large number of samples is required to more accurately assess field variability. The cube method is a popular laboratory procedure to determine K s because it allows use of smaller sample dimensions, while minimizing edge effects. This article describes the design and use of an alternate split container to enclose undisturbed peat cubes during measurement of K s and the application of this method to a field site in Northwest Territories, Canada. The method allows for simpler and more controlled K s measurements while also permitting anisotropy measurements. Matched tests on identical samples (K s range 21–314 m/d), using the split-container and wax methods, showed a good agreement for intermediate K s values; however, significant deviations occurred for low and high K s values. Hydraulic-conductivity measurements taken on field samples showed a decrease with depth and exhibited anisotropic hydraulic conductivity as expected based on previous studies. 相似文献