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11.
TOMOKO YAMAMOTO KO HASHIZUME JUN-ICHI MATSUDA TOMOHIKO KASE 《Meteoritics & planetary science》1998,33(4):857-870
Abstract— Nitrogen and noble gas isotopic compositions and C abundance of ureilites were analyzed using a stepwise combustion technique. Four Antarctic ureilites, ALHA77257, Asuka 881931, Yamato 791538 and Yamato 790981 were analyzed. Multiple N isotopic components were observed in these ureilites. The δ15N values of these N components ranged from +160 to ?120%. The minimum δ15N values of typically ?120% were observed at combustion temperatures at 700–900 °C where large amounts of C were released. A heavy N component was observed in only two ureilites, ALHA77257 and Asuka 881931. Silicate-enriched fractions and C-concentrated fractions were prepared for these two ureilites. We conclude that both the light N and the heavy N are trapped in the carbonaceous vein minerals. The lack of correction between the N/C ratio and the 36Ar/C ratio suggests that the primary carrier phase of the light N does not correspond to that of the planetary noble gases. We consider that the isotopically heavy N, which was observed in this study, is related to the heavy N observed among polymict ureilites. Small amounts (<0.5 ppm) of light N with the minimum δ15N value of ?120% were observed among the silicate fractions at the highest combustion temperature of 1200 °C, although the exact carrier phase of this light N is not known. We consider that the currently observed ureilites were produced by injection of several volatile-rich objects into volatile-poor ureilitic silicates. 相似文献
12.
Abstract— Nitrogen and Ar in more than 20 primitive ordinary chondrites were studied by a stepped combustion method. Several N carriers that are characterized by N isotopic composition, N release pattern and trapped Ar release pattern are recognized in the primitive ordinary chondrites. Large fractions of anomalous N and associated Ar are removed by acid treatment in most cases. The N isotopic anomalies cannot be explained by known presolar grains (with a possible exception of graphite), and some of the N isotopic anomalies may be due to unknown presolar grains. There is no specific relationship between the type of N carriers contained in an ordinary chondrite and the chemical type (H, L, or LL) of the chondrite. It is likely that as a result of impacts, the carriers of isotopically anomalous N were mixed in various parent bodies as rock fragments rather than as individual fine particles. The presence of distinctive N isotopic anomalies in primitive meteorites indicates that the primitive solar nebula may have been heterogeneous either spatially or temporally. 相似文献
13.
Hejuan Liu Zhengmeng Hou Patrick Were Yang Gou Xiaoling Sun 《Environmental Earth Sciences》2014,71(10):4447-4462
Deep saline aquifers still remain a significant option for the disposal of large amounts of CO2 from the atmosphere as a means of mitigating global climate change. The small scale Carbon Capture and Sequestration demonstration project in Ordos Basin, China, operated by the Shenhua Group, is the only one of its kind in Asia, to put the multilayer injection technology into practice. This paper aims at studying the influence of temperature, injection rate and horizontal boundary effects on CO2 plume transport in saline formation layers at different depths and thicknesses, focusing on the variations in CO2 gas saturation and mass fraction of dissolved CO2 in the formation of brine in the plume’s radial three-dimensional field around the injection point, and interlayer communication between the aquifer and its confining beds of relatively lower permeability. The study uses the ECO2N module of TOUGH2 to simulate flow and pressure configurations in response to small-scale CO2 injection into multilayer saline aquifers. The modelling domain involves a complex multilayer reservoir–caprock system, comprising of a sequence of sandstone aquifers and sealing units of mudstone and siltstone layers extending from the Permian Shanxi to the Upper Triassic Liujiagou formation systems in the Ordos Basin. Simulation results indicate that CO2 injected for storage into deep saline aquifers cause a significant pressure perturbation in the geological system that may require a long duration in the post-injection period to establish new pressure equilibrium. The multilayer simultaneous injection scheme exhibits mutual interference with the intervening sealing layers, especially when the injection layers are very close to each other and the corresponding sealing layers are thin. The study further reveals that injection rate and temperature are the most significant factors for determining the lateral and vertical extent that the CO2 plume reaches and which phase and amount will exist at a particular time during and after the injection. In general, a large number of factors may influence the CO2–water fluid flow system considering the complexity in the real geologic sequence and structural configurations. Therefore, optimization of a CO2 injection scheme still requires pursuance of further studies. 相似文献
14.
Joseph L. Awange Laban Ogalo Kwang-Ho Bae Paul Were Philip Omondi Paul Omute Monica Omullo 《Climatic change》2008,89(3-4):281-297
Recently, and perhaps most threatening, Lake Victoria water level has been receding at an alarming rate. A recent study suggested the possibility of the expanded hydroelectric power station in Uganda. However, since the lake receives 80% of its refill through direct rainfall and only 20% from the basin discharge, climatic contributions cannot be ignored, since the 80% water is directly dependant on it. It is therefore necessary to investigate climatic contribution to the declining Lake Victoria water level observed over a long period, i.e., 30 years. This contribution uses 30 years period anomalies for rainfall, river discharge and lake level changes of stations within Lake Victoria basin to analyse linear and cyclic trends of climate indicators in relation to Lake levels. Linear trend analysis using the Student’s t test indicate a decreasing pattern in rainfall anomalies, with the slope being statistically similar to those of water levels at both Kisumu, Maziba and Jinja stations for the same period of time (1976–1999), thus showing a strong correlation. On the other hand, cyclic trend analysis using Discrete Fourier Transform (DFT) shows cyclic period of water level to coincide with those of droughts and rainfall. The strong relationship between climatic indicators of drought and rainfall on one-hand and lake levels on the other hand signifies the need to incorporate climate information in predicting, monitoring and managing lake level changes. 相似文献
15.
土壤和白菜中低分子量有机酸的气相色谱分析 总被引：4，自引：0，他引：4
利用甲醇-硫酸混合液(体积比10∶7)对土壤和白菜中低分子量有机酸同时进行提取和甲酯化衍生,然后利用二氯甲烷液-液萃取,气相色谱法分析。土壤中7种低分子量有机酸(草酸、丙二酸、反丁烯二酸、琥珀酸、马来酸、L-苹果酸、柠檬酸)的添加回收率为81.93%~95.58%,白菜中的添加回收率为84.78%~106.99%,方法的检出限为0.72~4.14 mg/kg。方法用于测定根际、非根际土壤和白菜根系、茎叶中的低分子量有机酸,结果准确可靠。 相似文献
16.
Zhengmeng Hou Lars Wundram Robert Meyer Meinhardt Schmidt Steffen Schmitz Patrick Were 《Environmental Earth Sciences》2012,67(2):395-409
This paper presents an innovative well abandonment concept developed for the long-term containment of CO2 in depleted Rotliegend gas reservoirs. The new concept aims at amending the conventional standard well abandonment procedure, taking advantage of the natural creeping ability of the thick, homogeneous Zechstein rock salt formation located around 3,000?m in depth (Altmark area) and consists of four main sealing units: (1) a standard sealing element with cement from the reservoir to the impermeable caprock, (2) a salt plug created in the formerly reamed section of casing within the plastic Zechstein (Upper Permian) rock salt formation, (3) two bridge plugs at the bottom and top of the salt plug and (4) a standard sealing element with cement from the top bridge plug until the ground surface. This site-specific study mainly lays emphasis on the development and field testing of the naturally created salt plug, as a key component of the long-term wellbore sealing concept. Comprehensive numerical simulations conducted prior to and during the field test in 2010 and 2011 successfully predicted the evolution of convergence using downhole measurement data. Preliminary results comprise (1) proven convergence of the rock salt formation, (2) a successful coring and (3) restored integrity of Zechstein salt formation, as proven by the formation integrity test. Based on these results, the new long-term sealing concept has been successfully tested at the Altmark natural gas field and successful application of the concept on other sites with similar geological conditions is foreseen to be likely. 相似文献
17.
Land cover in Kenya is in a state of fl ux at different spatial and temporal scales. This compromises environmental
integrity and socioeconomic stability of the population hence increasing their vulnerability to the externalities of environmental
change. The Oroba-Kibos catchment area in western Kenya is one locality where rapid land use changes have taken place over
the last 30 years. The shrubs, swamps, natural forests and other critical ecosystems have been converted on the altar of agriculture,
human settlement, fuel wood and timber. This paper presents the results of a study that aimed at providing spatially-explicit
information for effective remedial response through (a) Mapping the land cover; (b) Identifying the spatial distribution of land
cover changes; (c) Determining the nature, rates and magnitude of the land cover changes, and; (d) Establishing the drivers of
land use leading to land cover changes in Oroba-Kibos catchment area. Bi-temporal Landsat TM imagery, fi eld observation,
household survey and ancillary data were obtained. Per-fi eld classifi cation of the Landsat TM imagery was performed in a GIS
and the resultant land cover maps assessed using the fi eld observation data. Post-classifi cation comparison of the maps was then
done to detect changes in land cover that had occurred between 1994 and 2008. SPSS was used to analyze the household survey
data and attribute the detected land cover changes to their causes. The fi ndings showed that 9 broad classes characterize the
catchment area including the natural forests, swamps, natural water bodies, woodlands, shrublands, built-up lands, grasslands,
bare lands and croplands. Croplands are dominant and accounted for about 65% (57122 ha) of the total land in 1994, which increased
at the rate of 0.89% to 73% (64772 ha) in 2008, while natural water bodies has the least spatial coverage accounting for
about 0.6% (561 ha) of the total land in 1994, which diminished at the rate of 3.57% to 0.3% (260 ha) in 2008. Climate, altitude,
access and rights to land, demographic changes, poverty, political governance, market availability and economic returns are the
interacting mix of proximate and underlying factors that drive the land cover changes in Oroba-Kibos catchment area. 相似文献
18.
In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales（ BS）, west of Ankara（central Anatolia）, are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS（1.83/2.62 ppm） are much lower than averages of UC, NASK and PAAS（uranium： 2.70/2.66/3.10 ppm; thorium： 8.50/12.30/14.60 ppm）. Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites（e.g. gneiss, schist） which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals（e.g. autunite, torbernite） which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements. 相似文献
19.
Abstract— The behavior of H, C, N and their isotopes in a thermally evolving planetesimal was evaluated by numerical simulation. Transportation of heat and gas molecules, and the chemical equilibrium involving these elements, were simulated. Our modeled planetesimals initially contain homogeneous amounts of radioactive heat source (26Al); and H, C, and N in forms of organic materials, graphite, and in some models, water ice. Vaporized gas molecules were transported from the interior of the planetesimal to its surface, although their transportation efficiencies were quite different among the three elements, primarily due to differences in their affinities to metallic Fe. Significant portions of these elements were redistributed into metallic Fe when the planetesimal was heated at 600 °C and above. Nitrogen showed the most prominent siderophile characteristics, resulting in fairly large concentrations of N trapped in metallic Fe, which is consistent with observations by Hashizume and Sugiura (1997). Efficiency of C transportation crucially depended on O fugacity. To realize effective C transportation, it was necessary to assume an oxidizing condition (log fO2 > log fO2,(FiF) + 1) in the initially accreted material. Water vapor, generated at the interior of the planetesimal and transported to its near surface, formed a water-rich layer under certain conditions, providing an environment sufficient for aqueous alteration of chondritic materials to occur. Variations in isotopic ratios of N in taenite observed among equilibrated ordinary chondrites can be explained by our gas transportation model. It is required, however, that carriers of isotopically anomalous N, perhaps presolar grains, were initially localized on a large spatial scale within a single planetesimal, which possibly suggests incorporation of preaccretionary objects as large as 0.1 × of the final mass of the ordinary chondrite parent body. 相似文献
20.