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771.
鄂尔多斯盆地三叠系延长组主要发育东北和西南两大沉积体系,东北的河流三角洲体系已为大量的勘探研究资料所证实,而西南体系因受勘探程度限制,目前研究不够。本文通过最新钻探成果,结合盆地西南部露头资料,确立盆地西南地区三叠系延长组为冲积扇-扇三角洲沉积体系,发育冲积扇、扇三角洲、湖泊(浊积)相。冲积扇以西南缘平凉崆峒山和汭水河剖面为代表,扇三角洲及湖泊(浊积)相为区内钻井剖面所证实。长6-长8为区内主力油层组,地层保存完整,钻探程度相对较高。扇三角洲前缘砂体类型以水下分流河道为主,局部发育河口坝,浊积体以厚层块状为主。长8亚期为扇三角洲前缘亚相最发育期,横向形成自西南向东北延伸的三支前缘砂体带,是石油聚集的重要区带;长7亚期随着湖盆沉降,周边抬升强烈,湖岸较陡,大量发育浊积体系;长6亚期湖退导致扇三角洲再次发育,但规模较长8亚期弱。扇三角洲前缘砂体单层厚度大,砂岩粒度较粗,颗粒分选及物性好,是石油富集的最有利相带。 相似文献
772.
773.
从市场机制对诚信建构的作用说起,通过对我国现行会计监管方式和实施机制的分析,认为现行会计监管方式难以实现其预定的目标。同时笔者对此问题的解决做出了思考。 相似文献
774.
Zongming Wang Yubo Zhang Bai Zhang Kaishan Song Zhixing Guo Dianwei Liu Fang Li 《中国地理科学(英文版)》2008,18(2):137-145
The landscape pattern of Da'an County, Northeast China has undergone significant changes since the 1950s as a result of climatic change and human activities. The aim of this paper is to quantitatively study landscape pattern and its spatial dynamics of Da'an County at the landscape level over the nearly 50-year span. Patch dynamics were examined according to land use and land cover change processes built from a series of images, as well as topographic maps, and temporal patterns built from landscape pattern metrics. The transition matrix of landscape patch types and changes of various landscape metrics were applied. The results showed that, from 1956 to 2000, the landscape within the study area had undertaken a complicated evolution in landscape structure and composition. The outstanding characteristic is that saline-alkali land increased and grassland decreased. As some smaller patches amalgamated, the heterogeneity of patch decreased. All those changes were the synthetic result of both climatic and anthropogenic influences, but the predominant factor was different in different parts. In the southern part of the study area, the landscape pattern changes resulted from the modification of climate obviously, while in the northern part, the landscape pattern changes were mainly caused by human activities, such as the conversion between farmland and saline-alkali land. This phenomenon showed that human activities played more important role in the north than in the south of Da'an County. 相似文献
775.
Yuanming Guo Chase Holton Hong Luo Paul Dahlen Paul C. Johnson 《Ground Water Monitoring & Remediation》2019,39(2):43-52
Groundwater elevation fluctuation has been recognized as one mechanism causing temporal indoor air volatile organic chemical (VOC) impacts in vapor intrusion risk assessment guidance. For dissolved VOC sources, groundwater table fluctuation shortens/lengthens the transport pathway, and delivers dissolved contaminants to soils that are alternating between water saturated and variably saturated conditions, thereby enhancing volatilization potential. To date, this mechanism has not been assessed with field data, but enhanced VOC emission flux has been observed in lab-scale and modeling studies. This work evaluates the impact of groundwater elevation changes on VOC emission flux from a dissolved VOC plume into a house, supplemented with modeling results for cyclic groundwater elevation changes. Indoor air concentrations, air exchange rates, and depth to groundwater (DTW) were collected at the study house during an 86-d constant building underpressurization test. These data were used to calculate changes in trichloroethylene (TCE) emission flux to indoor air, during a period when DTW varied daily and seasonally from about 3.1 to 3.4 m below the building foundation (BF). Overall, TCE flux to indoor air varied by about 50% of the average, without any clear correlation to changes in DTW or its change rate. To complement the field study, TCE surface emission fluxes were simulated using a one-dimensional model (HYDRUS 1D) for conditions similar to the field site. Simulation results showed time-averaged surface TCE fluxes for cyclic water-table elevations were greater than for stationary water-table conditions at an equivalent time-averaged water-table position. The magnitudes of temporal TCE emission flux changes were generally less than 50% of the time-averaged flux, consistent with the field site observations. Simulation results also suggested that TCE emission flux changes due to groundwater fluctuation are likely to be significant at sites with shallow groundwater (e.g., < 0.5 m BF) and permeable soil types (e.g., sand). 相似文献
776.
Phytoplankton growth rates and mortality rates were experimentally examined at 21 stations during the 2017 spring intermonsoon(April to early May) in the northern and central South China Sea(SCS) using the dilution technique, with emphasis on a comparison between the northern and central SCS areas which had different environmental factors. There had been higher temperature but lower nutrients and chlorophyll a concentrations in the central SCS than those in the northern SCS. The mean rates of phytoplankton growth(μ_0) and microzooplankton grazing(m) were(0.88±0.33) d~(–1) and(0.55±0.22) d~(–1) in the central SCS, and both higher than those in the northern SCS with the values of μ_0((0.81±0.16) d~(–1)) and m((0.30±0.09) d~(–1)), respectively.Phytoplankton growth and microzooplankton grazing rates were significantly coupled in both areas. The microzooplankton grazing impact(m/μ_0) on phytoplankton was also higher in the central SCS(0.63±0.12) than that in the northern SCS(0.37±0.06). The microzooplankton abundance was significantly correlated with temperature in the surface. Temperature might more effectively promote the microzooplankton grazing rate than phytoplankton growth rate, which might contribute to higher m and m/μ_0 in the central SCS. Compared with temperature, nutrients mainly affected the growth rate of phytoplankton. In the nutrient enrichment treatment,the phytoplankton growth rate(μn) was higher than μ_0 in the central SCS, suggesting phytoplankton growth in the central SCS was nutrient limited. The ratio of μ_0/μn was significantly correlated with nutrients concentrations in the both areas, indicating the limitation of nutrients was related to the concentrations of background nutrients in the study stations. 相似文献
777.
2004年全球重大气候事件概述 总被引:1,自引:3,他引:1
2004年全球气候持续偏暖。年初,暴雪席卷欧洲多国,美国受到罕见大雪袭击,南亚和墨西哥遭遇低温严寒。北半球夏秋季,西太平洋、大西洋热带风暴活动频繁。日本、菲律宾和美国受灾严重。年内,非洲、亚洲部分国家发生严重干旱;同时,南亚、南美洲及非洲多国暴雨致洪。年内,欧洲伊比利亚半岛、日本和澳大利亚遭遇高温热浪。 相似文献
778.
Forced regression and its sedimentary response to continental lacustrine rift basin: A case of the Member 3 of Shahejie Formation in Laizhouwan sag,Bohai Bay Basin
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Falling stage systems tract(FSST)is an offlap strata with strong relationship with hydrocarbon exploration,which is driven by relative lake-level fall and developed above the highstand systems tract and below the lowstand systems tract of a new sequence. It has no relationship with sediment supply. Based on the theory of sequence stratigraphy and sedimentology,3D seismic data,drilling core data,and well-logging data were comprehensively analyzed. The study showed that the FSST strata was formed in the Member 3 of Shahejie Formation in the Laizhouwan sag. The FSST can be divided into three units,namely as units P1,P2,and P3 from bottom to top. The P1 is the first unit of progradation downlap the bottom of the FSST. The top of the unit P3 is a sequence boundary exhibits subaerial unconformity. The seismic profile along the source direction is characterized by the low-angle oblique progradation reflection that downstream the center of lake basin from west to east. Incised valleys developed on the top of the FSST perpendicular to the source direction. Gamma-ray logging response is manifested by a series of funnel-shaped complex,indicating that the sedimentary response of the FSST was a cycle of coarsening-upward parasequence sets. Comprehensive studies on core interpretation and well-logging analysis showed that the FSST was a fluvial-delta sedimentary system with slumped fan deposits associated with the delta front. Consequently,the FSST is a common result of relative dry climate and falling of lake level,considering regional tectonic evolution,sediment supply,and paleo-climate change. The discovery of the FSST in the Laizhouwan sag has an important geological significance for the sedimentological interpretation,and it offers a guidance for further oil exploration in the study area. In addition,it also serves as a significant reference for future research on the FSST development and exploration in the continental lacustrine rift basin. 相似文献
779.
780.
利用江西省93个国家气象观测站降水量资料,对2014年ECMWF集合预报降水统计量进行逐6 h和24 h晴雨检验、降水分级检验及区域性暴雨检验。结果表明:1)10%、25%、Mode、融合、最小值在晴雨预报准确率方面较控制预报更有参考价值。2)对于全年降水分级检验,10%、25%、Mode、融合、最小值这5个统计量在小雨的预报方面较控制预报更有参考价值;中位数、概率对中雨的ETS评分要略高于控制预报;90%、75%、概率对大雨预报比控制预报好。对于暴雨预报,最大值、90%、融合比控制预报好;融合、最大值对大暴雨落区的指示意义不大,但对大暴雨量级降水的可能性可以供预报员参考。3)对于区域性暴雨预报,90%、融合、最大值的预报技巧比控制预报高,最大值虽然空报较严重,但对降水量级有一定的指示意义。集合预报各统计量对于强降水过程爆发或发展阶段的预报效果不如降水过程成熟期或末期好。 相似文献