检索结果-南通市图书馆

寒武纪早期海洋阶段性氧化驱动早期后生动物多样化进程

在线全文

学校读者我要写书评

暂无评论

地球科学 2018年第11期43卷 3873-3890页

作者：赵相宽史晓颖王新强汤冬杰中国地质大学地球科学与资源学院北京100083 中国地质大学生物地质与环境地质国家重点实验室北京100083 中国地质大学科学研究院北京100083

伊迪卡拉-寒武纪过渡期是地球历史上海洋环境与生命演化变革的关键时期之一.有研究认为海洋氧化可能是驱动早寒武世动物快速多样化的主要原因,但有关海洋氧化及硫化水体演变过程和发生时间的认识仍有分歧.运用ICP-MS、FESEM、EDS和XRD... 详细信息

伊迪卡拉-寒武纪过渡期是地球历史上海洋环境与生命演化变革的关键时期之一.有研究认为海洋氧化可能是驱动早寒武世动物快速多样化的主要原因,但有关海洋氧化及硫化水体演变过程和发生时间的认识仍有分歧.运用ICP-MS、FESEM、EDS和XRD技术对位于古陆架边缘-斜坡背景的湘西四都坪、黔东松江大桥等剖面牛蹄塘组黑色页岩进行氧化还原敏感元素、黄铁矿形态学、总有机碳及N、P等营养元素丰度变化进行高分辨研究.结果显示,研究区牛蹄塘沉积期底层海水条件经历了复杂的发展过程,表现为3个铁化与3个硫化时段的动态交互,在第3阶晚期转为亚氧化-氧化条件.不同相区的对比表明,海水氧化随时间由浅水向深水区扩展:台地相区发生在第2.晚期,陆架边缘出现在第3阶晚期,而深水盆地以持续铁化为主,晚期出现硫化,表明海洋氧化界面逐步加深下移.沉积物Mo/TOC,U/TOC值自下而上持续增加,与Cr、Mn、P、N丰度变化趋势一致,表明海水氧化程度逐步增强.主要化石类群的时空分布与海水氧化过程对应良好,表明海洋阶段性氧化与硫化水体消失对后生动物多样化进程有明显的控制作用.

关键词：草莓状黄铁矿氧化还原敏感元素海水Mo-U通量牛蹄塘组扬子地台生物地层学

区域场地土壤跨介质污染物多源清单:中国场地土壤污染防治的新策略

在线全文

学校读者我要写书评

暂无评论

Science Bulletin 2024年第5期69卷 566-569页

作者：李晔何天豪丁方方李小飞黄晔何尔凯蔡虹明史沛丽柳检李岩曲瑞娟郑旺谢云峰刘杏梅赵玲刘敏 Key Laboratory of Geographic Information Science(Ministry of Education) School of Geographic SciencesEast China Normal UniversityShanghai 200241China school of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China College of Environmental Natural Resource sciences Zhejiang UniversityHangzhou 310058China Technical Centre for Soil Agriculture and Rural Ecology and EnvironmentMinistry of Ecology and EnvironmentBeijing 100012China Institute of Surface-earth System Science School of Earth System ScienceTianjin UniversityTianjin 300072China State Key Laboratory of Pollution Control and resources Reuse School of the EnvironmentNanjing UniversityNanjing 210023China

china has experienced rapid economic development and industrialization during the past four decades,leading to widespread distribution of various types of industrial facilities[1..With the understanding of soil contamination induced by industrial sites and rapid urbanization,abandoned industrial sites are generally reclassified for urban land[{1..The remained brownfield sites(the sites of abandoned,idle,or under used industrial and commercial facilities where expansion or redevelopment is hindered by environmental contamination)exhibit great health risks to the residents due to that pollutants were continuously discharged intothe surrounding environments[3].

关键词：土壤污染防治 environments facilities

Nitrous oxide emissions following seasonal freeze-thaw events from arable soils in Northeast china

在线全文

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2018年第1期17卷 231-246页

作者： CHEN Zhe YANG shi-qi ZHANG Ai-ping JING Xin SONG Wei-min MI Zhao-rong ZHANG Qing-wen {1. Wen-ying YANG Zheng-li Key Laboratory for Agro-environment Ministry of Agriculture/Institute of Environment and Sustainable Development in Agriculture Chinese Academy of Agricultural Sciences Beijing 100081 P.R. China school of Life {1. Qinghai Normal University Xining 810008 P.R. China Key Laboratory for earth Surface Processes Ministry of Education/Department of Ecology College of Urban and Environmental Sciences Peking University Beijing 100871 P.R.China Center for earth System Science Tsinghua University Beiiina 100084. P.R.China Farmland Irrigation Research Institute Chinese Academy of Agricultural Sciences Xinxiang 453002 P.R. China

Seasonal soil freeze-thaw events may enhance soil nitrogen transformation and thus stimulate nitrous oxide （N2.） emissions in cold regions. However, the mechanisms of soil N2. emission during the freeze-thaw cycling in the field remain unclear. We evaluated N2. emissions and soil biotic and abiotic factors in maize and paddy fields over 2. months in Northeast china, and the structural equation model （SEM） was used to determine which factors affected N2. production during non-growing season. Our results verified that the seasonal freeze-thaw cycles mitigated the available soil nitrogen and carbon limitation during spring thawing period, but simultaneously increased the gaseous N2.-N losses at the annual time scale under field condition. The N2.-N cumulative losses during the non-growing season amounted to 0.71.and 0.55 kg N ha 1.for the paddy and maize fields, respectively, and contributed to 66 and 1.% of the annual total. The highest emission rates （1.9.2. 2.7.4 μg m-2.h-1. were observed during soil thawing for both fields, but we did not observe an emission peak during soil freezing in early winter. Although the pulses of N2. emission in spring were short-lived （1. d）, it resulted in approximately 80% of the non-growing season N2.-N loss. The N2. burst during the spring thawing was triggered by the combined impact of high soil moisture, flush available nitrogen and carbon, and rapid recovery of microbial biomass. SEM analysis indicated that the soil moisture, available substrates including NH4＋ and dissolved organic carbon （DOC）, and microbial biomass nitrogen （MBN） explained 32. 36, 1. and 51. of the N2. flux variation, respectively, during the non-growing season. Our results suggested that N2. emission during the spring thawing make a vital contribution of the annual nitrogen budget, and the vast seasonally frozen and snow-covered croplands will have high potential to exert a positive feedback on climate change considering the sensitive response of nitrogen biog

关键词： N2. non-growing season nitrogen biogeochemical cycling soil moisture snow cover structural equation model

Spatiotemporal changes of land desertification sensitivity in northwest china from {1.00 to 2.17

在线全文

学校读者我要写书评

暂无评论

Journal of Geographical sciences 2021年第1期31卷 46-68页

作者： WEI Wei GUO Zecheng shi Peiji ZHOU Liang {1. Xufeng LI Zhenya PANG Sufei XIE Binbin College of Geography and Environmental Science Northwest Normal UniversityLanzhou 730070China College of earth and Environmental {1. Lanzhou UniversityLanzhou 730000China Faculty of Geomatics Lanzhou Jiaotong UniversityLanzhou 730070China State Key Laboratory of resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchCASBeijing 100101China Key Laboratory of Ecohydrology of Inland River Basin/Gansu Qilian Mountains Ecological Research Center Northwest Institute of Eco-environment and ResourcesCASLanzhou 730000China school of Urban Economics and Tourism Culture Lanzhou City UniversityLanzhou 730070China

Sensitivity assessment is useful for monitoring land desertification. Research into how to prevent and control desertification is also important. In the arid region of northwest china, desertification is becoming worse and is a serious problem that affects local sustainable development. Based on remote-sensing and geographic information system technology, this study establishes a 'soil-terrain-hydrology-climate-vegetation' desertification sensitivity comprehensive evaluation system to reflect the spatiotemporal changes of land desertification, and proposes a spatial distance model to calculate a desertification sensitivity index. The spatiotemporal change characteristics of land desertification sensitivity in northwest china are quantitatively assessed from 2.00 to {2.7. Moreover, the main driving factors are analyzed using the geographical detector method. The results show the following.(1. Terrain, soil, climate, vegetation and hydrology affect and restrict each other, and constitute the background conditions of the distributions and changes of sensitivity to desertification in northwest china.(2. Desertification sensitivity generally displays a low distribution characteristic on the periphery of the area and a high one in the interior. The low-sensitivity regions are mainly in the five major mountain ranges(Altai Mountains, Tianshan Mountains, Kunlun Mountains, Altun Mountains and Qilian Mountains), while the high-sensitivity regions are mainly in regions such as the Junggar Basin, the Tarim Basin and the Inner Mongolia Plateau, as well as the Taklimakan Desert, Badain Jaran Desert and Tengger Desert. The spatial distribution of desertification sensitivity is obviously regional, and the high-and low-sensitivity regions have clear boundaries and a concentrated distribution.(3) With regard to spatiotemporal evolution, changes in desertification sensitivity since 2.00 have been predominantly stable, and the overall sensitivity has displayed a slowly decreasing trend

关键词： desertification sensitivity spatiotemporal change geographical detector GIS northwest china

Electronic structure and spatial inhomogeneity of iron-based superconductor FeS

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2020年第4期29卷 110-115页

作者： Chengwei wang Meixiao wang Juan Jiang Haifeng Yang Lexian Yang Wujun {2. Xiaofang Lai Sung-Kwan Mo Alexei Barinov Binghai Yan Zhi Liu Fuqiang Huang Jinfeng Jia Zhongkai Liu Yulin Chen State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology(SIMIT)Chinese Academy of SciencesShanghai 200050China school of Physical Science and Technology ShanghaiTech UniversityCAS-Shanghai Science Research CenterShanghai 200031China university of Chinese Academic of {1. Beijing 100049China Advanced Light Source Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA State Key Laboratory of Low Dimensional Quantum Physics Department of Physics and Collaborative Innovation Center for Quantum MatterTsinghua UniversityBeijing 100084China beijing National Laboratory for Molecular {1. and State Key Laboratory of Rare {2. Materials Chemistry and Applications College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Elettra-Sincrotrone Trieste ScPA TriesteBasovizza 34149Italy Max Planck Institute for Chemical Physics of Solids D-01187 DresdenGermany State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China Key Laboratory of Artificial Structures and Quantum Control(Ministry of Education) Department of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Physics Department Oxford UniversityOxfordOX13PUUK

Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical ***,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing *** this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline *** FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio ***,mixed with the 1.1.tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.

关键词： angle-resolved photoemission with spatially resolution scanning tunneling microscopy iron-based superconductor electronic band structure

MMS星座对磁层顶磁通量绳内离子惯性尺度结构的观测

在线全文

学校读者我要写书评

暂无评论

空间科学学报 2018年第2期38卷 147-168页

作者：刘杨濮祖荫谢伦郭瑞龙王晓钢肖池阶史全岐 DUNLOP M BOGDANOVA Y V MOORE T E RUSSELL C T LINDQVIST P A TORBERT R B POLLOCK C ZHAO Cong 北京大学地球与空间科学学院北京100871 中国科学院地质与地球物理研究所北京100029 哈尔滨工业大学物理系哈尔滨150001 北京大学物理学院北京100871 山东大学空间科学与物理学院威海264209 RAL Space Rutherford Appleton LaboratorySTFCDidcotOX11 0QXUK Goddard Space Flight Center NASAGreenbeltMDUSA university of California Los AngelesCAUSA Royal Institute of Technology StockholmSweden university of New Hamp{1.re DurhamNHUSA

利用MMS观测数据,对磁层顶通量绳内离子惯性尺度(d_i)的结构进行分析研究.结果发现,许多不同尺度(约1._i至数十d_i)的通量绳内都存在具有d_i尺度的电流j_m,其方向在磁层顶局地坐标系的-M方向,即与磁层顶查普曼-费拉罗电流同向,由电子在+... 详细信息

利用MMS观测数据,对磁层顶通量绳内离子惯性尺度(d_i)的结构进行分析研究.结果发现,许多不同尺度(约1._i至数十d_i)的通量绳内都存在具有d_i尺度的电流j_m,其方向在磁层顶局地坐标系的-M方向,即与磁层顶查普曼-费拉罗电流同向,由电子在+M方向的运动(v_(em))携带.这些电流结构具有以下特征:磁鞘与磁层成分混合,磁场为开放形态;离子去磁化,电子与磁场冻结;N方向(即垂直于磁层顶电流片方向)的电场E_n显著增大,幅度达到约2. mV·m^(-1.,并伴有明显的尖峰状起伏,该增强和尖峰状起伏的电场对应于霍尔电场.分析表明,电流、电子与离子运动的偏离以及霍尔电场之间遵从广义欧姆定律,三者密切关联.进一步对磁层顶磁重联的探测数据进行分析发现,在很多重联区内也存在与通量绳内相似的结构,其尺度约为d_i量级,其中霍尔电场E_N、电流j_M和电子速度v_(eM)均与通量绳内对应物理量的方向相同且幅度相近.基于上述观测事实,采用经典FTE通量绳模型,对通量绳内电流、电子运动和霍尔电场的起源进行了初步探讨,认为其来源于磁层顶无碰撞磁重联区内的相应结构,并且后者在离子尺度通量绳的形成过程中起到重要作用.

关键词：磁通量绳离子尺度电流霍尔电场磁层顶磁重联

在线全文

学校读者我要写书评

暂无评论

子午工程二期宽频地磁波监测仪研制

地球与行星物理论评（中英文） 2024年第1期55卷 6-14页

作者：于向前和冬华肖池阶宗秋刚施伟红刘斯陈鸿飞王永福邹鸿北京大学地球与空间科学学院北京100871 北京大学物理学院北京100871 长沙理工大学物理与电子科学学院长沙410114

地球的磁层中存在各种波现象,其频率从mHz延伸到数千Hz.这些波的研究一直是空间物理学研究的核心问题.针对目前世界上地磁台站的波监测设备均为各自测量相对变化、缺乏统一标定、无法进行从高纬到低纬联合观测、无法进行多台设备观测数... 详细信息

地球的磁层中存在各种波现象,其频率从mHz延伸到数千Hz.这些波的研究一直是空间物理学研究的核心问题.针对目前世界上地磁台站的波监测设备均为各自测量相对变化、缺乏统一标定、无法进行从高纬到低纬联合观测、无法进行多台设备观测数据的统一对比研究的现状,本文综合使用磁阻传感器(探测ULF频段:1.mHz~2.Hz)、巨磁感抗传感器(探测ELF频段:0.2.Hz~2.kHz)和线圈传感器(探测VLF频段:0.2.kHz~1. kHz)研制新一代的宽频地磁波监测仪,将这些监测仪放置在1.0}°E子午链附近的黑龙江漠河站(高纬)、北京十三陵站(中纬)、海南乐东站(低纬)等典型区域的地磁台站上,并对各个台站的设备进行统一的时间、振幅和频率标定,结合FY-3E、SMILE等近地空间卫星数据,全面提升对地球磁层的各种波现象的探测能力.研制的宽频地磁波监测仪的性能测试实验表明,其具有对一定频率(1.mHz~1. kHz)的波的探测能力;其幅度探测范围为:±65000 nT(ULF频段)、±1.00 nT(ELF频段)、±1.0 pT(VLF频段);在量程范围内又具有较低的非线性误差:ULF频段≤0.0446%、ELF频段≤0.51.、VLF频段≤1.1.%;噪声水平也较低:RMS(方均根)噪声≤0.5554 nT(ULF频段)、NPS(功率谱)噪声≤0.02. nT/√Hz(ELF频段)、NPS(功率谱)噪声≤0.2. pT/√Hz(VLF频段).所有这些特点使得所提出的宽频地磁波监测仪能够满足子午工程二期的波探测需求.

关键词：子午工程二期宽频地磁波监测仪磁阻传感器巨磁感抗传感器线圈传感器

Poleward-moving recurrent auroral arcs associated with impulse-excited standing hydromagnetic waves

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

earth and Planetary Physics 2019年第4期3卷 305-313页

作者： HuaYu Zhao Xu-Zhi Zhou Ying Liu Qiu-Gang Zong Robert Rankin YongFu wang QuanQi {1. Xiao-Chen Shen Jie Ren Han Liu XingRan Chen school of {1. and Space {2. Peking University Beijing 100871 China Department of Physics University of Alberta Edmonton Alberta T6G2J1 Canada school of Space Science and Physics Shandong University Weihai 264209 China Center for Space Physics Boston University Boston Massachusetts 02215 USA

In earth's high-latitude ionosphere, the poleward motion of east–west elongated auroral arcs has been attributed to standing hydromagnetic waves, especially when the auroral arcs appear quasi-periodically with a recurrence time of a few minutes. The validation of this scenario requires spacecraft observations of ultra-low-frequency hydromagnetic waves in the magnetosphere and simultaneous observations of poleward-moving auroral arcs near the spacecraft footprints. Here we present the first observational evidence from the multi-spacecraft THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission and the conjugated all-sky imager to support the scenario that standing hydromagnetic waves can generate the quasi-periodic appearance of poleward-moving auroral arcs. In this specific event, the observed waves were toroidal branches of the standing hydromagnetic waves, which were excited by a pulse in the solar wind dynamic pressure. Multi-spacecraft measurements from THEMIS also suggest higher wave frequencies at lower L shells (consistent with the distribution of magnetic field line eigenfrequencies), which indicates that the phase difference across latitudes would increase with time. As time proceeds, the enlarged phase difference corresponds to a lower propagation speed of the auroral arcs, which agrees very well with the ground-based optical data.

关键词： poleward-moving auroral arcs ULF waves standing hydromagnetic waves field-aligned currents solar wind dynamic pressure pulse

多源高分辨率卫星影像监测黑臭水体的适用性研究

在线全文

学校读者我要写书评

暂无评论

遥感学报 2022年第1期26卷 179-192页

作者：王茹申茜彭红春姚月李俊生汪明秀史佳睿徐雯婷江苏海洋大学海洋技术与测绘学院连云港222005 中国科学院空天信息创新研究院数字地球实验室北京100094 东华理工大学测绘工程学院南昌330105

高分辨率卫星的幅宽一般很小,受云雨和轨道回访周期影响,单颗卫星的短时段内覆盖能力有限,因此,单一高分辨率卫星常常无法满足一定时段内的黑臭水体监测需求,需要多源卫星协同监测黑臭水体。为了分析多源高分辨率影像对黑臭水体遥感监... 详细信息

高分辨率卫星的幅宽一般很小,受云雨和轨道回访周期影响,单颗卫星的短时段内覆盖能力有限,因此,单一高分辨率卫星常常无法满足一定时段内的黑臭水体监测需求,需要多源卫星协同监测黑臭水体。为了分析多源高分辨率影像对黑臭水体遥感监测的适用性,本文基于地物光谱仪实测的水体遥感反射率数据,以GeoEye-1.WorldView-2.北京二号(DMC3)、高景一号SV1.SuperView-1.以及GF-PMS系列(GF-1.1./1./1.、GF-2.GF-6)传感器波段进行等效计算,结果表明:(1.采用反射率比值模型——BOI(Black and Odorous water Index)模型,GeoEye-1.WorldView-2.SuperView-1.GF-1.1./1./1./2.6影像识别黑臭水体正确率均较高,分别为89.5%、89.5%、92.1%和92.1%。(2.BOI模型不适用于DMC3,这里采用了归一化水体指数NDWI≤0.55判别黑臭水体,识别正确率为89.5%。(3)BOI模型应用于仅有的2.同步卫星影像——GF-2.像,经实测数据验证,识别精度为83.3%,精度较高。针对通州区内的某重叠区,2.16年—2.2.年1.颗多源卫星影像协同观测的结果一致性较好,表明了多源遥感影像监测黑臭水体的适用性较好。综合考虑卫星影像空间分辨率和采购成本,给出了合理的协同观测建议。

关键词：遥感多源高分辨率影像黑臭水体监测适用性 BOI