Ns,K,R,M等值线图所展示的川滇地区强震的前兆图象     

郁曙君  李世愚 《地震地磁观测与研究》1998,19(4):37-47

充分展示了ＮＳ,Ｋ,Ｒ,Ｍ等值线图的预测效能。这种图定量、直观。利用他捕捉到了一些有效的前兆现象,其中最主要的是：①ＭＳ≥７．０地震前３年震中附近ＭＬ≥３．５地震频数显著增加;②ＭＳ≥７．０地震前１年研究区ＭＬ≥２．０地震频数降半;③ＭＳ≥６．０地震后地震活动数年不衰的地区是未来ＭＳ≥７．０地震发生的可能地点;④孟连—普洱及其附近地区余震中心偏离主震震中逼近未来强震震中;⑤普洱地区地震活动性低,次年发生ＭＳ≥６．０地震的可能性较小。文中用广义地震成核模型对现象①进行了物理解释。  相似文献   

Biological and environmental changes in Lake Baikal during the late Quaternary inferred from carbon, nitrogen and sulfur isotopes   总被引：1，自引：0，他引：1  

T Watanabe  H Naraoka  T Kawai 《Earth and Planetary Science Letters》2004,222(1):285-299

An 8-m continuous sediment core, approximately 250-ky-old at the bottom, from Academician Ridge in Lake Baikal, has been analyzed for the stable isotopes of carbon, nitrogen and sulfur, in order to study the paleoclimatic and paleobiological changes that occurred in the Eurasian continental interior. These isotopic changes are closely related to changes in vertical lake-water circulation between glacial and interglacial periods. Sedimentary organic carbon in cool periods is more enriched in ¹³C (−23.8‰ on average) than that in warm periods (−27.0‰ on average). The ¹³C-enrichment of organic carbon suggests a decrease of land-derived organic matter influx to the lake, less precipitation, and loss of terrestrial vegetation around Lake Baikal in cool periods. Pyrite in high total sulfur/total organic carbon (TS/TOC) layers shows strong depletion in ³⁴S (−20.8‰ to −32.4‰) during climate transitions from glacial to interglacial periods at the beginning of oxygen isotope stages (OIS) 1, 5 and 7. The ³⁴S-depleted pyrite indicates augmentation of dissimilatory sulfate reduction by sulfate reducing bacteria (SRB) at the sediment-water interface. Enhancement of aqueous sulfate concentrations and limitation of oxygen circulation to the surface sediments might also occur in the climate transition periods. The δ¹⁵N values of total nitrogen increase abruptly by ∼2‰ just after the δ³⁴S negative peaks, which may result from low nutrient concentrations in the euphotic zone associated with water circulation changes in Lake Baikal.  相似文献   

地下水三氮污染的研究进展   总被引：35，自引：1，他引：35  

罗泽娇  靳孟贵 《水文地质工程地质》2002,29(4):65-69

在查阅国内外相关文献的基础上，综述了三氮污染的产生、危害及地下水污染现状，三氮污染的分析测试方法，三氮迁移转化过程和模型的研究，以及地下水三氮污染防治研究的现状。提出了今后的研究方向，应从控制三氮污染源入手，加强包气带－饱和带的三氮耦合研究，加强深层地下水和高浓度三氮污染的研究。同时，要提高三氮污染的野外监测水平和三氮污染的治理技术研究。  相似文献   

Ar/Ar Single Grain Dating and Mineral Chemistry of Hornblendes South of the Red River Shear Zone (Vietnam): New Evidence for Early Proterozoic Tectonothermal Event     

Tran Ngoc Nam  Hironobu Hyodo  Tetsumaru Itaya  Takaaki Matsuda 《Gondwana Research》2002,5(4):801-811

The pre-Mesozoic metamorphic belt runs parallel to the Day Nui Con Voi - Red River shear zone in Vietnam to the south. The belt is mainly composed of hornblende gneisses, amphibolite lenses and mica-schists. Five hornblendes from a gneiss and an amphibolite were analyzed chemically and chronologically by Electron Probe Micro Analysis (EPMA) and ⁴⁰Ar/³⁹Ar methods. EPMA analyses show that hornblendes in the gneiss and the amphibolite have significant amount of edenite component and similar average composition. However, the recalculated Fe³⁺ content is significantly heterogeneous in a thin section while total Fe is nearly the same among the analyses. The rim of each crystal is higher in Fe³⁺/(Fe³⁺ + Fe²⁺) than the core. These chemical and petrological features suggest that the hornblendes have suffered significant oxidation, in particular, largely in the gneiss.

⁴⁰Ar/³⁹Ar analyses showed that the gneiss has a significant variation of plateau ages (2089±14, 1977±19 and 1873±13 Ma) among three hornblende grains, whereas the amphibolite gives the same plateau ages (2056±14 and 2044±21 Ma) for two grains. All grains of both samples have excess ages in the first few fractions at low temperatures and partial-loss ages between the excess and plateau spectra. The Ca/K ratios indicate some disturbed phases for the lower temperature spectra but the partial-loss ages are also derived from hornblende phase. These facts suggest that hornblende in the gneiss has experienced partial argon loss by oxidation and/or thermally activated argon diffusion process. However, the gneiss and the associated amphibolite have preserved the early Proterozoic tectono-metamorphic event in the hornblende crystals except for their rims, giving new evidence for the early Proterozoic event within the pre-Mesozoic metamorphic belt (northern Vietnam) south of the Red River shear zone in Indochina.  相似文献   

磁尾地向传播等离子体团的模拟研究          下载免费PDF全文

杨红昂  金曙平 《地球物理学报》2002,45(5):611-623

卫星观测证实了磁尾等离子体团与亚暴活动的相关性,除了具有北-南双极特征的尾向传播等离子体团外,还发现地向传播等离子体团,它们表现为南-北双极中性片事件和南-北双极瓣区讯号. 资料分析表明:南-北双极讯号的出现几率远低于北-南双极讯号,并且南-北双极事件主要发生于行星际磁场北向和地磁宁静条件,它们往往与小的孤立的地磁亚暴相关. 本文根据地磁宁静时期(IMF Bz北向且By≥Bz)越尾电场Ey分量的分布特点,对地向传播等离子体团作模拟研究. 两类算例的数值结果展示了通量绳磁结构及具有复杂闭合磁力线位形的等离子体团的基本特征,上述特征与尾向传播的等离子体团类似,与IMP 8卫星关于地向传播南-北中性片事件的观测特征大致相符. 数值结果还展示了与Schindler示意图相类似的磁力线拓扑位形,在一定程度上为南-北事件出现几率低作出了解释;并且揭示了磁尾中性片内越尾磁场分量By对磁重联发展的抑制作用. 本文的模拟研究说明:无论磁尾处于活动时期(IMF Bz为南向),还是宁静时期(IMF Bz为北向且By≥Bz),磁场重联均是磁尾等离子体加速和加热的通用机制.  相似文献   

安徽黄栗树地区构造特征及对金矿的控制作用     

张立明  刘青  朱琨  韩成林 《云南地质》2008,27(2):156-162

黄栗树地区有两种金矿化类型：接触交代型（矽卡岩型）和微细浸染型（卡林型）。在有利的地层、构造及岩浆活动等多重因素作用下形成。主干断裂控制金矿（化）体宏观带状分布,规模不大的复合型断裂或层间破碎带则控制矿（化）体定位。  相似文献   

巢湖沉积物有机碳分布变化特征   总被引：2，自引：0，他引：2  

刘清玉  戴雪荣  王立群 《上海国土资源》2008,(1):13-17

利用2003年7月用活塞取样器在湖泊靠近河口附近和湖泊内沉积最深区域内布点采集了柱样,对样品进行了有机碳和总氮含量等的测定,并对碳的分布变化特征及其影响因素进行了探讨。结果表明：AC4柱样样品有机碳含量变化整体上呈现出一个波动频繁且幅度较大的特点,AC3柱样整体上为缓慢渐变态势。AC4有机碳与细颗粒、总氮含量的相关性高于AC3柱样。两柱样的C／N比值垂向变化表明沉积物中的内、外源有机质在湖泊有机质中各占有一定比例,同时也反映了它们物质来源上有差异。可见由于位置差异导致的水动力条件、物源变化和降解作用等不同因素对其含量变化及C／N比值具有不同的影响。  相似文献   

霸王根茎叶非结构性碳与C:N:P计量特征对干旱的响应     

孙小妹  何明珠  周彬  李金霞  陈年来 《干旱区地理》2021,44(1):240-249

通过选取阿拉善地区3个典型霸王群落为研究对象,研究霸王器官间(根、茎、叶)生态化学计量比特征及非结构性碳水化合物(Non-structural carbohydrates,NSCs)的变化,以便加深对霸王生存策略的理解,更好的服务于荒漠生态系统的生态恢复。结果表明:霸王茎和叶中可溶性糖(Solu?ble sugar,SS)、淀粉(Starch,ST)和NSCs含量随干旱加剧均显著降低。根系中SS和NSCs在3个样点间差异不显著,ST先降低后增加,ST含量在Plot3中比在Plot1和Plot2中高19.3%和31.2%。干旱使霸王根、茎、叶中N、P含量显著下降,使根、茎、叶中C:N和C:P显著增高,叶片N:P<14。Plot1中霸王器官间SS、SS:ST和NSCs含量表现为叶片>根>茎,ST含量为茎>根>叶片;Plot2和Plot3中霸王器官间SS、ST和NSCs含量均为根>茎>叶片。3个样点中叶片相较于茎干和根系具有高的N、P含量和低的C:N和C:P。NSCs与C:N:P间的关系表明:根、茎、叶中的N含量与SS正相关,叶片N含量与根系ST负相关。以上结果表明霸王的茎干和根系可能扮演“营养库”的角色,霸王通过提高N、P利用效率来减缓水分亏缺使其生长受到N限制的影响。霸王通过调节器官间NSCs的积累及分配来适应干旱,采取将根系中ST转化为SS来调节渗透势的策略;并随干旱加剧将更多的碳水化合物投资分配到根部,以ST的形式存储,而N是影响霸王根系中ST与SS间转化和ST存储的关键元素。  相似文献   

Evaluating nitrate uptake in a Rocky Mountain stream using labelled 15N and ambient nitrate chemistry     

K. A. Hubbard Jr.  L. K. Lautz  M. J. Mitchell  B. Mayer  E. R. Hotchkiss 《水文研究》2010,24(23):3322-3336

Background aqueous chemistry and ¹⁵N_nitrate tracer injection methods were used to calculate in‐stream nitrate uptake metrics at Red Canyon Creek, a third‐order stream in the Rocky Mountains in the state of Wyoming, United States. ‘Net’ nitrate uptake lengths, which reflect both nitrate uptake and regeneration, and ‘gross’ nitrate uptake lengths, which exclude re‐mineralization, were quantified separately from background nitrate chemistry and ¹⁵N labelling tracer data, respectively. Gross nitrate uptake lengths, from tracer injections of ¹⁵N labelled nitrate, ranged from 502 to 3140 m. Net nitrate uptake lengths, from background nitrate chemistry downstream of a point source, ranged from 1170 to 4330 m. Diurnal changes in uptake lengths suggest the importance of nitrate utilization by autotrophs in the stream and benthic zone. The differences between net and gross nitrate uptake lengths along lower reaches of Red Canyon Creek allowed us to estimate the nitrate regeneration rate, which was 0·056–0·080 µmol m^?2 s^?1 during the day and 0·0062–0·0083 µmol m^?2 s^?1 at night. Spatial patterns of streambed pore water chemistry indicate those areas of the hyporheic zone where denitrification was likely occurring. Permanent log dams generated stronger redox gradients in the hyporheic zone than areas with transient beaver dams. By combining isotopically labelled nitrate additions, estimates of uptake from background aqueous nitrate chemistry and characterization of redox conditions in the hyporheic zone, we were able to determine the nitrate regeneration rate and the redox processes responsible for nitrogen cycling in the hyporheic zone. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

滑动面的插值方法及滑坡稳定性计算     

刘定恩  陈征宙  童立元  周超 《地球科学与环境学报》2000,22(4)

根据钻孔资料结合宏观地质调查资料分别作分段线形插值函数、拉格朗日插值函数和样条插值函数 ,用得出的插值函数来表征滑动面。并将插值函数与传统的圆弧滑动面假设分析对比。以南京狮子山东南坡滑坡为例 ,根据不同的插值滑动面 ,采用普遍条分法计算滑坡稳定性系数。最后 ,对不同的结果作了分析对比 ,认为过特征位置采用样条插值函数所表示的滑动面较好地符合实际情况  相似文献