土壤环境因子对土下岩溶溶蚀速率的影响——以重庆金佛山国家自然保护区为例   总被引：4，自引：0，他引：4       下载免费PDF全文

杨平恒章 程  孙玉川吴月霞高彦芳王冬银李林立 《中国地质》2007,34(5):920-956

通过野外溶蚀试片和测量土壤CO2浓度、水分、孔隙度、pH值和有机质含量的方法,探讨不同土地利用方式下土壤环境因子及其相互耦合对岩溶溶蚀速率的影响。研究结果表明,金佛山国家自然保护区不同土地利用方式下的平均溶蚀速率差异显著,总体表现为:竹林地>林地>草地>灌丛地>灌草丛地。不同土地利用方式下的土壤pH值与溶蚀速率呈很好的负相关,土壤水分含量、孔隙度与溶蚀速率呈正相关。山顶岩溶作用明显强于山下,这与重庆市百年一遇的大旱不无关系。土壤环境中CO2浓度、水分、孔隙度、pH值和有机质含量影响着岩溶溶蚀速率,同时这些土壤环境相互耦合也影响着岩溶溶蚀速率。  相似文献   

Organochlorine pesticides in fresh-fallen snow on East Rongbuk Glacier of Mt.Qomolangma (Everest)   总被引：2，自引：1，他引：2  

WANG Feng  ZHU Tong  XU BaiQing & KANG ShiChang State Key Joint Laboratory for Environmental Simulation & Pollution Control  College of Environmental Sciences  Peking University  Beijing  China  Institute of Tibetan Plateau Research  Chinese Academy of Sciences  Beijing  China 《中国科学D辑(英文版)》2007,50(7):1097-1102

During a field campaign in April 2005,fresh-fallen snow samples were collected on the East Rongbuk Glacier of the Mt. Qomolangma at four altitudes (6500 m,6300 m,6100 m and 5900 m),to study the role of Mt. Qomolangma as "cold-traps" for Persistent Organic Pollutants. From these snow samples col-lected at the highest-altitude,organochlorine pesticides (OCPs):HCB,p,p′-DDT and p,p′-DDD were detected,with the concentrations in the ranges of 44―72 pg/L,401―1560 pg/L,and 20―80 pg/L,re-spectively. The concentration of o,p′-DDT was around the method detection limit. Analysis of backward trajectories showed that the detected compounds came from the north of India,suggesting that DDTs detected in the snow were possibly originated from new emissions in this area. Relationships between the concentrations of OCPs in snow samples and the sampling altitudes were discussed. The altitudes had no obvious effect on HCB concentrations in the fresh-fallen snow,while increases in the concen-trations of p,p′-DDT and p,p′-DDD with increasing altitude were found,which was reversed compared to the trends observed in North America. Three factors likely resulted in this trend: (1) the properties of the target compounds; (2) the low temperatures at high altitudes; and (3) the location of the mountain sampling sites relative to their sources.  相似文献   

Elastic model for the gravity and elevation changes before the 2001 eruption of Etna volcano     

Daniele Carbone  Gilda Currenti  Ciro Del Negro 《Bulletin of Volcanology》2007,69(5):553-562

For 5 months before the 2001 Mt. Etna eruption, a progressive gravity decrease was measured along a profile of stations on the southern slope of the volcano. Between January and July 2001, the amplitude of the change reached 80 μGal, while the wavelength of the anomaly was of the order of 15 km. Elevation changes observed through GPS measurements during a period encompassing the 5-month gravity decrease, remained within 4–6 cm over the entire volcano and within 2–4 cm in the zone covered by the microgravity profile. We review both gravity and elevation changes by a model assuming the formation of new cracks, uniformly distributed in a rectangular prism. The inversion problem was formulated following a global optimization approach based on the use of Genetic Algorithms. Although it is possible to explain the observed gravity changes by means of the proposed analytical formulation, the results show that calculated elevation changes are significantly higher than those observed. Two alternative hypotheses are proposed to account for this apparent discrepancy: (1) that the assumptions behind the analytical formulation, used to invert the data, are fallacious at Etna, and thus, numerical models should be utilized; (2) that a second process, enabling a considerable mass decrease to occur without deformation, acted together with the formation of new cracks in the source volume.  相似文献   

Rock fracture as a precursor to lava dome eruptions at Mount St Helens from June 1980 to October 1986     

R. Smith  C. R. J. Kilburn  P. R. Sammonds 《Bulletin of Volcanology》2007,69(6):681-693

Following its plinian eruption on 18 May 1980, Mount St Helens (Washington State, USA) entered a period of intermittent lava-dome extrusion until 1986. Renewed extrusion was frequently preceded by accelerating rates of seismicity, with more precursory seismicity observed prior to eruptions later in the sequence. Here the failure forecasting method (FFM) is used to investigate changes in the observed rate of volcano–tectonic (VT) seismicity. The analysis indicates that: (1) all VT crises resulted in an eruption within 3 weeks (usually less than 10 days), (2) the majority of eruptions had VT precursors, and (3) patterns of precursory seismicity showed fluctuations about the ideal model trend. Thus, although these seismic events could be used to warn of an impending eruption, specific forecasts were subject to an uncertainty of weeks or more. It is proposed that: (1) increased seismicity prior to later eruptions is a result of a larger and more solidified dome acting as a greater impediment to magma ascent; (2) the consistency of seismic swarms resulting in an eruption indicates that stresses high enough to initiate fracturing in the country rock and lava dome carapace were only achieved once the approach to an eruption had already begun; and (3) discrepancies between models of accelerating rock fracture and the observed seismicity may arise due to a significant amount of the rocks deforming through ductile mechanisms rather than seismogenic fracture.  相似文献   

Reliability of NCEP/NCAR reanalysis data in the Himalayas/Tibetan Plateau     

XIE Aihong  REN Jiawen  QIN Xiang  KANG Shichang 《地理学报》2007,17(4):421-430

Due to the difficult logistics in the extreme high elevation regions over the Himala-yas and Tibetan Plateau, the observational meteorological data are very few. In 2003, an automatic weather station was deployed at the northeastern saddle of Mt. Nyainqentanglha (NQ) (30°24′44.3″ N, 90°34′13.1″ E, 5850 m a.s.l.), the southern Tibetan Plateau. In 2005, another station was operated at the East Rongbuk Glacier Col (28°01′0.95″ N, 86°57′48.4″ E, 6523 m a.s.l.) of Mt. Qomolangma. Observational data from the two sites have been com-pared with the reanalysis data from the National Centers for Environmental Predic-tion/National Center for Atmospheric Research (NCEP/NCAR), reliability of NCEP/NCAR reanalysis data has been investigated in the Himalayas/Tibetan Plateau region. The reanaly-sis data can capture much of the synoptic-scale variability in temperature and pressure, al-though the reanalysis values are systematically lower than the observation. Furthermore, most of the variability magnitude is, to some degree, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one day ahead of the observational data on Mt. Qomolangma, while on Mt. NQ it occurs basically in the same day.  相似文献   

川西老君沟和孟通沟花岗岩的地球化学特征、成因机制及对松潘-甘孜地体基底性质的制约   总被引：5，自引：5，他引：5  

赵永久 袁超周美夫  颜丹平龙晓平 李继亮 《岩石学报》2007,23(5):995-1006

老君沟岩体和孟通沟岩体是位于松潘-甘孜地体东部的中生代花岗岩,为碰撞过程中岩浆作用的产物,包含有地壳基底性质的重要信息。两岩体具有中等至较高的SiO_2含量(63.9～75.0wt%),具有准铝质和轻微过铝质(ACNK=0.86～1. 08)特征,属于中钾到高钾钙碱性系列。其中,老君沟岩体富Al_2O_3(14.2～16.0wt%)、K_2O(2.88～4.36wt%),贫MgO(0.38～1.98wt%),并具有高Sr(307～697ppm)低Y(12.2～21.0ppm)特征以及中等至较高的稀土分馏((La/Yb)_N>10),这些特征非常类似于下地壳熔融形成的埃达克岩。孟通沟岩体的主微量元素特征类似于老君沟岩体,但具有相对低的Sr(110～397 ppm)、稍高的Y(12.2～21.0ppm)和明显较低的Sr/Y比值(5～32)。两岩体均具有地壳特征的Nd-Sr同位素组成(ε_(Nd)(T)= -6.02～-3.11;I_(Sr)=0.7053～0.7075),排除了直接来自地幔岩浆的可能性,表明其可能来自于石榴石稳定区地壳物质的部分熔融。两岩体富含Rb(106～202ppm)、Cs(3.79～25.6ppm)而K_2O/Na_2O(0.56～1.12)比值较高,显示其可能来自黑云母的脱水熔融。由于黑云母的脱水熔融温度较高而剪切生热所能达致的温度较低,同造山的滑脱构造难以导致上述两个岩体的形成,地幔岩浆的底侵作用可能是导致下地壳物质部分熔融的主要原因。两岩体的源区成分和Nd模式年龄(T_(DM(Ⅱ))=1.23～1.44 Ga)均反映松潘-甘孜地体具有类似于扬子板块的中元古陆壳基底。  相似文献   

浙江古田山自然保护区常绿阔叶林群落特征   总被引：1，自引：0，他引：1  

胡正华  于明坚  方腾  丁炳扬  钱海源 《南京气象学院学报》2003,26(1):63-69

在对古田山自然保护区森林植被广泛调查的基础上，详细分析了常绿阔叶林群落特征，从该区森林植被的外貌特征、群落结构和种类组成上看，均具有我国典型亚热带常绿阔叶林的基本性质。  相似文献   

ALEXANDER THE GREAT'S MOUNTAIN*     

VERONICA DELLA DORA 《Geographical review》2005,95(4):489-516

ABSTRACT. The metaphorical power of natural landscapes and geographical objects has attracted an increasing amount of critical interest. The myth of Dinocrates planning to carve Mount Athos into the figure of Alexander the Great epitomizes the complex relationship between the insistent materiality of prominent geographical features such as mountains and imagination. Through an iconographic reading of different renderings of the Dinocratic myth in western Europe, this article explores the way Mount Athos turned into a powerful emblem circulating across space and time. While considering the continuity of a Classical vision projected on rock, the article focuses on its constant reappropriations and transformations in different historical and geographical contexts. Dinocratic Athos becomes a metaphor of egotism, power, and desire but also a free‐floating referent, reflecting a shifting relationship between the microcosm of the human body and the natural macrocosm.  相似文献   

A Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon, usa     

Michael A O'Neal  Katherine R Schoenenberger 《Quaternary Research》2003,60(2):233-241

Lichen thallus measurements from 22 surfaces of known age on Mount Baker, Mount Hood, and Mount Rainier are used to construct a regional Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon. Growth rates determined by measuring the largest thallus diameters on the same surfaces at Mount Rainier in 1976 and 2002 are used for comparison with lichenometric data from Mount Baker and Mount Hood. Similar lichen thallus diameter vs age relationships identified in the data from the three mountains suggest the presence of uniform growth rates over the 400-km range. A regional growth curve developed during our study shows three growth phases of successively slower growth: a rapid phase from 8 to 20 yr, a linear phase from 20 to 145 yr, and a slow phase of unknown duration beyond ca. 145 yr. Uncertainty in lichen growth rates beyond 145 yr limits projection of the curve beyond that age; however, the age range of the constrained growth curve covers an important period of recent climate variability. When applied in appropriate settings, our growth curve can be used to determine numeric ages to ±10 yr for surfaces between 20 and 145 years old in areas where other techniques are not applicable or do not provide unique or well-constrained ages.  相似文献   

Reserve Growth in Oil Fields of West Siberian Basin, Russia     

Mahendra K. Verma  Gregory F. Ulmishek 《Natural Resources Research》2003,12(2):105-119

Although reserve (or field) growth has proved to be an important contributing factor in adding new reserves in mature petroleum basins, it is a poorly understood phenomenon. Although several papers have been published on the U.S. fields, there are only a few publications on fields in other petroleum provinces. This paper explores the reserve growth in the 42 largest West Siberian oil fields that contain about 55% of the basin's total oil reserves.The West Siberian oil fields show 13-fold reserve growth 20 years after the discovery year and only about 2-fold growth after the first production year. This difference in growth is attributed to extensive exploration and field delineation activities between discovery and the first production year. Because of the uncertainty in the length of evaluation time and in reported reserves during this initial period, reserve growth based on the first production year is more reliable for model development. However, reserve growth models based both on discovery year and first production year show rapid growth in the first few years and slower growth in the following years. In contrast, the reserve growth patterns for the conterminous United States and offshore Gulf of Mexico show a steady reserve increase throughout the productive lives of the fields. The different reserve booking requirements and the lack of capital investment for improved reservoir management and production technologies in West Siberia are the probable causes for the difference in the growth patterns.The models based on the first production year predict that the reserve growth potential in the 42 largest oil fields of West Siberia for a five-year period (1998–2003) ranges from 270–330 million barrels or 0.34–0.42% per year. For a similar five-year period (1996–2001), models for the conterminous United States predict a growth of 0.54–0.75% per year.  相似文献