Microorganisms in Lianxian lateritic gold deposit in Guangdong and their effects on leaching of heavy metals     

陈炳辉刘琥琥  毋福海徐文烈 《中国地球化学学报》2005,24(2):144-148

Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudomonas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacteriura, Cotyttebacteriurn, and Moraxella, fungi such as Penicillium, Alter naria, Cladosporium, Saccharcornyces, Mucor, and the chemoautotrophic Thiobacillu.~. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G^ bacteria are better for leaching Cd.  相似文献   

DEFORESTATION IN NORTHEAST THAILAND, 1975–91: RESULTS OF A GENERAL STATISTICAL MODEL     

Gadsaraporn Wannitikul 《Singapore journal of tropical geography》2005,26(1):102-118

Using a general statistical model, this study attempts to characterise the trend of deforestation in the northeast region (Isan) of Thailand between 1975 and 1991, a period when the kingdom had sustained high rates of economic growth and steady increases in population. Using data obtained directly from government bodies on the 17 provinces comprising this heavily deforested region, the study examines the correlations between forest area and a set of six variables: population density, agricultural area, real per capita income, accumulated irrigated area, agricultural credit levels, and distance from Bangkok, the national political and economic centre. It also considers the effect of the two logging bans instituted in 1979 and since 1989. The study found a negative correlation between forest area and population density in particular, followed in ranking by agricultural credit, per capita income, the logging bans and distance from Bangkok. Viewed together with more recent data showing that rates of deforestation in the kingdom as a whole have slowed and appear to be stabilising, these results also suggest the beginnings in the 1990s of a forest transition – from an industrial to a post‐industrial stage in forest utilisation – in Thailand.  相似文献   

SEDIMENT TRANSPORT, DELTA GROWTH AND SEDIMENTATION IN LAKE NIGARDSVATN, NORWAY     

GUNNAR ØSTREM  NILS HAAKENSEN  HANS CHR. OLSEN 《Geografiska Annaler: Series A, Physical Geography》2005,87(1):243-258

ABSTRACT. The retreat of Nigardsbreen, an outlet glacier from the ice-cap Jostedalsbreen in south-central Norway, from its largest extent during the Little Ice Age, uncovered a proglacial lake during 1936–1967. This lake, Nigardsvatn, has been studied since 1968 in order to obtain data on solid material carried by the meltwater stream from the glacier, both in suspension and as bottom load. Between 70 and 85% of the suspended sediment has been deposited on the lake bottom, forming annual varves. The coarse material has been deposited in a delta, the formation of which started in 1968. Its growth, and hence the volume of total annual bottom load, has been surveyed annually for the past 36 years. In 1969 the entire bottom load was collected by building a fence-like net across the river. Material >3 cm was caught by this net, and formed approximately half the amount of suspended sediment transport during the same three-week period. Annual average deposition on the delta was 11800×10³ kg for the period 1968–2003. This is almost the same amount as carried in suspension from the glacier on an annual mean basis for the 36-year period. If conditions remain constant, the lake will be completely filled in about 500 years. The glacier erosion is calculated to be 0.3 mm/a.  相似文献   

The seismic structure of the Saurashtra crust in northwest India and its relationship with the Réunion Plume     

G. Surya Prakasa Rao  H. C. Tewari 《Geophysical Journal International》2005,160(1):319-331

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Near-surface seismic anisotropy, attenuation and dispersion in the aftershock region of the 1999 Chi-Chi earthquake   总被引：1，自引：0，他引：1  

Yunfeng Liu  Ta-Liang Teng  Yehuda Ben-Zion 《Geophysical Journal International》2005,160(2):695-706

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The crustal structure of central East Greenland—I: From the Caledonian orogen to the Tertiary igneous province     

Mechita C. Schmidt-Aursch  Wilfried Jokat 《Geophysical Journal International》2005,160(2):736-752

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A large landslide on the urban fringe of metropolitan Phoenix, Arizona   总被引：2，自引：1，他引：2  

John Douglass  Ronald I. Dorn  Brian Gootee 《Geomorphology》2005,65(3-4):321-336

A granitic rock avalanche, one of the largest Quaternary landslides in Arizona outside the Grand Canyon with a volume of approximately 5.25 M m³ and a width a little under 0.5 km, ran 1 km from the eastern McDowell Mountains. With lateral levees and pressure ridges, the rock avalanche deposit displays many features found on classic sturzstroms. Failure occurred along a major joint plane paralleling the slope with a dip of 44°, when a major base level lowering event in the Salt River system would have undermined the base of the failed slope, and probably during a period of more moisture than normally available in the present-day arid climate. Failure at the subsurface weathering front highlights the importance of the dramatic permeability change between grussified regolith and relatively fresh bedrock. Rock varnish microlaminations (VMLs) dating, in concert with other geomorphic evidence, suggests that the rock avalanche deposit is slightly older than 500 ka. The rock vanish results also have important implications for sampling strategies designed to use cosmogenic nuclide to date Quaternary landslide deposits. Discovery of a large landslide in close proximity to the extending urban fringe of metropolitan Phoenix argues for a more careful analysis of landslide hazards in the region, especially where rapid development excavates bedrock at the base of steep mountain slopes and where the subsurface weathering front is near the surface.  相似文献   

Temporal and spatial cyclicity of accretion at slow-spreading ridges—evidence from the Reykjanes Ridge     

Christine Peirce  Alex Gardiner  Martin Sinha 《Geophysical Journal International》2005,163(1):56-78

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Growth patterns and implications of complex dendrites in calcite travertines from Lýsuhóll, Snæfellsnes, Iceland     

BRIAN JONES  ROBIN W. RENAUT†  R. BERNHART OWEN‡  HELGI TORFASON§ 《Sedimentology》2005,52(6):1277-1301

Calcite dendrite crystals are important but poorly understood components of calcite travertine that forms around many hot springs. The Lýsuhóll hot-spring deposits, located in western Iceland, are formed primarily of siliceous sinters that were precipitated around numerous springs that are now inactive. Calcite travertine formed around the vent and on the discharge apron of one of the springs at the northern edge of the area. The travertine is formed largely of two types (I and II) of complex calcite dendrite crystals, up to 1 cm high, that grew through the gradual addition of trilete sub-crystals. The morphology of the dendrite crystals was controlled by flow direction and the competition for growth space with neighbouring crystals. Densely crowded dendrites with limited branching characterize the rimstone dams whereas widely spaced dendrites with open branching are found in the pools. Many dendrite bushes in the pools nucleated around plant stems. Growth of the dendrite crystals was seasonal and incremental. Calcite precipitation was driven by rapid CO₂ degassing of CO₂-rich spring waters during the spring and summer. During winter, when snow covered the ground and temperatures were low, opal-A precipitated on the exposed surfaces of the dendrites. Segmentation of dendrite branches by discontinuities coated with opal-A and overgrowth development around sub-crystals resulted from this seasonal growth cycle. The calcite dendrite crystals in the Lýsuhóll travertine differ in morphology from those at other hot springs, such as those at Lake Bogoria, Kenya, and Waikite in New Zealand. Comparison with the calcite dendrite crystals found at those sites shows that dendrite morphology is site-specific and probably controlled by carbonate saturation levels that, in turn, are controlled by the rate of CO₂ degassing and location in the spring outflow system.  相似文献   

上扬子地壳区域性地层岩石物性力学参数与滑动层位关系研究   总被引：5，自引：2，他引：5       下载免费PDF全文

孙岩  刘德良  朱文斌  郭继春  李本亮  郭建  王锋  赵忠岩 《地质科学》2005,40(4):532-538

在中下扬子地区地壳区域性滑动层位岩石物性力学参数研究的基础上,对上扬子地区地壳的相应岩层进行了系统的定量测试。其滑动层位各种参量在塑性、韧性和粘性上所表现出特征的规律,在我国南方型数字地层中,具有一定的普遍性和可比性。同时,也揭示了地壳的构造分层性,并可作为上扬子板块浅层地质—地球物理特征分析的重要依据和建库信息。  相似文献