International Association of Geomorphologists Newsletter No. 18 (3/2001)     

Paul Williams  Selma Simes De Castro  Janet Hooke  Wang Ying  Vít Vilímek  Karl‐Heinz Schmidt  Anto Raukas  Tsuguo Sunamura  Algimantas Cesnulevicios  Irasema Alcntara‐Ayala  James P. Terry  Milos Stankoviansky  Carol P. Harden 《地球表面变化过程与地形》2001,26(12):1353-1360

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远源沙尘暴对城市生态环境影响的初步研究     

胡克  吴东辉  杨德明  杨吉龙  陈姗 《吉林大学学报(地球科学版)》2001,31(2):176-179

200 0年 4月 5日～ 7日袭击我国西北地区北部、华北、东北南部、黄淮地区的扬沙或沙尘暴波及到长春市 ,带来了大量的降尘。据长春市西部 4个采样点测定 ,4月 7日伴随降雪的降尘量最高可达 13.0 g/m2 ,市区总降尘量超过 30 0 0t。泥雪样品在室温条件下自然融化后 ,经实验室 48h细菌培养 ,其细菌含量为每毫升 8.9～ 10 .5万个 ,每平方米泥雪的细菌侵入量达 6 .4亿个左右。扬沙或沙尘暴对城市造成了巨大的环境危害 ,而伴随着大量微生物的侵入 ,势必引起城市微生态环境的改变 ,威胁到城市的生态安全。  相似文献   

正热电离质谱同时测定硝酸盐中氮和氧同位素组成   总被引：2，自引：0，他引：2       下载免费PDF全文

尹德忠  肖应凯  逯海 《盐湖研究》2001,9(3):17-22

初步研究了一种硝酸盐中氮和氧同位素质谱测定的新方法。该法利用石墨的非还原热离子发射特性 ,建立了以测定 Cs2 NO2 + 离子的正热电离质谱测定硝酸盐中氮和氧同位素组成的过程 ,对方法的可行性、特点和存在的问题进行了讨论 ,并对几种测定氮和氧同位素的方法进行了比较。运用正热电离质谱法对几种不同厂家生产的硝酸盐试剂的氮和氧同位素组成进行了测定 ,发现氮和氧同位素组成存在较大的差异  相似文献   

Debris flow and slide deposits at the top of the Internal Liguride ophiolitic sequence, Northern Apennines, Italy: A record of frontal tectonic erosion in a fossil accretionary wedge     

Michele Marroni  Luca Pandolfi 《Island Arc》2001,10(1):9-21

Abstract In the Northern Apennines, the Internal Liguride units are characterized by an ophiolite sequence that represents the stratigraphic base of a late Jurassic–early Paleocene sedimentary cover. The Bocco Shale represents the youngest deposit recognized in the sedimentary cover of the ophiolite and can be subdivided into two different groups of deep sea sediments. The first group is represented by slide, debris flow and high density turbidity current-derived deposits, whereas the second group consists of thin-bedded turbidites. Facies analysis and provenance studies indicate, for the former group, small and scarcely evoluted flows that rework an oceanic lithosphere and its sedimentary cover. We interpret the Bocco Shale as an ancient example of a deposit related to the frontal tectonic erosion of the accretionary wedge slope. The frontal tectonic erosion resulted in a large removal of materials, from the accretionary wedge front, that was reworked as debris flows and slide deposits sedimented on the lower plate above the trench deposits. The frontal tectonic erosion was probably connected with subduction of oceanic crust characterized by positive topographic relief. This interpretation can be also applied for the origin of analogous deposits of Western Alps and Corsica.  相似文献   

Caracas, Venezuela, Site Effect Determination with Microtremors   总被引：1，自引：0，他引：1  

A.-M. Duval  S. Vidal  J.-P. Méneroud  A. Singer  F. De Santis  C. Ramos  G. Romero  R. Rodriguez  A. Pernia  N. Reyes  C. Griman 《Pure and Applied Geophysics》2001,158(12):2513-2523

—?Caracas 1967 earthquake caused heavy damage to multi-story buildings. In 1995, 184 microtremor measurement points were performed over the city. The measurement grid was more or less dense and covered the main part of the alluvial basin as well as surrounding rock basement. For each point, the horizontal record spectrum was divided by the vertical one (H/V ratio). Subsequently, the strongest value (Ao) of this ratio in a given frequency band was kept, as well as the frequency (Fo) where it occurred. Spatial interpolations of Ao and Fo were performed among all points of Palos Grandes district. A map was plotted representing a single surface where Ao is relief and Fo is represented by grey gradation. An alluvion thickness (H) map can be compared with this result. Damaged buildings are located on the same map. Fo decreases until 0.6?Hz when alluvion thickness (H) increases. Fo values fit with frequencies previously predicted from computation and with 1967 earthquake observations. Moreover, interpolation surfaces show that amplification (Ao) of H/V on microtremor is quite low above rock but is high on the south part of the basin. The maximum occurs over the non-urbanized zone. However the other area, where Ao is higher than 5, roughly corresponds to the location of the four collapsed buildings. Furthermore, the estimated natural frequency of these buildings was around Fo. Graphics showing H, Fo and Ao evolution through the basin were composed. Links between all these values are noticeable. Fo is claimed to be very similar to the resonance frequency of soil. As for Ao, it could be a fairly relevant sign of damage seriousness. Microtremor technique is an economic tool and it allows measurement grid as dense as desired. H/V ratio processing followed by interpolation of maximum values provides precise and useful information about expected site effect.  相似文献   

Heterogeneous enriched mantle materials and dupal-type magmatism along the SW margin of the São Francisco craton, Brazil     

L. a. Bizzi  M. J. De Wit  C. B. Smith  I. Mcdonald  R.A. Armstrong   《Journal of Geodynamics》1995,20(4)

The nature and restricted range of Dupal-type Sr, Nd and Pb isotopic compositions of Cretaceous kimberlites, tuffaceous diatremes of kamafugitic affinity and carbonatite complexes which intrude the southwestern São Francisco craton margin in Brazil, indicate that these magmas either interacted extensively with, or were derived from, a light rare earth element (LREE) enriched homogeneous lithospheric mantle source isotopically similar to the “enriched mantle I” (EMI) component. The shallow-derived alkalic rocks contain a greater proportion of this EMI-like component, whereas the lower time-averaged Rb/Sr, Nd/Sm and Pb/U ratios of the kimberlites compared to the other rock types suggest mixing of the EMI-like mantle material with variable amounts of mantle with a high ²³⁸U/²⁰⁴Pb (HIMU-like) component. Systematic variations in rock types and geochemistry on a regional scale are believed to be indicative of vertical geochemical heterogeneities which are translated into lateral heterogeneities by different depths of melting. It is proposed that HIMU- and EMI-like signatures in particular, are concentrated in laterally extensive but vertically distinctive portions of the mantle beneath the São Francisco craton. The EMI-type signatures appear to be restricted to shallow-derived volcanism, whereas the HIMU-type signatures may originate from a source that started melting deeper in the mantle. The Nd signatures of the EMI-type volcanics follow the evolution path defined by the NeoProterozoic crustal sequences which overlie and flank the craton margin. This suggests that the source of the EMI-type mantle signatures might be related to the tectono-thermal processes which led to the formation and evolution of such crustal sequences. The isotopic similarity of the sources of the studied rocks and of the high-Ti basalts of the northern Paraná basin to those of some Ocean Island Basalts with Dupal signatures in the South Atlantic (viz. in Walvis Ridge) is ascribed to processes by which continental lithosphere became firstly delaminated, and then contaminated a zone of South Atlantic asthenosphere from which hotspot islands have been erupting.  相似文献   

Retrogressive hydration of calc-silicate xenoliths in the eastern Bushveld complex: evidence for late magmatic fluid movement     

T. Wallmach  C.J. Hatton  S.A. De Waal  R.L. Gibson 《Journal of African Earth Sciences》1995,21(4)

Two calc-silicate xenoliths in the Upper Zone of the Bushveld complex contain mineral assemblages which permit delineation of the metamorphic path followed after incorporation of the xenoliths into the magma. Peak metamorphism in these xenoliths occurred at T=1100–1200°C and P <1.5 kbar. Retrograde metamorphism, probably coinciding with the late magmatic stage, is characterized by the breakdown of akermanite to monticellite and wollastonite at 700°C and the growth of vesuvianite from melilite. The latter implies that water-rich fluids (X_CO2 <0.2) were present and probably circulating through the cooling magmatic pile. In contrast, calc-silicate xenoliths within the lower zones of the Bushveld complex, namely in the Marginal and Critical Zones, also contain melilite, monticellite and additional periclase with only rare development of vesuvianite. This suggests that the Upper Zone cumulate pile was much ‘wetter’ in the late-magmatic stage than the earlier-formed Critical and Marginal Zone cumulate piles.  相似文献   

Results Of An Artificial Recharge Test And A Double Pumping Test As Preliminary Studies For Optimizing Water Supply In The Western Belgian Coastal Plain     

L. Lebbe  J. Tarhouni  E. Van Houtte  W. De Breuck 《Hydrogeology Journal》1995,3(3):53-63

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RESUMEN: En la planicie costera occidental de Bélgica, la mayor parte de la demanda de agua se abastece mediante captaciones en lentejones de agua dulce, bajo el cordón de dunas. Debido a la sobreexplotación, especialmente durante el verano, las captaciones están amenazadas por intrusiones de agua salada. Existe la posibilidad de utilizar recarga artificial, ya que en invierno una gran cantidad de agua dulce superficial se vierte al mar. Se presenta una propuesta para mejorar la gestión del agua en dicha región. Los estudios preliminares han consistido en dos ensayos: uno de recarga artificial en la zona de las dunas, y uno de doble bombeo en un cordón arenoso cerca de un canal de drenaje en la zona pantanosa de la planicie costera. La interpretación de los ensayos se realizó mediante modelación inversa. Los resultados del ensayo de recarga artificial han demonstrado la posibilidad de usar recarga artificial en la zona de captación de Koksijde. El ensayo de doble bombeo ha demonstrado que el cordón arenoso de Avekapelle, situado en la zona pantanosa, se puede utilizar como zona de captación.

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RéSUMé: Dans la partie occidentale de la plaine c?tière belge, la demande en eau est pour la plupart satisfaite par des captages d'eau souterraine. Les puits captent l'eau d'une lentille d'eau douce sous le cordon dunaire. Par suite d'une surexploitation, surtout pendant l'été, ces captages d'eau sont menacés par une intrusion d'eau salé. La recharge artificielle de la nappe peut être envisagée parce que, pendant l'hiver, de grandes quantités d'eau douce sont évacuées vers la mer. Une amélioration de la gestion de la ressource en eau est donc proposée. Deux essais ont été réalisés pour une étude préliminaire: un essai de recharge artificielle dans la région des dunes et un essai de double pompage prés d'un canal de drainage dans les polders. Ces deux essais ont été interprétés grace à une méthode inverse. L'essai de recharge artificielle a démontré les possibilités de recharge de la nappe pour le site de captage de Coxyde. L'essai de double pompage a montré que le d?me sableux d'Avekapelle, dans les polders, est une région de recharge qui convient.

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Über die Installation einer Apparatur für die Analyse des atmosphärischen Kohlensäuregehalts     

Walter Bischof  Arturo De Maio 《Pure and Applied Geophysics》1964,58(1):204-207

Zusammenfassung Die im vorläufigen Bericht beschriebene Anlage für die Analyse von atmosphärischem CO₂-Gehalt wurde vervollständigt. Es können nunmehr kontinuierliche Analysen sowie Einzelanalysen mit Gaspipetten ausgeführt werden. Die Arbeitsweise wird beschrieben und einige Resultate werden mitgeteilt. Es kann mit einer Messgenauigkeit von ±0.3 ppm gerechnet werden.

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Summary The second and the third part of the installation of the equipment for measuring the CO₂ content in the atmospheric air has been accomplished. It is now possible to make continuous local air analysis, and of samples collected in pipettes. The procedure is described and a few results reported. The measurement accuracy lies to within ±0.3 ppm.

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Riassunto Sono state completate la seconda e la terza parte dell'apparecchiatura per la misura del CO₂ atmosferico. Esse permettono l'analisi continua dell'aria locale e l'analisi di campioni raccolti in pipette; di queste si riporta un esempio. La precisione della misura è di ±0.3 ppm.

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Meteorologisches Institut der Universität Stockholm. Contribution No. 164.  相似文献   

Educational Facilities in Ground-Water Hydrology and Geology Outside the U. S. A. and Canada, 1963     

Roger J. M. De  Wiest Member NWWA 《Ground water》1964,2(2):18-24

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