Gully erosion in mountain areas: processes,measurement, modelling and regionalization     

John Wainwright  Nicolle Mathys  Michel Esteves 《地球表面变化过程与地形》2006,31(2):133-134

  相似文献   

Development and Application of Oxygen and Carbon Isotopic Measurements of Biogenic Carbonates by Ion Microprobe   总被引：1，自引：0，他引：1  

Claire Rollion-Bard  Denis Mangin  Michel Champenois 《Geostandards and Geoanalytical Research》2007,31(1):39-50

The analytical capabilities of the ims 1270 ion microprobe (SIMS) in determining O and C isotope compositions in biogenic carbonate samples have been tested. Results indicated that, with a spot size of ≊ 30 μm, the average reproducibility at the 1s level was 0.3‰ for oxygen isotopes and 0.6‰ for carbon isotopes. Nevertheless, this reproducibility can reach 0.2‰ for oxygen isotope determinations during some sessions. These reproducibilities allowed us to perform analyses on biogenic carbonate samples for environmental studies. In this paper, examples of oxygen and carbon isotope measurements are presented for a modern coral and the Holocene scleractinian coral, Porites lutea.  相似文献   

Multiscale tomography of buried magnetic structures: its use in the localization and characterization of archaeological structures     

Ginette Saracco  Frédérique Moreau  Pierre-Etienne Mathé  Daniel Hermitte  Jean-Marie Michel 《Geophysical Journal International》2007,171(1):87-103

We have previously developed a method for characterizing and localizing 'homogeneous' buried sources, from the measure of potential anomalies at a fixed height above ground (magnetic, electric and gravity). This method is based on potential theory and uses the properties of the Poisson kernel (real by definition) and the continuous wavelet theory. Here, we relax the assumption on sources and introduce a method that we call the 'multiscale tomography'. Our approach is based on the harmonic extension of the observed magnetic field to produce a complex source by use of a complex Poisson kernel solution of the Laplace equation for complex potential field. A phase and modulus are defined. We show that the phase provides additional information on the total magnetic inclination and the structure of sources, while the modulus allows us to characterize its spatial location, depth and 'effective degree'. This method is compared to the 'complex dipolar tomography', extension of the Patella method that we previously developed. We applied both methods and a classical electrical resistivity tomography to detect and localize buried archaeological structures like antique ovens from magnetic measurements on the Fox-Amphoux site (France). The estimates are then compared with the results of excavations.  相似文献   

Method of leakage study at the karst dam site. A case study: Khersan 3 Dam,Iran   总被引：1，自引：0，他引：1  

Zargham Mohammadi  Ezzatollah Raeisi  Michel Bakalowicz 《Environmental Geology》2007,52(6):1053-1065

The excellent topographic condition of the limestone canyons for dam construction may be rejected if they are karstified. Karst features cause the reservoir not to be impermeable enough to permit the water to fill it and leakage occurs and often increases with time. Moreover, karst features may involve the stability of the dam itself. A few operated dam sites at the Zagros Zone encountered a leakage problem. Furthermore, more than 30 dams are presently under study for construction in the Zagros Zone. Karst conditions and leakage potential were investigated at an under-study site (Khersan 3 Dam) for assessing the general methodology for the study of leakage potentials. Conventional methods for studying karst features, geological mapping, geomorphology and extensive borings were applied before the dam was constructed. These methods are not efficient enough to precisely reveal the karst structure, especially hidden and paleokarst, nor the hydrological behaviour of the karst structure in different settings of groundwater flow. Based on the present case study and previous applied approaches by other authors, this paper introduces a methodology by means of karst structure and functioning approaches at local and regional scales that cover the conventional methods and overcome their shortages. The proposed methodology should be applied before construction of a dam and should include three steps (a) recognition of geological and hydrogeological settings, (b) delineation and functioning of the karst system related to the future reservoir, and (c) assessment of the leakage potentials. Following this methodology, the most probable leakage zone(s) and path(s) at the dam site can be highlighted.  相似文献   

Sulphur behaviour in forest soils near the largest SO₂ emitter in northern Europe     

Galina Koptsik  Christine Alewell 《Applied Geochemistry》2007

The impact of 60 a of SO₂ emissions from a Ni–Cu plant in the Kola Peninsula (Russia) on soil S contents was assessed in podzols under pine forests. Sulphate desorption and the possible delay of acidification reversal was investigated, because the plant will be reconstructed in 2006 with an expected emission reduction of 90%. Sites were sampled along a pollution gradient in the prevailing wind direction from 1 to 66 km. The investigated podzols stored S mostly in the organic form. The concentrations of total and organic S in soil organic horizons tended to be higher near the smelter but were only weakly correlated with S deposition. No relationship between distance to smelter and S contents was found for the mineral horizons. Sulphate content and desorption behavior were highly variable due to natural variations of texture and extractable Al and Fe contents of the soils. The lack of a clear strong trend with distance from the smelter except in the organic layer indicated that long range transport and diffuse input of SO₄ played a major role rather than point source impact. It was concluded that biological turnover is most likely the regulating process in these soils and thus low to medium release of SO₄ is expected under decreasing deposition scenarios because organic S was the dominant fraction of total S in all soils.  相似文献   

Complete Coulomb stress changes induced by the Ms7.6 earthquake in Lancang-Gengma,Yunnan and triggering of aftershocks by dynamic and static stress     

Wu XiaoPing  Hu XiongLin  Michel Bouchon  Huang Yong  Hu JiaFu  Xie ChaoDi  Wang ShaoJin  Hu YiLi 《中国科学D辑(英文版)》2007,50(11):1655-1662

The spatiotemporal evolution patterns of complete Coulomb stress changes caused by 1988 Ms7.6 earthquake in Lancang-Gengma,Yunnan,are calculated and studied.And the triggering problems of Ms7.2 Gengma shock occurring 13 minutes after the main shock and of Ms5.0―6.9 aftershocks within 24 days after the main shock are discussed.The results show that the spatial distribution patterns of complete Coulomb stress changes of the Ms7.6 main shock are strongly asymmetric.The areas of positive dynamic and static Coulomb stress are both coincident well with the strong aftershocks' locations.The Ms7.2 Gengma shock and most of strong aftershocks are subjected to the triggering effect of dynamic and static Coulomb stresses induced by the Ms7.6 Lancang earthquake.  相似文献   

Hydrodynamics in the Gulf of Aigues-Mortes,NW Mediterranean Sea: In situ and modelling data     

Yann Leredde  Cléa Denamiel  Elena Brambilla  Christine Lauer-Leredde  Frédéric Bouchette  Patrick Marsaleix 《Continental Shelf Research》2007

The Gulf of Aigues-Mortes (NW Mediterranean Sea) is a midshelf zone whose scale is an intermediate between the nearshore scale (0–10 m depth) and the coastal scale (including the whole continental shelf). Its hydrodynamics is investigated for the first time. ADCP, CTD and thermosalinograph data were collected during three short cruises (HYGAM; March 6–7, 20–21, April 5–6, 2005). They were scheduled approximately every 15 days to sample the gulf circulation under different weather conditions. Moreover, the cruise data were used to validate the Symphonie model, a 3D primitive equations circulation model. The circulation features displayed by in situ data were well reproduced by Symphonie. A downscaling modelling approach was implemented, the largest scale being obtained by the replay of the MFSTEP regional model of the North-Western Mediterranean Sea.  相似文献   

Evaluation of streambed hydraulic conductivity heterogeneity in an urban watershed   总被引：3，自引：0，他引：3  

Robert J. Ryan  Michel C. Boufadel 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):309-316

It has long been understood that streambed hydraulic conductivity plays an important role in surface-subsurface solute exchange. Using a portable falling head permeameter in situ, we estimated the horizontal hydraulic conductivity, K, of the near-surface streambed sediments at a total of 85 locations encompassing two depth intervals: 7.5–10 and 10–12.5 cm. The measurements were conducted in an 80 m reach of Indian Creek, a small urban stream in Philadelphia, PA, USA. We found that the ln K data within each sediment layer were Gaussian, but the combined data set was not. The results indicated that while the mean hydraulic conductivity decreased with depth, horizontal heterogeneity (e.g. the variance) increased with depth. This strong contrast between layers suggests that they should be treated as separated entities in modeling studies. Variogram analyses across the stream suggested symmetry with respect to the thalweg in the upper layer and fractality in the lower layer. The variograms along the streams suggested that the K data are random.  相似文献   

Fishing for facts on the environmental effects of trawling and dredge fisheries: Reply to L?kkeborg.     

John S Gray  Paul Dayton  Simon Thrush  Michel J Kaiser 《Marine pollution bulletin》2007,54(4):497-500

  相似文献   

The oceanic substratum of Northern Luzon: Evidence from xenoliths within Monglo adakite (the Philippines)   总被引：2，自引：0，他引：2  

Betchaida D.  Payot  Sebastien  Jego  Rene C.  Maury  Mireille  Polve  Michel  Gregoire  Georges  Ceuleneer  Rodolfo A.  Tamayo Jr  Graciano P.  Yumul Jr  Herve  Bellon  Joseph  Cotten 《Island Arc》2007,16(2):276-290

Abstract   A 8.65 Ma adakitic intrusive sheet exposed near Monglo village in the Baguio District of Northern Luzon contains a suite of ultramafic and mafic xenoliths including in order of abundance: spinel dunites showing typical mantle-related textures, mineral and bulk rock compositions, and serpentinites derived from them; amphibole-rich gabbros displaying incompatible element patterns similar to those of flat or moderately enriched back-arc basin basalt magmas; and amphibolites derived from metabasalts and/or metagabbros of identical affinity. A single quartz diorite xenolith carrying a similar subduction-related geochemical signature has also been sampled. One amphibolite xenolith provided a whole-rock K–Ar age of 115.6 Ma (Barremian). We attribute the origin of this suite to the sampling by ascending adakitic magmas of a Lower Cretaceous ophiolitic complex located at a depth within the 30–35 km thick Luzon crust. It could represent an equivalent of the Isabela-Aurora and Pugo-Lepanto ophiolitic massifs exposed in Northern Luzon.  相似文献