Application of remote sensing in the study of geomorphic processes and lanforms in piedmont zone of Darjeeling Sub-Himalaya     

M M Jana 《Journal of the Indian Society of Remote Sensing》2002,30(1-2):61-72

The piedmont zone, located between the foothills of Darjeeling Sub-Himalaya and the flat plains of North Bengal is elongated from west to east and its average height varies from 150 m in the north to 50 m in the south. Morphologically, the region is divided into three distinct physiographic units. Many large and small rivers originated from the Darjeeling Sub-Himalayas intersect it. Most of these rivers have their large catchment area in the mountainous tract. The study area has about 350 cm of annual rainfall and peak discharge in the rivers is very high during monsoon period. Rivers carry large amount of sediments, gravels, and pebbles both in suspension and traction and these materials are deposited in the foothills of the Sub-Himalaya as fan deposits and on the riverbeds making braided channels. Landforms in the study area are mainly complex and their origins are influenced by neotectonic and fluvial activities. Many rivers terraces, palaeo-channels, out wash plains, valley-fills and channel bars are formed in the region due to both erosion and depositional processes. These processes and modifications of landforms are still going on in the region.  相似文献   

Numerical Modelling of Time-Harmonic Seismic Wave Fields in Simple Structures by the Gaussian Beam Method. Part I.     

Konop&#;skov&#;  Jana  &#;erven&#;  Vlastislav 《Studia Geophysica et Geodaetica》2002,46(1):67-83

Gaussian beam summation method is used for numerical modelling of seismic wave fields in several simple types of models of media. Main attention is paid to the waves reflected from a plane interface, namely from the vicinity of a critical point. Comparison with exact solutions shows that the Gaussian beam summation method yields sufficiently accurate results even in the singular region of the critical point. By summation of Gaussian beams of waves reflected in the overcritical region even head waves are obtained. In the second part of this work, we shall investigate sensitivity of the results to various parameters, for example, to the initial width of a Gaussian beam, to the parameters of the summation of Gaussian beams, etc.  相似文献   

Records of organochlorine pesticides in soils and sediments on the southwest of Buenos Aires Province,Argentina     

Norma Tombesi  Karla Pozo  Andrés Arias  Mónica Alvarez  Petra Pribylova  Ondrej Audy  Jana Klánová 《Environmental Earth Sciences》2018,77(11):403

The present study fills a gap in the knowledge in regards to the occurrence of banned pesticides at both coastal and inland locations at the Southwest Buenos Aires region, Argentina. Superficial sediment and soil samples were collected from different sites along the Bahia Blanca Estuary and surrounding sites to assess the concentration levels and spatial distribution of 12 selected organochlorine pesticides (OCs); 13 spatial locations including inland and shore-coast were sampled to evaluate occurrence and concentration levels of hexachlorocyclohexanes α-HCH, β-HCH, δ-HCH, γ-HCH, dichlorodiphenyltrichloroethane and its degradation products (DDXs: p,p′-DDT, o,p′-DDT, p,p′-DDE, o,p′-DDE, p,p′-DDD, o,p′-DDD) and the polychlorobenzenes PeCB (pentachlorobenzene) and HCB (hexachlorobenzene). After cleaning and extractions steps, samples were analyzed by means of gas chromatography/mass spectrometry. ∑OCs (sum of all studied compounds) ranged between 0.206 and 1040 ng g^?1 dw (mean?=?82.4 and SD?=?277 ng g^?1 dw). Total HCHs (sum of α-HCH, β-HCH, γ-HCH and δ-HCH) ranged from 0.0858 to 0.876 ng g^?1 dw (mean?=?0.43 and SD?=?0.23 ng g^?1 dw), DDXs (sum of p,p′and o,p′ isomers) from 0.080 to 1040 ng g^?1 dw (mean?=?81.3 and SD?=?277 ng g^?1 dw). Lower concentrations were found for PeCB (mean?=?0.095 and SD 0.17 ng g^?1 dw) and HCB (mean?=?0.56 and SD 1.7 ng g^?1 dw). Principal component analysis (PCA) permitted the extraction of underlying information about common factors, providing an overview of the distribution of pesticides and allowing the characterization of sites in regards to the major pesticide signature.  相似文献   

<Superscript>10</Superscript>Be surface exposure dating of the last deglaciation in the Aare Valley,Switzerland     

Lorenz Wüthrich  Ezequiel Garcia Morabito  Jana Zech  Mareike Trauerstein  Heinz Veit  Christian Gnägi  Silke Merchel  Andreas Scharf  Georg Rugel  Marcus Christl  Roland Zech 《Swiss Journal of Geoscience》2018,111(1-2):295-303

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied ¹⁰Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.  相似文献   

Contribution of some ozone depleting substances (ODS) and greenhouse gases (GHGs) on total column ozone growth at Srinagar (34°N, 74.8°E), India     

P K Jana  D K Saha  D Sarkar 《Journal of Earth System Science》2013,122(1):239-252

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Sea-floor sediment distribution in the Gulf of Mexico   总被引：1，自引：0，他引：1  

William L. Balsam  Jana Payne Beeson   《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(12):1421-1444

Carbonate content, smear-slide analysis and diffuse reflectance spectrophotometry were utilized to determine modern sediment composition and distribution throughout the Gulf of Mexico. In all, 186 core top and grab samples distributed throughout the Gulf were analyzed. Reflectance spectra were taken from thick smear slides from the near ultraviolet, through the visible, and into the near infrared. The first derivatives of the percent reflectance data were subjected to factor analysis producing factors that grouped covarying first-derivative wavelengths. Factors were interpreted by comparison to first-derivative curves for known sediment components and minerals. Interpretation was aided by the mapping of both calcium carbonate content and smear-slide sediment classes. The most easily interpreted factor solution was produced by analyzing only the visible region of the spectrum and extracting seven factors which explained 98% of the cumulative variance. These factors, in order of their relative importance, are interpreted as (1) marl and calcareous clay, (2) glauconite, (3) kaolinite, (4) organic matter, (5) phosphorite, (6) hematite, and (7) goethite. Some factor maps are consistent with known sources of fluvial sediment input; for example, kaolinite is deposited off rivers draining the southeastern US. Other factor maps are related to the origin of the material in the factor, glauconite, for example, being confined to low sedimentation regions of the outer shelf. The most unusual observation concerns the distribution of hematite, which appears to be transported from the rivers of south Texas, primarily the Rio Grande, across the shelf then eastward downslope along the base of the Sigsbee Escarpment. This eastward transport seems to be explainable only by transport in bottom currents flowing along the base of the Sigsbee Escarpment.  相似文献   

Potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs) in a sensitive bedrock aquifer (Canada)     

Jana Levison  Kent Novakowski  Eric J. Reiner  Terry Kolic 《Hydrogeology Journal》2012,20(2):401-412

It is necessary to understand the presence, movement, and persistence of contaminants in aquifers to develop adequate groundwater protection plans. Fractured bedrock aquifers with thin overburden cover are very sensitive to contamination, and little is known about transport processes from the ground surface to depth in this setting. This study was undertaken to investigate the potential of groundwater contamination by polybrominated diphenyl ethers (PBDEs), which are flame retardants, in a natural fractured bedrock aquifer in Canada proven to be sensitive to contamination. PBDEs, which had not been previously measured in groundwater in detail, were detected in the study aquifer at concentrations greater than those observed in surface-water bodies. Potential sources include manure, septic tanks, and the atmosphere. From this scoping study, it is evident that additional surveys of PBDE concentrations in groundwater are warranted, especially in settings with high potential source concentrations coupled with sensitive aquifers.  相似文献   

Seismic activity in the Czech Republic in 2012     

Jan Zedník  Jana Pazdírková 《Studia Geophysica et Geodaetica》2014,58(2):342-348

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Chemical composition and evolution of tourmaline-supergroup minerals from the Sb hydrothermal veins in Rožňava area,Western Carpathians,Slovakia     

Bačík  Peter  Dikej  Jakub  Fridrichová  Jana  Miglierini  Marcel  Števko  Martin 《Mineralogy and Petrology》2017,111(4):609-624

Mineralogy and Petrology - Tourmaline-supergroup minerals are common gangue minerals in Sb-hydrothermal veins on Betliar – Straková, Čučma – Gabriela and...  相似文献   

Quantification of the Attenuation of Storm Surge Components by a Coastal Wetland of the US Mid Atlantic     

Anne-Eleonore Paquier  Jana Haddad  Seth Lawler  Celso M. Ferreira 《Estuaries and Coasts》2017,40(4):930-946

Coastal wetlands are receiving increased consideration as natural defenses for coastal communities from storm surge. However, there are gaps in storm surge measurements collected in marsh areas during extreme events as well as understanding of storm surge processes. The present study evaluates the importance and variation of different processes (i.e., wave, current, and water level dynamics with respect of the marsh topography and vegetation characteristics) involved in a storm surge over a marsh, assesses how these processes contribute to storm surge attenuation, and quantifies the storm surge attenuation in field conditions. During the Fall of 2015, morphology and vegetation surveys were conducted along a marsh transect in a coastal marsh located at the mouth of the Chesapeake Bay, mainly composed of Spartina alterniflora and Spartina patens. Hydrodynamic surveys were conducted during two storm events. Collected data included wave characteristics, current velocity and direction, and water levels. Data analysis focused on the understanding of the cross-shore evolution of waves, currents and water level, and their influence on the overall storm surge attenuation. Results indicate that the marsh area, despite its short length, attenuates waves and reduces current velocity and water level. Tides have a dominant influence on current direction and velocity, but the presence of vegetation and the marsh morphology contribute to a strong reduction of current velocity over the marsh platform relative to the currents at the marsh front. Wave attenuation varies across the tide cycle which implies a link between wave attenuation and water level and, consequently, storm surge height. Storm surge reduction, here assessed through high water level (HWL) attenuation, is linked to wave attenuation across the front edge of the marsh; this positive trend highlights the reduction of water level height induced by wave setup reduction during wave propagation across the marsh front edge. Water level attenuation rates observed here have a greater range than the rates observed or modeled by other authors, and our results suggest that this is linked to the strong influence of waves in storm surge attenuation over coastal areas.  相似文献