An overview of hydrometeorological datasets from a small agricultural catchment (Nučice) in the Czech Republic     

Tailin Li  Jakub Jeřábek  Nina Noreika  Tomáš Dostál  David Zumr 《水文研究》2021,35(2):e14042

We introduce the freely available web-based Water in an Agricultural Landscape—NUčice Database (WALNUD) dataset that includes both hydrological and meteorological records at the Nučice experimental catchment (0.53 km²), which is representative of an intensively farmed landscape in the Czech Republic. The Nučice experimental catchment was established in 2011 for the observation of rainfall–runoff processes, soil erosion processes, and water balance of a cultivated landscape. The average altitude is 401 m a.s.l., the mean land slope is 3.9%, and the climate is humid continental (mean annual temperature 7.9°C, annual precipitation 630 mm). The catchment is drained by an artificially straightened stream and consists of three fields covering over 95% of the area which are managed by two different farmers. The typical crops are winter wheat, rapeseed, and alfalfa. The installed equipment includes a standard meteorological station, several rain gauges distributed across the basin, and a flume with an H-type facing that is used to monitor stream discharge, water turbidity, and basic water quality indicators. Additionally, the groundwater level and soil water content at various depths near the stream are recorded. Recently, large-scale soil moisture monitoring efforts have been introduced with the installation of two cosmic-ray neutron sensors for soil moisture monitoring. The datasets consist of observed variables (e.g. measured precipitation, air temperature, stream discharge, and soil moisture) and are available online for public use. The cross-seasonal, open access datasets at this small-scale agricultural catchment will benefit not only hydrologists but also local farmers.  相似文献   

The GEOMON network of Czech catchments provides long-term insights into altered forest biogeochemistry: From acid atmospheric deposition to climate change     

Filip Oulehle  Milan Fischer  Jakub Hruška  Tomáš Chuman  Pavel Krám  Tomáš Navrátil  Miroslav Tesař  Miroslav Trnka 《水文研究》2021,35(5):e14204

In 1994, a network of small catchments (GEOMON) was established in the Czech Republic to determine input–output element fluxes in semi-natural forest ecosystems recovering from anthropogenic acidification. The network consists from 16 catchments and the primary observations of elements fluxes were complemented by monitoring of biomass stock, element pools in soil and vegetation, and the main water balance components. Over last three decades, reductions of SO₂, NO_x and NH₃ emissions were followed by sulphur (S) and nitrogen (N) deposition reductions of 75% and 30%, respectively. Steeper declines of strong acid anion concentrations compared to cations (Ca, Mg, Na, K, NH₄) in precipitation resulted in precipitation pH increase from 4.5 to 5.2 in bulk precipitation and from 4.0 to 5.1 in spruce throughfall. Stream chemistry responded to changes in deposition: S leaching declined. However at majority of catchments soils acted as a net source of S to runoff, delaying recovery. Stream pH increased at acidic streams (pH < 6) and aluminium concentration decreased. Stream nitrate (NO₃) concentration declined by 60%, considerably more than N deposition. Stream NO₃ concentration was tightly positively related to stream total dissolved nitrogen to total phosphorus (P) ratio, suggesting the role of P availability on N retention. Trends in dissolved organic carbon fluxes responded to both acidification recovery and to runoff temporal variation. An exceptional drought occurred between 2014 and 2019. Over this recent period, streamflow decreased by ≈ 40% on average compared to 1990s, due to the increases of soil evaporation and vegetation transpiration by ≈ 30% and declines in precipitation by ≈ 15% on average across the elevational gradient. Sharp decreases of stream runoff at catchments <650 m a.s.l. corresponded to areas of recent forest decline caused by bark beetle infestation on drought stressed spruce forests. Understanding of the interactions among legacies of acidification and eutrophication, drought effects on the water cycle and forest disturbance dynamics is requisite for effective management of forested ecosystems under anthropogenic influence.  相似文献   

Progress in Danube Loess and Paleoenvironment Study     

Xuechao Wu  Qingzhen Hao  B Marković Slobodan  Yu Fu  Namira  Yang Song  Zhengtang Guo 《地球科学进展》2020,35(4):363-377

Danube loess, located at the westernmost part of the widespread Eurasian loess belt, is one of the most well-preserved aeolian dust deposits in Europe with the basal age dating back over 1 Ma. Owing to its unique location and formation processes, Danube loess plays an important role in understanding the linkage of climate changes in different climate regimes over Eurasian continent and paleoclimatic changes in middle-high northern latitudes. Major research advances of the Danube loess, including compositions, provenance, chronology, stratigraphy and paleoenvironment changes were systematically reviewed and the focuses of future research were suggested. To better understand loess provenance, the compositions of sediments in all the potential source areas should be investigated, and methodological study of provenance indicators and application of multi-proxies approaches need to be carried out. Chronologically and stratigraphically, feldspar luminescence dating and tephrochronology methods should be widely used, and the establishment of a uniform stratigraphic framework and correlation scheme should be constrained by precise chronology. In terms of the paleoenvironment, it is necessary to conduct high-resolution multi-proxies reconstruction of paleoenviroment for the entire loess-paleosol sequence, extending from the last interglacial period (130 ka to present) to interval of last 1 Ma. The future progress in Danube loess is crucial to improving the study of continental paleoclimate comparison and paleoclimate dynamics over the Eurasian loess region.  相似文献   

Experimental investigation of seismic behaviour of the ancient Protiron monument model     

Željana Nikolić  Lidija Krstevska  Pavao Marović  Hrvoje Smoljanović 《地震工程与结构动力学》2019,48(6):573-593

Throughout history, dry-stone masonry structures have been strengthened with different types of metal connectors in order to increase their resistance which enabled their survival, especially in the seismically active area. One such example is the ancient Protiron monument placed in the Peristyle square of the Diocletian's Palace in Split, Croatia. The Protiron was built at the turn of the 3rd century as a stone masonry structure with dowels embedded between its base, columns, capitals and broad gable. The stone blocks in the broad gable were connected by metal clamps during restoration at the beginning of the 20th century. In order to study the seismic performance of the strengthened stone masonry structures, an experimental investigation of seismic behaviour of a physical model of the Protiron was performed on the shaking table. The model was designed as a true replica model in a length scale of 1:4 and exposed to representative earthquake with increasing intensities up to collapse. The tests provided a clear insight into system behaviour, damage mechanism and failure under intensive seismic load, especially into the efficiency of connecting elements, which had a special role in increasing seismic resistance and protection of the structure from collapse. Additionally, this experiment provided valuable data for verification and calibration of numerical models for strengthened stone masonry structures.  相似文献   

A triple porosity scheme for fluid/solid substitution: theory and experiment     

Yongyang Sun  Boris Gurevich  Maxim Lebedev  Stanislav Glubokovskikh  Vassili Mikhaltsevitch  Junxin Guo 《Geophysical Prospecting》2019,67(4):888-899

Quantifying the effects of pore-filling materials on elastic properties of porous rocks is of considerable interest in geophysical practice. For rocks saturated with fluids, the Gassmann equation is proved effective in estimating the exact change in seismic velocity or rock moduli upon the changes in properties of pore infill. For solid substance or viscoelastic materials, however, the Gassmann theory is not applicable as the rigidity of the pore fill (either elastic or viscoelastic) prevents pressure communication in the pore space, which is a key assumption of the Gassmann equation. In this paper, we explored the elastic properties of a sandstone sample saturated with fluid and solid substance under different confining pressures. This sandstone sample is saturated with octadecane, which is a hydrocarbon with a melting point of 28°C, making it convenient to use in the lab in both solid and fluid forms. Ultrasonically measured velocities of the dry rock exhibit strong pressure dependency, which is largely reduced for the filling of solid octadecane. Predictions by the Gassmann theory for the elastic moduli of the sandstone saturated with liquid octadecane are consistent with ultrasonic measurements, but underestimate the elastic moduli of the sandstone saturated with solid octadecane. Our analysis shows that the difference between the elastic moduli of the dry and solid-octadecane-saturated sandstone is controlled by the squirt flow between stiff, compliant, and the so-called intermediate pores (with an aspect ratio larger than that of compliant pore but much less than that of stiff pores). Therefore, we developed a triple porosity model to quantify the combined squirt flow effects of compliant and intermediate pores saturated with solid or viscoelastic infill. Full saturation of remaining stiff pores with solid or viscoelastic materials is then considered by the lower embedded bound theory. The proposed model gave a reasonable fit to the ultrasonic measurements of the elastic moduli of the sandstone saturated with liquid or solid octadecane. Comparison of the predictions by the new model to other solid substitution schemes implied that accounting for the combined effects of compliant and intermediate pores is necessary to explain the solid squirt effects.  相似文献   

Geophysical evidence of the Eastern Marginal Fault of the Cheb Basin (Czech Republic)     

Vratislav Blecha  Tomáš Fischer  Petr Tábořík  Jan Vilhem  Radek Klanica  Jan Valenta  Petra Štěpančíková 《Studia Geophysica et Geodaetica》2018,62(4):660-680

The western part of the Bohemian Massif hosts an intersection of two regional fault zones, the SW-NE trending Oh?e/Eger Graben and the NNW-SSE trending Mariánské Lázně Fault, which has been reactivated several times in the geological history and controlled the formation of the Tertiary Cheb Basin. The broader area of the Cheb Basin is also related to permanent seismic activity of M_L 3+ earthquake swarms. The Eastern Marginal Fault of the Cheb Basin (northern segment of the Mariánské Lázně Fault) separates the basin sediments and underlying granites in the SW from the Kru?né Hory/Erzgebirge Mts. crystalline unit in the NE. We describe a detailed geophysical survey targeted to locating the Eastern Marginal Fault and determining its geometry in the depth. The survey was conducted at the Kopanina site near the Nový Kostel focal zone, which shows the strongest seismic activity of the whole Western Bohemia earthquake swarm region. Complex geophysical survey included gravimetry, electrical resistivity tomography, audiomagnetotellurics and seismic refraction. We found that the rocks within the Eastern Marginal Fault show low resistivity, low seismic velocity and density, which indicates their deep fracturing, weathering and higher water content. The dip of the fault in shallow depths is about 60° towards SW. At greater depths, the slope turns to subvertical with dip angle of about 80°. Results of geoelectrical methods show blocky fabric of the Cheb Basin and deep weathering of the granite bedrock, which is consistent with geologic models based on borehole surveys.  相似文献   

Anisotropies of in-phase,out-of-phase,and frequency-dependent susceptibilities in three loess/palaeosol profiles in the Czech Republic; methodological implications     

František Hrouda  Martin Chadima  Josef Ježek  Jaroslav Kadlec 《Studia Geophysica et Geodaetica》2018,62(2):272-290

The relationship between the anisotropy of frequency-dependent magnetic susceptibility (fdAMS) and the anisotropy of out-of-phase magnetic susceptibility (opAMS) was investigated theoretically and also empirically at three loess/palaoesol profiles in Prague and in Southern Moravia. The data treatment was made in terms of mean susceptibility, degree of AMS, and orientations of principal susceptibilities. It has shown that the fdAMS and opAMS can serve as indicators of the preferred orientations of ultrafine magnetic particles that are on transition between superparamagnetic and stable single domain states in rocks, soils and environmental materials. In loess/palaeosol sequences, the fdAMS and opAMS correlate reasonably, because they are due to magnetic particles of similar grain sizes. The fdAMS and opAMS can be both coaxial with standard AMS (i.e. anisotropy of in-phase susceptibility - ipAMS) or non-coaxial indicating slightly different orientations of viscous magnetic particles.  相似文献   

A multiscale work-analysis approach for geotechnical structures     

Hao Xiong  Zhen-Yu Yin  François Nicot 《国际地质力学数值与分析法杂志》2019,43(6):1230-1250

This paper presents a second-order work analysis in application to geotechnical problems by using a novel effective multiscale approach. To abandon complicated equations involved in conventional phenomenological models, this multiscale approach employs a micromechanically-based formulation, in which only four parameters are involved. The multiscale approach makes it possible a coupling of the finite element method (FEM) and the micromechanically-based model. The FEM is used to solve the boundary value problem (BVP) while the micromechanically-based model is utilized at the Gauss point of the FEM. Then, the multiscale approach is used to simulate a three-dimensional triaxial test and a plain-strain footing. On the basis of the simulations, material instabilities are analyzed at both mesoscale and global scale. The second-order work criterion is then used to analyze the numerical results. It opens a road to interpret and understand the micromechanisms hiding behind the occurrence of failure in geotechnical issues.  相似文献   

Visibility of Prominences Using the He <Emphasis Type="SmallCaps">i</Emphasis> D<Subscript>3</Subscript> Line Filter on the PROBA-3/ASPIICS Coronagraph     

S. Jejčič  P. Heinzel  N. Labrosse  A. N. Zhukov  A. Bemporad  S. Fineschi  S. Gunár 《Solar physics》2018,293(2):33

We determine the optimal width and shape of the narrow-band filter centered on the He?i D₃ line for prominence and coronal mass ejection (CME) observations with the ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun) coronagraph onboard the PROBA-3 (Project for On-board Autonomy) satellite, to be launched in 2020. We analyze He?i D₃ line intensities for three representative non-local thermal equilibrium prominence models at temperatures 8, 30, and 100 kK computed with a radiative transfer code and the prominence visible-light (VL) emission due to Thomson scattering on the prominence electrons. We compute various useful relations at prominence line-of-sight velocities of 0, 100, and 300 km?s^?1 for 20 Å wide flat filter and three Gaussian filters with a full-width at half-maximum (FWHM) equal to 5, 10, and 20 Å to show the relative brightness contribution of the He?i D₃ line and the prominence VL to the visibility in a given narrow-band filter. We also discuss possible signal contamination by Na?i D₁ and D₂ lines, which otherwise may be useful to detect comets. Our results mainly show that i) an optimal narrow-band filter should be flat or somewhere between flat and Gaussian with an FWHM of 20 Å in order to detect fast-moving prominence structures, ii) the maximum emission in the He?i D₃ line is at 30 kK and the minimal at 100 kK, and iii) the ratio of emission in the He?i D₃ line to the VL emission can provide a useful diagnostic for the temperature of prominence structures. This ratio is up to 10 for hot prominence structures, up to 100 for cool structures, and up to 1000 for warm structures.  相似文献   

Zinc-rich and copper-bearing amphiboles from sulfide-free ore occurrences of the Pelagonian Massif,Republic of North Macedonia     

Chukanov  Nikita V.  Zubkova  Natalia V.  Jančev  Simeon  Pekov  Igor V.  Ermolaeva  Vera N.  Varlamov  Dmitry A.  Belakovskiy  Dmitriy I.  Britvin  Sergey N. 《Mineralogy and Petrology》2020,114(2):129-140

Mineralogy and Petrology - This paper describes specific features of isomorphism of unusual amphiboles containing up to 23&nbsp;wt% ZnO and up to 1.3&nbsp;wt% CuO from sulfide-free...  相似文献