Contamination of some reservoirs and lakes in Republic of Bulgaria by microcystins     

Vera Pavlova  Pavel Babica  Detelina Todorova  Zlatka Bratanova  Blahoslav Mar&#x;lek 《洁净——土壤、空气、水》2006,34(5):437-441

This paper presents the results from analyses of water samples from 15 Bulgarian reservoirs and lakes for detection of microcystins presence by high‐performance liquid chromatography (HPLC) coupled to a ultraviolet (UV) and photo diode array (PDA) detector. In 3 of the studied drinking water reservoirs cyanobacterial blooms were not detected. Cyanobacterial blooms were observed in 6 of 12 investigated water bodies used for fishing and water sports. Microcystis was the dominant cyanobacterial genus. The concentration of total microcystins in the biomasses ranged from 8 to 1070 μg g^–1 (d.w.). Microcystin‐LR and microcystin‐RR were the predominant microcystins, followed by microcystin‐YR. Presence of dissolved microcystins was obtained in one water sample with concentration of total microcystins 1.64 μg L^–1. Presence of microcystin‐LF and ‐LW or unknown peaks possessing characteristic microcystin‐like UV‐spectra were not detected. Those first results for occurrence of microcystins in some Bulgarian reservoirs and lakes are a contribution to the knowledge on their distribution.  相似文献   

Modélisation glacio-hydrologique et gestion des ressources en eau dans les Andes équatoriennes : l’exemple de Quito     

Jean-Christophe Pouget  David Proaño  Andrea Vera  Marcos Villacís  Thomas Condom  Marisa Escobar 《水文科学杂志》2017,62(3):431-446

La forte croissance socio-économique de Quito a conduit à d’importants projets de transferts interbassins, intensifiant la mobilisation des ressources d’altitude situées dans des zones écologiques sensibles et connaissant une fonte accélérée des glaciers. Afin d’étudier divers scénarios d’évolutions, nous proposons une modélisation du continuum climat/glacier/hydrologie/gestion des ressources en eau. Utilisant l’outil Water Evaluation and Planning (WEAP), nous avons développé : (1) une modélisation hydro-climatologique semi-distribuée avec des données mensuelles homogénéisées par vectorisation régionale ; (2) une modélisation de la production en eau des glaciers et de leur évolution interannuelle ; (3) une modélisation en unités hydrologiques distinguant différentes couvertures de sols ; et (4) une modélisation de la gestion distinguant droits, allocation et usages de l’eau. Nous présentons les résultats du calage hydrologique mensuel (1963–2006), en étudiant particulièrement l’équifinalité de diverses paramétrisations. Nous montrons la souplesse, la robustesse et les limites de la modélisation proposée, contribuant à cerner différentes incertitudes dans l’évaluation de scénarios prospectifs.  相似文献   

Characteristics of the Flare Phenomenon in Blazar AO0235+164 in Gamma,Optical, and Radio Bands     

V. S. Bychkova  A. E. Volvach  L. N. Volvach  N. S. Kardashev  M. G. Larionov  V. V. Vlasyuk  O. I. Spiridonova  A. Lähteenmäki  M. Tornikoski  J. Tammi  E. Järvelä  R. J. C. Vera  W. Chamani  S. Enestam 《Astrophysical Bulletin》2018,73(3):293-297

The active core of the galaxy AO0235+164 is monitored in the optical and radio bands at millimeter wavelengths. Using the multifrequency data obtained in gamma, optical and radio bands, the characteristics of its radiation in the active phase of 2015–2016 are studied. The cross-correlation method was used to determine the delays of the 2015 flare that took place in AO0235+164 in different bands. The analysis made it possible to establish that, in comparison with the previous flare phenomena, changes in the orientation of the emissions (jets) have occurred. The angle θ between the jets and the direction towards the observer has decreased by a factor of \(\sqrt 2 \), resulting in a twofold increase in the γ-factor. The obtained value γ ≈ 40 is the most extreme value ever observed in AO0235+164 over the entire span of observations.  相似文献   

Long-term influence of maritime access works on the distribution of cohesive sediments: analysis of historical and recent data from the Belgian nearshore area (southern North Sea)     

Michael Fettweis  Jean-Sébastien Houziaux  Isabelle Du Four  Vera Van Lancker  Cecile Baeteman  Mieke Mathys  Dries Van den Eynde  Frederic Francken  Stanislas Wartel 《Geo-Marine Letters》2009,29(5):321-330

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Effects of basement structural and stratigraphic heritages on volcano behaviour and implications for human activities （the IGCP project 455）     

Alessandro Tibaldi Alfredo Mahar F. A. Lagmaye Vera V. Ponomareva 《《幕》》2005,28(3):158-170

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Classification problems of samples of finite mixtures of compositions     

Carles Barceló  Vera Pawlowsky  Eric Grunsky 《Mathematical Geology》1995,27(1):129-148

A discriminant technique based on mixture models is presented to be applied when observations are a sample of a mixture of compositions with each component following an additive logistic normal distribution on the d-dimensional simplex. The efficiency of this discriminant technique is compared empirically with the efficiency of the standard discriminant technique based on logcontrast. Simulated compositional data and a real dataset are used to carry out these comparisons.  相似文献   

Seismic analysis and distribution of a bottom-simulating reflector (BSR) in the Chilean margin offshore of Valdivia (40° S)     

Cristián Rodrigo  Emilio Vera  Antonio González-Fernández 《Journal of South American Earth Sciences》2009,27(1):1-10

Multi-channel seismic (MCS) reflection data recorded offshore from Valdivia (40° S), in the Chilean margin, were processed to obtain a seismic image to establish structural characteristics and relate them to the presence of the bottom-simulating reflector (BSR). Seismic structure velocity of the BSR was determined using 1-D forward modeling. Recorded seismograms for two representative common mid-point (CMP) gathers were compared with synthetics, using different physical parameters to fit the waveforms. Our results confirm the presence of gas hydrates above the BSR. The BSR spatial continuity appears to be either interrupted or irregular due to the presence of faults. Tectonic movements can change the gas hydrate stability zone and consequently the BSR disappears or becomes weaker. Structural and topographic factors, differences in concentration, vertical distribution characteristics and internal structure of gas hydrates can influence BSR amplitude behavior. Variability in the concentration, volume, and extra supply of free gas coming from faults could be the main factors in the change of BSR amplitudes. The inclusion of the attenuation factor in the modeling supports the existence of free gas below the BSR. It is possible that the free gas below the BSR is distributed in bubbles or “bags”.  相似文献   

Support Vector Machines for Classification of?Aggregates by Means of IR-Spectra     

Vera Hofer  Juergen Pilz  Thorgeir S. Helgason 《Mathematical Geology》2007,39(3):307-319

The increasing physical and technical demands placed on construction materials, especially as they are being used more and more up to the limits of their mechanical strength, has led the aggregates industry to search for more efficient methods of quality control. Information from theoretical work on rock spectra in near-infrared and mid-infrared light as well as achievements gained in signal processing can all be used to improve quality control in an economically acceptable manner. As engineering properties of aggregates are to a great extent determined by the petrological composition of the rock aggregates, the question is, whether a statistical classification rule for identification of rock aggregates can be developed. However, the classification of rocks is complicated by the fact that the optical behavior of minerals forming the rock often appears muted. In addition, minor constituents may dominate the spectrum. Furthermore, the relevant spectra form high dimensional data that are extremely difficult to analyze statistically, especially when curves are very similar. In this paper, support vector machines for classification of rock spectra are investigated, since they are appropriate in classifying highly dimensional data such as spectra.  相似文献   

Factors influencing the release of dissolved organic carbon and dissolved forms of nitrogen from a small upland headwater during autumn runoff events   总被引：1，自引：0，他引：1  

Richard Cooper  Vera Thoss  Helen Watson 《水文研究》2007,21(5):622-633

We identify and assess the relative importance of the principal factors influencing the release of dissolved organic carbon (DOC) and dissolved forms of nitrogen (N) from a small upland headwater dominated by podzolic soils during a sequence of autumn runoff events. We achieve this by subjecting high‐resolution hydrometeorological and hydrochemical data to an R‐mode principal component factor analysis and a stepwise multivariate regression analysis. We find that the release of DOC and N is influenced by four principal factors, namely event magnitude, soil water flow through the Bs horizon, the length of time since the soil profile was last flushed, and rewetting of the H horizon. The release of DOC and dissolved organic nitrogen (DON) is most strongly influenced by the combination of event magnitude and soil water flow through the Bs horizon, and to a lesser extent by the length of time since the soil profile was last flushed. Rewetting of the H horizon also influences the release of DOC, but this is not the case for DON. The release of nitrate (NO₃‐N) is most strongly influenced by the combination of the length of time since the soil profile was last flushed and rewetting of the H horizon, and to a lesser extent by event magnitude. Soil water flow through the Bs horizon does not influence the release of NO₃‐N. We argue that the mechanisms by which the above factors influence the release of DOC and N are probably strongly associated with moisture‐dependent biological activity, which governs the turnover of organic matter in the soil and limits the availability of NO₃‐N in the soil for leaching. We conclude that the release of DOC and N from upland headwaters dominated by podzolic soils is largely controlled by the variable interaction of hydrometeorological factors and moisture‐dependent biological processes, and that a shift in climate towards drier summers and wetter winters may result in the release of DOC and N becoming increasingly variable and more episodic in the future. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Monitoring Changes of Ice Streams Using Time Series of Satellite-Altimetry-Based Digital Terrain Models     

Ute C. Herzfeld  Craig S. Lingle  Cecily Freeman  Chris A. Higginson  Michael P. Lambert  Li-Her Lee  Vera A. Voronina 《Mathematical Geology》1997,29(7):859-890

The Antarctic Ice Sheet plays a major role in the global system, and the large ice streams discharging into the circumpolar sea represent its gateways to the world's oceans. Satellite radar altimeter data provide an opportunity for mapping surface elevation at kilometer-resolution with meter-accuracy. Geostatistical methods have been developed for the analysis of these data. Applications to Seasat data and data from the Geosat Exact Repeat Mission indicate that the grounding line of Lambert Glacier/Amery Ice Shelf, the largest ice stream in East Antarctica, has advanced 10–12 km between 1978 and 1987–89. The objectives of this paper are to explore possibilities and limitations of satellite-altimetry-based mapping to capture changes for shorter time windows and for smaller areas, and to investigate some methodological aspects of the data analysis. We establish that one season of radar altimeter data is sufficient for constructing a map. This allows study of interannual variation and is the key for a time-series analysis approach to study changes in ice streams. Maps of the lower Lambert Glacier and the entire Amery Ice Shelf are presented for austral winters 1978, 1987, 1988, and 1989. As a first step toward understanding the dynamics of the ice-stream/ice-shelf system, elevation changes are calculated for grounded ice, the grounding zone, and floating ice. In the absence of (sufficient) surface gravity control for the Lambert Glacier/Amery Ice Shelf area, altimetry-based maps may facilitate improvement of geoid models as they provide constraints on the terrain correction in the inverse gravimetric problem.  相似文献