A comparison of winter mercury accumulation at forested and no-canopy sites measured with different snow sampling techniques     

Sarah J. Nelson  Kenneth B. Johnson  Kathleen C. Weathers  Cynthia S. Loftin  Ivan J. Fernandez  Jeffrey S. Kahl  David P. Krabbenhoft 《Applied Geochemistry》2008

Atmospheric mercury (Hg) is delivered to ecosystems via rain, snow, cloud/fog, and dry deposition. The importance of snow, especially snow that has passed through the forest canopy (throughfall), in delivering Hg to terrestrial ecosystems has received little attention in the literature. The snowpack is a dynamic system that links atmospheric deposition and ecosystem cycling through deposition and emission of deposited Hg. To examine the magnitude of Hg delivery via snowfall, and to illuminate processes affecting Hg flux to catchments during winter (cold season), Hg in snow in no-canopy areas and under forest canopies measured with four collection methods were compared: (1) Hg in wet precipitation as measured by the Mercury Deposition Network (MDN) for the site in Acadia National Park, Maine, USA, (2) event throughfall (collected after snowfall cessation for accumulations of >8 cm), (3) season-long throughfall collected using the same apparatus for event sampling but deployed for the entire cold season, and (4) snowpack sampling. Estimates (mean ± SE) of Hg deposition using these methods during the 91-day cold season in 2004–2005 at conifer sites showed that season-long throughfall Hg flux (1.80 μg/m²) < snowpack Hg (2.38 ± 0.68 μg/m²) < event throughfall flux (5.63 ± 0.38 μg/m²). Mercury deposition at the MDN site (0.91 μg/m²) was similar to that measured at other no-canopy sites in the area using the other methods, but was 3.4 times less than was measured under conifer canopies using the event sampling regime. This indicates that snow accumulated under the forest canopy received Hg from the overstory or exhibited less re-emission of Hg deposited in snow relative to open areas. The soil surface of field-scale plots were sprayed with a natural rain water sample that contained an Hg tracer (²⁰²Hg) just prior to the first snowfall to explore whether some snowpack Hg might be explained from soil emissions. The appearance of the ²⁰²Hg tracer in the snowpack (0–64% of the total Hg mass in the snowpack) suggests that movement of Hg from the soil into the snowpack is possible. However, as with any tracer study the ²⁰²Hg tracer may not precisely represent the reactivity and mobility of natural Hg in soils.  相似文献   

Coupling of watersheds and coastal waters: An introduction to the dedicated issue     

Ivan Valiela 《Estuaries and Coasts》1992,15(4):429-430

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Mayfly communities in a prealpine stream system of Switzerland     

Daniel Hefti  Ivan Tomka 《Aquatic Sciences - Research Across Boundaries》1991,53(1):20-38

The mayfly fauna of twelve localities belonging to a calcareous stream system of the Swiss Prealps was investigated during the last three years. The stream system was divided into three distinct topographical sections, each characterized by specific thermic and geomorphologic components. Thirty-five mayfly species, that belonged to different faunistic groups according to their respective longitudinal distribution, were found. A coefficient of interspecific association was determined for every pair of species. Non-parametric indices of diversity, as well as a parametric analysis, were calculated for the three stations investigated quantitatively. The faunistic classification of the twelve stations reflected the main topographical organization of the stream system.  相似文献   

Calendar of events     

Ivan Vaní?ek  Martin Vaní?ek 《Geotechnical and Geological Engineering》1991,9(2):154-154

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River runoff changes and recent climatic fluctuations in Bulgaria     

Ivan Vassilev  Bojidar  N. Georgiev 《GeoJournal》1996,40(4):379-385

Some estimates of global climatic change in the next 100 years suggest a general warming and rainfall decrease on the Balkan Peninsula. Our studies suggest that in Bulgaria climatic changes have already started. Because water resources to a great extent depend upon climate dynamics, this paper develops the linkage of climatic fluctuations and water resources using time-series analysis of climatic parameters and some river runoff characteristics and their correlation. One of the main conclusions, based on the results, is that climatic change manifested in the last 15 years has significantly influenced river runoff. A study of the recent prolonged drought and the influence of changes on water resources and human activity begins with characterizing climate-hydrology linkages. The results of this study point to several problems of regional and local importance.  相似文献   

The analysis of four cosmic dust particles     

I. Kapišinský  V. Figusch  A. Hajduk  J. Ivan  K. Iždinský 《Earth, Moon, and Planets》1995,68(1-3):347-360

A set of four stratospheric particles was reanalysed. These particles registered in the NASA Cosmic Dust Catalogs (CDCs) were classified in the Houston Johnson Space Center (JSC) as the particles of cosmic origin (C). Present energy-dispersive X-ray (EDX) spectra confirmed previous classification and revealed additional features in the chemical composition of the cosmic dust particles.The particles are extremely fine-grained aggregates with bulk chondritic composition. Somewhat higher content of oxygen may indicate a presence of hydroxide containing minerals in their phase composition.  相似文献   

The determination of the regional part of the vertical gradient anomaly by a geodetic method     

Dr. Ivan I. Mueller 《Pure and Applied Geophysics》1961,48(1):1-6

Summary The significance of the vertical gradients of gravity is great in geophysics and also in geodesy. In geophysics the observed vertical gradients can give valuable information about mass distributions close to the surface of the earth and in geodesy they may be used in determining the shape of the equipotential surfaces. The observed vertical gradients are very sensitive to masses close to the surface of the earth and they change very rapidly. Therefore, they should not be used for purposes such as the reduction of the observed gravity to the sea level. The normal vertical gradients are not the best either for this purpose because they are much too uniform on the surface of the earth. The best values for practical purposes are probably the regional vertical gradients.This paper presents a method to determine the regional vertical gradient anomalies in large areas from geodetic observations which, added to the normal part, will give the regional vertical gradients.  相似文献   

Ecology of an anchialine cave in the Adriatic Sea with special reference to its thermal regime   总被引：1，自引：0，他引：1  

Maja Novosel  Branko Jal&#;i&#;  An&#;elko Novosel  Mira Pasari&#;  Antonieta Po&#;ar-Domac  & Ivan Radi&#; 《Marine Ecology》2007,28(S1):3-9

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Neotectonics of the central parts of the Balkan Peninsula: Basic features and concepts   总被引：1，自引：1，他引：0  

Ivan S. Zagorčev 《International Journal of Earth Sciences》1992,81(3):635-654

The neotectonic movements on the Balkan Peninsula occurred after the last intense thrusting (Early Miocene), and after the Early — Middle Miocene planation. They were controlled by extensional collapse of the Late Alpine orogen, and by extension behind the Aegean arc, and were influenced by the complicated vertical and horizontal movements in the Pannonian region. The Stara-planina and Dinarian-Hellenic linear neotectonic morphostructures inherited the Alpine orogenic zones (Balkanides and Dinarides-Hellenides) and bounded the Central-Balkan neotectonic region. The linear morphostructures were tilted towards the Pannonian and Euxinian basins and the North-Aegean trough.The Central-Balkan neotectonic region has a complicated block structure (horst-and-graben pattern) dominated by the NNW-SSE Struma and Vardar lineaments, the WNW-ESE Sava and Marica lineaments, and the Middle-Mesta and North Anatolian fault zones. The dominating Serbo-Macedonian neotectonic swell was rifted, and subsided along the Struma and Vardar lineaments. The range of the vertical neotectonic displacements reached a maximum of 3–4 km, and even up to 6 km at the edges of the Pannonian and Aegean basins. The general doming of the region was controlled by the isostatic uplift of a thickened crustal lens (Rhodope Massif) in the southern margin of the Eurasian plate. The collapse of the complicated domal structure began along the main (Struma, Vardar and Marica) lineaments in the central parts of the dome, and continued in the Pliocene and Quaternary along a more external contour bounded by the Stara-planina and Dinarian-Hellenic linear morphostructures.

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Zusammenfassung Die neotektonischen Bewegungen der Balkan-Halbinsel begannen nach den letzten intensiven Überschiebungen (frühes Miozän) und nach der frühbis mittelmiozänen Verebnung. Gesteuert wurden die Bewegungen durch den Dehnungskollaps des spätalpinen Orogens, der Dehnung hinter dem Ägäischen Bogen und den komplizierten vertikalen und horizontalen Bewegungen in der pannonischen Region. Die neotektonische Region des Zentralbalkans liegt zwischen den linearen, neotektonischen Morphostrukturen der Strara-planina und der Dinariden-Helleniden. Sie übernahmen die alpidischen Orogenzonen der Balkaniden und Dinariden-Helleniden und wurden zum Pannonischen-, dem Präkarpatischen- und dem Nordägäischen Trog geneigt.Die Region zeigt einen komplizierten Blockaufbau (Horst- und Grabenstrukturen), der von den NNW-SSE streichenden Struma- und Vardar-Lineamenten, von den WNW-ESE verlaufenden Sava- und Marica-Lineamenten und der Mittelmesta- und der Nordanatolischen Bruchzone dominiert war. Die Serbo-mazedonische neotektonische Schwelle war von Bruchspaltenbildung und Absenkung parallel der Struma- und Vardar-Lineamente betroffen. Die Höhe der vertikalen Versatzbeträge erreichte ein Maximum von 3–4 km; an den Rändern des Pannonischen und Ägäischen Beckens sogar mit bis zu 6 km. Die allgemeine Aufwölbung der Region wurde durch isostatische Hebung der verdickten Krustenteile (Rhodopisches Massiv) am Südrand der Eurasischen Platte bedingt. Der Kollaps der komplizierten Domstruktur begann in dessen Zentralteil entlang der Hauptlineamente (Struma-, Vardar- und Marica-Lineament) und setzte sich, während des Pliozäns und Quartärs, in den peripheren Bereichen, parallel zu den äußeren Begrenzungen (Balkaniden, Dinariden-Helleniden) der linearen Morphostrukturen, fort.

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Résumé Les mouvements néotectoniques dans la péninsule balkanique ont eu lieu après les derniers charriages d'âge miocène inférieur et la pénéplanation du Miocène inférieur et moyen. Ils ont été régis par l'affaissement extensionnel de l'orogène alpin tardif, par l'extension derrière l'arc égéen et par les mouvements verticaux et horizontaux complexes dans la région panonnienne. La région néotectonique centrebalkanique est située entre les morphostructures néotectoniques linéaires de Stara-Planina et des Dinarides-Hellénides. Celles-ci sont héritées des zones orogéniques alpines des Balkanides et des Dinarides-Hellénides et ont été inclinées vers les bassins panonnien, euxinien et nord-égéen.La région possède une structure en blocs (horsts et grabens) compliquée, dominée par les linéaments NNW-SSE de Struma et du Vardar, les linéaments WNW-ESE de Sava et de Marica et les zones faillées de Moyenne Mesta et d'Anatolie du nord. La ride néotectonique serbo-macédonienne a subi rifting et subsidence au long des linéaments de Struma et du Vardar. Les déplacements néotectoniques verticaux ont atteint 3 à 4 km au maximum, et même 6 km dans les bordures des bassins panonniens et égéen. Le soulèvement en dôme de la région a été provoqué par la montée isostatique d'une portion épaissie de l'écorce (massif du Rhodope) dans la marge méridionale de la plaque eurasiatique. L'affaissement de cette structure en dôme complexe a commencé le long des linéaments principaux (de Struma, Vardar et Marica) dans les parties centrales du dôme et a continué pendant le Pliocène et le Quaternaire le long d'un contour plus externe limité par les morphostructures néotectoniques linéaires de Stara-Planina et dinarohellénique.

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THE RETREAT OF SURFACE MINE SPOIL BANK SLOPES     

M. J. Haigh 《The Professional geographer》1977,29(1):62-65

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