Redox Potential and Seasonal Porewater Biogeochemistry of Three Mountain Wetlands in Southeastern Kentucky, USA     

Yvonne Thompson  Brian C. Sandefur  A. D. Karathanasis  Elisa D’Angelo 《Aquatic Geochemistry》2009,15(3):349-370

Redox potentials (Eh) were monitored bimonthly and porewater chemistry was analyzed seasonally at three slightly-acidic, high-elevation Kentucky wetlands that differed in hydrology, parent materials, and vegetation. At all sites, Eh values were below 300 mV, which indicated that reducing conditions persisted within the upper 90 cm and fluctuated mainly within the range of iron and sulfate reduction. Significant relationships of Eh values with depth were observed only at the Martins Fork wetland, where precipitation was the primary water source. The strongest and most stable reducing conditions, observed at the Kentenia site, reflected consistently high water levels, which were sustained by ground water. The third wetland (Four Level) was distinguished by irregular Eh fluctuations coinciding with strong seasonal ground-water upwelling. Although Fe³⁺ and SO₄ ²⁻ were the primary terminal electron acceptors in all wetlands, porewater chemistry also varied significantly by season and soil depth in response to piezometric water level fluctuations. Additional factors that influenced porewater chemistry included: (1) the presence of limestone parent materials that affected porewater pH, Ca²⁺, and Mg²⁺; and (2) the prevalence of sphagnum moss or graminoid species that influenced dissolved organic carbon, CO₂, and CH₄. Results from this study indicated the diverse range and importance of multiple factors in controlling biogeochemical processes and properties in small, high-elevation Appalachian wetlands.  相似文献   

A large daylight geodesic dome for quantification of whole-ecosystem CO₂ and water vapour fluxes in arid shrublands     

John A. Arnone  III  Daniel Obrist 《Journal of Arid Environments》2003,55(4):629-643

We designed, constructed, calibrated and field-tested a lightweight (30 kg), 4.2 m diameter, 16.4 m³ polyethylene-covered dome static chamber ecosystem gas exchange cuvette that can quantify ecosystem CO₂ and water vapour fluxes as low as 0.1 μmol CO₂ m⁻² s⁻¹ and 0.1 mmol H₂O m⁻² s⁻¹ with little impact on environmental conditions. Fluxes measured in May 2001 in an intact Great Basin sagebrush ecosystem at midday were significantly higher than in an adjacent post-wildfire successional ecosystem, with observed ranges from –0.71 to 1.49 μmol CO₂ m⁻² s⁻¹ for CO₂ and from –0.09 to 0.53 mmol H₂O m⁻² s⁻¹ for water vapour.  相似文献   

Changes in eruptive style during the A.D. 1538 Monte Nuovo eruption (Phlegrean Fields, Italy): the role of syn-eruptive crystallization     

Claudia D’Oriano  Elisa Poggianti  Antonella Bertagnini  Raffaello Cioni  Patrizia Landi  Margherita Polacci  Mauro Rosi 《Bulletin of Volcanology》2005,67(7):601-621

The Monte Nuovo eruption is the most recent event that occurred at Phlegrean Fields (Italy) and lasted from 29 September to 6 October 1538. It was characterized by 2 days of quasi-sustained phreatomagmatic activity generating pumice-bearing pyroclastic density currents and forming a 130-m-high tuff cone (Lower Member deposits). The activity resumed after a pause of 2 days with two discrete Vulcanian explosions that emplaced radially distributed, scoria-bearing pyroclastic flows (Upper Member deposits). The juvenile products of Lower and Upper Members are, respectively, phenocryst-poor, light-coloured pumice and dark scoria fragments with K-phonolitic bulk compositions, identical in terms of both major and trace elements. Groundmass is formed by variable proportions of K-feldspar and glass, along with minor sodalite and Fe-Ti oxide present in the most crystallized samples. Investigations of groundmass compositions and textures were performed to assess the mechanisms of magma ascent, degassing and fragmentation along the conduit and implications for the eruptive dynamics. In pumice of the Lower Member groundmass crystal content increases from 13 to 28 vol% from the base to the top of the sequence. Products of the Upper Member consist of clasts with a groundmass crystal content between 30 and 40 vol% and of totally crystallized fragments. Crystal size distributions of groundmass feldspars shift from a single population at the base of the Lower Member to a double population in the remaining part of the sequence. The average size of both populations regularly increases from the Lower to the Upper Member. Crystal number density increases by two orders of magnitude from the Lower to the Upper Member, suggesting that nucleation dominated during the second phase of the eruption. The overall morphological, compositional and textural data suggest that the juvenile components of the Monte Nuovo eruption are likely to record variations of the magma properties within the conduit. The different textures of pumice clasts from the Lower Member possibly reflect horizontal gradients of the physical properties (P, T) of the ascending magma column, while scoriae from the second phase are thought to result from the disruption of a slowly rising plug crystallizing in response to degassing. In particular, crystal size distribution data point to syn-eruptive degassing-induced crystallization as responsible for the transition in eruptive style from the first to the second phase of the eruption. This mechanism not only has been proved to profoundly affect the dynamics of dome-forming calc-alkaline eruptions, but may also have a strong influence in driving the eruption dynamics of alkaline magmas of intermediate to evolved compositions.Editorial responsibility: J. Donnelly-Nolan  相似文献   

Kinematic and geochronological constraints on shear deformation in the Ferriere-Mollières shear zone (Argentera-Mercantour Massif,Western Alps): implications for the evolution of the Southern European Variscan Belt     

Simonetti  Matteo  Carosi  Rodolfo  Montomoli  Chiara  Langone  Antonio  D’Addario  Enrico  Mammoliti  Elisa 《International Journal of Earth Sciences》2018,107(6):2163-2189

International Journal of Earth Sciences - In the Western Alps, a steeply dipping km-scale shear zone (the Ferriere-Mollières shear zone) cross-cuts Variscan migmatites in the...  相似文献   

Temporal trends in extreme rainfall intensity and erosivity in the Mediterranean region: a case study in southern Tuscany,Italy   总被引：2，自引：0，他引：2  

Chiara Vallebona  Elisa Pellegrino  Paolo Frumento  Enrico Bonari 《Climatic change》2015,128(1-2):139-151

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Shaking table tests of a full-scale flat-bottom manufactured steel silo filled with wheat: Main results on the fixed-base configuration     

Stefano Silvestri  Sulyman Mansour  Matteo Marra  Johann Distl  Marco Furinghetti  Igor Lanese  Enrique Hernndez-Montes  Caterina Neri  Michele Palermo  Alberto Pavese  Elisa Rizzo Parisi  Adam Jan Sadowski  Francesco Selva  Tomoyo Taniguchi  Laura Vadrucci  Felix Weber 《地震工程与结构动力学》2022,51(1):169-190

This paper reports on a series of shaking table tests on a full-scale flat-bottom steel silo filled with soft wheat, characterized by aspect ratio of around 0.9. The specimen was a 3.64-m diameter and 5.50-m high corrugated-wall cylindrical silo. Multiple sensors were used to monitor the static and dynamic response of the filled silo system, including accelerometers and pressure cells. Numerous unidirectional dynamic tests were performed consisting of random signals, sinusoidal inputs, and both artificial and real earthquake records. The objectives of this paper are (i) to provide a general overview of the whole experimental campaign and (ii) to present selected results obtained for the fixed-base configuration. The measured data were processed to assess the static pressures, the dynamic overpressures (related to the effective mass) and the accelerations of monitored points on the silo wall, and to identify the basic dynamic properties (fundamental frequency of vibration, damping ratio, dynamic amplification factors) of the filled silo. The main findings are discussed and compared with the predictions given by available theoretical models and code provisions. It is found that the fundamental frequency slightly decreases with increasing acceleration, while it slightly increases with increasing compaction of the granular material. For close-to-resonance input, the dynamic amplification (in terms of peak values of accelerations) increases along the height of the silo wall up to values of around 1.4 at the top surface of the solid content. The dynamic overpressures appear to increase with depth (differently from the EN1998-4 expectations), and to be proportional to the acceleration.  相似文献   

Mélanges and other types of block-in-matrix formations in the Cantabrian Zone (Variscan Orogen,northwest Spain): origin and significance     

Juan Luis Alonso  Alberto Marcos  Elisa Villa  Angela Súarez  Oscar Antonio Merino-Tomé  Luis Pedro Fernández 《International Geology Review》2015,57(5-8):563-580

Block-in-matrix formations in the Variscan foreland of Spain (Cantabrian Zone) occur in two different geological settings. The major block-in-matrix formations are mélanges, which appear as carpets beneath or ahead of submarine thrust systems. These mélanges may reach up to kilometric thickness and are mostly composed of broken formations (boudinaged sequences) of late Carboniferous age and scattered ‘exotic’ blocks derived from older Palaeozoic formations. Moreover, the mélanges in the Cantabrian Zone also include subordinate debris flow deposits with a chaotic block-in-matrix fabric (olistostromes). The source of the mélange blocks was the front of advancing nappes, chiefly the upper part of the nappe stacks. Therefore, the Cantabrian mélanges are interpreted as originated through submarine sliding and slumping associated with steep slopes at the orogenic front. The different types of rock bodies of these mélanges may be related to the degree of lithification of the sediments or rocks during slumping. So, broken formations are boudinaged sequences where the boudins or blocks resulted from extensional faults developed in lithified or semilithified limestones and sandstones, whereas the unlithified muddy matrix underwent continuous deformation. The scattered ‘exotic’ blocks ranging in age from early Cambrian to early Carboniferous were incorporated into the mélanges as individual blocks from competent well-lithified formations, originally located in the lower part of the nappe stacks. Although the Cantabrian Zone mélanges include olistostromic intervals, most of the olistostromes of this zone occur in a different geological setting. They are usually intercalated in the normal marine deposits of the Variscan foreland basin and, in contrast to the mélanges, they are mostly related to the margins of carbonate platforms, ahead of moving nappes. Finally, other instances of olistostromes are related to slopes generated by limb rotation of growth folds, which developed on submarine wedge-top successions.  相似文献   

Intense drought and flooding events in the Rio Negro and relation with the tropical Pacific and Atlantic variability modes     

Andreoli  Rita Valéria  da Silva  Simone Nazaré Rodriguez  de Souza  Rodrigo Augusto Ferreira  Kayano  Mary Toshie  Garcia  Sâmia Regina  Capistrano  Vinícius Buscioli  Armijos  Elisa 《Theoretical and Applied Climatology》2017,129(1-2):551-576

The relationship of the hydrological variability of the Rio Negro in Manaus and the dominant large-scale climate variability patterns for the 1902–2007 period is investigated using the quantile method and composite analyses. Variations of the Rio Negro Level (RNL) during its 3-month high (May to July—MJJ) and low (October to December—OND) phases are examined separately. The El Niño (La Niña) related maximum warming (cooling) in the central tropical Pacific during its mature and decaying stages modulates the atmospheric circulation in the tropics and displaces the Walker circulation cell eastward (westward), so that its sinking (rising) branch occurs over western Amazon and causes negative (positive) precipitation anomalies in this region. These anomalous climate conditions occur before the Rio Negro high phase (MJJ) and contribute to reduce (increase) the RNL and lead to a very low (very high) event in the river. On the other hand, the SST variability modes in the tropical Atlantic mainly during the transition from wet to dry season modulate the precipitation variations over western Amazon in OND. The very high events are more frequent after the 1960’s decade and the very low events, before the 1930’s decade. Therefore, the occurrence of these events contains a multidecadal scale variability. The results also indicate that the variations in the rainfall in western Amazon occur up to 9 months in advance and modulate the RNL in Manaus. The results presented here might be useful for monitoring purposes of the RNL.

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Water and soil quality at two eastern-Kentucky (USA) coal fires     

Trent Garrison  James C. Hower  Alan E. Fryar  Elisa D’Angelo 《Environmental Earth Sciences》2016,75(7):574

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Influence of microclimate and geomorphological factors on alpine vegetation in the Western Swiss Alps     

Elisa Giaccone  Miska Luoto  Pascal Vittoz  Antoine Guisan  Grégoire Mariéthoz  Christophe Lambiel 《地球表面变化过程与地形》2019,44(15):3093-3107

Among the numerous environmental factors affecting plant communities in alpine ecosystems, the influence of geomorphic processes and landforms has been minimally investigated. Subjected to persistent climate warming, it is vital to understand how these factors affect vegetation properties. Here, we studied 72 vegetation plots across three sites located in the Western Swiss Alps, characterized by high geomorphological variability and plant diversity. For each plot, vascular plant species were inventoried and ground surface temperature, soil moisture, topographic variables, earth surface processes (ESPs) and landform morphodynamics were assessed. The relationships between plant communities and environmental variables were analysed using non-metric multi-dimensional scaling (NMDS) and multivariate regression techniques (generalized linear model, GLM, and generalized additive model, GAM). Landform morphodynamics, growing degree days (sum of degree days above 5°C) and mean ground surface temperature were the most important explanatory variables of plant community composition. Furthermore, the regression models for species cover and species richness were significantly improved by adding a morphodynamics variable. This study provides complementary support that landform morphodynamics is a key factor, combined with growing degree days, to explain alpine plant distribution and community composition. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献