Rockfalls detached from a lateral moraine during spring season. 2010 and 2011 events observed at the Rebaixader debris-flow monitoring site (Central Pyrenees, Spain)     

Marcel Hürlimann  Clàudia Abancó  José Moya 《Landslides》2012,9(3):385-393

Instability processes at glacial deposits represent an important hazard in mountainous areas. During the spring seasons of 2010 and 2011, two falls of large boulders (18 and 55? m³) initiated in a lateral moraine in the Rebaixader catchment (Central Pyrenees, Spain). Detailed information was gathered due to the debris-flow monitoring system installed along the torrent. Meteorological data showed that the two rockfalls were triggered without important rainfall amounts. Field surveys, ground vibration acquired at geophones and the movie recorded with a video camera provided unique information on the rockfall occurrence and dynamics. In addition, the information gave an excellent opportunity to show the importance of monitored data for the calibration of model parameters for runout simulations. The analysis focussed on the 2011 event and showed that the boulder passed rolling and bouncing through the monitored torrent reach. The velocity estimates in this reach range from 3 to 9 ?m/s. The 2011 rockfall was also back-analysed by a two-dimensional physically based model, which was fitted by the monitored and field data. The results of the simulation coincided well with recorded measurements, although the output could be improved by the application of a three-dimensional model.  相似文献   

Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA     

Philip T. Harte  Joseph D. Ayotte  Andrew Hoffman  Kinga M. Révész  Marcel Belaval  Steven Lamb  J. K. B?hlke 《Hydrogeology Journal》2012,20(6):1189-1201

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO ₃ ^– ), iron (Fe²⁺), manganese (Mn²⁺), and sulfate (SO ₄ ^2– ). Redox conditions were evaluated also based on methane (CH₄), excess nitrogen gas (N₂) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100?m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.  相似文献   

Full‐scale Applications of Membrane Filtration in Municipal Wastewater Treatment Plants     

Marek Holba  Karel Plotěný  Lukáš Dvořák  Marcel Gómez  Iveta Růžičková 《洁净——土壤、空气、水》2012,40(5):479-486

The performance of one pilot‐scale and two full‐scale membrane bioreactors (MBR) were evaluated based on the control of main operational parameters, composition of microbial community and pathogens concentration in the treated outlet. Plants were designed for 0.75 m³/day (A), 60 m³/day (B) and 30 m³/day (C). Inlet and outlet samples were monitored for chemical oxygen demand (COD), biological oxygen demand, total suspended solids, ammonia nitrogen concentration (NH₄–N), nitrate nitrogen concentration, total Kjeldahl nitrogen, total phosphorus and phosphate phosphorus concentration concentrations. Plants showed good COD removal: 91.9% for Plant A, 97.8% for Plant B and 94.2% for Plant C. The targeted nitrogenous ion was NH₄–N due to the requirements for outlet limits. NH₄–N removal was moderate for Plant A (73.3%) and Plant B (86.1%) and excellent for Plant C (>99%). Excellent phosphorus removal was achieved by Plant A (average outlet concentration was 0.7 mg/L, efficiency 84.7%). Unsatisfactory results for phosphorus removal were achieved at the full‐scale plants due to operational problems. The dependency between the extracellular polymeric substances increase and decreasing mixed liquor volatile suspended solids for both lab and full‐scale plants was confirmed. Soluble microbial product concentrations were reduced by 65–68% after coagulant dosage for Plant A. Outlets from the MBR plants were monitored for the presence of pathogens (thermotolerant coliforms, Escherichia coli, intestinal Enterococci and culturable microorganisms at 22 and 37°C). The treated effluent from Plant A, B and C met Czech national legislation regarding reuse criteria (standards) for environment, irrigation and swimming purposes. Plants B and C were not able to achieve requirements for potable water and personal hygiene quality standards.  相似文献   

Influence of plankton concentration on gametogenesis and spawning of the black lip pearl oyster Pinctada margaritifera in Ahe atoll lagoon (Tuamotu archipelago, French polynesia)     

Fournier J  Levesque E  Pouvreau S  Pennec ML  Moullac GL 《Marine pollution bulletin》2012,65(10-12):463-470

Pearl culture industry represents one of the dominant business sector of French Polynesia. However, it still entirely relies on unpredictable spat collection success. Our aim was to assess the influence of natural plankton concentration fluctuations on maturation and spawning of the black lip pearl oyster Pinctada margaritifera, during a 4months survey conducted in Ahe atoll lagoon. Plankton concentration was assessed by chlorophyll a extraction and by microscope counts while gonadic index, gonado-visceral dry weights and histology were used to measure pearl oysters reproduction activity. We found that (i) plankton concentration fluctuations were mainly related to wind regime, (ii) gametogenesis rate was mainly related to plankton concentration, (iii) spawning occurred when maximal gonad storage was reached, (iv) plankton concentration was the main spawning synchronizing factor. These results contribute explaining P. margaritifera spat collection variability in French Polynesian atoll lagoon.  相似文献   

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera,Tenerife (Canary Islands)     

Carles Soriano  Daniele Giordano  Inés Galindo  Marcel Hürlimann  Paola Ardia 《Bulletin of Volcanology》2009,71(8):919-932

During rheomorphism subsequent to fallout deposition, a portion of the densely welded fallout of the La Grieta Member flowed back into the vent from where it was erupted, while the rest of it flowed down the outer slopes of the Las Cañadas caldera in Tenerife. The welded fallout and conduit-vent structure are physically connected and constitute a rare example of this type of deposits rooted to its feeder conduit and exposed in the caldera wall. The lower part of the vent-filling rheomorphic rocks shows gas bubbles and cavities that increase in size (up to 4 m) down vent. Bubbles are deformed against other bubbles, against the steep vent walls, flattened parallel to the flow foliation planes, and elongated parallel to the flow lineation and flow fold axes. The preservation of such giant bubbles, rather than their formation, seems to be a pretty unique feature of the phonolitic products investigated here and it is likely the result of the combination of factors that acted to preserve, in the surrounding of the glass transition interval, the sealing and the late stage cooling of a pressurized system. In addition, strain drop at the base of the vent-filling rheomorphic flow caused by flow stopping against vertical vent walls may have promoted rapid gas exsolution and the formation of large bubbles.  相似文献   

LA-ICP-MS analysis of single fluid inclusions in a quartz crystal — A methodological survey     

Boriana G. Kotzeva  Marcel Guillong  Elitsa Stefanova  Nikolay B. Piperov 《Journal of Geochemical Exploration》2009

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Trace element geochemistry of K-rich impact spherules from howardites   总被引：1，自引：0，他引：1  

Jean-Alix Barrat  Akira Yamaguchi  Richard C. Greenwood  Claire Bollinger  Marcel Bohn  Ian A. Franchi 《Geochimica et cosmochimica acta》2009,73(19):5944-5958

The howardite–eucrite–diogenite (HED) achondrites are a group of meteorites that probably originate from the asteroid Vesta. Howardites are complex polymict breccias that sometimes contain, in addition to various rock debris, impact melt glasses which show an impressive range of compositions. In this paper we report on the geochemistry and O isotopes of a series of 6 Saharan polymict breccias (4 howardites and 2 polymict eucrites), and on the trace element abundances of high-K impact spherules found in two of them, Northwest Africa (NWA) 1664 and 1769, which are likely paired.The high-K impact spherules found in the howardites NWA 1664 and NWA 1769 display remarkable trace element patterns. Compared to eucrites or howardites, they all show prominent enrichments in Cs, Rb, K, Li and Ba, strong depletion in Na, while the REE and other refractory elements are unfractionated. These features could not have been generated during impact melting of their host howardites, nor other normal HED target materials. The involvement of Na-poor rocks, and possibly rocks of granitic composition, appears likely. Although these lithologies cannot be well constrained at present, our results demonstrate that the surface of Vesta is certainly more diverse than previously thought. Indeed, despite the large number of available HED meteorites (about 1000 different meteorites), the latter are probably not sufficient to describe the whole surface of their parent body.  相似文献   

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   

Modelling the dynamics of snow cover, soil frost and surface ice in Norwegian grasslands     

Stig Morten Thorsen  Anne-Grete Roer  & Marcel van Oijen 《Polar research》2010,29(1):110-126

Studying the winter survival of forage grasses under a changing climate requires models that can simulate the dynamics of soil conditions at low temperatures. We developed a simple model that simulates depth of snow cover, the lower frost boundary of the soil and the freezing of surface puddles. We calibrated the model against independent data from four locations in Norway, capturing climatic variation from south to north (Arctic) and from coastal to inland areas. We parameterized the model by means of Bayesian calibration, and identified the least important model parameters using the sensitivity analysis method of Morris. Verification of the model suggests that the results are reasonable. Because of the simple model structure, some overestimation occurs in snow and frost depth. Both the calibration and the sensitivity analysis suggested that the snow cover module could be simplified with respect to snowmelt and liquid water content. The soil frost module should be kept unchanged, whereas the surface ice module should be changed when more detailed topographical data become available, such as better estimates of the fraction of the land area where puddles may form.  相似文献   

Etropus crossotus, an annual flatfish species; age and growth of the fringed flounder in South Carolina     

Marcel J. M. Reichert 《Journal of Sea Research》1998,40(3-4)

Fringed flounder, Etropus crossotus, a small flatfish common along the southeastern coast of the US, were collected along the South Carolina coast in the fall of 1992, and in the North Inlet estuary from August 1992 until July 1994. Standard length was 82% of total length and the relationship between standard length and wet weight showed near-isometric growth with no significant differences between males and females. Dry weight was 21% of wet weight and ash-free dry weight 14% of wet weight with no significant differences between sexes. Daily increments in the sagittal otoliths were used for age determination. No annual structures could be identified. The maximum age was about 14.5 months. Age-at-length was not different between the sexes. The relationship between age and length was exponential, with age (in days) equalling an e power of 4.242 + 0.135 × standard length (in cm). Back-calculated hatch dates and catches of early juveniles indicated a spawning season that lasted from March to October. Females started to be sexually mature at 7 to 7.5 cm standard length, but 50% maturity was reached at 8 to 8.5 cm. Females could grow to that size within one spawning season. Individuals hatched early in the spawning season could produce eggs in the latter portion of that season's spawning period.  相似文献