Sediment load calculations from point measurements in sand-bed rivers     

Seema C.SHAH-FAIRBANK  Pierre Y JULIEN 《国际泥沙研究》2015,(1):1-12

Point velocity and suspended sediment concentration measurements are used to calculate the total sediment discharge in sand-bed rivers.Calculations with the Series Expansion of the Modified Einstein Point Procedure(SEMEPP) depend on grain diameter d_s and settling velocity ω,flow depth h,shear velocity u*,and sampling depth h_p.This procedure extends the applicability of the Modified Einstein Procedure(MEP) by using point sediment concentration and velocity measurements.This procedure is tested using the laboratory data from Coleman,and field measurements from the Enoree,Middle Rio Grande and Mississippi Rivers.Based on 801 point measurements over 124 verticals at flow depths ranging from 0.17 m to 33.5 m and sediment concentrations less than 0.1 kg L~(-1),the accuracy of the calculations depends on u*/ω and h_p/d_s.Point measurement techniques like SEMEPP are well-suited when u*/ω 5 where at least 60%of the total sediment load is measured when 90%of the flow depth is sampled.The determination of sediment discharge from point measurements is most accurate in deep rivers when h_p/d_s 10.000.and u*/ω10.Point measurements are not well-suited for shallow rivers and laboratory flumes where h 0.5 m and when u*/ω 2.  相似文献   

Influence of bottom trawling on sediment resuspension in the ‘Grande-Vasière’ area (Bay of Biscay,France)     

Baptiste Mengual  Florence Cayocca  Pierre Le Hir  Robin Draye  Pascal Laffargue  Benoit Vincent  Thierry Garlan 《Ocean Dynamics》2016,66(9):1181-1207

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Objective assessment of the contribution of the RECOPESCA network to the monitoring of 3D coastal ocean variables in the Bay of Biscay and the English Channel     

Julien Lamouroux  Guillaume Charria  Pierre De Mey  Stéphane Raynaud  Catherine Heyraud  Philippe Craneguy  Franck Dumas  Matthieu Le Hénaff 《Ocean Dynamics》2016,66(4):567-588

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Quantification and Genotyping of Rotavirus A within Two Wastewater Treatment Processes          下载免费PDF全文

Chourouk Ibrahim  Nadia Cherif  Salah Hammami  Pierre Pothier  Abdennaceur Hassen 《洁净——土壤、空气、水》2016,44(4):393-401

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Mineralogical analyses and in vitro screening tests for the rapid evaluation of the health hazard of volcanic ash at Rabaul volcano, Papua New Guinea   总被引：1，自引：1，他引：0  

Jennifer S. Le Blond  Claire J. Horwell  Peter J. Baxter  Sabina A. K. Michnowicz  Maura Tomatis  Bice Fubini  Pierre Delmelle  Christina Dunster  Herman Patia 《Bulletin of Volcanology》2010,72(9):1077-1092

The continuous ash and gas emissions from the Tavurvur cone in Rabaul caldera, Papua New Guinea, during 2007–08, raised concerns regarding how exposure would affect the respiratory health of nearby populations and impact on the environment. As part of a formal evaluation of the effects of volcanic emissions on public health, we investigated the potential health hazard of the ash using a suite of selected mineralogical analyses and in vitro toxicity screening tests. The trachy-andesitic ash comprised 2.1–6.7 vol.% respirable (sub-4 μm diameter) particles. The crystalline silica content was 1.9–5.0 wt.% cristobalite (in the bulk sample) with trace amounts of quartz and/or tridymite. Scanning electron microscopy showed that the ash particles were angular with sparse, fibre-like particles (∼3–60 μm max. diameter) observed in some samples, which we confirmed to be CaSO₄ (gypsum, at <6 wt.% in the bulk samples) and not asbestiform fibres. The ash specific surface area was low (0.1–2.7 m² g⁻¹). The leached solution from one of the ash samples was slightly acidic (pH 5.6), but did not contain high levels of toxic metals (such as F, Cu, Zn, Mn, As, Ni and Cd) when compared to previously tested volcanic ash leachates. Ash samples generated potentially-harmful hydroxyl radicals through an iron-mediated catalytic reaction, in the range of 0.15–2.47 μmol m⁻² (after 30 min of reaction). However, measurement of particle oxidative capacity (potential oxidative stress reaction using ascorbic acid) and silica-like injury to red blood cells (erythrolysis assay, i.e. measurement of cell death) nevertheless revealed low biological reactivity. The findings suggest that acute exposure to the ash would have a limited potential to exacerbate pre-existing conditions such as asthma or chronic bronchitis, and the potential for chronic exposure leading to silicosis was low.  相似文献   

Timing and duration of partial melting and magmatism in the Variscan Montagne Noire gneiss dome (French Massif Central)     

Trap  Pierre  Roger  Françoise  Cenki-Tok  Bénédicte  Paquette  Jean-Louis 《International Journal of Earth Sciences》2017,106(2):453-476

International Journal of Earth Sciences - Unravelling the detailed pressure–temperature–time-deformation (P–T–t-D) evolution of magmatic and metamorphic rocks provides...  相似文献   

In situ identification,pairing, and classification of meteorites from Antarctica through magnetic susceptibility measurements     

Luigi Folco  Pierre Rochette  Jrme Gattacceca  Natale Perchiazzi 《Meteoritics & planetary science》2006,41(3):343-353

Abstract— We report on the effectiveness of using magnetic measurements in the search for meteorites on the Antarctic ice sheet, which is thus far the Earth's most productive terrain. Magnetic susceptibility measurements carried out with a pocket meter (SM30) during the 2003/04 PNRA meteorite collection expedition to northern Victoria Land (Antarctica) proved to be a rapid, sensitive, non‐destructive means for the in situ identification, pairing, and classification of meteorites. In blue ice fields characterized by the presence of moraines and glacial drifts (e.g., Miller Butte, Roberts Butte, and Frontier Mountain), magnetic susceptibility measurements allowed discrimination of meteorites from abundant terrestrial stones that look like meteorites thanks to the relatively high magnetic susceptibility of the former with respect to terrestrial rocks. Comparative measurements helped identify 16 paired fragments found at Johannessen Nunataks, thereby reducing unnecessary duplication of laboratory analyses and statistical bias. Following classifications schemes developed by us in this and previous works, magnetic susceptibility measurements also helped classify stony meteorites directly in the field, thereby providing a means for selecting samples with higher research priority. A magnetic gradiometer capable of detecting perturbations in the Earth's magnetic field induced by the presence of meteorites was an efficient tool for locating meteorites buried in snow along the downwind margin of the Frontier Mountain blue ice field. Based on these results, we believe that magnetic sensors should constitute an additional payload for robotic search for meteorites on the Antarctic ice sheet and, by extension, on the surface of Mars where meteorite accumulations are predicted by theoretical works. Lastly, magnetic susceptibility data was successfully used to crosscheck the later petrographic classification of the 123 recovered meteorites, allowing the detection of misclassified or peculiar specimens.  相似文献   

Assessment of the ecological status of Mediterranean French coastal waters as required by the Water Framework Directive using the Posidonia oceanica Rapid Easy Index: PREI     

Sylvie Gobert  Stphane Sartoretto  Valrie Rico-Raimondino  Bruno Andral  Aurelia Chery  Pierre Lejeune  Pierre Boissery 《Marine pollution bulletin》2009,58(11):1727-1733

This paper describes the PREI (Posidonia oceanica Rapid Easy Index), a method used to assess the ecological status of seawater along Mediterranean French coasts. The PREI was drawn up according to the requirements of the Water Framework Directive (WFD 2000/60/EC) and was tested on 24 and 18 stations in PACA (Provence-Alpes-Côtes d’Azur) and Corsica, respectively. The PREI is based on five metrics: shoot density, shoot leaf surface area, E/L ratio (epiphytic biomass/leaf biomass), depth of lower limit, and type of this lower limit. The 42 studied stations were classified in the first four levels of status: high, good, moderate and poor. The PREI values ranged between 0.280 and 0.847; this classification is in accordance with our field knowledge and with our knowledge of the literature. The PREI was validated regarding human pressure levels (r² = 0.74). (http://eurex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2000:327:0001:0072:EN:PDF).  相似文献   

Isotopic fractionation of zinc in tektites     

Frederic Moynier  Pierre Beck  Fred Jourdan  Qing-Zhu Yin  Uwe Reimold  Christian Koeberl 《Earth and Planetary Science Letters》2009,277(3-4):482-489

Tektites are terrestrial natural glasses produced during a hypervelocity impact of an extraterrestrial projectile onto the Earth's surface. The similarity between the chemical and isotopic compositions of tektites and terrestrial upper continental crust implies that the tektites formed by fusion of such target rock. Tektites are among the driest rocks on Earth. Although volatilization at high temperature may have caused this extreme dryness, the exact mechanism of the water loss and the behavior of other volatile species during tektite formation are still debated. Volatilization can fractionate isotopes, therefore, comparing the isotope composition of volatile elements in tektites with that of their source rocks may help to understand the physical conditions during tektite formation.For this study, we have measured the Zn isotopic composition of 20 tektites from four different strewn fields. Almost all samples are enriched in heavy isotopes of Zn compared to the upper continental crust. On average, the different groups of tektites are isotopically distinct (listed from the isotopically lightest to the heaviest): Muong-Nong type indochinites (δ^66/64Zn = 0.61 ± 0.30‰); North American bediasites (δ^66/64Zn = 1.61 ± 0.49‰); Ivory Coast tektites (δ^66/64Zn = 1.66 ± 0.18‰); the Australasian tektites (others than the Muong Nong-type indochinites) (δ^66/64Zn = 1.84 ± 0.42‰); and Central European moldavites (δ^66/64Zn = 2.04 ± 0.19‰). These results are contrasted with a narrow range of δ^66/64Zn = 0–0.7‰ for a diverse spectrum of upper continental crust materials.The elemental abundance of Zn is negatively correlated with δ^66/64Zn, which may reflect that isotopic fractionation occurred by evaporation during the heating event upon tektite formation. Simple Rayleigh distillation predicts isotopic fractionations much larger than what is actually observed, therefore, such a model cannot account for the observed Zn isotope fractionation in tektites. We have developed a more realistic model of evaporation of Zn from a molten sphere: during its hypervelocity trajectory, the molten surface of the tektite will be entrained by viscous coupling with air that will then induce a velocity field inside the molten sphere. This velocity field induces significant radial chemical mixing within the tektite that accelerates the evaporation process. Our model, albeit parameter dependent, shows that both the isotopic composition and the chemical abundances measured in tektites can be produced by evaporation in a diffusion-limited regime.  相似文献   

Biochemical indicators for the bioavailability of organic carbon in ground water   总被引：1，自引：0，他引：1  

Chapelle FH  Bradley PM  Goode DJ  Tiedeman C  Lacombe PJ  Kaiser K  Benner R 《Ground water》2009,47(1):108-121

The bioavailability of total organic carbon (TOC) was examined in ground water from two hydrologically distinct aquifers using biochemical indicators widely employed in chemical oceanography. Concentrations of total hydrolyzable neutral sugars (THNS), total hydrolyzable amino acids (THAA), and carbon-normalized percentages of TOC present as THNS and THAA (referred to as "yields") were assessed as indicators of bioavailability. A shallow coastal plain aquifer in Kings Bay, Georgia, was characterized by relatively high concentrations (425 to 1492 μM; 5.1 to 17.9 mg/L) of TOC but relatively low THNS and THAA yields (∼0.2%–1.0%). These low yields are consistent with the highly biodegraded nature of TOC mobilized from relatively ancient (Pleistocene) sediments overlying the aquifer. In contrast, a shallow fractured rock aquifer in West Trenton, New Jersey, exhibited lower TOC concentrations (47 to 325 μM; 0.6 to 3.9 mg/L) but higher THNS and THAA yields (∼1% to 4%). These higher yields were consistent with the younger, and thus more bioavailable, TOC being mobilized from modern soils overlying the aquifer. Consistent with these apparent differences in TOC bioavailability, no significant correlation between TOC and dissolved inorganic carbon (DIC), a product of organic carbon mineralization, was observed at Kings Bay, whereas a strong correlation was observed at West Trenton. In contrast to TOC, THNS and THAA concentrations were observed to correlate with DIC at the Kings Bay site. These observations suggest that biochemical indicators such as THNS and THAA may provide information concerning the bioavailability of organic carbon present in ground water that is not available from TOC measurements alone.  相似文献