Multi-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France)     

Pascal Goderniaux  Serge Brouyère  Alexis Gutierrez  Nicole Baran 《Hydrogeology Journal》2010,18(7):1729-1740

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize a sandy aquifer that is affected by diffuse pollution (Brévilles spring catchment, Val d’Oise, France), and to quantify the transfer time in the saturated zone, a multi-tracer test involving a new technique, the ‘finite volume point dilution method’, has been performed in natural flow conditions. In November 2005, injections of four different tracers took place in four piezometers involving different locations and depths in the aquifer. Recovery of the tracers was observed at two different places near the aquifer outlet. A particularly long and unusual monitoring exercise (27 months) demonstrated the existence of several different velocities within the sandy layer, which seems to be linked to the decrease of hydraulic conductivity with depth. The new insight and parameter quantification brought by interpretation of these tests contribute to a better characterization of the saturated zone. The particularly long-term monitoring exercise also gives new information to understand and forecast the trend and persistence of groundwater contamination by pesticides in the catchment.  相似文献   

Mobility of arsenic in a Bangladesh aquifer: Inferences from geochemical profiles, leaching data, and mineralogical characterization   总被引：3，自引：0，他引：3  

Christopher H. Swartz  Nicole Keon Blute  Borhan Badruzzman  Daniel Brabander  Jenny Jay  James Besancon  Harold F. Hemond 《Geochimica et cosmochimica acta》2004,68(22):4539-4557

Aquifer geochemistry was characterized at a field site in the Munshiganj district of Bangladesh where the groundwater is severely contaminated by As. Vertical profiles of aqueous and solid phase parameters were measured in a sandy deep aquifer (depth >150 m) below a thick confining clay (119 to 150 m), a sandy upper aquifer (3.5 to 119 m) above this confining layer, and a surficial clay layer (<3.5 m). In the deep aquifer and near the top of the upper aquifer, aqueous As levels are low (<10 μg/L), but aqueous As approaches a maximum of 640 μg/L at a depth of 30 to 40 m and falls to 58 μg/L near the base (107 m) of the upper aquifer. In contrast, solid phase As concentrations are uniformly low, rarely exceeding 2 μg/g in the two sandy aquifers and never exceeding 10 μg/g in the clay layers. Solid phase As is also similarly distributed among a variety of reservoirs in the deep and upper aquifer, including adsorbed As, As coprecipitated in solids leachable by mild acids and reductants, and As incorporated in silicates and other more recalcitrant phases. One notable difference among depths is that sorbed As loads, considered with respect to solid phase Fe extractable with 1 N HCl, 0.2 M oxalic acid, and a 0.5 M Ti(III)-citrate-EDTA solution, appear to be at capacity at depths where aqueous As is highest; this suggests that sorption limitations may, in part, explain the aqueous As depth profile at this site. Competition for sorption sites by silicate, phosphate, and carbonate oxyanions appear to sustain elevated aqueous As levels in the upper aquifer. Furthermore, geochemical profiles are consistent with the hypothesis that past or ongoing reductive dissolution of Fe(III) oxyhydroxides acts synergistically with competitive sorption to maintain elevated dissolved As levels in the upper aquifer. Microprobe data indicate substantial spatial comapping between As and Fe in both the upper and deep aquifer sediments, and microscopic observations reveal ubiquitous Fe coatings on most solid phases, including quartz, feldspars, and aluminosilicates. Extraction results and XRD analysis of density/magnetic separates suggest that these coatings may comprise predominantly Fe(II) and mixed valence Fe solids, although the presence of Fe(III) oxyhydroxides can not be ruled out. These data suggest As release may continue to be linked to dissolution processes targeting Fe, or Fe-rich, phases in these aquifers.  相似文献   

Characterisation of the seismological pattern in a slowly deforming intraplate region: Central and western France     

Yves Mazabraud  Nicole Bthoux  Sbastien Deroussi 《Tectonophysics》2005,409(1-4):175-192

We analyzed the seismicity of central and western France, using historical data, a compilation of all recorded earthquakes from 1962 to 2002 (4574 events, relocated), and all published focal mechanisms (119 focal solutions). The aim is to understand what are the causes of earthquakes and stress accumulation in a slowly deforming intraplate region. The distribution of earthquakes and focal mechanisms is first correlated with recognized faults, geological structures and tomographic images. Then, in order to better understand the distribution of hypocenters and seek deeper crustal sources for stress accumulation, Euler solutions are computed from the available Bouguer anomaly data. The analysis of the obtained pattern for heat flow values, provides a better understanding of the concentration of seismicity in some particular zones.Two different behaviors of this slowly deforming intraplate region are evidenced. One is linked to the presence of a hot spot under the Massif Central, the other to reactivation of the Hercynian structural heritage. Our results highlight that several possible sources for earthquake clustering can be invoked in central–western France.  相似文献   

长白山天池火山千年大喷发岩浆含水量研究——熔融包裹体含水量的红外光谱测试   总被引：1，自引：0，他引：1  

李霓  Nicole  METRICH  樊祺诚 《岩石学报》2006,22(6):1465-1472

长白山天池火山在公元一千年左右曾发生过大规模喷发，其产物为大面积分布的灰白色碱流质浮岩和碎屑流，在其斑晶矿物橄榄石、钙铁辉石和碱性长石中均可见到熔融包裹体。在最主要的斑晶矿物——碱性长石中含有数量众多且个体也较大的熔融包裹体，多数含有一个以上的气泡，其中部分含有子晶，根据形貌特征的不同可分为截然不同的两组包裹体。这些熔融包裹体带有大量喷发前地下岩浆的信息，成为研究地下深部的岩浆在复杂的溢流-爆炸喷发中所发生变化的最好媒介。也是本文的研究对象，通过其中挥发份尤其是水的含量，可以推知天池火山发生大喷发的原因。经Nicolet Magna-IR 550红外光谱仪测定，这些熔融包裹体的含水量较高，达1．6％-3．6％，为当时天池火山发生了巨大规模爆炸喷发的原因提供了强有力的证据。但目前红外光谱仪的应用范围还比较有限，有待今后拓宽其应用领域。  相似文献   

Dust in Hostile Environments     

Jean-Pierre J. Lafon  Nicole Berruyer 《Astrophysics and Space Science》1998,260(1-2):265-268

  相似文献   

Sediment accumulation along a glacially impacted mountainous coastline: north-east Gulf of Alaska   总被引：2，自引：0，他引：2  

John M. Jaeger  Charles A. Nittrouer  Nicole D. Scott  & John D. Milliman 《Basin Research》1998,10(1):155-173

Tectonically active coastal regions of the world recently have been suggested to supply the bulk of sediment from land to the oceans. Seabed sampling on the continental shelf and in coastal embayments of the north-east Gulf of Alaska (Alsek River to Prince William Sound) was performed to examine the temporal and spatial variability of sediment accumulation in a mountainous coastal setting. Cores of varying lengths (30–300 cm) were collected at 84 stations to provide information on sedimentary processes using radiochemical (²¹⁰Pb and ¹³⁷Cs) techniques. Four types of ²¹⁰Pb activity profiles were observed, dominantly reflecting steady-state sediment accumulation. However, nonsteady-state profiles also were measured, resulting in part from episodic deposition near glacier-fed rivers and on the Copper River Delta. Sediment accumulation rates in the eastern half of the study area are highest at midshelf depths (≈100 m) (≥10 mm yr^?1) and near rivers draining the Bering Glacier (≈20 mm yr^?1). On the Copper River Delta, sediment accumulation rates are highest for the delta front (> 20 mm yr^?1) and decrease westward along the sediment dispersal route. Total annual sediment accumulation is 90–140×10⁶ tons yr^?1 on the shelf in the study area. Annual sediment accumulation for the total marine environment in the study area (including Icy and Yakutat Bays) exceeds 250×10⁶ tons yr^?1, potentially making this region the largest sink for sediment in North America. Spatial patterns in sediment accumulation on the shelf are similar between centennial and Holocene time-scales, reflecting the dominance of the Copper River and Bering and Malaspina glaciers as sediment sources. Temporal variability in accumulation rates between centennial and Holocene time-scales exists for portions of the study area near fiords and demonstrates the considerable changes that occur in sediment supply during glacial advances and retreats.  相似文献   

Archean adakites from the Ashuanipi complex,eastern Superior Province,Canada: geochemistry,geochronology and tectonic significance   总被引：1，自引：0，他引：1  

Percival  John A.  Stern  Richard A.  Rayner  Nicole 《Contributions to Mineralogy and Petrology》2003,145(3):265-280

Contributions to Mineralogy and Petrology - Adakitic geochemical features characterize the Desliens suite of pre-tectonic diorite to tonalite sills intruded into volcanogenic greywackes of the...  相似文献   

Holocene paleoenvironmental change inferred from two sediment cores collected in the Tibetan lake Taro Co     

Laug  Andreas  Haberzettl  Torsten  Pannes  Andre  Schwarz  Anja  Turner  Falko  Wang  Junbo  Engels  Stefan  Rigterink  Sonja  Börner  Nicole  Ahlborn  Marieke  Ju  Jianting  Schwalb  Antje 《Journal of Paleolimnology》2021,66(3):171-186

Journal of Paleolimnology - The Tibetan Plateau, also known as the “Water Tower of Asia” because of its function as a water storage and supply region, responds dramatically to modern...  相似文献   

P–T paths reconstruction of a collisional event: The example of the Thiviers-Payzac Unit in the Variscan French Massif Central     

Manuel Duguet  Nicole Le Breton  Michel Faure 《Lithos》2007,98(1-4):210-232

Because of late metamorphic and tectonic overprints, the reconstruction of prograde parts of P–T paths is often difficult. In the SW Variscan French Massif Central, the Thiviers-Payzac Unit (TPU) is the uppermost allochthon emplaced above underlying units. The TPU experienced a Barrovian metamorphism coeval with a top-to-the-NW ductile shearing (D2 event) in Early Carboniferous times (ca. 360–350 Ma). The tectonic setting of the D2 event, compression or synconvergence extension, remains unclear. Using the THERMOCALC software and the model system MnNCKFMASH, the peak P–T conditions are estimated from garnet rims and matrix minerals and the prograde evolution is deduced from garnet core compositions. The combination of these two approaches demonstrates that the TPU experienced pressure and temperature increases before reaching peak conditions at 6.6–9.0 +/− 1.2 kbar and 615–655 +/− 35 °C. This kind of P–T path shows that the regional D2 event corresponds to crustal thickening.  相似文献   

Primary production in Long Island sound     

Nicole L. Goebel  James N. Kremer  Christopher A. Edwards 《Estuaries and Coasts》2006,29(2):232-245

Daily and annual integrated rates of primary productivity and community respiration were calculated using physiological parameters measured in oxygen-based photosynthesis-irradiance (P-I) incubations at 8 stations throughout central and western Long Island Sound (cwLIS) during the summer and autumn of 2002 and 2003 and the late spring of 2003. Each calculation takes into account actual variations in incident irradiance over the day and underwater irradiance and standing stock with depth. Annual peak rates, ±95% confidence interval of propagated uncertainty in each measurement, of gross primary production (GPP, 1,730±610 mmol O₂ m⁻² d⁻¹), community respiration (R_c, 1,660±270 mmol O₂ m⁻² d⁻¹), and net community production (NCP, 1,160±1,100 mmol O₂ m⁻² d⁻¹) occurred during summer at the western end of the Sound. Lowest rates of GPP (4±11 mmol O₂ m⁻² d⁻¹), R_c (−50±300 mmol O₂ m⁻² d⁻¹), and NCP (−1,250±270 mmol O₂ m⁻² d⁻¹) occurred during late autumn-early winter at the outer sampled stations. These large ranges in rates of GPP, R_c, and NCP throughout the photic zone of cwLIS are attributed to seasonal and spatial variability. Algal respiration (R_a) was estimated to consume an average of 5% to 52% of GPP, using a literature-based ratio of R_a:R_c. From this range, we established that the estimated R_a accounts for approximately half of GPP, and was used to estimate daily net primary production (NPP), which ranged from 2 to 870 mmol O₂ m⁻² d⁻¹ throughout cwLIS during the study. Annual NPP averaged 40±8 mol O₂ m⁻² yr⁻¹ for all sampled stations, which more than doubled along the main axis of the Sound, from 32±14 mol O₂ m⁻² yr⁻¹ at an eastern station to 82±25 mol O₂ m⁻² yr⁻¹ at the western-most station. These spatial gradients in productivity parallel nitrogen loads along the main axis of the Sound. Daily integrals of productivity were used to test and formulate a simple, robust biomass-light model for the prediction of phytoplankton production in Long Island Sound, and the slope of the relationship was consistent with reports for other systems.  相似文献