Fluorescent molecular hydrogen in the Eagle nebula     

L. E. Allen  M. G. Burton  S. D. Ryder  M. C. B. Ashley  J. W. V. Storey 《Monthly notices of the Royal Astronomical Society》1999,304(1):98-108

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Bioremediation in Fractured Rock: 1. Modeling to Inform Design,Monitoring, and Expectations          下载免费PDF全文

Claire R. Tiedeman  Allen M. Shapiro  Paul A. Hsieh  Thomas E. Imbrigiotta  Daniel J. Goode  Pierre J. Lacombe  Mary F. DeFlaun  Scott R. Drew  Carole D. Johnson  John H. Williams  Gary P. Curtis 《Ground water》2018,56(2):300-316

Field characterization of a trichloroethene (TCE) source area in fractured mudstones produced a detailed understanding of the geology, contaminant distribution in fractures and the rock matrix, and hydraulic and transport properties. Groundwater flow and chemical transport modeling that synthesized the field characterization information proved critical for designing bioremediation of the source area. The planned bioremediation involved injecting emulsified vegetable oil and bacteria to enhance the naturally occurring biodegradation of TCE. The flow and transport modeling showed that injection will spread amendments widely over a zone of lower‐permeability fractures, with long residence times expected because of small velocities after injection and sorption of emulsified vegetable oil onto solids. Amendments transported out of this zone will be diluted by groundwater flux from other areas, limiting bioremediation effectiveness downgradient. At nearby pumping wells, further dilution is expected to make bioremediation effects undetectable in the pumped water. The results emphasize that in fracture‐dominated flow regimes, the extent of injected amendments cannot be conceptualized using simple homogeneous models of groundwater flow commonly adopted to design injections in unconsolidated porous media (e.g., radial diverging or dipole flow regimes). Instead, it is important to synthesize site characterization information using a groundwater flow model that includes discrete features representing high‐ and low‐permeability fractures. This type of model accounts for the highly heterogeneous hydraulic conductivity and groundwater fluxes in fractured‐rock aquifers, and facilitates designing injection strategies that target specific volumes of the aquifer and maximize the distribution of amendments over these volumes.  相似文献   

Bioremediation in Fractured Rock: 2. Mobilization of Chloroethene Compounds from the Rock Matrix          下载免费PDF全文

Allen M. Shapiro  Claire R. Tiedeman  Thomas E. Imbrigiotta  Daniel J. Goode  Paul A. Hsieh  Pierre J. Lacombe  Mary F. DeFlaun  Scott R. Drew  Gary P. Curtis 《Ground water》2018,56(2):317-336

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Large-scale mines and local-level politics: between New Caledonia and Papua New Guinea     

Matthew Allen 《The Australian geographer》2019,50(4):547-549

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欧洲大西洋及北海南部海岸全新世泥滩沼泽沉积序列     

AlienJRL  李杨帆 《海洋地质前沿》2004,20(5):6-8

1全新世记录Godwin(1943)早期对广泛分布于欧洲西北部海岸中一晚全新世夹层泥炭的观测表明,上述因子和过程(包括一些区域的显著性)已完成对整个研究区相似地层序列的塑造。仅在主要的潮沟和海岸离岸砂坝发育处或相对海平面下降的稳定期的结果有明显的偏差。  相似文献   

Spatial demography of Calanus finmarchicus in the Irminger Sea     

M.R. Heath  J. Rasmussen  J. Allen  A.S. Brierley  A. Bunker  R. Davidson  W.S.C. Gurney  S. Hay  A.G. Hirst  A. Ingvarsdottir  P. Lindeque  D. Montagnes  R. Pollard  R.A. Saunders  G. Smerdon  P. Walsham  L. Webster 《Progress in Oceanography》2008,76(1):39-88

Continuous Plankton Recorder data suggest that the Irminger Sea supports a major proportion of the surface-living population of the copepod Calanus finmarchicus in the northern North Atlantic, but there have been few studies of its population dynamics in the region. In this paper, we document the seasonal changes in the demographic structure of C. finmarchicus in the Irminger Sea from a field programme during 2001/2002, and the associations between its developmental stages and various apparent bio-physical zones. Overwintering stages were found widely at depth (>500 m) across the Irminger Sea, and surviving females were widely distributed in the surface waters the following spring. However, recruitment of the subsequent generation was concentrated around the fringes of the Irminger Sea basin, along the edges of the Irminger and East Greenland Currents, and not in the central basin. In late summer animals were found descending back to overwintering depths in the Central Irminger Sea. The key factors dictating this pattern of recruitment appear to be (a) the general circulation regime, (b) predation on eggs in the spring, possibly by the surviving G0 stock, and (c) mortality of first feeding naupliar stages in the central basin where food concentrations appear to be low throughout the year.We compared the demographic patterns in 2001/2002 with observations from the only previous major survey in 1963 and with data from the Continuous Plankton Recorder (CPR) surveys. In both previous data sets, the basic structure of G0 ascent from the central basin and G1 recruitment around the fringes was a robust feature, suggesting that it is a recurrent phenomenon. The Irminger Sea is a complex mixing zone between polar and Atlantic water masses, and it has also been identified as a site of sporadic deep convection. The physical oceanographic characteristics of the region are therefore potentially sensitive to climate fluctuations. Despite this, the abundance of C. finmarchicus in the region, as measured by the CPR surveys, appears not to have responded to climate factors linked to the North Atlantic Oscillation Index, in contrast with the stocks in eastern Atlantic areas. We speculate that this may because biological factors (production and mortality), rather than transport processes are the key factors affecting the population dynamics in the Irminger Sea.  相似文献   

A Lagrangian biogeochemical study of an eddy in the Northeast Atlantic     

T.D. Jickells  P.S. Liss  S. Turner  J. Read  L.M. Cardenas  F. Carse  M. Hamren-Larssen  M. Steinke  A. Thompson  S.D. Archer  C.S. Law  P.D. Nightingale  C.E. Widdicombe  L.C. Gilpin  G. Savidge  P. Hadziabdic  R. Upstill-Goddard  R. Simó  A. Allen 《Progress in Oceanography》2008,76(3):366-398

We report the results of an experiment in the Northeast Atlantic in which sulphur hexafluoride (SF₆) was released within an eddy and the behaviour of trace gases, nutrients and productivity followed within a Lagrangian framework over a period of 24 days. Measurements were also made in the air above the eddy in order to estimate air-sea exchange rates for some components. The physical, biological and biogeochemical properties of the eddy resemble those of other eddies studied in this area, suggesting that the results we report may be applicable beyond the specific eddy studied. During a period of low wind speed at the start of the experiment, we are able to quantitatively describe and balance the nutrient and carbon budgets for the eddy. We also report concentrations of various trace gases in the region which are similar to those observed in other studies and we estimate exchange rates for several trace gases. We show that the importance of gas exchange over other loss terms varies with time and also varies for the different gases. We show that the various trace gases considered (CO₂, dimethyl sulphide (DMS), N₂O, CH₄, non-methane-hydrocarbons, methyl bromide, methyl iodide and volatile selenium species) are all influenced by physical and biological processes, but the overall distribution and temporal variability of individual gases are different to one another. A storm disrupted the stratification in the eddy during the experiment, resulting in enhanced nutrient supply to surface waters, enhanced gas exchange rates and a change in plankton community, which we quantify, although overall productivity was little changed. Emphasis is placed on the regularity of storms in the temperate ocean and the importance of these stochastic processes in such systems.  相似文献   

Hydrogeology and geochemistry of near-shore submarine groundwater discharge at Flamengo Bay,Ubatuba, Brazil     

June A. Oberdorfer  Matthew Charette  Matthew Allen  Jonathan B. Martin  Jaye E. Cable 《Estuarine, Coastal and Shelf Science》2008

Near-shore discharge of fresh groundwater from the fractured granitic rock at Flamengo Bay, Ubatuba, Brazil, is strongly controlled by the local geology. Freshwater flows primarily through a zone of weathered granite to a distance of 24 m offshore. In the nearshore environment this weathered granite is covered by about 0.5 m of well-sorted, coarse sands containing pore water with sea water salinity, with an abrupt transition to much lower salinity once the weathered granite is penetrated. Further offshore, low-permeability marine sediments contain saline porewater, marking the limit of offshore migration of freshwater. Freshwater flux rates based on tidal signal and hydraulic gradient analysis indicate a fresh submarine groundwater discharge of 0.17–1.6 m³/day per m of shoreline. Dissolved inorganic nitrogen and silicate are elevated in the porewater relative to seawater, and appeared to be a net source of nutrients to the overlying water column. The major ion concentrations suggest that the freshwater within the aquifer has a short residence time. Major element concentrations do not reflect in situ alteration of the granitic rocks, possibly because the alteration occurred prior to development of the current discharge zones, or because of large volumes of water discharge in this high rainfall region.  相似文献   

Comparison of bulk and compound-specific δC analyses and determination of carbon sources to salt marsh sediments using n-alkane distributions (Maine,USA)     

Benjamin R. Tanner  Maria E. Uhle  Claudia I. Mora  Joseph T. Kelley  Patrick J. Schuneman  Chad S. Lane  Evan S. Allen 《Estuarine, Coastal and Shelf Science》2010

Sources of sedimentary organic matter to a Morse River, Maine (USA) salt marsh over the last 3390 ± 60 RCYBP (Radiocarbon Years Before Present) are determined using distribution patterns of n-alkanes, bulk carbon isotopic analysis, and compound-specific carbon isotopic analysis. Marsh foraminiferal counts suggest a ubiquitous presence of high marsh and higher-high marsh deposits (dominated by Trochammina macrescens forma macrescens, Trochammina comprimata, and Trochammina inflata), implying deposition from ∼0.2 m to 0.5 m above mean high water. Distributions of n-alkanes show a primary contribution from higher plants, confirmed by an average chain length value of 27.5 for the core sediments, and carbon preference index values all >3. Many sample depths are dominated by the C₂₅ alkane. Salicornia depressa and Ruppia maritima have similar n-alkane distributions to many of the salt marsh sediments, and we suggest that one or both of these plants is either an important source to the biomass of the marsh through time, or that another unidentified higher plant source is contributing heavily to the sediment pool. Bacterial degradation or algal inputs to the marsh sediments appear to be minor. Compound-specific carbon isotopic analyses of the C₂₇ alkane are on average 7.2‰ depleted relative to bulk values, but the two records are strongly correlated (R² = 0.89), suggesting that marsh plants dominate the bulk carbon isotopic signal. Our study underscores the importance of using caution when applying mixing models of plant species to salt marsh sediments, especially when relatively few plants are included in the model.  相似文献   

A quantitative technique for assessing the roundness of pottery sherds in water currents     

J. R. L. Allen 《Geoarchaeology》1989,4(2):143-155

The shape property of transposed pottery sherds that changes most rapidly due to wear during water transport in natural sedimentary environments is roundness, the degree of curvature of edges and corners. of the many methods for the measurement of particle roundness, which are briefly reviewed, that proposed by Wadell (1932, 1933) is considered to specify roundness best. A simple and rapid procedure for the measurement of the Wadell projection roundness is described, which yields roundness values having a precision of the order of a few percent, the precision improving with the degree of roundness. the technique is therefore suitable for the analysis of large samples of transposed and transported sherds.  相似文献