Estimating Flow Using Tracers and Hydraulics in Synthetic Heterogeneous Aquifers   总被引：2，自引：0，他引：2  

Marie Larocque  Peter G. Cook  Klaus Haaken  Craig T. Simmons 《Ground water》2009,47(6):786-796

Regional ground water flow is most usually estimated using Darcy's law, with hydraulic conductivities estimated from pumping tests, but can also be estimated using ground water residence times derived from radioactive tracers. The two methods agree reasonably well in relatively homogeneous aquifers but it is not clear which is likely to produce more reliable estimates of ground water flow rates in heterogeneous systems. The aim of this paper is to compare bias and uncertainty of tracer and hydraulic approaches to assess ground water flow in heterogeneous aquifers. Synthetic two-dimensional aquifers with different levels of heterogeneity (correlation lengths, variances) are used to simulate ground water flow, pumping tests, and transport of radioactive tracers. Results show that bias and uncertainty of flow rates increase with the variance of the hydraulic conductivity for both methods. The bias resulting from the nonlinearity of the concentration–time relationship can be reduced by choosing a tracer with a decay rate similar to the mean ground water residence time. The bias on flow rates estimated from pumping tests is reduced when performing long duration tests. The uncertainty on ground water flow is minimized when the sampling volume is large compared to the correlation length. For tracers, the uncertainty is related to the ratio of correlation length to the distance between sampling wells. For pumping tests, it is related to the ratio of correlation length to the pumping test's radius of influence. In regional systems, it may be easier to minimize this ratio for tracers than for pumping tests.  相似文献   

International viewpoint and news     

Anne Marie de Grosbois 《Environmental Geology》2008,54(6):1353-1354

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Upcoming international events     

Anne Marie de Grosbois 《Environmental Geology》2008,55(3):699-703

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Applicability of Kinetic Models for In Situ Combustion Processes with Different Oil Types     

Na Jia  David H.-S. Law  Paul Naccache  Marie Ann Giddins 《Natural Resources Research》2017,26(1):37-55

The in situ combustion (ISC) process is of interest as an enhanced oil recovery method because it is an alternative to traditional steam-based processes for heavy oil and bitumen recovery. ISC is a technique applicable outside the window of reservoir conditions deemed appropriate for steam injection (such as deeper and thinner reservoirs). The process involves complex chemical reactions and physical recovery mechanisms, and predicting the likelihood of successful ISC in field applications remains challenging. This paper describes a numerical investigation of the capability of different ISC kinetic models to predict the combustion behaviors of different types of oils (light oil, heavy oil, and bitumen). Three kinetic models (of Coats, Crookston, and Belgrave) were selected from literature and compared using data from four published combustion-tube experiments. The comparison procedure is as follows: (1) validate the numerical modeling of each kinetic model by matching the selected experimental results or duplicating the numerical results found in published literature; (2) adjust fluid viscosities and densities to match the fluid properties of each experiment;and (3) use each validated kinetic model to predict the performance of the other experiments without further tuning the kinetic parameters. The knowledge derived from the experiments provides guidance for choosing the appropriate kinetic model when no other data are available and for the preliminary design and screening study of a potential ISC project.  相似文献   

Principles of Paleoclimatology, Thomas M. Cronin     

Jeannine‐Marie St‐Jacques 《Journal of Paleolimnology》2001,26(3):353-354

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Migration moderate, ‘Master Weaver’ and inspirational team leader: reflecting on the lasting legacy of Graeme Hugo in three spheres of migration policy     

Marie McAuliffe 《The Australian geographer》2016,47(4):383-389

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Scanning Electron Microscopy for the Life Sciences H. Schatten (ed.) New York: Cambridge University Press, 2013. 298pp. ISBN: 978‐0‐521‐19599‐7. Hardback: US$120.          下载免费PDF全文

Jean‐Marie Volland 《Marine Ecology》2016,37(1):235-235

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Vik,Marte Lange. 2015. Landskapsdemokrati som metafor og materialitet: Eksempler på landskapspraksiser i møte med den europeiske landskapskonvensjonen     

Finn Arler  Marie Stenseke 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(2):128-130

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Age et croissance de Raja batis et de Raja naevus en Mer Celtique     

Du Buit  Marie Henriette 《ICES Journal of Marine Science》1977,37(3):261-265

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Uptake of platinum group elements by the marine macroalga, Ulva lactuca     

Andrew Turner  Marie S. Lewis  Leyla Shams  Murray T. Brown 《Marine Chemistry》2007,105(3-4):271-280

Uptake of environmentally relevant platinum group elements (PGE) by the marine macroalga, Ulva lactuca, has been studied. Removal of nM concentrations of Rh(III), Pd(II) and Pt(IV) added to filtered sea water appeared to proceed via pseudo-first-order kinetics, with respective forward rate constants of either 0.0039 or 0.0042 h^− 1, 0.0058 or 0.0096 h^− 1 and 0.0017 or 0.0032 h^− 1, depending on whether an irreversible or reversible reaction was invoked. The (quasi-) equilibrium distribution coefficients, derived from linear fits to uptake (sorption) isotherms, were about 1400, 900 and 350 mL g^− 1 on a dry mass basis for Rh, Pd and Pt, respectively. With increasing sea water pH, over the range 7.9 to 8.4, uptake of Rh by Ulva increased considerably, whereas a small increase in Pt removal was observed; in contrast, uptake of Pd exhibited no clear dependence on pH. The percentage of metal taken up that was internalised within cells, evaluated by washing selected algal samples in 3 mM EDTA, was about 40% for Rh, 80% for Pd and 95% for Pt. Results of this study were interpreted in terms of what is known about the aqueous speciation of PGE in sea water. Thus, Rh exists as cationic hydrated chloride complexes which are readily adsorbed at the algal surface. Palladium has an exceptional affinity for organic ligands, and uptake (and internalisation) appears to be governed by competition for Pd²⁺ from aqueous and algal binding sites. Platinum (IV) exists predominantly as a series of (mainly) negatively charged chloride and mixed hydroxychloride complexes that have little propensity to interact with the algal surface; however, its high degree of internalisation requires at least some interaction with specific and perhaps physiologically active sites.  相似文献